Cerulean cataract, first described by Vogt (1922), is an autosomal dominant, early-onset, bilateral cataract with complete penetrance. Newborns appear asymptomatic until the age of 18 to 24 months, at which time they can be clinically diagnosed by slit-lamp examination through the appearance of tiny blue or white opacities that form first in the superficial layers of the fetal lens nucleus. The opacities progress throughout the adult lens nucleus and the cortex, forming concentric layers, with central lesions oriented radially. Histologically the lesions appear to be tapered cavities between lens fibers. Progression of the cataract is slow, such that patients may have lens extractions between the ages of 16 and 35 years (Armitage et al., 1995). The preferred title/symbol of this entry was formerly 'Cataract, Congenital, Cerulean Type, 1; CCA1.'

Classic congenital or infantile nystagmus presents as conjugate, horizontal oscillations of the eyes, in primary or eccentric gaze, often with a preferred head turn or tilt. Other associated features may include mildly decreased visual acuity, strabismus, astigmatism, and occasionally head nodding. Eye movement recordings reveal that infantile nystagmus is predominantly a horizontal jerk waveform, with a diagnostic accelerating velocity slow phase. However, pendular and triangular waveforms may also be present. The nystagmus may rarely be vertical. As these patients often have normal visual acuity, it is presumed that the nystagmus represents a primary defect in the parts of the brain responsible for ocular motor control; thus the disorder has sometimes been termed 'congenital motor nystagmus' (Tarpey et al., 2006; Shiels et al., 2007). For a discussion of genetic heterogeneity of congenital nystagmus, see NYS1 (310700).

FRMD7-related infantile nystagmus (FIN) is characterized by either the onset of horizontal, conjugate, gaze-dependent nystagmus in the first six months of life or periodic alternating nystagmus (with cyclical changes of nystagmus direction) of infantile onset. Binocular vision and color vision are normal and visual acuity is typically better than 6/12. An abnormal head posture is seen in approximately 15% of affected individuals. The eyes are structurally normal and electrophysiologic studies (e.g., visual evoked potential, electroretinogram) are normal. Affected females report slightly better visual acuity than affected males; however, no differences between males and females in the amplitude, frequency, and waveform of nystagmus are observed.

Prolonged electroretinal response suppression-2 (PERRS2), also referred to as bradyopsia-2, is an autosomal recessive childhood-onset retinopathy characterized by markedly delayed dark and light adaptation, mild photophobia, difficulty seeing moving objects, moderately reduced visual acuity, normal color vision, normal fundi, and reduced rod and cone responses with prolonged recovery on electrophysiologic assessment (summary by Michaelides et al., 2010). For a discussion of genetic heterogeneity of prolonged electroretinal response suppression (PERRS), see 608415.