Visual Development of Children With Infantile Nystagmus Syndrome (INS)

Abstract

Purpose:: Infantile nystagmus syndrome (INS) can be idiopathic or associated with ocular or systemic disease, such as albinism, optic nerve hypoplasia (ONH) or retinal disease. INS causes a developmental loss of visual acuity as a direct result of the inability to maintain stable foveal vision. Current literature lacks information about the visual maturation in common forms of INS. This study examined visual acuity development in patients with INS.

Methods:: Children with INS were classified as idiopathic INS (N=79; age=27+20m) or as INS associated with albinism (N=68; age=29+21 m), bilateral ONH (N=22; age=31+23 m) or retinal disease (N=30; age=30+23 m). Visual acuity was assessed with Teller Cards for younger children and with optoypes for older children. Visual acuity data were expressed as absolute values and deviations from age-corrected norms, and were analyzed for 3 age groups (<24 m; 24-48 m; >48 m).

Results:: All patient groups showed subnormal visual acuity. Patients with idiopathic INS showed mildly reduced visual acuity early in life (mean±SE= 0.80±0.04 logMAR) and a gradual improvement with age (mean±SE= 0.32±0.04 logMAR at >48 m) that paralleled normative development curve. Patients with albinism showed a similar trend with a mild deficit in visual acuity early in life (mean±SE= 0.85±0.04 logMAR) and slow improvement in visual acuity but failed to keep pace with the normative curve, showing a gradual increase in acuity deficit. The groups with ONH (mean acuity=0.96±0.10) and retinal disease (mean acuity=1.03±0.04) exhibited more severe deficits in visual acuity early in life (<24 m). The retinal disease group had no significant change in visual acuity across age (1.03±004 at <24 m to 0.99±0.06 at >48 m) and, thus, had a rapid increase in acuity deficit compared with normative curve. The ONH group displayed slow improvement of visual acuity with a plateau at 24 m (0.54±0.07) through >48 m (0.48±0.07), with only a small increase in acuity deficit compared with the normative curve.

Conclusions:: The pattern of visual acuity development differs among sub-types of children with infantile nystagmus syndrome. Careful characterization of the visual acuity development in sub-types of INS are important for planning and analysis clinical trials to evaluate treatment success.

Keywords: nystagmus • visual development