The polymerase chain reaction (PCR) and nucleic acid hybridization assays are recently introduced molecular techniques that allow for the identification of extremely small quantities of specific nucleic acids. These techniques have significant advantages over more conventional laboratory techniques, but also have some limitations. They are bound to have tremendous potential in diagnostic ophthalmic pathology and also in investigative pathology for deciphering the pathophysiology of ocular diseases. Despite their increased sensitivity and specificity, the results will still have to be co-related with clinical findings for maximum impact. For an ophthalmologist to derive maximum benefit, knowledge of these techniques, and their advantages, and limitations is essential. This article describes the basic concepts of molecular biology and the techniques of PCR, nucleic acid hybridization, and immunohistochemistry.

This report deals with our experience in the management of threshold retinopathy of prematurity (ROP). A total of 45 eyes of 23 infants were subjected to treatment of threshold ROP. 26.1% of these infants had a birth weight of >l,500 gm. The preferred modality of treatment was laser indirect photocoagulation, which was facilitated by scleral depression. Cryopexy was done in cases with nondilating pupils or medial haze and was always under general anaesthesia. Retreatment with either modality was needed in 42.2% eyes; in this the skip areas were covered. Total regression of diseases was achieved in 91.1% eyes with no sequelae. All the 4 eyes that progressed to stage 5 despite treatment had zone 1 disease. Major treatment-induced complications did not occur in this series. This study underscores the importance of routine screening of infants upto 2,000 gm birth weight for ROP and the excellent response that is achieved with laser photocoagulation in inducing regression of threshold ROP. Laser is the preferred method of treatment in view of the absence of treatment-related morbidity to the premature infants.

We compared the results of strabismus surgery using adjustable and non-adjustable hang-back muscle recessions in 38 patients having concomitant exotropia. The two groups were matched for age of the patient, type of concomitant exotropia, amount of deviation, and type and amount of muscle surgery. At 6 months follow-up, 18 of the 19 patients (95%) in the adjustable hang-back recession group and 17 of the 19 patients (90%) in the non-adjustable hang-back recession group had ocular alignment within 10 prism diopters (PD) of orthophoria. At the most recent follow-up (mean 3.4 years), 12 of the 13 patients (92%) in adjustable hang-back recession group and 12 of the 14 patients (86%) in non-adjustable hang-back recession group had ocular alignment within 10 PD of orthophoria. There was no statistically significant difference in success rates between the two groups at 6 months postoperatively and at the most recent follow-up. This preliminary study suggests that non-adjustable hang-back muscle recession can be considered for routine concomitant exotropia.

A prospective study of 500 consecutive patients of primary angle closure glaucoma was undertaken to study the clinical profile of the three subtypes: acute, subacute, and chronic. A record of age and sex distributions, symptomatology, the best corrected visual acuity, gonioscopy, visual fields, methods of control of intraocular pressure, and status of the second eye was maintained. Statistical analysis of these parameters and the subtypes of angle closure glaucoma was carried out using the chi-square test. Angle closure glaucoma constituted 45.9% of all primary adult glaucomas seen. 24.8% of these had acute angle closure glaucoma, 31.2% subacute, and 44% chronic glaucoma. Angle closure glaucoma occurred maximally in the sixth decade and females constituted 51.4% of those affected. The difference in symptoms among the subtypes was significant (p<0.001). More than 80% of the chronic eyes had no significant symptoms. Visual field defects specific for glaucoma were seen in only 15.1% of chronic glaucoma eyes. Bilaterality was commonest in subacute angle closure glaucoma (95.5%) and least in acute angle closure 35.5%. Nd YAG iridotomy alone or with topical medication controlled the intraocular pressure in 48.3% of acute angle closure glaucoma, 78.8% of subacutes, and 30% of chronic eyes. Statistically, each parameter reviewed was significantly different among the subtypes. There are considerable differences as well as an overlap of clinical features in the subtypes of angle closure glaucoma, which suggest some anatomical differences or dissimilar pathogenic mechanisms in these eyes.

Potassium hydroxide (KOH) preparation is an underutilized modality in the diagnosis of mycotic keratitis. We have earlier shown its utility in the diagnosis of Nocardia and Acanthamoeba keratitis. The aim of this study was (i) to evaluate the sensitivity, specificity and predictive value of KOH preparation, and (ii) to compare its efficacy with other methods of corneal scraping examination, for the diagnosis of mycotic keratitis. The study was conducted in two phases. In phase I, randomized corneal scrapings were examined by KOH, Gram's stain, and lactophenol cotton blue (LPCB) in 91 infectious keratitis subjects. In phase II, 53 corneal scrapings were stained with KOH and calcofluor white (CFW), and viewed with bright field (KOH) and fluorescence (CFW) microscopy. The KOH and CFW readings were recorded by an observer masked to the clinical findings and culture results. Nineteen scrapings were examined by two masked observers. In 22 culture positive fungal keratitis patients in phase I, the sensitivity of KOH, Gram's stain, and LPCB methods was 100%, 86.4%, and 77.3%, respectively. In phase II, the specificities of KOH and CFW were identical (83.8%), while the sensitivities were 81.2% and 93.7%, respectively (p = 0.59), in 16 culture positive mycotic keratitis patients. There was no significant difference between the negative and positive predictive values of KOH and CFW. Furthermore, no significant interobserver variability was found in the specificity and sensitivity. The KOH method compares well with other microscopy methods in the diagnosis of keratomycosis and has a definite place in the armamentarium of diagnostic techniques.

The development of mild but significant inflammation probably attributable to viscoelastic ophthalmic solutions in cataract surgery was recently brought to the notice of the authors, and hence a study of the effects of these solutions available in India, on cell cultures was undertaken. We studied the effects of 6 viscoelastic ophthalmic solutions (2 sodium hyaluronate designated as A and B, and 4 hydroxypropylmethylcellulose designated as C, D, E and F) on HeLa, Vero and BHK-21 cell lines in tissue culture microtitre plates using undiluted, 1:10 and 1:100 dilutions of the solutions, and in cover slip cultures using undiluted solutions. Phase contrast microscopic examination of the solutions was also done to determine the presence of floating particles. The products D and F produced cytotoxic changes in HeLa cell line and these products also showed the presence of floating particles under phase contrast microscopy. Other products did not have any adverse effects on the cell lines nor did they show floating particles. The viscoelastic ophthalmic pharmaceutical products designated D and F have cytotoxic effects on HeLa cell line which appears to be a useful cell line for testing these products for their toxicity. The presence of particulate materials in products D and F indicates that the methods used for purification of the solution are not effective.

The use of artificial drainage devices (ADDs) or "setons" in glaucoma surgery is generally restricted to patients with refractory glaucoma at high risk for failure from conventional filtration surgery. ADDs, both valved and nonvalved are currently available in this country. Recently, some of these devices have been propogated as primary treatment even for primary glaucomas. This article examines the role of ADDs in the modern management of the glaucomas. Specific indications for ADDs and methods to reduce the complication of overfiltration are discussed. The use of antimitotics, such as 5-fluorouracil or mitomycin, with traditional filtration has decreased the indications for ADDs. The literature and our experience confirm that currently there is no role for use of ADDs as a primary procedure in most glaucomas.

The aim of this study was to investigate cataract surgery procedures and caseloads among Indian ophthalmologists in private and government practices. Members of the All India Ophthalmological Society and state ophthalmic societies were surveyed by mail questionnaire in December 1995. Out of 6,800 surveyed, 2,098 responses (31%) were received. Over 61% of the 990,249 reported cataract surgeries were carried out in private facilities with 24% of private patients receiving extracapsular cataract extraction (ECCE) and 41% ECCE with intraocular lens (IOL). Intracapsular cataract extraction remains more common in government facilities with 62% of cases. Over 85% of all surgeons reported some experience with ECCE/IOL. Surgeons operating in both private and government facilities carry an average annual caseload of 861 cataract surgeries, which is twice that of their colleagues operating exclusively in either private or government settings. Although the questionnaire response rate was low, the findings suggest that ECCE is more common in India than is generally recognized, and with the recent availability of low-cost IOLs, its popularity is rapidly expanding.

In general, better understanding of the need and usage of statistics would benefit the medical community in India. This paper explains why statistical analysis is needed, and what is the conceptual basis for it. Ophthalmic data are used as examples. The concept of sampling variation is explained to further corroborate the need for statistical analysis in medical research. Statistical estimation and testing of hypothesis which form the major components of statistical inference are construed. Commonly reported univariate and multivariate statistical tests are explained in order to equip the ophthalmologist with basic knowledge of statistics for better understanding of research data. It is felt that this understanding would facilitate well designed investigations ultimately leading to higher quality practice of ophthalmology in our country.