|Year : 1990 | Volume
| Issue : 4 | Page : 153-155
Visual acuity testing in cataract-An insight (cataract classification density based).
SK Angra, BK Pal
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi- 110 029, India
S K Angra
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi- 110 029
Source of Support: None, Conflict of Interest: None
The senile cataracts have been graded on the basis of density objectively. The letter visual acuity, laser interferometric visual acuity and pin hole visual acuity were compared in various grades of cataracts and controls (phakic and aphakic) in 140 eyes. It was found that good correlation exists in all eyes except when cataract density is grade III or IV. The laser interferometry has good prognostic value when the predictability is assessed in early stages of cataract (Grade I & II).
|How to cite this article:|
Angra S K, Pal B K. Visual acuity testing in cataract-An insight (cataract classification density based). Indian J Ophthalmol 1990;38:153-5
|How to cite this URL:|
Angra S K, Pal B K. Visual acuity testing in cataract-An insight (cataract classification density based). Indian J Ophthalmol [serial online] 1990 [cited 2020 Feb 25];38:153-5. Available from: http://www.ijo.in/text.asp?1990/38/4/153/25513
In the era of modern science, different sophisticated instruments like clinical interferometers, blue field entopic test and potential acuity meter (RAM), have been developed which can measure the potential macular resolution capability in presence of ocular media opacity. These instruments can, measure visual acuity quantitatively in presence of even cataract. Various controversial reports have emanated in the literature regarding efficacy of these procedures.  We endeavoured to classify cataracts according to density and tried to evaluate the laser visual acuity with letter visual acuity and pinhole visual acuity in cataract and age sex matched controls to assess the predictability potentials for post cataract extraction visual gains.
| MATERIAL & METHODS|| |
Age sex matched cataracts (100 eyes) and controls (40 eyes) were entered into this study. The control eyes were without any ocular media opacity. All eyes included in this study were with normal macula having normal macular function tests i.e. Maddox rod test and colour discrimination test. We categorized the cataracts into four grades according to the structures visible by direct ophthalmoscopy through dilated pupils.
Grade 1 -Mildly diminished red fundus glow (media slightly hazy, optic disc and cup visible; veins and arteries can be differentiated).
Grade II -Moderately diminished red fundus glow (media hazy, optic disc visible but not the optic cup; vessels seen but differentiation of arteries and veins not possible).
Grade III -Markedly diminished red fundus glow (only glow is seen, details not visible)
Grade IV -No red fundus glow visible.
On this basis the groups were made:Group - I:Age sex matched controls
A. Phakic control eyes (20) B. Aphakic control eyes (20)
Group II: Cataract Patients
A. Grade I Cataract (20) B. Grade II Cataract (20) C. Grade III Cataract(20).
Group III :Cataract patients who underwent surgery. A. Grade III Cataract (20) B. Grade IV Cataract (20).
In all eyes, with full mydriasis, best corrected letter visual acuity (LVA), pin hole visual acuity (PHA) and laser interferometer (Rodenstock retinometer) visual acuity (LIVA) measurements were done [Figure - 1].
Group III (A&B) eyes have udergone cataract removal by standard intracapsular cataract extraction method. After six weeks of surgery the best postoperative visual acuity with various modalities were measured. Eyes with any intraoperative and post operative complication which might affect the visual outcome have been excluded from the study.
| Observations|| |
Results showed that in 90% phakic control eyes, the LIVA and LVA were equal whereas in aphakic control eyes, it is only in 60% of the eyes, the correlation coefficient (r) being 0.86 in phakic controls and 0.71 in aphakic controls.
Correlating laser interferometer visual acuity and letter visual acuity in the cataract group we noted that in grade I cataract best corrected letter visual acuity ranged from 6/9-6/18 (Mean 0.53 + 0.10). All of these eyes had 6/6 vision with laser interferometer. In grade II cataract the best corrected letter visual acuity ranged from 6/12 - 6/36 (Mean 0.32 + 0.10). 85% of these eyes had 6/6 vision with laser interferometer and 15% had 6/9-6/12 vision. Grade-III cataract best corrected letter visual acuity ranged from 1/60-6/60 (Mean 0.05 + 0.02) and with laser interferometry only 60% of the eyes had 6/6 vision, 20% had 6/9 and 20% had 6/12 vision.
The mean letter visual acuity in grade I cataract is 0.53 + 0.10 and it came down to very low in grade III cataract which is 0.05 + 0.02. But mean laser interferometer visual acuity in grade I cataract is 1.0 and in grade III cataract it still maintains a relatively better visual acuity of 0.83 + 0.21,
Laser interferometer measured retinal visual acuity is better than letter visual acuity in all grades of cataract except the mature cataract group where patients lacked appreciation of interference fringes. The pin hole measured one Snellen line better visual acuity in 35% of grade-I and grade-II cataracts, but it was less than that measured by laser interferometer. In grade III and IV cataracts letter visual acuity and pin hole visual acuity were equal[Figure - 2]
Regarding the value of laser interferometer in predicting postoperative visual acuity our study showed that only 35% cases gave accurate prediction, 50% false negative result (pre-operative laser interferometer visual acuity less than post-operative letter visual acuity) and in 15% cases false positive result (pre-operative LIVA better than postoperative LVA), the correlation coefficient (r) being 0.07 [Figure - 2].
| Discussion|| |
There is a need for predicting post surgery visual gains before undertaking cataract surgery. The laser interferometer can measure the potential macular resolution capability even in presence of cataract. This prediction according to Goldman  Faulkner  & Billore et al [l] is good. But according to Hallyday & Ross , Bernth Peterson  & Dubey  this is poor. Thus the capability of this modality to predict post-operative visual acuity is clouded.
In our study we have graded cataracts into four groups depending on its density which obscure the visibility of retinal structures in direct ophthalmoscopy. Goldman et al  divided his patients on plain mirror examination depending on opacity in the red reflex. Datiles et al  divided their patients into two groups depending on visibility of optic disc only. Our classification is more objective and accurate in terms of cataract density considering the red glow and visibility of details of two retinal structures as parameters. The inter observer and intra observer variability was less than 5%. To generalise the early immature cataract come under grade I or Grade II cataract, and advance immature cataract in Grade III and mature as well as hypermature cataracts in grade IV cataract.
In our study 90% of the emetropes had equal laser interferometer and best corrected letter visual acuity and in 10% of the eyes laser interferometer visual acuity is more than best corrected letter visual acuity and in these eyes best corrected letter visual acuity of 6/6 could not be achieved due to optical irregularities in the eye. The correlation co-efficient(r) between laser interferometer visual acuity and best corrected letter visual acuity is 0.86 which is very highly significant. Whereas Billore et al  showed that 99.5% cases of emetropic eyes with 6/6 vision had equal vision with these modalities, Hallyday and Ross  found 85% of control (both phakic and aphakic) eyes had equal laser interferometer and letter visual acuity.
In 60 aphakic eyes (20 control, 40 post-operative cataract eyes) laser interferometer and letter visual acuity is equal in 60% of the eyes, the correlation coefficient (r) being 0.72. In 40% of the eyes laser interferometer visual acuity is higher than letter visual acuity (one line disparity in 35% cases and 2 lines disparity in 5% of the eyes). It indicates that though these eyes have higher retinal visual acuity with spectacles or contact lenses this cannont be achieved. It can be explained by the presence of the optical irregularities caused by the surgery on these eyes.
We found that pin hole gives better vision than best corrected letter visual acuity in grade I and II immature cataract but less than measured by laser interferometer. But in advance immature cataract ( Grade III cataract) pin hole visual acuity and letter visual acuity is similar. The Laser interferometer gives better visual acuity than pin hole visual acuity. This finding corroborates well with that of Schoeman Leeuwang who showed that laser interferometer gives 1.4 times better vision than pin hole vision.
The correlation coefficient (r) between pre-operative laser interferometer visual acuity and post-operative best corrected letter visual acuity in our study is 0.07 which is very poor, and similar to that found by Bernth Petersen sub i.e. 0.07 - 0.10. But other authors have found good correlation coefficient as 0.055 - 0.811.
Our study showed 15% false positive results (eg. Schoeman Leeuwang et al :12% Halliday et al  :16%). Since we have ruled out macular pathology preoperatively and excluded cases with operative complications, these false positive results are secondary (resultant of optical problems) and not primary (due to macular/retinal diseases).
In our study 50% of the cataracts showed false negative result, due to dense advance immature cataract (Grade III cataract) as we have ruled out other causes like examination with undilated pupil and communication gap between patient and examiner. The fact that all of these patients who gave false negative result, had postoperative vision of 6/6, indicates that lower preoperative values were due to denseness of the cataract interfering in laser beam penetration. This is more evident with mature cataract (Grade IV cataract) who failed to perceive interference fringes in 100% of the cases.
Thus we are of the opinion that laser interferometer cannot measure accurately the retinal visual acuity in eyes with cataracts in grade III & IV.
In our country most of the cataract surgery are undertaken in advance stages of cataract. In theme., cases the value of laser interferometer for predicting post-operative visual acuity is poor. Most of these cases will not be able to perceive the interference fringes or will give false negative values. So it is advisable to measure the potential macular resolution capability in patient with cataract at the very early stages when patients seek advice though the surgery for cataract may be undertaken at a later date.
The senile cataracts have been graded on the basis of density objectively. The letter visual acuity, laser interferometric visual acuity and pin hole visual acuity were compared in various grades of cataracts and controls (phakic and aphakic) in 140 eyes. It was found that good correlation exists in all eyes excep` when cataract density is grade III or IV. The laser interferometry has good prognostic value when the predictability is assessed in early stages of cataract (Grade I & II).
| References|| |
Goldmen H: Anezkar C. & Conaro S; : Retinal Visual acuity determination in cataract eye with interference fringes, Arch. Ophthalmol 98:1778, 1980.
Fulkner, W., Laser interferometric prediction of post-op. visual acuity in patients with cataract, Am, J. Ophthalmol. 95:626, 1983.
Halliday B.L., Ross, J.E. : Comparison of two interferometers for predicting visual acuity in patients with cataract, Brit. J. Ophthalmol. 67:273, 1983.
Bernth-Peterson, P., Clinical evaluation of Visometer for macula testing in cataract patient, Acta Ophthalmol. 60:525. 1982.
Dubey A.K., Masani AP & Shroff AP, Quantitative assessment of conventional macular tests in cases of cataract, lnd.J.Ophthal. 31, (Supple) : 895. 1983.
Datiles, M.B.. Kaiser K.M. : Prediction of potential vision through hazy media, Inst. Ophthal. Vis. Sc. 26 (Suppl.) : 308, 1985.
Billore OP & Shroff AP: Retinal Visual acuity in cataractous eye, Ind. J. Ophthalmol. 32:476-1984.
Gyton D.L., Misleading prediction of P.O. visual acuity. Arch. Ophthalmol 104:189, 1986.
Schoeman - Leeuwangh A.N. & Come R.A., Stenopic and interference vision, Int. Ophthalmol 2:157, 1980.
[Figure - 1], [Figure - 2]