|Year : 1956 | Volume
| Issue : 4 | Page : 88-91
Progress of electroretinography in India
Dept. of Ophthalmology, Mahatma Gandhi Memorial Hospital, Indore M.P, India
|Date of Web Publication||10-May-2008|
R P Dhanda
Dept. of Ophthalmology, Mahatma Gandhi Memorial Hospital, Indore M.P
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dhanda R P. Progress of electroretinography in India. Indian J Ophthalmol 1956;4:88-91
In a previous paper read at the last annual conference of the society I had dealt with the introductory part on normal electro-retinography, and electro-reretinography in siderosis with and without night-blindness.
This paper concerns itself however only to the second stage of work of the electro-retinographic unit at the Mahatma Gandhi Medical College, Indore with a grant of the Indian Council of Medical Research, where studies on cases of cataract and glaucoma were started in April, 1955.
On the basis of discussions regarding dynamics of intra-capsular cataract extractions by Goldsmith (1943) Kirby (1949) and Harrington (1951), stimulus to further application of electro-retinography to clinical ophthalmic conditions like cataract has been provided by Derrick Vail (1952) by his discussion on the zonule membrane vs. cataract extraction, Karpe and Vanio-Mattilla (1951) having already done some work on ERG. in Cataract.
Increased frequency of detachment of retina after intracapsular extractions has been indicated in the statistics of experienced eye Surgeons in all countries during the last 25 years. Various explanations have been forwarded to explain this. Derrick Vail has indicated that the pull on the retina through the suspensory ligament during intracapsular extraction is responsible for the detachment of retina. It was therefore proposed to extend elecro-retinography to cataract cases in the hope that it may be possible to establish the cause of detachment of retina in cases where cataract extraction has been clone. It may also be possible to tell in advance whether a particular eye after operation has the potential danger of a future detachment.
Similarly glaucoma is a condition where pathological changes in the retina and optic nerve may alter the electro-retinogram. Much work has not been done on this aspect but electro-retinogram being directly dependent on the functioning capacity of the retina, it may be that electro-retinograph may help in the prognostic aspect of the disease.
| Electroretinography in Cataract|| |
In all 56 eyes with different grades of lens opacity were investigated by electroretinography. In all these cases standards already adopted were continued, i.e. 5 minutes dark adaptation before recording an ERG. Sec, stimulus repeated every 15 seconds and an illumination of So Lux.
The following table gives the results of the investigations in comparison with the findings in normal Indians of similar age group :
This suggests that b-potential may be reduced by the formation of cataract but more important to note is that a good amount of electric potential can be recorded in cases of mature cataract where the vision is reduced to hand movements. This implies that even a very small amount of light passing through a nearly opaque lens and the spongy iris is enough to bring the retina to appreciable activity. One could conclude from this that retina behaves more or less on the lines of "all or none phenomenon".
That electro-retinograhhy is the most precise means of determining the prognosis of particular case is proved by the following interesting observations:-
An extinguished electro-retinogram in an eye with mature cataract was noted. the cataract was removed and a detachment of retina was discovered, which explained the loss of electrical response (the other eye was normal with b-pot. of 3o mV. Another case with mature cataract where light-perception was present but light projection was doubtful had extinguished electro-retinogram. Secondary retinitis pigmentosa was discovered after cataract extraction, and this explained the prognostic utility of electroretinography. (An extinguished ERG. in retinitis pigmentosa and total detachment of retina are by now established facts,) (Karpe, 1945). In either case an extinguished ERG was the only preoperative guide to the poor prognosis.
| Explanation|| |
In post operative changes in electro-retinogram we have some interesting observations. Electro-retinograms have been repeated 15 days after the operation in 18 cases. Of these 10 after intracapsular operation, 7 after extracapsular operation and 1 after currette evactuation.
In all the 10 intracapsular cases the average b-potential after operation increased in every case. In 7 extracapsular cases the b-potential after operation decreased in 5 and was unchanged in 2 as in the following table.
This observation possibly leads one to suggest that the retinal l activity is disturbed more in cases of extra capsular operation than in intra capsular. This incidentally explains that the breaking of suspensory ligament intracapsular method does not affect the function of retina. It may be hypothetised that the so called increased frequency of detachment of retina after intra capsular surgery may be incidental rather than factual. It may be stated that the author having practised intra-capsular surgery rather faithfully and without regret for the last 13 years has yet to come across a case of post operative detachment of retina in his cases.
| Electro-Retinography in Glaucoma|| |
16 eyes with chronic glaucoma and average introcular tension of 58 mm. Hg, b-pot. was .202 mV. (the highest being .275 and lowest being .05)
6 eyes of secondary glaucoma with an average tension of 9o mm. Hg. had an average b-pot. of 190 mV. (the highest being .275 mV. and lowest being . 10 mV.)
3 blind eyes with absolute glaucoma and 75 mm. Hg. tension had an average b-pot. of .120 mV.
These findings also throw interesting light on the pathology of glaucoma. The presence of fair amount of b-potential even in a case of glaucoma with no perception of light is strongly suggestive that a loss of vision in cases of glaucoma may be mainly due to its effect on the optic nerve. This also incidentally and possibly supports the hypothesis put forward by Dr. Mathur of Agra (1955) about the possible existance of a space called fourth chamber in front of optic disc. If that be presumed true it could be explained that the effect of raised intra ocular tension is transmitted to the optic disc through this space. Presence of this electrical response proves that the retinal function continues to remain good even though it is exposed to a very high degree of intra-ocular tension.
The higher b-potential in cases of secondary glaucoma during the intumescence stage of cataract is explained by the short duration of pathology and also explains that the retinal activity being good, the return of vision after relief of tension in these secondary cases is expected to be good indicating good visual prognosis.
Electro-retinographic studies in India during the last four years have thus established that elect ro-retinography is one of the precise means of determining the functional capacity of the retina even when ophthalmoscopic changes are either absent as in the cases of Vitamin A deficiency or cannot be detected as in the cases of cataract.
| Summary|| |
An electro-retinography study in cases of cataract and glaucoma is presented. In cataract, the b-potential remains better after intra-capsular than after extra capsular surgery.
In glaucoma a fair amount of b-potential is maintained.
| References|| |
Derrick Vail. 1952.-Arch. Ophth., 48.
Dhanda, R. P. 1955.-Arch. Ophth., 54.
Dhanda, R. P. 1955- J. Ind. Med. Assoc., 25.
Dhanda, R. P. 1956-Ind. J. Med. Res. 44.
Dhanda, R. P. 1956-Ind. J. Ped., 23
Goldsmith, J. 1943-Arch. Ophth., 29.
Harrington, D. O. 1951-Am. J. Ophth., 34
Henkes, H. E. 1951-Ophthalmologica, 12.
Holmgren, F. 1865-Upsala Lak Foren Forh, 1.
Karpe, G. 1945-Acta Ophth. Suppl., 24.
Karpe, G. etc. 1950--Acta Ophth.. 28.
Karpe, G. and Vanio Mattila, 1951-Acta Ophth., 29.
Kirby, D. B. 1949--Am. J. Ophth., 31
Linsley, D. B. and Hunter, W. S. 1939 Trans. Amer. Ophth. Soc., 29.
[Table - 1], [Table - 2]