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).

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

Differential diagnosis:

  • Posterior staphyloma
  • Macular coloboma – also similar like toxoplasmosis scar
  • Cryo spots


  • 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.

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.

AD: Autosomal dominant; CMV: Cytomegalovirus; CNS: central nervous system; Cs: centistokes; PPV: pars plana vitrectomy; PVR: proliferative vitreoretinopathy; RRD: rhegmatogenous retinal detachment; RD: retinal detachment; SiO: silicone oil;

Location Birmingham Midlands Eye Centre 76 Dudley Road Birmingham B18 7QH UK Phone 0121 554 3801 Hours Mr Ch'ng | Vitreoretinal Clinic Sessions: Monday: 8.30am - 12.30pm Wednesday (alternate): 8.30am - 5.00pm Thursday: 8.30am - 12.30pm Friday: 8.30am - 12.30pm | Vitreoretinal Theatre Sessions: Wednesday (alternate): 8.30am - 5.00pm & Friday (emergency cases): 1.30pm - 5.00pm | Eye Casualty Session: Monday 1.00pm - 4.30pm |
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