The refractive state of a mouse model of clinical disease associated with high myopia

Abstract

Abstract: : Purpose:To determine if the mouse eye develops refractive errors associated with specific mutations causing eye disease. The nob mouse shares the same mutation in the Nyx gene on the X chromosome that has been linked to the complete form of congenital stationary night blindness (CSNB). CSNB is associated with a high incidence of myopia (∼10 diopters (D)).Methods:Pigmented nob mice from an inbred colony originating in BALB/cByJ and crossed to C57BL/6J were used. The refractive errors of male nob mice (n = 11) and littermate controls (n = 5) were followed using an automated eccentric photorefractor between 4 and 54 weeks of age. Eyes were cyclopleged and pupil size measured by the photorefractor. Additional mice of both sexes were used to correlate refractive values with eye size using weight, frozen cross–sections, and magnified video images of whole eyes. Results:The refractive errors of pigmented nob mice were slightly more hyperopic than normal littermates at all ages (+9.70 ±1.22 vs +8.49 ±1.28D; p = n.s.). The pupil size became larger with age in both nobs and littermates (2.26 ±0.17 vs 2.09 ±0.24, p = n.s.). Eye weight and video morphometry resulted in the most accurate eye size measurements: eye weight, 20.36 ±2.60 and 20.82 ±2.46 mg; axial lengths: 3.54 ±0.17 and 3.56 ±0.19 mm for nob and littermate controls, respectively. In general, larger eyes were associated with less hyperopia. Conclusions: nob mice do not show the same high myopia relative to normals as seen in patients with CSNB. Based on schematic eye calculations, a 4 µm change in axial length may induce 1 D of refractive change¹. Thus, sensitive techniques to measures eye size are needed to confirm refractive measurements. Additional studies may determine if other murine strains develop refractive errors in association with specific mutations, as in the human population. ¹ Remtulla S, Hallett PE. Vision Res 1985;1:21–32.

Keywords: myopia • refractive error development • mutations