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 (138degrees, 0.59; P = 0.01) and children with esotropic amblyopia (120degrees, 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.