Year : 1990 | Volume
: 38 | Issue : 1 | Page : 14--16
Macular dazzling test in central serous retinopathy using electronic flash
Suresh Kumar Verma, Akhoury S.B Sahai
Nalanda Medical College and Hospital, Patna-7, India
Suresh Kumar Verma
Recovery time after dazzling the macula by conventional electronic flash used by the photographer instead of the light of an ophthalmoscope was recorded in 100 normal subjects and 50 cases of active central serous retinopathy. In normal subjects the recovery time after macular dazzling test was 10 to 54 seconds. There was no difference in value between the two sexes. The recovery value increases with the advancement of age. The recovery time was 10 to 15 minutes in cases of active central serous retinopathy and there was no delay in recovery time in healed central serous retinopathy. The values elicited by electronic flash were repeatable in comparison to the technique of dazzling the macula by light of an ophthalmoscope.
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Verma SK, Sahai AS. Macular dazzling test in central serous retinopathy using electronic flash.Indian J Ophthalmol 1990;38:14-16
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Verma SK, Sahai AS. Macular dazzling test in central serous retinopathy using electronic flash. Indian J Ophthalmol [serial online] 1990 [cited 2022 Jan 27 ];38:14-16
Available from: https://www.ijo.in/text.asp?1990/38/1/14/24555
Macular dazzling test is one of the methods of subjective exploration of the macula by dazzling the macula and then measuring the length of time which the subject takes to regain the previous level of visual acuity. This is also known as the photostress test; done previously by a light source of an ophthalmoscope or a pen torch. Dazzling the macula by a simple electronic flash used by the photographers is an easily performable manoeuvre requires less co-operation of the subjects and the results are repeatable in comparison to the dazzling of the macula by the light of an ophthalmoscope or a pen torch. The purpose of the work is to analyse the result on healthy subjects and cases of active and healed CSR by dazzling the macula by conventional electronic flash and to compare it with the results of other authors.
MATERIAL AND METHODS
The cases were divided into two groups, Group I consisted of 100 normal subjects and group II of 50 cases of active CSR. The patients of Group I came into out patient department with mild red eyes or presbyopic strain. The patients of Group ll came with diminished vision. The acuity of vision of both groups were ascertained. Detailed fundus examination and retinoscopy under full mydriasis was done.
MDT was performed by an Olympus electronic flash Guide No.20 in meters with 100 ASA with 1/2000 secbnds.
An electronic stop watch was used to record the time interval. The electronic flash was kept at a distance of 3 to 5 cms from one eye, the other eye being covered with an eye pad. The patient was directed to look directly into the tube of the flash. Then dazzle was produced by pushing the test knob of the flash. At the instance at which the dazzle was produced the stop watch was started. The subject was asked to read. The stopwatch was started the movement the dazzle was produced. The moment at which he reads the same line of the Snellen's chart as before dazzling, the stop watch was stopped. The time interval was considered the MDT recovery time. The other eye was tested in the same manner. In healthy subjects the test was done both for distant vision and near vision. The test was carried out in patients with CSR in the same way for distant vision; but test for near vision was not done. The patients of CSR were followed for six months and MDT was done at fortnightly intervals.
1. In normal eyes the MDT recovery time was longer for distant vision (mean 28 seconds) than near vision (mean 23 seconds).The range of variation for distance was 10 to 54 seconds and for near 8 to 50 seconds [Table 1] 2.The MDT recovery time was similar in the right and left eyes in normal subjects, longer for distance and shorter for near vision [Table 2]
3.There was no marked difference in the MDT recovery time between male and female subjects. [Table 2]
4.The recovery time for MDT showed an increasing tendency with the advancement of age, more marked in the subjects over forty years of age.[Table 3]
5.In the eyes with active CSR the recovery time after MDT was 10 to 15 minutes on an average.
6.As active CSR progressed to the healing stage and vision improved the recovery time also gradually improved.
7.As the lesion healed completely the recovery time also came back to normal.
There are various methods of examination of the functional ability of the macula. They are usually divided into objective and subjective methods. The main objective method is retinography which can give useful information. The subjective methods are numerous and some of these have been used since early in the history of ophthalmology. Some of the tests are:1.Measurement of visual acuity.
2.Measurement of central field of vision
3.The tests for metamophopsia(Amsler's chart)
A convenient and useful subjective method- is the one which was proposed by J.Bailiart and which consisits of dazzling the macula by exposure to the light of an ophthalmoscope and then measuring the time of recovery of vision. The characteristic of this test is that it utilises an induced fatigue as utilised for the examination of the heart.
Most authors ,,, have used the light of their ophthalmoscope to produce dazzling, varying the light exposure from 15 seconds to 1 minute. Lavingia  exposed the macula for 30 seconds to the light of the ophthalmoscope. Glaser et al used a light source consisting of an electric bulb which produced 2340 lux instead of an ophthalmoscope. F.Gomez Ulla et al  used a conventional electronic flash of low guide No. similar to Lemirini and Carrerarase. In this paper the electronic flash has been used because this technique is faster and in addition there is no need for exceptional co-operation from the subject being examined. In contrast both the light bulb used by Glaser and ophthalmoscope light requires a greater amount of patient co-operation because he must concentrate his attention on the light source constantly for a period which varies from 15 seconds to 1 minute. On the other hand the use of the conventional electronic flash proposed by Lemirini and Carrearssrequires virtually no co-operation from the patient because he has to concentrate on the light source for 2 to 4 seconds only.
The average value of MDT recovery time for distant vision (10 - 54 seconds) falls approximately close to the figure considered normal in other published papers i.e. Lavingia (15 to 52 seconds); F.Gomez Ulla et al(7 to 55 seconds) and George A Chilaris (10 to 50 seconds). The average value of MDT recovery time for near vision is also approximately closer to the normal value in the experiment of F.Gomez Ulla et al (5 to 50 seconds). There was virtually no difference in MDT values for the right eye and the left eye and the two sexes. As reported in the paper of F.Gomez Ulla et al the MDT recovery time in his work increases with the advancement of age especially after the age of forty. This indicates the involutionary senile phenomenon in which the eye is also trapped.
Recovery from dazzling is presumed to be due to the rate of visual pigments bleaching and resynthesis and is dependent on the relation between the retinal pigment epithelium, Muller cells and photorecepters?. Illumination causes exhaustion of the macula (a kind of induced fatigue) and the longer the recovery time the greater is the exhaustion of the macula (more severe the alterations are). Generally it can be said that an important factor determining the time of recovery is the distance between the pigment and neuroepithelium. When oedema is interposed between these two layers, for example in CSR the recovery time is greater.
In CSR, Lavingia & recorded the recovery time after photostress test as more than 5 minutes and Joel S Glaser et al- recorded the recovery time beyond 8 minutes. In a case of CSR recorded by George A Chilaris it took about 20 minutes for full recovery .
In this paper it took about 10 minutes on an average for full recovery after MDT by an electronic flash. Lavingia B; Glaser J.S.et al and George A Chilaris noted no delay in the recovery time as in this paper, in cases of resolved CSR.
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