Leber Congenital Amaurosis

Leber congenital amaurosis is characterized by severe and/or early loss of visual acuity; sluggish or absent pupillary responses; subnormal and/or undetectable electroretinogram in dark and light conditions; absence of transduction of visual signals from brain photoreceptors; presence of oculodigital sign; family history corresponding to autosomal recessive disorder.

Oculodigital sign of Franschette is an indicator but not specific to leber congenital amaurosis. Children tend to poke, rub, and prod at their eyes leading to the eye receding into the socket due to orbital fat cushion atrophy, rubbing may cause corneal injury leading to keratoconus.

Absence of oscillation or eye fixation in response to visual stimuli is noted from 6 weeks or more of neonatal life. Retinal examination may have normal results or defects of the pigmentary dystrophy, macula, photophobia, nystagmus, and refractive errors.

Vision is massively affected by leber congenital amaurosis in acuity and function. Patients eventually have vision of 20/400 or less; some can’t see light at all while others function at the level of light perception. Patients typically have stable severe loss of vision, with some having progressive loss and other even show some improvement in adolescence or early adulthood, which may be due to mutations occurring in genes and/or maturation of central pathways. Visual loss is due to cataract, keratoconus or progressive macular lesions.

Hyperopia is the most common refractive error seen , but high myopia has been observed. Nystagmus, cataract, photophobia, keratoconus, Franceschetti oculodigital sign, and night blindness are all characteristics of leber congenital amaurosis, with symptoms varying with the patient’s mutations.

Retina appear normal at first, several anomalies will develop later on which include macular coloboma, clearly demarcated retina gap due to atrophy, spots of chorioretinal degeneration, retinal pigment migrating in various patterns, subretinal flecks scattered on the retina, retina marbled appearance, separate pigmented lesions in retinal pigment epithelium, swelling or deposition of protein around the optic disk, growth of fragile and disordered new vessels around the disc, lesions of the macula with translucent appearance to retinal pigment epithelium vessels, normal pigment in para-arteriolar region in CRB1 subtype.