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Editor,—Among a variety of optic disc anomalies, colobomas and optic nerve pits are known to be closely related.1 Previous studies2 have shown that retinal detachment in eyes with choroidal coloboma is often caused by retinal breaks within the coloboma. However, the pathogenesis of non-rhegmatogenous retinal detachment correlating with optic disc coloboma has not been well defined. Here, we report a case of optic disc and choroidal coloboma associated with an unusual form of macular detachment complicated by retinoschisis.
A 35 year old Japanese woman complaining of blurred vision in the left eye was referred to Kyorin University Hospital on 1 October 1996. Her best corrected visual acuity was 20/20 in the right eye and 20/200 in the left. Indirect ophthalmoscopy of the left eye revealed a serous macular detachment associated with an apparent macular hole with irregular margins (Fig 1). Slit lamp fundus biomicroscopy with a +90 D preset lens disclosed a serous detachment of macula with a schisis-like separation between the inner and outer retina and an outer lamellar macular hole. The macular hole appearing to be of full thickness under indirect ophthalmoscopy was determined to be a lamellar hole of the outer retina. Posterior vitreous detachment was not present. Scanning laser ophthalmoscopy (SLO) using argon laser also showed the inner retinal layer covering the detached outer layer, creating a double ring appearance. Fluorescein angiography (FA) confirmed hypofluorescence of the disc coloboma during its early phase but revealed hyperfluorescence during the late phase with no leakage from the retinal vessels. The region with retinoschisis and retinal detachment did not demonstrate hyperfluorescence at any phase (Fig 2).
Disc colobomas and optic nerve pits are often complicated with sensory macular retinal detachment, but their symptoms rarely become significant before the age of 20.3 Based on a review of 15 patients with optic nerve pits and maculopathy, Lincoff and associates4 suggested that the retinal elevation is most often due to communication between the optic nerve pit and a schisis-like separation of the inner and outer retinal layers and that a full thickness macular retinal detachment may occur secondarily and in association with an outer lamellar macular hole. This finding was recently confirmed by optical coherence tomography (OCT).5In addition, OCT suggests that the formation of an outer lamellar macular hole may be secondary to chronic cystoid macular oedema. To our knowledge, however, this mechanism has not been identified in eyes with optic disc coloboma. Lincoff et al suggested that in eyes with a maculopathy associated with optic disc pits, the fluid from the pits entering the disc elevates the nerve fibre layer, causing a schisis-like separation of the inner retinal layers. Even though FA of the present case did not show the origin of subretinal fluid, we were able to confirm our diagnosis of retinoschisis and lamellar macular hole based on fundus examinations including SLO and FA, which clearly revealed an elevated inner layer connected to the disc coloboma. These findings are very similar to those of Lincoffet al’s cases demonstrating an irregular and partial thickness macular hole and schisis with an outer layer detachment which dose not extend to the optic disc. Non-rhegmatogenous retinal detachment may occur in association with disc colobomas. We believe that the pathogenesis of the schisis-like separation identified in optic nerve pits and optic disc colobomas may be similar.
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