|Year : 1984 | Volume
| Issue : 6 | Page : 513-515
Retinal visual acuity in myopia
OP Billore, AP Shroff, PH Masani
Rotary Eye Institute, Navsari, Gujarat, India
O P Billore
Rotary Eye Institute, Navsari, Gujarat
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Billore O P, Shroff A P, Masani P H. Retinal visual acuity in myopia. Indian J Ophthalmol 1984;32:513-5
Rodenstock Retinometer measures retinal and cortical function independent of the influence of the optical media of the eye. It provides quantitative information and the qualitative assessment of entoptic phenome≠non. The basis of this device is the generation of a spatially extended set of interference fringes in the patient's eye by a laser used as a coherent light source. The result defined as `retinal visual acuity' provides information on the resolving power of the retina.
| Material and methods|| |
In the present study retinal visual acuity was measured in 300 myopic patients before refraction. It was compared whether retinal visual acuity predicted by retinometer tallied with post mydriatic test or with contact lens correction or not. These cases of myopia were grouped into simple and pathological myopia with central degeneration.
The Rodenstock Retinometer is mounted on RO 2030 Slit Lamp, The slit lamp is adjusted to the eye to be examined and then slit image is focussed sharply on the cornea. Retinometer is switched on and two small red dots are focussed in the patient's pupil by moving the joy stick of the slit lamp. With clear media normal setting is used by rotating knob 3 to setting 1. Rotating Knob 1 serves for chan≠ging the density of interference fringes in steps corresponding to values of the retinal visual acuity from 0.03 to 1.0 Direction of fringe pattern is changed by a knob so that it is verified whether patient is replying correctly or not.
| Observation|| |
In the present study retinal visual acuity was recorded in 30) cases of myopia before refraction. It was observed that RVA was mere than LVA  (Snellen's visual acuity) in 95.3% cases and equal to in 3.66% cases. RVA was equal to corrected visual acuity (LVA 2 ) in 38.66% cases. It was found that in 56.66% cases RAA was more than LVA  after spectacle and contact lens correction [Table - 1]. This suggest that in these cases expected vision was not achieved as predicted by Retinometer. Reason may be due to change in transparency of the ocular media or degenerative changes in the retina.
From the [Table - 2] it was observed that 6/12 to 6/6 vision was predicted by retinometer in 53.66% cases but achieved in 38.44% cases. Similarly 6/36 to 6/18 vision was predicted in 39.88% cases and achieved in 47.66% cases. Similarly below 6/60 vision was predicted in 6.6% cases and achieved in 14.83%cases.
It was observed that in cases of myopia with central degeneration, retinal visual acuity was much higher than the corrected visual acuity. In 88.72% cases uncorrected visual acuity was below 6/60 but retinometer predicted between 6/36 to 6/6 in 88.68% cases. but actually was gained in 68.01 % cases only. Below 6/60 vision was predicted in 1 1.21% only but achieved in 32.36% cases showing that this include those cases in which RVA was predicted above 6/60 but corrected vision could not be obtained as desired.
| Discussion|| |
In myopia cases retinal visual acuity was higher than uncorrected visual acuity in 95.3% cases. In 38.66% cases visual acuity was gain≠ed by glasses or contact lens showing the retinometer prediction was accurate in this group. Still in 56.66% cases visual acuity could not be corrected by spectacle or contact lens as predicted by retinometer. Why this could not be corrected in these cases is difficulty to answer ? It may be possible that grating acuity measured by interference fringe method is slightly higher than when measured by letters. Grating acuity requires only detec≠tion of the orientation of lines in a more pri≠mitive type of form vision than recognition of letters which requires not only that the com≠ponent parts are resolved but that they are also integrated to a recognizable whole. But RVA in 500 normal cases with 6/6 vision tallied with Snellen's visual acuity in 99.5% cases.
This shows accuracy and dependability of the retinometer. Similarly in Amblyopia cases RVA was much higher side but on close follow up and repeated pleoptic treatment resulted in gaining of desired visual acuity as predicted by retinometer in few cases. Retinometer can be used as a routine method before refraction since it provides quantitative estimation of visual acuity to be with clear media.
- In simple myopia retinometer predicts maximum visual acuity that can be achieved with glasses correction or contact lens.
- In myopia with central degeneration Retinal visual acuity was higher than the corrected visual acuity.
| References|| |
Billore, O.P., Shroff, A.P., R.J. Mirza and Paresh Antani, 1983, Ind. J. Ophthalmol 31 : 1029.
Billore, O.P., Shroff, A.P., 1983, Ind. J. Opthalmol, 31 : 383.
Billore. O.P., Sharoff, A.1. and Jadliwala, J.M. and MasaniĄ P.H. Retinal Visual acuity in Cataractous eyes-paper will be presented in forth≠coming All India Conference which will be held in Cochin, 1984.
[Table - 1], [Table - 2], [Table - 3]