Binocular Visual Function in Patients With Boston Type I Keratoprostheses

Purpose: To report the postoperative binocular function of patients with Boston type I keratoprostheses implantation for unilateral visual impairment. Methods: Seventeen patients who underwent implantation of a Boston type I keratoprosthesis and had a best-corrected visual acuity better than 20/50 in the contralateral eye before surgery were evaluated. All subjects prospectively underwent sensory testing of binocular function including Bagolini lenses, Worth-4-dot test, stereoacuity at distance and near, and double Maddox rods. In addition, an assessment of ocular rotations and alignment was performed on each subject. Results: Twenty patients with best-corrected visual acuity better than 20/50 in the contralateral eye at the time of keratoprothesis surgery were identified. Seventeen of the 20 patients underwent binocular visual testing, with 16 of 17 (94%) demonstrating binocular function. Second-degree fusion at near was demonstrated via the Worth-4-dot test in 13 of 17 (76%) patients. Third-degree fusion at near was demonstrated in 7 of 17 (41%) patients. Patients with better postoperative sensory binocular function tended to be of younger age (P = 0.05) and have better postoperative visual acuity (P = 0.006). Five patients were found to have some degree of ocular misalignment. Overall, patients with strabismus had worse binocularity (P = 0.04). Conclusions: Implantation of the Boston type I keratoprosthesis in patients with good preoperative visual acuity in the fellow eye is associated with useful binocular function in greater than 90% of patients.