|Year : 2002 | Volume
| Issue : 4 | Page : 328-329
Optic nerve entrance coloboma associated with situs inversus
Vasudev A Rao, T Sambath, MP Madhavaranga, N Nair
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Education and Research, Pondicherry-605 006, India
Vasudev A Rao
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Education and Research, Pondicherry-605 006
Source of Support: None, Conflict of Interest: None
A rare case of optic nerve entrance coloboma associated with situs inversus is reported.
Keywords: Optic nerve coloboma, situs inversus
|How to cite this article:|
Rao VA, Sambath T, Madhavaranga M P, Nair N. Optic nerve entrance coloboma associated with situs inversus. Indian J Ophthalmol 2002;50:328-9
|How to cite this URL:|
Rao VA, Sambath T, Madhavaranga M P, Nair N. Optic nerve entrance coloboma associated with situs inversus. Indian J Ophthalmol [serial online] 2002 [cited 2020 Jun 4];50:328-9. Available from: http://www.ijo.in/text.asp?2002/50/4/328/14754
Coloboma involvement of the optic nerve generally takes one of two forms; (a) the optic nerve coloboma is associated with a retinochoroidal coloboma, and (b) the coloboma involves only the optic nerve, i.e., the coloboma at the optic nerve entrance. The retinochoroidal coloboma involving the nerve alone is rare. The purpose of the present communication is to report one such rare case of optic nerve entrance coloboma associated with situs inversus.
| Case report|| |
A 27-year-old female presented to us with complaints of decreased vision in right eye since childhood. She had undergone intracapsular cataract extraction in the right eye five years earlier elsewhere. Her left eye was blind following trauma 15 years previously. The best corrected vision in the right eye was 6/18 (+4D Sph/ +1 D cyl @ 180?) The corneal diameter measured 10 mm in both meridians. Fundus examination showed coloboma involving only the optic disc; a rim of the superonasal part of disc was present, the blood vessels arising from this part of the disc showing a pattern of situs inversus ([Figure - 1]). The rest of the fundus was tesselated and normal. The visual field was constricted (Humphrey visual field analyser) ([Figure:2]). Her left eye was phthisical. There were no associated systemic abnormalities. There was no similar family history.
| Discussion|| |
Optic nerve head coloboma is an unusual entity. It occurs due to incomplete or abnormal coaptation of only the extreme proximal end of the embryonic fissure while the rest of the fissure closes normally. In the present case, the coloboma occupied almost the entire disc except a rim of the superonasal part. The embryonal fissure is situated inferonasally and hence its failure to close may have spared the superior part of the disc from the coloboma. The coloboma was sharply delimited with a bowl-shaped excavation. This reflects the aplasia of Bergmeister's papilla in association with incomplete fusion of embryonic fissures, and the backward displacement of the lamina cribrosa in the region of the coloboma.
In optic disc coloboma, the visual acuity depends primarily upon the integrity of the papillomacular bundle it may be mildly to severely decreased and as such it is difficult to predict from the appearance of the disc alone. In the patient described here the decrease in visual acuity was caused not only by the coloboma (causing field constriction) but also by the associated factors of myopia, amblyopia and situs inversus.
Three patterns of retinal blood vessels in association with disc coloboma are described earlier. They are: (1) blood vessels emerge from the lower part of the disc coloboma and turn upward. Vessels for the upper fundus go directly over the less excavated portion of disc, whereas those for the lower half of fundus bend sharply downward, kinking over the sharp inferior edge. (2) normal arrangement of blood vessels emanate from or slightly above the centre of the coloboma. (3) blood vessels emerge separately from all around the edge of the coloboma, in which case all the blood vessels are cilioretinal vessels. The retinal vessels emerged from the nasal side of the disc (instead of the temporal) as if rotated through 180?. The anomalous insertion of the optic stalk into the optic vesicle may have resulted in dysversion of the nerve head.
The patient described here did not show any such specific vascular pattern. This presentation was unique, and was similar to situs inversus. In general patients with optic disc coloboma should be kept on longterm follow up for fundus examination. These eyes with isolated optic disc colobomas are prone to develop serous macular detachments, in contrast to the rhematogenous detachments that complicate retinochoroidal coloboma.
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[Figure - 1]