Contrast sensitivity in amblyopia: the fellow eye of untreated and successfully treated amblyopes.

Purpose: We sought to investigate contrast sensitivity on the fellow eyes of amblyopic and successfully treated amblyopic subjects.

Methods: Contrast sensitivity was tested monocularly on both eyes of 48 amblyopic patients (mean age, 11.51 years) and of 22 successfully treated amblyopic subjects (visual acuity 20/20 in each eye; mean age, 11.22 years). Inclusion criteria were visual acuity in the amblyopic eye 20/40 or better (mild amblyopia) and 20/20 or better in the fellow eye, steady fixation, no signs of congenital, latent or manifest/latent nystagmus on clinical examination. Twenty normal subjects (20 eyes) were used as age-matched controls.

Results: Contrast sensitivity functions from the fellow eye of the 48 amblyopic patients, even those who had never been treated with occlusion therapy before, were significantly decreased (P < 0.001) compared with control subjects. Both the previously amblyopic and the fellow eye of the 22 "cured" amblyopic subjects demonstrated significantly lower values (P < 0.001) compared with control patients.

Conclusions: We suggest that the nonamblyopic, "normal" eye of amblyopic patients behaves abnormally when evaluated for contrast sensitivity functions. Neither the previously amblyopic nor the fellow eyes of successfully treated subjects were comparable with controls. Occlusion therapy may not be implicated for depressed contrast sensitivity of the fellow eye in amblyopia. The assessment of contrast sensitivity can provide important information on the visual function and the influence of occlusion therapy in amblyopia.