Visual acuity development of children with infantile nystagmus syndrome

Abstract

Purpose: Infantile nystagmus syndrome (INS) can be idiopathic or associated with ocular or systemic disease. The ocular oscillation of INS directly contributes to loss of visual acuity. In this study, visual acuity development in patients with INS was examined.

Methods: Children with INS were classified as having idiopathic INS (n = 84) or INS with an associated sensory deficit: INS and albinism (n = 71), bilateral optic nerve hypoplasia (ONH; n = 23), or congenital retinal disorder (n = 36). Visual acuity was assessed with Teller cards and/or optotypes, and the data were analyzed for three age groups (<24 months, 24-48 months, and >48 months).

Results: Patients with idiopathic INS showed mildly reduced visual acuity early in life and gradual maturation with age that paralleled a normative curve. Patients with albinism also showed a mild visual deficit early in life but failed to keep pace with the normative curve, showing a gradual increase in visual acuity deficit. Patients with ONH and congenital retinal disorders exhibited more severe visual acuity deficits during infancy. The ONH group displayed slow improvement of visual acuity with a plateau at 24 months through >48 months, with a small increase in visual acuity deficit. The congenital retinal disorder group had no significant change in visual acuity across age and had a rapid increase in visual acuity deficit.

Conclusions: The pattern of visual acuity development differs among children with INS, depending on the presence or absence of associated sensory system deficits. Careful characterization of visual system differences in patients with INS is important if visual acuity is an outcome in clinical trials.

Figure 1.

Number of tests across ages of the subjects at their first visits in four patient groups: idiopathic INS (n = 84), INS associated with albinism (n = 71), INS associated with ONH (n = 23), and INS associated with congenital retinal disorders (n = 36).

Figure 2.

Visual acuity scores for individual visits in children with (A) idiopathic INS, (B) INS associated with albinism, (C) INS associated with bilateral ONH, and (D) INS associated with congenital retinal disorders. Shaded area: tolerance limits of norms of visual acuities measured by TACs (●) (Salomao SR, et al. IOVS 1996;37:ARVO Abstract 4902).^,,, Dashed line: mean monocular acuity measured by crowded HOTV optotypes (▾). Solid line: mean monocular acuity measured by ETDRS chart (). Dotted line: mean acuity measured by Lea symbol (○), linear Allen (▵) symbols, and isolated symbol (□) acuity tests.

Figure 3.

The courses of the patients who had three consecutive visits. (A) Idiopathic INS (n = 7), (B) INS associated with albinism (n = 13), (C) INS associated with bilateral ONH (n = 3), and (D) INS associated with congenital retinal disorders (n = 8). Shaded area: tolerance limits of norms of visual acuities measured by TACs (●) (Salomao SR, et al. IOVS 1996;37:ARVO Abstract 4902).^,,, Dashed line: mean monocular acuity measured by crowded HOTV optotypes (▾). Solid line: mean monocular acuity measured by ETDRS chart (). Dotted line: mean acuity measured by Lea symbol (○), linear Allen (▵) symbols, and isolated symbol (□) acuity tests.

Figure 4.

Visual acuity (logMAR) plotted as a function of age in months (on a logarithmic scale) for each subtype (idiopathic INS, INS associated with albinism, INS associated with bilateral ONH, achromatopsia, LCA, retinal degeneration, foveal hypoplasia) to illustrate the approximate linear trends. Solid black lines: longitudinal linear mixed-effect model fixed-effects predictions. Solid gray line: linear regression prediction based on the normative data. Dashed gray lines: denote the 95% prediction interval for patients in the normative group. Open colored circles: crossed-sectional data from individual subject. Circles connected by colored lines: longitudinal data from individual subjects.