Positive angle kappa: a sign of albinism in patients with congenital nystagmus

Abstract

Purpose To determine whether the association of positive angle kappa and congenital nystagmus is a distinguishing feature of albinism. Design Observational case series. Methods Prospective examination of the location of the corneal light reflex in patients with albinism and idiopathic congenital nystagmus. Results A positive angle kappa in at least one eye was noted in 20/21 (95%) patients with albinism versus 4/12 (33%) patients with congenital nystagmus ( P = .0003, Fisher exact test). A positive angle kappa in both eyes was noted in 15/21 (71.4%) patients with albinism versus 2/12 (16.6%) patients with idiopathic congenital nystagmus ( P = .0039, Fisher exact test). Conclusion A positive angle kappa in patients with congenital nystagmus is associated with albinism. The pathophysiology of the positive angle kappa may relate to the anomalous decussation of optic axons that characterizes the albinotic visual system.