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Editor,—I have read with interest the paper by Foley-Nolan et al 1 on the use of atropine as an alternative to occlusion for treating amblyopia. Presumably all the patients entering their trial had strabismus, otherwise there would not have been suppression but some degree of normal binocularity. It should be pointed out that the daily instillation of atropine into the fixing eye, as advocated by Worth,2 may be of use only in those cases in whom the visual acuity of the squinting eye is ‘not much less than 6/36’; in fact, the mean visual acuity in 36 of their atropine treated group was 6/60. But if amblyopia ex anopsia is of such magnitude that central fixation is lost, in the most distressing cases cycloplegia of the fixing eye will prove useless, the patient will keep on using the fixing eye, treated with atropine or not. Only occlusion, permanent occlusion, 6 days a week, will do the trick. On the other hand, if there is no strabismus, but orthotropia, and some degree of normal binocularity, the results of any treatment, and the pertinent indications, would depend on the ultimate cause of the disturbance.
I felt that a chance to clarify the point was in order.
Editor,—In our published trial, the patients were assigned to two treatment groups, group A where they were treated with atropine penalisation, and group P where they were treated with occlusion on therapy. In both groups approximately 90% had strabismus. The mean visual acuities in groups A and P before treatment were 6/50 and 6/60 respectively.
Previous experimental work has shown that a reduction in spatial pattern stimuli alone and not light is all that is necessary to shift dominance to the non-dominant eye. Therefore, it is reasonable to expect that penalisation by degrading visual stimuli should be effective even if there was no strabismic deviation.
We agree that, previously, atropine penalisation treatment of amblyopia was considered to be useful only for lesser degrees of amblyopia. However, as can be seen from our results substantial improvements were achieved in group A, where the pretreatment mean visual acuity was 6/50.