|Year : 1983 | Volume
| Issue : 2 | Page : 49-53
Retinal sensitivity in amblyopia
BS Goel, R Maheshwari, S Jalal Uddin
Institute of Ophthalmology, A.M.U.Aligarh, India
B S Goel
Institute of ophthalmology, A.M.U. Aligarh. (U.P.)
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Goel B S, Maheshwari R, Jalal Uddin S. Retinal sensitivity in amblyopia. Indian J Ophthalmol 1983;31:49-53
Adelstein and scully suggested a general depression in function of the retina over the whole field in amblyopia. A decreased sensitivity of the foveal cones in amblyopia was observed by Zanen and Szucs. oppel and kranke and Lavergene. This suggests that there is a relationship of retinal sensitivity to amblyopia. With this background in mind the present work has been undertaken to elucidate the effect of amblyopia on retinal sensitivity.
| Material and method|| |
A total of 418 eyes were studied which were grouped (i) Amblyopic group-I86 eyes. (ii) Non-amblyopic group--176 eyes and, (iii) Control group-56 eyes.
The investigations in each case were carried out with special reference to the following
(i) Visual Acuity and refraction
(ii) Full orthoptic investigations
(iii) Quantitative analysis of the Central Field of vision by Friedmann's visual field analyser to determine the retinal sensitivity.
Retinal sensitivity with the help of visual field analyser [Figure - 1] was determined in log units, for all the 46 points individually, for both the eyes separately as per manufacturers (Clement Clarke Ltd, London.) instructions. The results were compared for the values obtained in an amblyopic. nonamblyopie and control groups. The overall results thus obtained were analysed with regards to various parameters and the irinter relationship.
The amblyopic patients were subjected for treatment (occlusion) and at the end of the treatment when a maximum improvement was attained the above investigations were repeated to find out the change in retinal sensitivity and other values in relation to visual improvement.
| Observations|| |
1. Retinal Sensitivity
(a) Average Sensitivity
In amblyopic group the retinal sensitivity of 15 positions from 'P' to 'A' ranged from 0.62 to 1.99 log units with an average of 1.60 ±0.29 log units (mean ± S.D). In non-amblyopic group the Corresponding values ranged from 1.93 to 2.16 log units with an average of 1.83 ± 0.17 log units. While in control group these values ranged from 1.79 to 2.01 log units with an average of 1.93 ! 0.07 log units. Further statistical analysis on comparing the data for various groups showed that the retinal sensitivity in amblyopic eyes was significantly less than in non-amblyopic eyes (P<0.001) and control group (p<0.001) [Table - 1].
(b) individual retinal point sensitivity:
1 n some of the cases from all the three groups the retinal sensitivity on individual points was taken. The findings are shown in [Table - 2]. In Amblyopic group the values were practically sane on all the points, except that the values were least (1.48 +0.42) at point `A' which is the most peripheral point. The highest retinal sensitivity was at point 'E' (1.700.28). Whereas the least values in non-amblyopic group were 1.71 ±0.23 at point 'A' and highest 1.90±0.20 at point 'N'. Similarly in control group the lowest retinal sensitivity recorded was 1.82 - 0.06 at point 'K' and highest was 1.98 ± 0.07 at 'P' and 'E' points.
In amblyopic group, an average retinal sensitivity of 1.79±0.1 1 log units was observed in the age group of 6 to 10 years. This age group showed the maximum retinal sensitivity. while it decreased gradually from this age group onwards. A small decrease in the values of the retinal sensitivity was observed in nonamblyopic group also. In control group the average retinal sensitivity was 1.95.-0.6 log units and 1.89 ± 0.11 log units in the age groups of I I to 40 years respectively.
The average retinal sensitivity in strabismic amblyopes was 1.57 ± 0.28 log units, in anisometropic ambloypes was 1.62 ± 0.33 log units in ametropic amblyopes it was 1.68 x_0.19 logunits while in amblyopes due to combined aetiology the value of average retinal sensitivity was 1.38±0.36 logunits [Table - 3]. It shows that the decrease in retinal sensitivity is maximum in amblyopes of combined aetiology followed by strabismic group, anisometropic group and ametropic group i.e. in ametropic amblyopes the sensitivity was maximum.
11. Relation of visual acuity to Retinal sensitivity : -
In cases who had vision less than 6/60 the average retinal sensitivity was 1.31 ± 0.33 log units, in cases of 6/60 vision it was 1.44± 0.31 log units, of 6/36 vision the sensitivity was 1.56±0.21 log units, of 6/24 vision the average sensitivity was 1.69±0.15 log units of 6/18 vision the average sensitivity was 1.70±0.30 log units and in cases having vision of 6/12 the sensitivity wss 1.80±0.16 logunits. Thus it was observed that better the visual acuity greater was the average retinal sensitivity. [Table - 4].
111. Effect of treatment on retinal sensitivity :
In cases who showed the improvement in visual acuity by at at least one line of Snellen's chart by occlusion treatment it was observed that the average pre and post treatment retinal sensitivity was 1.74±0.22 and 1,87±0.09 logunits respectively. This change was statistically highly significant (P<0.001). While in cases where visual acuity remained unchanged did not show any improvement in retinal sensitivity after the treatment.
| Discussion|| |
The observations thus made suggest that there is a statistically significant fall in the total 15 points average retinal sensitivity in the amblyopic eyes as compared to the nonamblyopic (0.23 log units) and control eyes (0.33 log units). This difference suggests some depression in function of the retina of the amblyopic eyes in toto. Adelstein and scullys also suggested a general depression in retinal functions of the amblyopic eyes over the whole field thus supporting this observation.
As it is seen that the retinal sensitivity is low in amblyopia. a correlation has been made between this depression and reduction in the visual acuity. It has been seen that there is a relationship between the retinal sensitivity and the visual acuity meaning thereby that greater the fall in the visual acuity, more is the depression in retinal sensitivity. When individual points of the analyser are concerned it is seen that the retinal sensitivity gradually decreases from the centre (P) towards the periphery (A) with slight individual variations. This shows that there is a greater depression of the retina in the centre than in the periphery in amblyopia.
The retinal sensitivity in general decreases with increasing age in non-amblyopic and normal eyes. However it has been seen that this difference is accentuated in amblyopic group. The older the age greater is the depression in retinal sensitivity. This indirectly may have been due to the greater duration of amblyopia. This also supports the view that depression in the retinal sensitivity is an important feature of amblyopia. When retinal sensitivity was analysed in relation to aetiology it was seen that the cases of combined aetiology had maximum depression followed by strabismus, anisometropia and ametropia alone. We have also observed similar depression of retinal sensitivity in astigmatism and meridional amblyopia more so in the axis corresponding to greater ametropia (Goel et ale).
The effect of occlusion treatment on retinal sensitivity has also been discussed, and it has been observed that the total average 15 point retinal sensitivity improved in cases who showed improvement in visual acuity by treatment. and this improvement in retinal sensitivity was statistically highly significant. Since a decreased retinal sensitivity has been observed in amblyopes in general, an improvement suggests that there is a reversible change.
The following conclusion are made :
1. The average retinal sensitivity is significantly low in amblyopic group as compared to non-amblyopic and control group. This gradually decreases from the centre (Point P) towards the periphery (Point `A') suggesting a greater depression of the retina in the centre than in the periphery. Not only this but retinal sensitivity also decreases with increasing age in non-amblyopic and control group but more so in amblyopic group.
2. The retinal sensitivity is nearly in direct relationship to visual acuity, meaning thereby that lesser is the visual acuity greater is the depression in retinal sensitivity.
3. The cases of combined aetiology show maximum depression of retinal sensitivity followed by strabismic, anisometropic and ametropic cases.
4. With occlusion treatment when vision improves the retinal sensitivity also improves suggesting a reversible change.
| Summary|| |
A total of 418 eyes studied with special reference to the measurement of retinal sensitivity on Friedmann Visual Field analyser in log units. The average 15 point retinal sensitivity and individual point retinal sensitivity have been studied against several, variables viz. age of the patient, aetiology of the amblyopia, visual status of the patient and effect of occlusion treatment. The probable role of retinal sensitivity in improving the vision has also been highlighted.
| References|| |
Adelstein, A. M. and Scully, J., 1967 Brit. Med., J., 3:334.
Zanen, J. and Szucs. S. 1956 Amer. J. Ophthalmol. 43:322.
Oppel, O. and Kranke, D., 1958, Arch Ophthalmol. 159 : 1121.
Lavergene, G., 1961, Bull. Soc. Beige. Ophthalmol.
Goel, B.S. and Moiz, A., 1981, Retinal sensitivity in meridional amblyopia, under publication ophthalmic research.
[Figure - 1]
[Table - 1], [Table - 2], [Table - 3], [Table - 4]