Albinism and the Eye

Albinism is a group of inherited disorders of melanin synthesis, with reduced pigment in the skin, hair and eyes (oculocutaneous albinism, autosomal recessive) or predominantly in the eyes (ocular albinism, X-linked).

• Oculocutaneous albinism types: OCA1 (tyrosinase gene, the most severe, with complete absence of pigment in OCA1A), OCA2 (P gene, the commonest type worldwide and in sub-Saharan Africa, with some pigment accumulating over time), OCA3 (TYRP1, rufous), OCA4 (SLC45A2), and rare types. Syndromic forms include Hermansky-Pudlak syndrome (bleeding diathesis, pulmonary fibrosis, granulomatous colitis) and Chediak-Higashi syndrome (immunodeficiency, giant lysosomal granules).
• All forms share the same ocular features, caused by melanin deficiency during development: foveal hypoplasia, misrouting of optic nerve fibres at the chiasm (too many fibres cross), and iris and fundus hypopigmentation.
• Visual impairment is lifelong, nonprogressive, and results from foveal hypoplasia, nystagmus and refractive error. Skin cancers are a major burden in sunny regions.

• Nystagmus: infantile, pendular or jerk, noticed at 2 to 3 months, with a null zone and compensatory head posture, and damped on convergence.
• Visual acuity 6/18 to 6/60 (typically 6/24 to 6/36 in OCA2 and better in pigmented forms), and improves modestly with age.
• Photophobia, and glare in daylight.
• Iris transillumination: translucent iris showing a red reflex, whether complete (OCA1A) or partial. Fundus with hypopigmentation, visible choroidal vessels, absent foveal reflex, and macular hypoplasia.
• Refractive errors: astigmatism, high hypermetropia or myopia in over 50 percent.
• Strabismus (esotropia or exotropia, 40 to 50 percent), absent or reduced stereopsis, and amblyopia.
• Hair and skin: white to yellow brown hair, pale pink skin that burns, no tanning. Skin may be minimally pigmented in OCA2 and ocular albinism, so diagnosis can be delayed.
• Hermansky-Pudlak syndrome: easy bruising, epistaxis, prolonged bleeding after surgery or dental extractions, and later dyspnoea. Chediak-Higashi syndrome: recurrent infections and silvery hair.

• Clinical examination of the iris (transillumination at slit lamp), fundus, and OCT of the macula showing absent foveal pit and persistence of inner retinal layers (graded by degree of foveal hypoplasia).
• Visual evoked potentials with asymmetrical (crossed) responses on monocular stimulation, indicating chiasmal misrouting.
• Cycloplegic refraction at diagnosis.
• Genetic testing: tyrosinase, OCA2, TYRP1, SLC45A2, GPR143, and the genes of Hermansky-Pudlak syndrome (HPS1 and others), with genetic counselling.
• Syndromic screening when there is bleeding or infection history: platelet function tests (absent dense bodies on electron microscopy), full blood count with blood film for giant granules (Chediak-Higashi), lung function, and referral to haematology.
• Exclusion of other causes of nystagmus: Leber congenital amaurosis, achromatopsia, congenital stationary night blindness (electroretinogram), cone dystrophy, and neurological disease (imaging when atypical).

• Full spectacle correction as early as possible, including for high astigmatism, and contact lenses for high refractive error and nystagmus damping. Tinted or photochromic lenses (typical tint 50 to 85 percent), brimmed hats and polarised sunglasses for photophobia.
• Amblyopia: patching or atropine penalisation for strabismic or anisometropic amblyopia in early childhood.
• Nystagmus: contact lenses, prisms (base out to induce convergence, or yoked prisms to shift the null zone), and surgery for a significant head turn: horizontal muscle recession and resection to shift the null zone to primary position (2 to 3 months to adjust the effect). Drug therapy has limited benefit: gabapentin 300 mg three times daily or memantine 5 to 10 mg, which is mostly used in acquired nystagmus.
• Strabismus surgery when angles are large, with the realistic aim of cosmesis and head posture rather than binocularity.
• Low vision support: large print, magnifiers, telescopes (monocular, for distance), electronic devices and screen reader software, orientation and mobility training, classroom seating at the front, and educational assessment. Visual acuity 6/18 or better is required to hold a driving licence in many regions (the legal requirement varies), so the patient is counselled.
• Skin protection: broad spectrum sunscreen SPF 50 or higher, protective clothing, avoiding midday sun, and annual skin examination from adolescence (high risk of squamous cell carcinoma, basal cell carcinoma and melanoma in sun exposed regions, often at young ages). In sub-Saharan Africa, early dermatology referral is important and sun protection programmes reduce mortality.
• Hermansky-Pudlak syndrome: avoid aspirin and other drugs affecting platelets, desmopressin 0.3 micrograms/kg before surgery, platelet transfusion for major bleeding, and pulmonary surveillance (high resolution CT) from adulthood. Chediak-Higashi syndrome: haematopoietic stem cell transplantation to correct the immunodeficiency.
• Genetic counselling for parents: recurrence risk of 25 percent in autosomal recessive types and 50 percent of male offspring for carrier mothers in X-linked types.
• Psychosocial support is important because of stigma, which in some communities leads to exclusion, and the person is supported with educational and community resources.