Indian Journal of Ophthalmology

: 1984  |  Volume : 32  |  Issue : 5  |  Page : 435--436

Amblyopia-its treatment with CAM stimulator

JN Rohatgi, Bimal Chandra 
 Department of Ophthalmology, Patna Medical College and Hospital Patna, India

Correspondence Address:
J N Rohatgi
Department of Ophthalmology, Patna Medical College & Hospital, Patna

How to cite this article:
Rohatgi J N, Chandra B. Amblyopia-its treatment with CAM stimulator.Indian J Ophthalmol 1984;32:435-436

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Rohatgi J N, Chandra B. Amblyopia-its treatment with CAM stimulator. Indian J Ophthalmol [serial online] 1984 [cited 2022 Jul 4 ];32:435-436
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As early as 1743 Buffon[1] suggested and practised occlusion of the sound eye to improve vision in the amblyopic. This con­ventional occulusion has ever since remained as the sheet anchor for the treatment of amblyopia-strabismic, anisometropic or stimulas deprivation modified off and on by the use of pleoptics in patients with eccentric fixation. [1]

In children prolonged occlusion of the good eye is psychologically distressing; educationally disruptive, tedious and a great strain on the parents and hence, many a times given up halfway through. Still no short cut method could be available till 1978 when Banks, Campbell, Hess and watson published their series of treating amblyopia with the use of a new instrument known as CAM vision stimulator.[2],[3] The usefulness of this instrument was also discussed by Eggors (1979).[4]

With this instrument, the period of occlu­sion of the sound eye is cut down to only seven minutes a day (one session) while the, amblyopic eye is being exercised. The num­ber of session varies from ten to twenty at a stretch. This may have to be repeated at short intervals to sustain the improvement of visual acuity in the amblyopic eye.


Twenty cases of amblyopia (in one eye) of varying age group from 5 to 20 years have been treated by this method during the last one year. These included cases where after suc­cessful surgery to correct the deviation in the squinting eye, patients have not been able to carry out occlusion of the sound eye. This was causing a tendency for the deviation to relapse in a few cases because of poor visual acuity. Such cases did well with CAM vision stimulator.

The patient's normal eye is covered and he is shown the large square wave grating disc, which is placed on the central spindle of the apparatus and the perspex plate-cover placed over it. The patient is now seated in front of the apparatus and (he) is asked to draw or play games on the perspex plate with the clinician or another patient whilst the disc is rotated under the plate. The disc is rotated for one or two minutes and then the next finer grating is placed on the spindle and the game recom­mended. Treatment lasts for seven minutes and during this time all the finer gratings than the one the patient started with should be used.

After treatment is finished, the visual acuity for distance and/or near is assessed.


The age-group of the twenty cases treated with CAM stimulator during the last twelve months is as follows- [Table 1].

It would, thus appear that majority of the cases were in the age group above six years, when it is felt that with conventional occlu­sion there is not much chance of improving vision in the amblyopic eye.

Of these twenty cases, six were cases of anisometrdpic amblyopia and fourteen were cases of Omblyopia, associated with con­vergent squint in whom conventional occlu­sion had been tried before surgery but without much success so far vision improvement (in amblyopic squinting eye) was concerned. Some of these cases also had post-operative occlusion for varying periods. In these also the vision did not improve to more than 6/36­6/24. Two of the patients had eccentric fixa­tion - [Table 2].

Thus, so far vision improvement is con­cerned, it would be described as follows­-

(i) No improvement - 2 cases

(ii) Improvement upto 6/36 to 6/18 - 6 cases

(iii) Improvement upto 6/12 to 6/6 - 12 cases


It is now known that visual cortical cells respond best to gratings of certain size (spatial frequency), orientation and contrast Therefore, a stimulus which is designed to exercise fully the majority of the visual cells, should contain high contrast gratings at all orientations. With this idea in mind, this device was constructed on which sharp­edged, high contrast gratings are placed and rotated so as to occupy all orientational positions.


This method is thus simple, effective and the cost is low. Our results are only for twenty (20) cases. More and more amblyopic children are being given, this treatment and one would however, like to treat at least a hun­dred or more such cases before giving a final judgement regarding the efficacy of this treatment.


1Duke-Elder S. and Wybar KC., 1973. "System of Ophthalmology", 6, Kimpton, London.
2Bankes, Campbell, Hess and Watson 1978. Brit J. Ortho. 35: 1.
3Campbell F. W.,1979. Trans. Ophthalmol. Soc. U.K 99: 326.
4Eggers H.M., 1979. Trans. Ophthalmol. Soc. U.K 99: 457.