Orthoptic Changes following Photorefractive Keratectomy

Abstract

Purpose: To report orthoptic changes after photorefractive keratectomy (PRK).

Methods: This interventional case series included 297 eyes of 150 patients scheduled for PRK. Complete ophthalmologic evaluations focusing on orthoptic examinations were performed before and 3 months after PRK.

Results: Before PRK, 2 (1.3%) patients had esotropia which remained unchanged; 3 (2%) patients had far exotropia which improved after the procedure. Of 12 cases (8%) with initial exotropia at near, 3 (2%) cases became orthophoric, however 6 patients (4%) developed new near exotropia. A significant reduction in convergence and divergence amplitudes (P < 0.001) and a significant increase in near point of convergence (NPC) (P < 0.006) were noticed after PRK. A reduction ≥ 10 PD in convergence amplitude and ≥ 5 PD in divergence amplitude occurred in 10 and 5 patients, respectively. Four patients had initial NPC > 10 cm which remained unchanged after surgery. Out of 9 (6%) patients with baseline stereopsis > 60 seconds of arc, 2 (1.33%) showed an improvement in stereopsis following PRK. No patient developed diplopia postoperatively.

Conclusion: Preexisting strabismus may improve or remain unchanged after PRK, and new deviations can develop following the procedure. A decrease in fusional amplitudes, an increase in NPC, and an improvement in stereopsis may also occur after PRK. Preoperative evaluation of orthoptic status for detection of baseline abnormalities and identification of susceptible patients seem advisable.

Keywords: Orthoptic Changes; Photorefractive Keratectomy; Strabismus.