Look and Stare Optokinetic Nystagmus in Healthy Subjects and in Patients with No Measurable Binocularity. A Prospective Study

Abstract

The aim of our study was to assess the difference between look and stare optokinetic nystagmus (OKN) in healthy subjects and in patients with early onset strabismus and no measurable binocularity. OKN was elicited monocularly with black and white stripes moving horizontally or vertically at 15, 30, 45 and 60 degrees /s. Subjects were instructed either to follow individual stripes across the screen (look OKN) or to fixate stripes in the centre of the screen (stare OKN). We examined 20 healthy subjects (mean age 29 years; range 21 - 39), and 10 patients with no measurable binocularity (mean age 12.7 years; range 5 - 37). OKN gain was measured with photo-oculography. In both groups and at stimulation with the higher velocities gains for look OKN were significantly better than for stare OKN, and gains with horizontal stimuli were significantly better than with vertical stimuli (p < 0.05). In the group with no measurable binocularity horizontal look and stare OKN answers were significantly better for temporal-to-nasal stimulation than for nasal-to-temporal stimulation (p < 0.05). The performance of look or stare OKN influences the gain in healthy subjects and in patients with no measurable binocularity. Data about both modes of OKN stimulation are helpful to better interpret OKN responses especially in subjects with poor cooperation.