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Retinal Coloboma

  • Rare – 0.14% general population.

  • 40% leads to RD.

  • Due to defective closure of the embryonic fisure

  • Typically inferonasal quadrant

  • Genetic associations – PAX6 gene (AD); Sonic HedgeHog (SHH) gene; CHARGE syndrome

  • Environmental causes – teratogenic drugs (thalidomide, alcohol, LSD, carbamazine); Maternal Vitamin A & E deficiency; radiation; hyperthermia; infection (CMV, toxoplasmosis).

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Clinical features:

  • 80% bilateral

  • 85% has iris colonoma.

  • 50% Nystagmus

  • Parents noticed child cannot follow objects

  • Leukocoria or squint may be present

  • 40% RD with high risk of PVR (8%)

  • Rare – CNV

  • 40% microphthalmia

  • 20% myopic

  • Long term – cataract and glaucoma

  • Poor visual prognosis long-term if macular involved

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Differential diagnosis:

  • Posterior staphyloma

  • Macular coloboma – also similar like toxoplasmosis scar

  • Cryo spots

Management:

  • Prophylactic laser barrage retinopexy with gentle laser burns – debatable.

  • RD – break usually in the intercalary membrane (60%) from round atrophic holes and difficult to find due to absent choroid. Treat with encirclement band + PPV + 360 degrees endolaser + 5000 Cs SiO.

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Other colobomas of interest:

  • Optic nerve coloboma – AD; bilateral (60%); may have microphthalmia and non-RRD; may have associated CNS abnormalities; can be confused with optic disc pit maculopathy.

  • Morning glory syndrome – associated with transsphenoidal basal encephalocele; RD due to small slit-lke reak at edge of anomalous disc (peripapillary break); exudative RD can happen as well; treat with PPV or peripapillary laser.

  • Optic nerve hypoplasia – similar enviromental risk factors to coloboma; double ring sign (classical); associated with De Morsier syndrome (septo-optic hypoplasia) – which also has absent septum pellucidum and pituitary gland dysfunction.

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