[Evaluation of macular functional capacity by helium-neon laser interferometry]

We describe the principles of the measure of visual acuity by using the laser interference retinometer. Interference fringes are projected on the retina, with variation of direction and thickness varied, to study the functional capacity of the macula. This method is particularly useful in patients with cataracts, because it is much less influenced by the clarity of the media than Snellen chart listing. We give the results of a series of 122 eyes with cataract, comparing pre-operative laser acuity and post-operative Snellen visual acuity. The pre-operative interfermometric measure is possible in 77% of the cases, but in most cases of mature cataract or dense posterior subcapsular opacities, the patients do not discern any interference fringes. In immature cataracts according to other results of the literature, post-operative Snellen visual acuity reaches preoperative laser acuity in 60% of the cases, and is better in 29% of the cases. Clinical conditions such as macular degeneration, cystoid macular oedema, amblyopia, visual field cuts through fixation or myopic choroïdopathy, may make the interferometer test unreliable.