Indian Journal of Ophthalmology

CURRENT OPHTHALMOLOGY
Year
: 2001  |  Volume : 49  |  Issue : 4  |  Page : 215--34

Review of findings of the Andhra Pradesh Eye Disease Study : policy implications for eye-care services.


R Dandona, L Dandona 
 International Centre for Advancement of Rural Eye Care, L.V. Prasad Eye Institute, Hyderabad, India

Correspondence Address:
R Dandona
International Centre for Advancement of Rural Eye Care, L.V. Prasad Eye Institute, Hyderabad
India

Abstract

The Andhra Pradesh Eye Disease Study (APEDS) was conducted in order to design long-term strategies to reduce blindness in the background of non-availability of recent population-based data on various aspects of blindness. The objectives of APEDS were to determine the prevalence and causes of blindness and visual impairment, prevalence of and risk factors for major eye diseases, barriers to eye-care services, and quality of life among the visually impaired. Multistage sampling was used to select 11,786 subjects of all ages from 24 urban clusters and 70 rural clusters in one urban and three rural areas belonging to different parts of Andhra Pradesh, with the aim of obtaining a study sample representative of the urban-rural and socioeconomic distribution of the population of this state. A total of 10,293 subjects underwent a detailed interview and dilated eye examination by trained professionals. The adjusted prevalence of blindness (presenting visual acuity <6/60 or central visual field <20 degrees in the better eye) was 1.84%, and moderate visual impairment (presenting visual acuity <6/18-6/60 or equivalent visual field loss in the better eye) was 8.1%. Cataract and refractive error were responsible for 60.3% of blindness and 85.7% of moderate visual impairment. Increasing age, decreasing socioeconomic status, female gender, and rural area of residence were associated with higher risk of blindness. Projections from APEDS suggest that there were 18.7 million blind people in 2000 in India, and that this number is likely to increase to 24.1 million and 31.6 million in 2010 and 2020 respectively, if the current trend continues. This review summarizes the findings of APEDS and discusses the implications of these data on the policy and planning of eye-care services.



How to cite this article:
Dandona R, Dandona L. Review of findings of the Andhra Pradesh Eye Disease Study : policy implications for eye-care services. Indian J Ophthalmol 2001;49:215-34


How to cite this URL:
Dandona R, Dandona L. Review of findings of the Andhra Pradesh Eye Disease Study : policy implications for eye-care services. Indian J Ophthalmol [serial online] 2001 [cited 2020 Jun 2 ];49:215-34
Available from: http://www.ijo.in/text.asp?2001/49/4/215/14696


Full Text

Concern about the rapidly increasing burden of avoidable blindness globally, particularly in the developing countries, led to the launch of a global initiative for the elimination of avoidable blindness, VISION 2020: The Right to Sight, in February 1999.[1-4]This is a collaborative initiative which involves the World Health Organization (WHO), the International Agency for Prevention of Blindness (IAPB), many non-governmental organisations (NGO), governments, industry, and the community.[4] The task of implementing VISION 2020 rests with governments of the countries that have identified blindness and visual impairment as a public health problem, assisted by inter-governmental organisations such as WHO and the international NGOs, which are collaborators in this endeavour. This global initiative is expected to facilitate setting priorities, co-ordinating work, and establishing new partnerships for advocacy, and should help mobilise resources.[1-4]

In order to set priorities to effectively reduce blindness, comprehensive assessment of the magnitude and causes of blindness in all age groups through well-designed population-based epidemiology studies is needed. Such assessment forms the basis of developing policy to reduce blindness. Much of the blindness-control related activity in India during the past decade was based on a national survey conducted by the Government of India in 1986-89. This cross-sectional national survey, called the WHO-NPCB survey, was conducted by the National Programme for Control of Blindness (NPCB) in collaboration with WHO to assess the magnitude and causes of blindness in the country. The prevalence of blindness (presenting visual acuity <6/60 in the better eye) in this survey was estimated to be 1.49%.[5]The NPCB's efforts in the subsequent decade focused almost exclusively on cataract as the results obtained from this survey indicated that 80% of the blindness in India was due to cataract.[5] However, this survey did not include detailed dilated fundus and visual field examination, which is likely to have resulted in underestimation of the non-cataractous causes of blindness such as glaucoma, retinal disease, and optic atrophy.[6] Based on the findings of the WHO-NPCB survey, seven states including Andhra Pradesh, were selected to be covered under the World Bank-assisted Cataract Blindness Control Project as these states accounted for approximately two-thirds of the blind population in the country in the WHO-NPCB Survey.[7] This project was started in the year 1994 and ends in 2002.

The prevalence of blindness (presenting visual acuity <6/60 in the better eye) in the state of Andhra Pradesh was reported as 1.5% in the WHO-NPCB survey.[5] In the background of non-availability of recent population-based data on the various aspects of blindness, the Andhra Pradesh Eye Disease Study (APEDS) was recently conducted in order to plan long-term strategies to reduce blindness. The objectives of APEDS were to determine the prevalence and causes of blindness and visual impairment, prevalence of and risk factors for major eye diseases, barriers to eye-care services, and quality of life among the visually impaired.[6,8,9]

This review summarises the findings from APEDS and discusses the implications of these data on the policy and planning of eye-care services.

 APEDS Methodology



The methodology of APEDS has been described in detail previously.[6,8-27] A brief description of various aspects of the methodology follows.

 Study Design



A multistage sampling procedure was used to select 24 urban and 70 rural clusters from one urban and three rural areas in different parts of the state of Andhra Pradesh, to obtain a study sample representative of the urban-rural and socioeconomic distribution of the population of this state. These four areas[Figure:1] were located in Hyderabad (urban), West Godavari district ("well-off" rural), and Adilabad and Mahabubnagar districts (poor rural).

The urban sample was selected from blocks stratified by socioeconomic status and religion whereas the rural sample was selected from villages stratified by caste as described previously.[6, 8-27] Diagrammatic representation of the sampling strategy for APEDS is shown in[Figure:2].

A total of 94 clusters were selected for APEDS using stratified random sampling such that the proportion of each socioeconomic status in the sample would be similar to that in the population of the state. The selected clusters were mapped from the north-east corner to the southwest corner of the cluster in a serpentine fashion. The number of households and members in each household were listed in each cluster. Every second to fifth household was systematically selected in each cluster to obtain a roughly equal number of households in each cluster. Approximately half the clusters in each of the four areas were randomly assigned to have persons of all ages in the selected households eligible for the study, and the other half to have only those 30 years of age or more eligible for the study. This was done to obtain similar numbers of participants grouped as less than and more than 30 years of age. The individuals who were visiting the household temporarily for a period of less than 6 months, and students who were staying together but not cooking in the house, and those members of the household who had died after the initial contact but before the examination, were ineligible for the study.

In case of refusal of a selected household to participate in the study, the members were contacted again and attempts were made to convince them to participate. If unsuccessful after five attempts, basic information about the members and their eye health was collected, if possible. No monetary incentive was offered for participation in the study but the subjects were offered priority attention at the L.V. Prasad Eye Institute, Hyderabad or the base hospital in the rural study areas if the eye condition detected needed attention.

A total of 11,786 persons were sampled in all the four areas of APEDS of which 8,832 were in the three rural areas. Eligible persons were interviewed by trained investigators. Pre-coded instruments (questionnaires) were used to collect data from the subjects. Information on subjects 15 years of age or less was collected from one of the parents of the subject. The collected information included family demographic data, individual demographic data, diet, ocular and systemic history, history of exposure to risk factors for eye diseases, visual function, quality of life, barriers to utilisation of eye-care services, and awareness of eye diseases. Information on visual function, quality of life, barriers to utilisation of eye-care services, and awareness of eye diseases was not collected for subjects 15 years of age or less.

The subjects were then invited for detailed eye examination at a local site. Written informed consent was obtained from subjects before examination. The consent form was read aloud by the receptionist at the examination site in presence of all the other subjects on that day for the subjects who could not read and write. These subjects gave their left thumb impression after understanding and agreeing with the content of the consent. This study was approved by the Ethics Committee of the L. V. Prasad Eye Institute. APEDS was conducted from October 1996 to February 2000.

 Clinical examination



The eye examination conducted in APEDS has been described in detail previously.[6, 8-20] The examinations were done by four ophthalmic technicians and four ophthalmologists who had received special training in the procedures of this study for documenting the clinical findings in a standardised manner. In brief, the eye examination included measurement of presenting and best-corrected distance and near visual acuities under standardised conditions with logMAR charts,[28] external eye examination, assessment of pupillary reaction, anterior segment examination using slitlamp biomicroscope, measurement of intraocular pressure using Goldmann applanation tonometer, gonioscopy, and lens, vitreous, and posterior segment examination (indirect ophthalmoscopy using 20 D lens and slitlamp biomicroscopy using 78 D lens) after dilatation unless contraindicated due to risk of angle closure.

Automated visual fields were done with the Humphrey visual field analyser[29] (Humphrey Instruments Inc, San Leandro, USA) using the threshold central 24-2 strategy in those participants assessed to have any suspicion of glaucoma, any other optic nerve pathology, higher visual pathway lesion, or significant macular lesion according to uniform predefined criteria. If the visual field was abnormal or unreliable, it was repeated on another day. Anterior segment pathology was photographed with Nikon photo-slitlamp (Nikon Corporation, Tokyo, Japan), and optic disc, macular or other retinal pathology with a Zeiss fundus camera (Carl Zeiss, Jena, Germany).

Examination was done using portable equipment in the subject's home in cases where some physical disability precluded their coming to the clinic. This examination was essentially similar to the one at the clinic except that gonioscopy, posterior segment examination using 78 D lens, automated visual fields, and photography were not done.

 APEDS staff



APEDS staff consisted of a principal investigator (LD) who had the overall scientific and administrative responsibility for the study; a co-investigator (RD) responsible for the scientific and administrative aspects of the study, coordinating all the procedures of the study, work of the staff, management of data, and quality control; a statistician for management of the databases and analysis system for the study; ophthalmologists responsible for the anterior and posterior segment examination; ophthalmic technicians responsible for visual function assessment, refraction, conducting the external and anterior segment examination, visual fields and photographs; four field investigators for subject recruitment and interviews; two data entry operators for entering data into the databases; one receptionist at study site; one patient care assistant; one housekeeping staff; a driver for transporting subjects to and from the study site in a van; and a security guard for the study site.

The APEDS instruments (data collection formats) were designed primarily by the principal investigator and the co-investigator of the study, who also trained the field investigators and the clinical team in the study procedures.

 Data management

Data Entry



All the households and the subjects within the household were given a unique identification number. This identification number included the identification for study area, mandal, ward, cluster, household, and the subject. Data on each subject were recorded on APEDS data collection forms, each of which had self-coded options for each question. The field investigators completed the APEDS interview forms, and the APEDS examination form was completed by clinicians at the examination site.

Data were then entered into a computer by two data entry operators using the FoxPro programme with internal consistency checks.[8] Data entered by one operator were checked by the other operator after completion of each cluster. This was done at random on 10% of all the data entered for each cluster. Monthly range and consistency checks were done using SPSS (Windows) to determine and verify outliers.

 Quality control



Validity of the methods of the study was tested over a series of focus group discussions and trial runs. The group consisted of eye-care professionals, public health experts, and field investigators. Pilot studies were done both in urban and rural areas to check the validity and reliability of the methods used in APEDS. Modifications were made wherever necessary until found satisfactory.[8]

Reliability checks were done at various levels. Reliability was tested amongst the field investigators for administration of the APEDS instruments, and between the principal investigator and the clinical team at examination site for clinical findings. Data entered in the FoxPro database were checked for accuracy on an on-going basis using the method described previously.

Quality control was an on-going process to maintain the quality of the data obtained and entered. In addition, there were monthly meetings between the principal investigator, co-investigator, field investigators, and the clinical team to review the procedures of the study and to clarify the procedures. Random checks were performed for both the field and the clinical work.

 Statistical analysis



Analyses were done using the SPSS software (SPSS for Windows, Chicago: SPSS Inc.). For the four areas separately and the three rural areas combined, the prevalence was adjusted for the estimated age and gender distribution of the population in India. To obtain composite estimates for the overall prevalence with all the four areas combined, the prevalence was adjusted for the estimated urban-rural distribution in India in addition to the estimated age and gender distribution. The design effect of the sampling strategy was calculated using the prevalence in each cluster,[30] and the 95% confidence intervals (CIs) of the estimates were adjusted accordingly.

 Definitions and causes of visual impairment



Blindness and moderate visual impairment[6,9-11]

Blindness was defined as presenting visual acuity Low vision[12]

Low vision was defined as the permanent visual impairment that was not correctable with refractive error correction or surgical intervention. The subjects with best-corrected distance visual acuity (refusal) and those who agreed to participate in the study and attended the interview but did not attend the clinical examination (drop-out). On comparing subjects who participated in the study with those who did not participate, the following groups were less likely to participate: those 16-29 years of age (pBlindness[6, 9]



After adjusting for the estimated age, gender and urban-rural distribution of the population of India in 2000,[31, 32]the prevalence of blindness was 1.84% (95% CI 1.49-2.19%). Of this blindness, 9.8% was due to visual field constriction. With multivariate analysis, the odds of having blindness increased with increasing age and decreasing socioeconomic status, and were 37% higher for females than for males. When the three rural APEDS areas only were considered, the prevalence of blindness was 2.03% (95% CI 1.64-2.42%).

The prevalence of blindness with the more conservative definition of presenting visual acuity Moderate visual impairment[10, 11]



In addition to the 1.84% prevalence of blindness in this sample, the adjusted prevalence of moderate visual impairment was 8.1% (95% CI 6.9-9.3%). Visual field loss was responsible for 0.96% of the moderate visual impairment. On considering the rural APEDS areas only, the age and gender adjusted prevalence of moderate visual impairment was 8.9% (95% CI 7.5-10.3%). With multivariate analysis, the odds of having moderate visual impairment increased with increasing age and decreasing socioeconomic status, and were 47% higher for females as compared to males and and 112% higher for those living in rural areas as compared to those in the urban area.

The majority of moderate visual impairment was caused by refractive error (45.8%) and cataract (39.9%). The prevalence of moderate visual impairment caused by refractive error and cataract was 2.9% (95% CI 1.8-3.4%) and 2.2% (95% CI 1.0-3.3%) respectively in the urban area, and was 4.0% (95% CI 3.3-4.7%) and 3.6% (95% CI 2.9-4.4%) respectively in the rural areas. The prevalence of moderate visual impairment due to refractive error, cataract, amblyopia and corneal diseases was higher in the rural areas than in the urban areas whereas that caused by retinal diseases, optic atrophy, and glaucoma was similar.

 Low vision[12]



After adjusting for age, gender, and urban-rural distribution of the population of India in the year 2000,[31, 32] the prevalence of low vision was 1.05% (95% CI 0.82-1.28%). The most frequent causes of low vision included retinal diseases (35.2%), amblyopia (25.7%), optic atrophy (14.3%), glaucoma (11.4%), and corneal diseases (8.6%). Multivariate analysis showed that the prevalence of low vision was significantly higher with increasing age, and there was a trend towards higher prevalence with decreasing socioeconomic status. The age and gender adjusted prevalence of low vision in only the rural areas of APEDS was 1.14% (95% CI 0.87-1.41%).

Variation was seen in the causes of low vision with age. Retinal diseases and optic atrophy as causes of low vision increased with increasing age. Glaucoma was the cause of low vision from 40 years of age onwards. The adjusted prevalence of low vision for males was 1.06% (95% CI 0.77-1.35%) and for females 1.04% (95% CI 0.75-1.33%). Females had a higher prevalence of low vision caused by optic atrophy whereas males had a higher prevalence of low vision caused by glaucoma and corneal diseases.

 Cataract[6, 9-11]



As described previously, cataract was found to be the leading cause of blindness in APEDS.[6, 9] With multivariate analysis, the odds of having blindness due to cataract were 96% higher for females than males, and 72% higher for those living in the rural areas as compared with those living in the urban area.[9] Cataract was also the second most frequent cause of moderate visual impairment in APEDS.[10, 11]

Total potential blindness due to cataract was calculated by taking into account the blindness prevented due to prior cataract surgery (included subjects who had had successful cataract surgery in one eye, but the other eye was blind; and subjects who had had cataract surgery in both eyes and at least one eye was not blind after surgery), blindness due to cataract currently, and the blindness due to cataract surgery-related causes (included cataract surgery complications and aphakia). The potential cataract blindness for the four areas is shown in. The total potential cataract blindness was the highest in West Godavari, the "well-off' rural area and was the least in Mahabubnagar, one of the poor rural areas. Blindness prevented due to cataract surgery was the highest in Hyderabad, the urban area.

 Cataract Surgery Outcome[13]



In the urban area of APEDS, the prevalence of having had cataract surgery in one or both eyes in those >

50 years old was 14.6% (95% CI 11.4-17.8%). Of the eyes that had undergone cataract surgery, 21.4% (95% CI 14.4-28.4%) were blind (presenting visual acuity Refractive error[6, 9-11, 14, 15]



Refractive error was the the second major cause of blindness and the leading cause of moderate visual impairment in APEDS.[6, 9-11]

Total potential blindness due to refractive error was calculated by taking into account the blindness prevented with use of refractive correction (included subjects who had myopia or hyperopia of 5 D or higher in both eyes and were using refractive correction and were not blind), blindness due to refractive error currently, and refractive error-related amblyopia.[9] The potential refractive error blindness (does not include aphakia) for the four areas. The total potential refractive error blindness and the refractive error blindness prevented with appropriate correction were the highest in Hyderabad. Refractive error blindness currently was higher in the rural areas compared with Hyderabad, and amblyopia blindness was the highest in one of the poor rural areas, Mahabubnagar.

Distribution of refractive error in the population has been reported from APEDS.[14, 15] In subjects <

15 years of age, the prevalence of myopia (spherical equivalent worse than -0.50 D in the worse eye) was 3.19% (95% CI 2.24-4.13%) and of hyperopia (spherical equivalent worse than +0.50 D in the worse eye) was 62.6% (95% CI 57.0-68.1%) under cycloplegia. In this age group, myopia increased with increasing age. Children in urban areas had 83% higher odds of having myopia compared to those in the rural area. Hyperopia was more prevalent in subjects well-off rural study area.

 Open-angle glaucoma[16]



Definite primary open-angle glaucoma (POAG) was defined as obvious glaucomatous optic disc damage and visual field loss in the presence of an open angle, and suspected POAG as suspected glaucomatous optic disc damage without definite visual field loss. Ocular hypertension (OHT) was defined as intraocular pressure (IOP)>

22 mmHg without glaucomatous optic disc damage or visual field loss in the presence of an open angle. Glaucomatous optic disc damage or IOP>

22 mmHg secondary to an obvious cause, and with an open angle, was defined as secondary open-angle glaucoma.

In the urban area of APEDS, the adjusted prevalence of definite POAG, suspected POAG, and OHT was 1.62% (95% CI 0.77-2.48%), 0.79% (95% CI 0.39-1.41%), and 0.32% (95% CI 0.10-0.78%) in subjects 30 years of age or older, and was 2.56% (95% CI 1.22-3.91%), 1.11% (95% CI 0.43-1.78%), and 0.42% (95% CI 0.11-1.12%) in subjects 40 years of age or older, respectively. The prevalence of POAG increased significantly with age (pAngle-closure glaucoma[17]



Manifest primary angle-closure glaucoma (PACG) was defined as IOP >

22 mmHg or glaucomatous optic disc damage with visual field loss in the presence of an occludable angle. An occludable angle was defined as pigmented posterior trabecular meshwork not visible by gonioscopy in three-quarters or more of the angle circumference.

In the urban area of APEDS, the adjusted prevalence of manifest PACG and occludable angles without angleclosure glaucoma were 0.71% (95% CI 0.34-1.31%) and 1.41% (95% CI 0.73-2.09%) respectively in subjects 30 years of age or older, and was 1.08% (95% CI 0.36-1.80%) and 2.21% (95% CI 1.15-3.27%) respectively in subjects 40 years of age or older. With multivariate analysis, the prevalence of manifest PACG and occludable angles increased significantly with age (pDiabetic retinopathy[18]



The adjusted prevalence of self-reported diabetes in the urban area of APEDS in subjects >

30 years of age was 7.8% (95% CI 5.8-9.9%). Diabetes was diagnosed at age >

30 years in 98.4% of the subjects. The duration since diagnosis of diabetes was Uveitis[19]



Uveitis was considered as anterior if keratic precipitates, cells in anterior chamber, or posterior synechiae were present without signs of inflammation in the vitreous and fundus. Intermediate uveitis was defined as inflammation primarily in the anterior vitreous, ora serrata, or pars plana, in the form of cells in anterior vitreous or exudates in vitreous or on pars plana or ora serrata. If exudates were present on pars plana or ora serrata, the intermediate uveitis was termed pars planitis. Uveitis in the form of retinitis and/or choroiditis was considered as posterior uveitis. Uveitis was considered as active if cells were present in the anterior chamber or vitreous, or if exudates were present in the vitreous or pars plana or ora serrata, or if on-going retinitis, choroiditis or vasculitis were present. In the absence of these features, inactive uveitis was diagnosed in the presence of sequelae of previous uveitis, which included keratic precipitates, posterior synechiae, and chorioretinal scars distinctly suggestive of previous chorioretinitis.

The adjusted prevalence of active or inactive uveitis unrelated to previous surgery or trauma was 0.73% (95% CI 0.44-1.14%). The adjusted prevalence of active uveitis was 0.37% (95% CI 0.19-0.70%), of which 0.06% was anterior, 0.25% intermediate, and 0.06% posterior. The adjusted prevalence of inactive uveitis was 0.36% (95% CI 0.17-0.68%), which included macular chorioretinitis scars (0.26%), anterior (0.07%), and previous vasculitis involving the whole eye (0.03%). The prevalence of visual impairment due to uveitis of Ocular trauma[20]



The adjusted prevalence of history of ocular trauma or evidence of ocular trauma by examination was 3.97% (95% CI 2.52-5.42%) in the urban area of APEDS. Blindness in at least one eye due to trauma was present in 0.6% (95% CI 0.2-1.0%) subjects. With multivariate analysis, the odds of blindness in at least one eye due to trauma were 6 times higher for those in the age group 30-39 years as compared to participants aged below 30 years, 4 times higher for those belonging to lower socioeconomic status, and 2.5 times higher for males though this did not reach statistical significance.

Trauma resulting in blindness had occurred by the age of 15 years in 55%, and before the age of 40 years in 92.1%; and a majority (53.6%) of trauma had occurred during play. With multivariate analysis, the odds for any ocular trauma were 2 times higher for males, and 2.5 times higher for labourers as compared with other occupations.

 Non-clinical Findings from APEDS



The subjective data were collected only from subjects >15 years of age as explained in the methodology section.

 Utilisation of eye-care services[21, 22]



Utilisation of eye-care services was defined as accessing eye-care services by those who had noticed change in their vision over the last 5 years. Utilisation of eye-care services was analysed for subjects >15 years of age who had visual impairment (presenting visual acuity Barriers to utilisation of eye-care services[21,22]



Barriers to utilisation of eye-care services were the reasons given by the subjects who had visual impairment and had noticed change in vision over the last 5 years but had not utilised eye-care services. Barriers to utilisation of eye-care services were categorized as personal, social, and economic. Barriers to utilisation of eye-care services that were directly related to the subject were considered as personal, barriers related to family members as social, and the barriers directly related to money as economic.

The prevalence of different types of barriers to utilisation of eye-care services for subjects >15 years of age who had visual impairment and had not utilised eye-care services for the noticed change. Among all those above 15 years of age in the population, 3.7% cited personal barriers, 1.8% cited social barriers, and 3% cited economic barriers for not utilising eye-care services. These barriers were more in the rural areas (9.8%) as compared with the urban area (4.7%). Among the rural areas, Mahabubnagar, one of the poor rural areas, had the most barriers to utilisation of eye-care services (12.2%).

With multivariate analysis, the odds of having barriers to utilisation of eye-care services were significantly higher for subjects > 40 years of age as compared with those Use of spectacles[23]



In the background of a significant burden of blindness and moderate visual impairment due to refractive error, the use of spectacles was assessed in this population and its demographic associations in order to identify those groups in the population who are likely to be not using spectacles for refractive error correction, and to formulate effective strategies to reach these groups.

Of all the subjects >15 years of age using spectacles, 13.8% had spherical equivalent +3.00 D or worse. The adjusted prevalence of current spectacles use in these subjects was 34.2% (95% CI 30.3-38%), and of previous spectacles use was 12.3% (95% CI 10.3-14.3%). With multivariate analysis, the odds of using spectacles currently were higher for those with any level of education, those living in urban area (odds ratio 3.15; 95% CI 2.13-4.64), and for those with aphakia or pseudophakia (odds ratio 22.3; 95% CI 9.3-53.3) as compared with those with myopia or hyperopia.

Of those who had used spectacles previously, 25.9% had discontinued the use because they felt that the prescription was incorrect, 19.6% had lost their spectacles and could not afford to buy a new pair, and 17.9% felt the spectacles were uncomfortable.

 Fear of blindness and perceptions about blind people[24]



The fear of contracting illnesses and disabilities including blindness, and perceptions of population towards blind people was assessed in APEDS. This information would assist in planning of eye health promotion strategies that could help reduce blindness in the population. Subjects >15 years of age were interviewed regarding fear of illness/disability and their perceptions towards the blind people. The fear of blindness was assessed in comparison to cancer, severe mental illness, heart attack, losing limbs, deafness, inability to speak, and paralysis. The subjects were asked whether they agreed or disagreed with the following statements about blind people prior to the clinical examination: (a) blind people have to depend on sighted people to do most of their things; (b) blind people can never really be happy; (c) not much should be expected from a blind person; (d) and losing one's sight means losing one's self.

All the illnesses and disabilities assessed were feared by the majority of the population. The prevalence of fear of blindness was 90.9% (95% CI 89.1-92.8%) and 92.1% (95% CI 90.6-93.6%) in urban and rural areas respectively. Multivariate analysis showed that the fear of blindness were significantly higher in those with any level of education as compared with those with no education (odds ratio 2.77; 95% CI 2.23-3.46), and in those living in the rural areas as compared with those living in the urban area (odds ratio 1.28; 95% CI 1.03-1.59). The proportions of those having positive feelings towards blind people were more in the urban area as compared with the rural areas. More of those in the urban study area disagreed with the statements that blind people can never really be happy and losing one's sight is losing one's self

 Awareness[25, 26]



Eye Diseases[25]

Subjects >15 years of age responded to a structured questionnaire on cataract, glaucoma, nightblindness, and diabetic retinopathy to field investigators. Having heard of the eye disease in question was defined as awareness and having some understanding of the eye disease was defined as knowledge.

In the urban area of APEDS, the adjusted prevalence of awareness of cataract was 69.8% (95% CI 63.5-76.1%), of night blindness was 60% (95% CI 51.8-68.1%), of diabetic retinopathy was 27% (95% CI 20-34%), and of glaucoma was 2.3% (95% CI 0.9-3.7%). Knowledge of all these eye diseases was poor. Education played a significant role in awareness of all the eye diseases. Subjects 30 years and older were significantly more aware of all eye diseases assessed except night blindness. With multivariate analysis, females were significantly less aware of night blindness (odds ratio 0.78; 95% CI 0.63-0.97). People of upper socioeconomic status had 120% higher odds of being more aware of night blindness, and those belonging to upper and middle socioeconomic strata had 179% higher odds of being more aware of diabetic retinopathy. Muslims were significantly more aware of cataract (odds ratio 2.36; 95% CI 1.84-3.02) and less aware of night blindness (odds ratio 0.52; 95% CI 0.42-0.64) compared with Hindus. The major source of awareness of the eye diseases was a family member/friend/relative suffering from that particular eye disease.

Eye donation[26]

The information about distribution and demographic associations of awareness and willingness to donate eyes could help in developing strategies to increase procurement of corneas for dealing with corneal blindness. Subjects >15 years of age were interviewed regarding awareness about eye donation and willingness to pledge eyes for donation. Awareness was defined as having heard of eye donation and knowledge was defined as having some understanding about eye donation.

In the urban area of APEDS, the adjusted prevalence of awareness about eye donation was 73.8% (95% CI 66.5-81.0%). Only 21.2% of those who were aware of eye donation had knowledge about eye donation. With multivariate analysis, awareness about eye donation was found significantly less in illiterate subjects (odds ratio 0.1, 95% CI 0.1-0.2), subjects >70 years of age (odds ratio 0.3, 95% CI 0.2-0.6), subjects belonging to lower socioeconomic status (odds ratio 0.4, 95% CI 0.3-0.6), and in females (odds ratio 0.6, 95% CI 0.5-0.8). Media was the major source of information about eye donation. Forty five percent (95% CI 37.4-52.5%) of the subjects were willing to pledge eyes for donation but only 1.9% (95% CI 0.2-3.7%) subjects had pledged eyes already. Willingness to pledge eyes for donation was significantly lower in Muslims (odds ratio 0.18, 95% CI 0.13-0.24) compared to Hindus, and in subjects >60 years of age (odds ratio 0.30, 95% CI 0.20-0.50).

 Blindness Projections from APEDS[33]



The data from APEDS were extrapolated for India in the absence of current country-wide population-based data on the magnitude of blindness. However, these extrapolations have to be viewed as approximations as they are based on data from one state.

The number of blind persons in India in 2000 was estimated to be 18.7 (95% CI 15.2-22.3) million, of which 9.5 million were blind due to cataract-related causes and 3 million due to refractive error-related causes. If there were no change in the current trend of blindness, the number of blind persons in India would increase to 24.1 (95% CI 19.7-28.4) million in 2010, and to 31.6 (95% CI 26.4-36.9) million in 2020.

The projections were also made for 2010 and 2020 for the number of persons blind from various causes under varying degrees of emphasis in the policy to control blindness. With the assumption that if effective strategies were put in place to eliminate 95% of the cataract and refractive error blindness by 2020, blindness due to cataract and refractive error would be prevented in 15.6 million and 4.2 million persons respectively, who would otherwise be blind in 2020 if the current trend continued. In addition, if strategies to prevent 90% of the preventable blindness due to corneal disease and glaucoma are successful by 2020, blindness would be prevented in an additional 3.6 million persons in 2020 who would otherwise be blind.

 Implications for Eye-care Service Delivery



In the background of the target of the NPCB to reduce the prevalence of blindness to 0.3% by 2000, we found that the prevalence of blindness in Andhra Pradesh has increased to 1.84% instead. It implies that the number of blind people in Andhra Pradesh has increased by 40% from 1 to 1.4 million over the last decade. Similarly, the number of blind people in India currently is estimated to be over 18 million,[33] and not 12 million as widely quoted for planning purposes.[5, 7, 34] We defined blindness in APEDS as presenting visual acuity community participation.[35]

 Disease control



There is a need to define the priorities for blindness regarding the specific causes of blindness based on the current population-based data. APEDS data suggest that cataract and refractive error are responsible for 60% of the total blindness, both of which are easily treatable causes of blindness.[6, 9] In addition, 19% of the total blindness was caused by other preventable causes: such as corneal diseases, glaucoma, complications of cataract surgery, and amblyopia. The short-term emphasis should be on cataract-related and refractive error-related causes, and the long-term emphasis should include corneal diseases and glaucoma as well.

The data from APEDS suggest that a little over half of the blindness currently in India is due to cataract-related causes, including cataract, complications of cataract surgery, and uncorrected aphakia after cataract surgery. However, the national survey of 1986-89 attributed 80% of the blindness to cataract,[5] and we have previously shown that this is likely to be a large overestimation as detailed dilated eye examination was not done in that survey which would lead to attributing some of the blindness due to glaucoma, optic atrophy, and retinal disease erroneously to cataract.[6] A more realistic estimate of the proportion of blindness due to cataract-related causes a decade ago is likely to be 60%.[6, 9]The large numbers of people blind due to cataract-related causes in India in 2000 suggests that the number of people suffering from cataract-related blindness has not reduced over the past decade,[33] even with the predominant focus of the NPCB on cataract and despite the assistance through the World Bank loan during 1994-2001 to reduce cataract blindness.[7] In addition, recent data also suggest that in the population approximately one-fourth or more of the eyes after cataract surgery are blind in India.[13, 36-39] This unacceptably high failure rate, and the large number of cataract surgeries in India being done on persons who are not blind, are probably responsible for the lack of reduction in the number of persons with cataract-related blindness over the past decade in India.[9]

Refractive error as a cause of blindness has not received adequate worldwide attention so far because until recently best-corrected visual acuity has been commonly used to define blindness in many surveys around the world. By definition this excludes refractive error blindness as those living with vision poor enough to qualify as blind due to lack of adequate refractive correction are not classified as blind because the best-corrected refractive correction would improve their vision.[40] Refractive error blindness is easily treatable with spectacles. It is important to consider strategies to reduce refractive error-related blindness as the onset of such blindness is usually at a young age, leading to a greater loss in years of productivity compared to those with cataract blindness, which occurs later in life.[33, 40]

The majority of corneal blindness in India is estimated to be due to corneal opacity after childhood fever, probably due to precipitation of vitamin A deficiency consequent to measles or debilitation.[9] This blindness is preventable through improvements in primary health care, including adequate intake of vitamin A-rich foods and vitamin A supplementation. This supplementation, which is supposed to be done along with immunization, has been reported to have an inadequate coverage in the population of India.[41] The other major causes of corneal blindness were keratitis and use of harmful traditional eye medicine.[9]

Blindness due to primary angle-closure glaucoma is potentially avoidable if this condition is detected early but blindness due to primary open-angle glaucoma is more difficult to prevent. Prevention of blindness due to primary angle-closure glaucoma would involve early detection of occludable angles using slitlamp and gonioscopy, and treatment with peripheral iridotomy or iredectomy.[17] A portion of the blindness due to primary open-angle glaucoma may be preventable if the disease is detected early through adequate examination of the optic disc, and appropriate therapy is instituted.[16]

In addition to the treatable and preventable causes of blindness, the other causes of blindness include retinal disease, such as retinitis pigmentosa, age-related maculopathy, myopic degeneration, and chorioretinitis; optic atrophy and congenital eye anomalies. Blindness due to these causes is mostly not treatable or preventable at present but it is possible that breakthroughs in the understanding of these conditions in future may change this scenario. In addition, it is possible that blindness due to diabetic retinopathy may become significant in India due to the aging and urbanization of the population.[18] The persistence of a significant amount of incurable blindness would require adequate rehabilitation services for the incurably blind.

To reduce blindness related to specific diseases in India, policy makers could emphasise the following.[6, 9, 42]

Strategies to reduce cataract blindness should lay more emphasis on improvement in the quality of cataract surgery and follow-up care, and on increasing the number of cataract surgeries among those who are blind in both the eyes./,/li>

Consistently defining blindness using "presenting visual acuity" rather than "best-corrected visual acuity" definition as the latter results in exclusion of refractive error blindness by not taking into account the level of vision with which people actually function in their daily lives. Strategies to reduce refractive error blindness would have to include implementation of screening programs to detect refractive error blindness in the population, good-quality refractive services, and facilitate provision of spectacles at an affordable price to the underprivileged.

Health education and behavioural change in the population should be attempted for early diagnosis and treatment of blinding corneal diseases and should be an integral part of comprehensive eye-care services.

Strategies to reduce glaucoma blindness should encourage practicing the diagnostic skills required for early detection of primary glaucoma, which currently are not

commonly practiced.

 Human Resource Development



The current estimate of the ophthalmologist: population ratio in India is1:100,000.[43] In addition to the ophthalmologists, eye-care services are also provided by optometrists, ophthalmic technicians, and opticians. These eye-care providers mostly offer refractive services. However, there are no reliable data on the number of these eye-care providers in India. The high prevalence of blindness in India suggests a consumer-provider mismatch as the ophthalmologists are concentrated in urban areas whereas much of the blindness is in rural areas.[6, 9] In addition, inadequate attention has been paid to develop the administrative and para-medical eye-care personnel in India.[44] Eye-care service delivery has concentrated mostly on ophthalmologists, resulting in inefficiency of the eye-care service delivery system. The two main issues that need to be addressed with regard to human resources are training and availability. The aim of human resource development should be to train eye-care providers to provide eye-care services to the population with a "team approach" rather than the "doctor-only" approach,[42]and to make the trained eye-care personnel available where they are needed the most, that is in the underserved areas. The specific actions that could be emphasised by the policy makers include the following:[6, 9, 42]

Developing and encouraging administrative and para-medical eye-care cadres, including those for outreach programmes, and rehabilitation services.

Upgrading the training systems by making them standardised and practically effective, and regulating and monitoring the quality of training programmes by developing accreditation systems.

Making continuing medical education a must for all clinical staff, including renewal of medical practice license based on this criterion.

Developing mechanisms/systems to encourage trained eye-care personnel to provide eye-care services in the underserved rural areas. It should be made compulsory for all medical and paramedical eye-care personnel to serve in the underserved rural areas for a minimum specified period at least and having monitoring systems in place to ensure that these rotations are actually implemented.

Providing attractive benefits and reasonable professional environment to eye-care personnel for serving in underserved rural areas.

 Infrastructure



Eye-care services in India are provided by the government, non-governmental organisations, and private sector. These services range from services free of cost to the economically underprivileged, to charges covering the costs relating to only the consumables in case of surgery, and to charges with profit margins. Most of the eye-care infrastructure is concentrated in the urban areas making access of these services difficult for those living in the rural parts of the country. The data from APEDS and other studies in India also suggest that even when eye-care services are available, use of these services varies across population based on socioeconomic status, gender, and other culturally-based factors.[21, 22, 45-47]Reduction in blindness would be possible only if the patterns of use of eye-care services are taken into account when planning and implementing the services as this would help in identifying the factors that determine the use or low use of eye-care services. The emphasis needs to be on developing reasonable-quality sustainable infrastructure in the underserved rural areas that will serve the eye-care needs of the population in the long-term. The specific actions that could be taken include the following:[6, 9, 42]

Enhancing community participation in planning infrastructure and its functioning.

Making available reasonable-quality sustainable infrastructure to provide good-quality, sufficient quantity, comprehensive eye-care services in the underserved areas on a long-term basis.

Considering the barriers to utilisation of eye-care services as perceived by the people to develop effective strategies for optimal use of the infrastructure.

Getting fund allocation to develop this infrastructure by emphasising the long-term social and economic returns to the community.

 Implications for Eye-care Providers



The implications of the findings of APEDS for the eye-care providers are discussed in terms of availability, accessibility, affordability, and accountability of the eye-care services.

 Availability and accessibility of eye-care services



Data from APEDS, and also recent data from Rajasthan, suggest that a large proportion of those with blindness live in the rural areas.[6, 9, 48] The rural areas of India are underserved in health-care including eye-care services. Hence, a major reason for the high burden of blindness is that appropriate treatment of blindness, (chiefly cataract surgery and refractive services) is not easily available to the majority. There is evidence that accessibility of the services is particularly difficult for the poor.[21, 22, 45-47] Hence the aim should be to increase the availability and accessibility of eye-care services, particularly cataract surgery and refraction services. An eye-care model which provides services in the underserved areas is being experimented within Andhra Pradesh. This is showing some success in providing good-quality, comprehensive, and financially sustainable eye-care delivery in the rural areas.[49]

The specific actions that could be taken by the eye-care providers to reduce blindness by improving provision of eye-care services include the following:[22]

Widespread experiments to provide good-quality and sustainable eye-care services in rural underserved areas.

Increase in the "outreach" activity. This activity should be targeted at those living in the rural areas and those belonging to lower socioeconomic strata in urban populations.

Reaching out to school-going children through "school-screening programmes" and other school-aged children though "outreach" activities in the community.[40]

Active eye-health promotion activities in the community. The aim of eye-health promotion would be to increase awareness in the population about eye diseases causing blindness. This will help in early detection and treatment resulting in reduction of blindness.

 Affordability of eye-care services



Economics plays a major role in the use of any healthcare service, including eye-care. Data from APEDS suggest that of the 8.5% of the population >15 years of age with visual impairment who had barriers to utilisation of eye-care services, 36% had cited economic barriers.[22] The acceptance of cataract surgery in a population in Tamil Nadu was the highest when the majority of the economic aspects of the surgery were taken care of (free surgery, free spectacles, free transportation to the site, and free meals during the stay at hospital) thus indicating that economics play a very important role in acceptance of cataract surgery,[45] but there is also evidence from Karnataka that economic barriers to cataract surgery may have reduced over time.[47]It is possible that the reduction in economic barriers is due to the availability of free cataract surgery under the World Bank Programme as part of NPCB. However, there are suggestions that free cataract surgery is often utilised by even those who can afford to pay. In addition, "could not afford to buy another pair of spectacles" was the second major reason for people to discontinue use of spectacles in APEDS.[23]

Eye-care service providers should aim at providing affordable eye-care services in addition to making these services available and accessible. The specific actions that can be taken in this regard include the following:[22]

Cross-subsidisation of eye-care services wherein those who can afford to pay for eye-care services are charged for and enough profit is made to provide eye-care at no cost to those who cannot afford to pay.

Increase the affordability of spectacles for the poor. A profit could be made on those who can pay for the spectacles, and in turn provide spectacles at cost price or no cost to the poor.

Increase the volume of cataract surgery which would in turn lower the cost per cataract surgery for the provider. This reduction in the cost could then translate into lower cost of surgery for the patient.

Seek donations or grants from local philanthropists, national and international organisations, and government to support eye-care services for those who cannot afford to pay.

 Acceptability of eye-care services



In addition to the eye-care services being available, accessible, and affordable, they should also be acceptable to the people. "Fear of cataract surgery" or "fear of eyes getting spoilt" have been commonly reported as barriers to cataract surgery in studies from Tamil Nadu and Karnataka.[45-47]There are data now to suggest that these fears may not be unjustified as 25% to 40% of the eyes have been reported blind following cataract surgery, from APEDS and from some other states of India.[13, 36-39] Such poor outcome of cataract surgery could be a barrier to acceptance of cataract surgery by the people. This poor outcome also includes those who were blind due to inadequate refractive correction of aphakia after cataract surgery.

Data from APEDS suggest that among those with spherical equivalent +3.00 D or worse who had previously used spectacles but later discontinued them, 43.8% had discontinued using spectacles because they felt that either the prescription was incorrect or that the spectacles were uncomfortable.[23] These data clearly highlight the sub-optimal quality of refractive services.

In order to increase the acceptance of eye-care services, the visual outcome after cataract surgery and refractive correction has to be acceptable. The specific actions to improve acceptance of eye-care services include the following:

Monitor the visual outcome of all cataract surgeries. This monitoring would also help in reducing surgical complications over a period of time.

Ensure good-quality cataract surgery and follow-up for all patients irrespective of their capacity to pay for the surgery.

Further attempt to shift from the "camp-approach" to "base hospital-approach" for cataract surgeries.

Ensure that refraction is performed by personnel adequately trained in refraction procedures to provide reasonable-quality prescription.

Encourage proper fitting of the spectacles frame so that discomfort does not result in discontinuance.

 Accountability of eye-care services



The issues related to accountability of eye-care services relate to the contribution of eye-care providers towards reducing blindness. It is estimated that about 3.5 million cataract surgeries were performed in India in 2000, of which about half were done with intraocular lens (IOL) implantation.[50] In addition, as mentioned previously, a high rate of poor visual outcome following cataract surgery, including that due to lack of aphakic correction, has been reported from some states of India. It is estimated that about one-third of the cataract surgeries are being performed on people blind in both eyes. Provision of cataract services without IOL implantation and a high proportion on those not blind in both eyes raises the issue of accountability of those involved in providing cataract services.

Quality of eye-care services include the comprehensiveness of the service. Data from APEDS suggest that majority of glaucoma was undiagnosed in this population, primarily because a dilated eye examination is not routinely practiced in India.[16, 17] The specific issues that need to be addressed to increase the accountability of eye-care services include the following:

Increasing the number of cataract surgeries on bilaterally blind people.

Increasing the number of cataract surgeries with IOL implantation.

Establishing screening programmes to detect refractive error blindness and provide services to treat it.

Providing complete eye examination to the patients, including measurement of IOP and examination of the fundus in order to increase the detection rate of glaucoma and posterior segment eye diseases.

Improving health promotion activities in the community by increasing awareness about common eye diseases, their prevention, and treatment.

The above can be achieved by using an "eye-care team" approach rather than the "doctor-only approach". This means that the ophthalmologist could concentrate on providing treatment, including surgeries to the patients and have assistance in the work-up of a patient, including refraction from para-medical personnel. In addition, the non-clinical responsibilities, such as administration, can be handled by a manager. This approach will translate into increase in the number of patients seen, services provided, and surgeries performed.

If the goal of VISION 2020 to eliminate avoidable blindness by 2020 is to be achieved in India, the disease control, human resource and infrastructure development would have to be built upon a foundation of community participation, and all stakeholders in eye care would have to participate in this process.

 Acknowledgements



The Andhra Pradesh Eye Disease Study was supported by Hyderabad Eye Research Foundation, Hyderabad, India and Christoffel-Blindenmission, Bensheim, Germany. Dr. Rakhi Dandona was supported in part by RB McComas and Hugh Noel Puckle scholarships from the University of Melbourne, Melbourne, Australia.

The authors thank the participants of APEDS for their participation in the study, the entire APEDS team, Dr. Gullapalli N. Rao for support, and Prof. Hugh R. Taylor and Dr. Catherine A. McCarty for guidance in the study design.

References

1World Health Organization. Global initiative for the elimination of avoidable blindness. Geneva: World Health Organization, (WHO/PBL/97.61),1997.
2Thylefors B. A global initiative for the elimination of avoidable blindness[editorial]. Am J Ophthalmol 1998;125:90-3.
3Pararajasegaram R. Vision 2020 - The Right to Sight: From strategies to action[editorial]. Am J Ophthalmol 1999;128:359-60.
4Foster A. Vision 2020: the Right to Sight. IAPB News. January 2000, number 25, p 3-4.
5Government of India. Survey of blindness in India (1986-89): Summary and results. In: Present status of National Programme for Control of Blindness (NPCB) 1992. New Delhi: Ministry of Health and Family Welfare, Government of India, 1992. PP 79-100.
6Dandona L, Dandona R, Naduvilath TJ, McCarty CA, Nanda A, Srinivas M, et al. Is current eye-care-policy focus almost exclusively on cataract adequate to deal with blindness in India? lancet 1998;351:1312-16.
7Jose R, Bachani D. World Bank-assisted cataract blindness control project. Indian J Ophthalmol 1995;43:35-43.
8Dandona R, Dandona L, Naduvilath TJ, Nanda A, McCarty CA. Design of a population-based study of visual impairment in India: The Andhra Pradesh Eye Disease Study. Indian J Ophthalmol 1997;45:251-57.
9Dandona L, Dandona R, Srinivas M, Giridhar P, Vilas K, Prasad MN, et al. Blindness in the Indian state of Andhra Pradesh. Invest Ophthalmol Vis Sci 2001;42:908-16.
10Dandona L, Dandona R, Naduvilath TJ, McCarty CA, Mandal M, Srinivas M, et al. Burden of moderate visual impairment in an urban population in southern India. Ophthalmology 1999;106:497-504.
11Dandona R, Dandona L, Srinivas M, Giridhar P, Prasad MN, Vilas K, et al. Moderate visual impairment in India: the Andhra Pradesh Eye Disease Study. Br J Ophthalmol; In press.
12Dandona R, Dandona L, Srinivas M, Giridhar P, Nutheti R, Prasad MN. Planning for low-vision services in India: A population based perspective. Ophthalmology. In press.
13Dandona L, Dandona R, Naduvilath TJ, McCarty CA, Mandal M, Srinivas M, et al. Population-based assessment of the outcome of cataract surgery in an urban population in southern India. Am J Ophthalmol 1999;127:650-58.
14Dandona R, Dandona L, Naduvilath TJ, Srinivas M, McCarty CA, Rao GN. Refractive errors in an urban population in southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999;40:2810-18.
15Dandona R, Dandona L, Srinivas M, Giridhar P, McCarty CA, Rao GN. Population-based assessment of refractive error in India. Clinical Exp Ophthalmol In press.
16Dandona L, Dandona R, Srinivas M, Mandal P, John RK, McCarty CA, et al. Open-angle glaucoma in an urban population in southern India the Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107:1702-9.
17Dandona L, Dandona R, Srinivas M, Mandal P, John RK, McCarty CA, et al. Angle-closure glaucoma in an urban population in southern India: the Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107:1710-16.
18Dandona L, Dandona R, Naduvilath TJ, McCarty CA, Rao GN. Population-based assessment of diabetic retinopathy in an urban population in southern India. Br J Ophthalmol 1999;83:937-40.
19Dandona L, Dandona R, John RK, McCarty CA, Rao GN. Population-based assessment of uveitis in an urban population in southern India. Br J Ophthalmol 2000;84:706-9.
20Dandona L, Dandona R, Srinivas M, John RK, McCarty CA, Rao GN. Ocular trauma in an urban population in southern India: The Andhra Pradesh Eye Disease Study. Clinical Exp Ophthalmol 2000;28:350-56.
21Dandona R, Dandona L, Naduvilath TJ, McCarty CA, Rao GN. Utilisation of eye-care services in an urban population in southern India: The Andhra Pradesh Eye Disease Study. Br J Ophthalmol 2000;84:22-7.
22Dandona R. Barriers to eye-care services in the Indian state of Andhra Pradesh: Recommendations for action. PhD Thesis, University of Melbourne, Melbourne, Australia, 2001.
23Dandona R, Dandona L, Kovai V, Giridhar P, Prasad MN, Srinivas M. Population-based study of spectacles use in southern India. Indian J Ophthalmol. In press.
24Giridhar P, Dandona R, Prasad MN, Vilas K, Dandona L. Fear of blindness and perceptions about blind people: the Andhra Pradesh Eye Disease Study. Indian J Ophthalmol; submitted.
25Dandona L, Dandona R, John RK, McCarty CA, Rao GN. Awareness of eye diseases in an urban population in southern India. Bull World Health Organ 2001;79:96-102.
26Dandona R, Dandona L, Naduvilath TJ, McCarty CA, Rao GN. Awareness of eye donation in an urban population in India. Aust NZJ Ophthalmol 1999;27:166-69.
27Dandona L, Dandona R, Srinivas M, Mandal P, McCarty CA, Rao GN. Unilateral visual impairment in an urban population in southern India. Indian J Ophthalmol 2000;48:59-64.
28Ferris FL, Kassoff A, Bresnick GH, Bailey I. New visual acuity charts for clinical research. Am J Ophthalmol 1982;94:91-6.
29Humphrey Field Analyzer II User's Guide. San Leandro: Humphrey Instruments Inc, 1994.
30Bennett S, Woods T, Liyanage WM, Smith DL. A simplified general method for cluster-sample surveys of health in developing countries. World Health Stat Quart 1991;44:98-106.
31US Census Bureau. International data base. http://www.census.gov (accessed December 2000).
32United Nations. World urbanization prospectus. New York: United Nations;1998.
33Dandona L, Dandona R, John RK. Estimation of blindness in India from 2000 through 2020: implications for blindness-control policy. Natl Med J India; In press.
34National blindness control programme. In: Planning Commission, Government of India. Ninth Five Year Plan 1997-2002. Volume II. Chapter 3.4.120. http://www.nic.in/ninthplan/ (accessed May 2001).
35Dandona L. Blindness control in India: beyond anachronism. Lancet 2000;356:s25.
36Limburg H, Foster A, Vaidyanathan K, Murthy GVS. Monitoring visual outcome of cataract surgery in India. Bull World Health Organ 1999;77:455-60.
37Singh AJ, Garner P, Floyd K. Cost-effectiveness of publicfunded options for cataract surgery in Mysore, India. Lancet 2000;355:180-84.
38Anand R, Gupta A, Ram J, Singh U, Kumar R. Visual outcome following cataract surgery in rural Punjab. Indian J Ophthalmol 2000;48:153-58.
39Murthy GVS, Ellwein LB, Gupta S, Tanikachalam K, Ray M, Dada VK. A population-based eye survey of older adults in a rural district of Rajasthan. II. Outcomes of cataract surgery. Ophthalmology 2001;108:686-92.
40Dandona R, Dandona L. Refractive error blindness. Bull World Health Organ 2001;79:237-43.
41Mortality, morbidity, and immunization. In: International Institute for Population Sciences. National Family Health Survey (NFHS-2) 1998-99. India. Chapter 6. http://www.nfhsindia.org (accessed May 2001).
42Dandona R, Dandona L, Rao GN. Recent blindness data from India: policy implications in the context of VISION 2020. IAPB News 2001;32:6-7.
43Rao GN. Ophthalmology in India[editorial]. Arch Ophthalmol 2000;118:1431-32.
44Dandona L, Dandona R, Shamanna BR, Naduvilath TJ, Rao GN. Developing a model to reduce blindness in India: The International Centre for Advancement of Rural Eye Care. Indian J Ophthalmol 1998;46:263-68.
45Brilliant GE, Lepkowski JM, Zurita B, Thulasiraj RD. Social determinants of cataract surgery utilisation in South India. Arch Ophthalmol 1991;109:584-89.
46Fletcher AE, Donoghue M, Devavaram J, Thulasiraj RD, Scott S, Abdalla M, et al. Low uptake of eye services in rural India: a challenge for programmes of blindness prevention. Arch Ophthalmol 1999;117:1393-99.
47Vaidyanathan K, Limburg H, Foster A, Pandey RM. Changing trends in barriers to cataract surgery in India. Bull World Health Organ 1999;77:104-9.
48Murthy GVS, Gupta S, Ellwein LB, Munoz SR, Bachani D, Dada VK. A population-based eye survey of older adults in a rural district of Rajasthan. I. Central vision impairment, blindness, and cataract surgery. Ophthalmology 2001;108:679-85.
49Dandona L, Dandona R, Shamanna BR, Rao GN. A model for high-quality sustainable eye-care services in rural India. In: Pararajasegaram R, Rao GN, editors. World blindness and its prevention: Volume 6. Hyderabad: International Agency for the Prevention of Blindness;2001.
50Bachani D. National programme development for prevention of blindness in India. In: Pararajasegaram R, Rao GN, editors. World Blindness and its Prevention: Volume 6. Hyderabad: International Agency for the Prevention of Blindness;2001.