Sir,

The case report of a child with atypical chorioretinal colobomata is presented. The defects are unusual as they lie along both the superior and inferior maculopapillar bundles and yet a vision of 6/5 is still present.

Colobomas result from incomplete closure of the embryonic fissure around weeks 5–8 gestation.1 Closure starts at the equator and continues anteriorly and posteriorly. Any insult during this time can create defects of varying size and location. Colobomas may extend from the iris margin to the optic disc and involve one or more defects along the fusional lines. Typical colobomas are seen inferonasally.

Atypical colobomas are found outside this area and therefore do not originate in a defect of embryonic fissure closure. They are thought to be either pathogenic in origin or owing to faulty differentiation of ocular structures.2, 3 Macular colobomas have been described as sharply defined, oval, or round central defects.4 Paramacular colobomas are described as solitary oval- or torpedo-shaped chorioretinal lesions located temporal to the fovea in one or both eyes.5 Neither accurately describes the colobomas present in this case.

Case report

A 5-year-old girl presented to us after her first optician's visit. Some areas of retinal pallor (Figure 1) were noted and referred to Eye Clinic. The patient was entirely asymptomatic. There were no developmental concerns raised by the family, she was attending school and doing well. Further questioning revealed a full term pregnancy with no perinatal problems. There was no past medical history and she had never been on any regular medications. There was no family history of note. She had no siblings.

Figure 1
figure 1

Right fundus photograph.

Full size image

Ocular examination revealed a visual acuity of 6/5 in each eye. No nystagmus was present. Anterior segments, optic discs, and the left fundus were normal. The right fundus had two well-demarcated chorioretinal defects. The edges of the defects gently sloped, demonstrating the thickness of the inner ocular layers down to sclera. The two defects were arcuate in nature, above and below the macula. A corresponding scotoma was present.

Comment

It is rare to see chorioretinal colobomas in these locations. The presence of a normal visual acuity despite such extensive involvement of the maculopapillar bundles is remarkable.

Both retinochoroidal and optic nerve colobomas may be associated with systemic abnormalities.6 Abnormalities can affect the central nervous, cardiovascular, genitourinary, musculoskeletal, gastrointestinal, and nasopharyngeal systems. These should be appropriately investigated. Other chorioretinal defects do not require such investigation.