|Year : 1979 | Volume
| Issue : 4 | Page : 174-177
Value of electro-physiological investigations in retinal detachment
DK Gahlot, PK Khosla, HK Tewari
R.P. Centre for Ophthalmic Sciences, New Delhi, India
D K Gahlot
Asst. Prof. of Ophth. R. P. Centre for Ophthalmic Sciences, Ansari Nagar, New Delhi-16
|How to cite this article:|
Gahlot D K, Khosla P K, Tewari H K. Value of electro-physiological investigations in retinal detachment. Indian J Ophthalmol 1979;27:174-7
|How to cite this URL:|
Gahlot D K, Khosla P K, Tewari H K. Value of electro-physiological investigations in retinal detachment. Indian J Ophthalmol [serial online] 1979 [cited 2013 May 24];27:174-7. Available from: http://www.ijo.in/text.asp?1979/27/4/174/32618
Electrophysiology as applied to eye has contributed so much towards the understanding of complex electrical changes in the retina and has shown its potential value in assessing retinal function. However the value of electrodiagnostic tests in the study of retinal detachments as observed in the literature (Jacobson et al, 1958; Rendahl, 1961; Black et al, 1967 and others) is rather controversial. The present paper deals with the analysis of investigations in our cases of retinal detachment before and after surgery.
| Material and Methods|| |
(44) cases of retinal detachment were selected where both pre-and post-operative data of electrophysiological investigations was recorded. These investigations it eluded electro retinography and electro oculography.
Electro retinography (ERG) was recorded in both eyes simultaneously with dilated pupils using a bipolar corneal contact lens electrode with a 40 diopter lens as modified by Papst. The recording parameters were: sensitivity, 1000 u volts per cm. time constant, 1.2 seconds and filter, 70 Hz. The stimulation was provided by grass photo stimulator PS2 each flash coming after every 10 seconds and the b-wave amplitude was taken into account and compared without normal value (0.2 my 20.10 mv).
Electro oculography (EOG) was recorded from both eyes separately according to the methode of Gahlot and Hansan ;1974) and the ratio was calculated on the basis of light peak/dark through X100. Any value above 185 was considered normal. The recording parameters were: senstivity 1000 u volts per centimeters, time constant 2.5 seconds and filter 70 Hz. To maintain constancy or records identical parameters were utilised each time using mingograph 800 (Elema schonander). The pre and post operative data was then correlated with the extent of detachment and the surgical results.
Out of the 44 cases 12 had total detachment i.e. involving all 4 quadrants (Group I), 11 had sub-total detachment i.e. 3 quadrants (Group 1I), 15 half detach. ment i.e. 2 quadrants (Group TIE) and 6 segmental detachment i.e. only 1 quadrant (Group IV).
[Table - 1] shows the pre-operative data of 44 patients. Out of 12 patients having total retinal detachment all had flat ERG; 11 with sub-total detachment, 9 had flat (Extinguished) and 2 sub-normal ERG (less than 0.1 mv); 15 with half detachment 12 had flat, 2 sub-normal and one normal ERG and in 6 with segmental detachment 4 had flat, and 2 sub-normal ERG. Thus out of 44 patients 37 had flat, 6 sub-normal and only 1 normal ERG response.
Regarding FOG out of 44, 22 had flat and 22 subnormal ratio. In the group of total detachment (12) S had flat (ratio 100) and 4 sub-normal (ratio less than 185) in sub-total group (11) 5 had flat and 6 sub-normal, in half group (15) 6 had flat and 9 sub-normal and in segmental group (6) 3 had flat and 3 sub-normal EOG ratio. None of these groups - was found to have a normal ratio of 185 or above.
To evaluate the post-operative data the patients were regrouped on the basis of their preoperative ERG and EGG response and the extent of detachment. It was noticed [Table - 2] that in group I of 37 showing a flat ERG response 33 remained same after operation while 4 improved. In group 11 of 6 showing sub-normal response 3 remained same while 3 deteriorated and in group III with normal ERG response there was only one case who also deteriorated.
Each group was further divided into r sub-groups with varying degree of detachment. The details of which are given in [Table - 2]. It is found that out of total 44, 36 patients remained same, 4 deteriorated while the other 4 improved.
As regards EOG out of 4I cases, 31 remained same, 7 deteriorated and 6 improved. In group I with flat FOG response, 17 remained same and 5 improved. In group II w th sub-normal response, 22 cases, 14 did not show any change, 7 deteriorated and I improved. - In group III with normal response there was no case.
[Table - 3] shows the details of the changes in the ERG & EOG response of the fellow eye after successful detachment surgery. In group-I of 5 cases with flat ERG response and 3 cases with flat FOG response all remained same, none improved. In group-II with subnormal ERG (2), one improved and one remained same, while in 14 FOG subnormal response, 12 remained same and 2 improved. In group-11I of normal ERG response (37), 36 did not change and one deteriorated. Among cases with normal EOG response (26), 21 remained same and 5 deteriorated. The findings in the detached or fellow eye with regard to improvement or deterioration in ERG or EOG response could not be correlated with the success or failure of surgery or post operative visual improvement.
| Discussion|| |
The value of electrodiagnostic tests is greater in those cases where due to opacities in the media ophthalmoscopic examination is either difficult or not possible. The results of our series also confirm that both ERG and EOG are proportional to the extent of detachment and that out of the two, ERG is affected earlier and more than EOG. There appears to be a general agreement on this point. However, the role of these tests in pre- or post operative assessment is controvertial.
In our series, we find that the improvement or deterioration in ERG and EOG in immediate post-operative period is not always related to anatomical success or failure although often improvement is seen in fully settled cases.
The importance of examining the fellow eve in cases of retinal detachment seems to have been over emphasised. It is observed that in majority of cases the pre and post operative findings remain the same and in the rest the change is inconsistent. Thus, it is felt that ERG and EOG in the fellow eye does not provide the operative prognosis of the detached eye.
Thus on the basis of this study it may be concluded that (i) ERG and EOG is proportional to the extent of detachment. (ii) ERG and EOG response of the detached eye does not always reflect the operative results. (iii) ERG and EOG in the fellow eye also shows changes but do not indicate the operative prognosis on the detached eye. (iv) ERG and EOG improvement or deterioration in the detached as well as in the fellow eye does not depend upon the anatomical or visual results following surgery. (v) ERG is a better parameter than EOG in evaluation of these cases.
| Summary|| |
44 cases of retinal detachment have been investigated electrophysiologically (ERG and EOG) both pre and post operatively and correlation has been drawn with the extent of detachment. The results of the detached and the fellow eye indicate that ERG and EOG only have a diagnostic and no prognostic value.
| References|| |
|1.||Blach, R.K. & Debrman, J., 1967, T.O.S. U.K. 87,263. |
|2.||Jacobson, J.H., Basar, D., Carrol, J., Stephens, G. and Saphir, A., 1958, Arch. Ophthal., 59, 515. |
|3.||Rendahl, I., 1961, Acta. Ophthal., 64, 1-83. |
[Table - 1], [Table - 2], [Table - 3]