Contrast Sensitivity in Microtropic and Anisometropic Eyes of Successfully Treated Amblyopes

To assess and compare contrast sensitivity function in the previously amblyopic and non-amblyopic "normal" eyes of patients with microtropia and anisometropia who achieved 20/20 visual acuity after occlusion therapy.

Contrast sensitivity was tested monocularly on both eyes of 34 successfully treated microtropic and 15 anisometropic subjects (visual acuity 20/20 in both eyes). Contrast sensitivity function was evaluated by CSV-1000E and age-matched nomograms were used (spatial frequencies of 3, 6, 12, and 18 cycles per degree [cpd]) for comparison.

The mean age of subjects was 11.2±1.3 years in the microtropic group, 9.8±1.7 years in the anisometropic group (7-12 years); the mean follow-up time was 16.4±3.2 months (12 to 92) in the microtropic group and 27.7±1.8 months (12-84) in the anisometropic group. Statistical comparison of the microtropic amblyopic eyes versus non-microtropic eyes showed significant differences at spatial frequencies of 3, 12 and 18 cpd (3 cpd, t=2.8, p=0.007; 6 cpd, t=1.1 p=0.261; 12 cpd, t=2.2, p=0.033; 18 cpd, t=2.2, p=0.030). When anisometropic eyes were compared with non-anisometropic eyes, there was a significant difference only at 12 cpd (t=2.1 p=0.049). The comparison of non-amblyopic eyes versus age-matched nomograms revealed no differences at any of the spatial frequencies (p>0.05 for all).

Contrast sensitivity was decreased in patients with amblyopia, especially in the microtropic group. The assessment of contrast sensitivity function may serve as a new parameter for termination of occlusion therapy.