Binocular visual field changes after surgery in esotropic amblyopia.

Purpose: To determine binocular visual field (BVF) changes after strabismus surgery in children with large angle esotropia, and whether these changes can be predicted, using a prism to correct the preoperative angle of deviation.

Methods: Monocular visual field (MVF) and BVF were measured by Goldmann perimetry in healthy adults (n = 6) using a range of prisms. Visual fields were then measured in normal children (n = 19) and in children with large angle esotropic amblyopia (n = 28). The visual field was measured preoperatively with and without a prism equal to the angle of esotropia. A further evaluation was made at 2 and 18 months postoperatively.

Results: In healthy adults, prisms had no significant effect on the extent of MVF or BVF. There was no significant difference in the MVF in children with and without strabismus. There was a significant reduction in the BVF and in the ratio of the BVF to MVF between normal children (138 degrees, 0.59; P = 0.01) and children with esotropic amblyopia (120 degrees, 0.57; P = 0.02). Postoperatively, there was a significant improvement in the BVF (P = 0.02), which was maintained at 18 months. The increase in BVF was significantly greater than the variation in repeat fields (P = 0.04), with 8 of 13 children showing an increase in the BVF above the 95% CI of the repeatability measurements. There was a good linear correlation between the size of the preoperative BVF in the presence of a prism and the postoperative BVF (r = 0.90 P = 0.001).

Conclusions: Children with esotropic amblyopia demonstrate a significant reduction in their BVF. Prisms correcting the preoperative angle could be used to predict the potential increase in the BVF after surgery. Patients with a BVF/MVF approaching that found in normal children, however, may not show an improvement in the size of their BVF after surgery.