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Show Journal of Clul/clll i......'ClaLl-opflthalrnoloSy 13(':'): 15':'-154, 1993 Feature Photo Superior Segmental Optic Hypoplasia In Identical Twins Michael C. Brodsky, M.D., George T. Schroeder, M.D., and Ron Ford, C.R.A. © 1993 Raven Press, Ltd., New York Key Words: Superior segmental optic nerve hypoplasia- Monozygotic twins-Diabetes mellitus. We describe superior segmental optic hypoplasia in two 15-year-old male monozygotic twins. The mother had a 25-year history of Type 1 diabetes at the time of pregnancy. Both twins were healthy and developmentally normal. An older sister had unilateral superior segmental optic hypoplasia. Corrected visual acuity was 20/30 in both twins. Twin 1 had superior segmental hypoplasia of the right optic disc (Fig. IA). The nasal aspect of the left optic disc appeared segmentally hypoplastic (Fig. IB). Humphrey 60-2 visual field testing in the right eye showed an inferior nonaltitudinal defect with mild superior constriction (Fig. IC). The left visual field showed severe peripheral constriction with a small central island of preserved vision (Fig. 10). In twin 2, both optic discs showed superior From the University of Arkansas for Medical Sciences, Little Rock, Arkansas, U.S.A. Address correspondence and reprint requests to Dr. Michael C Brodsky, Arkansas Children's Hospital, 800 Marshall, Little Rock, AR 72202, US.A 152 segmental hypoplasia (Fig. 2A,B). Visual field abnormalities in the right eye were virtually identical to those in the right eye of twin 1 (Fig. 2C). The left visual field showed diffuse peripheral constriction which was worse inferiorly (Fig. 20). COMMENT Superior segmental optic nerve hypoplasia was first recognized as a distinct clinical entity by Petersen and Walton (1) in 1977. They described 17 children of diabetic mothers who had segmental optic nerve hypoplasia, good visual acuity, and inferior altitudinal or sector visual field defects. Subsequent cases of superior segmental optic hypoplasia have consistently involved offspring of insulindependent diabetic mothers (2,3). Kim et al. (3) defined the ophthalmoscopic features of superior segmental optic nerve hypoplasia as consisting of (a) pallor of the superior disc; (b) relative superior entrance of the central retinal artery; (c) a superior peripapillary scleral halo; and (d) thinning of the superior peripapillary nerve fiber layer. They noted that the visual field defects in these patients were not typical of acquired optic nerve defects and questioned whether a regional SUPERIOR SEGMENTAL OPTIC HYPOPLASIA 153 A c B o FIG. 1. Optic disc photographs and Humphrey 60-2 visual fields in twin 1. (A) Right optic disc shows typical findings of superior segmental hypoplasia. Note relative pallor of the superior optic disc, relative superior entrance of the central retinal artery, superior peripapillary crescent, and thinning of the superior peripapillary nerve fiber layer. (B) Left optic disc shows segmental hypoplasia of the nasal optic disc. (C) Right visual field shows an inferior nonaltitudinal defect with mild superior constriction. (0) Left visual field shows severe peripheral constriction. impairment in retinal development could play a role in the pathogenesis. Congenital malformations occur two to three times more commonly in infants whose mothers have insulin-dependent diabetes mellitus at conception (5). Considerable evidence exists that these malformations result from metabolic abnormalities early in the first trimester (5). As with any teratolOgic event, it is possible that affected individuals have an underlying genetic susceptibility. Petersen and Holmes (4) found no cases of optic nerve hypoplasia in 28 children of diabetic mothers and concluded that, despite a high prevalence of maternal diabetes, superior segmental optic hypoplasia is a rare anomaly. As in our patients, superior segmental optic hypoplasia often occurs in patients without other systemic anomalies. The teratologic mechanism by which insulindependent maternal diabetes selectively interferes with the early gestational development of supe- I Clin Neuro-ophthalmol. Vol. 13, No.2, 1993 154 M. C. BRODSKY ET AL. B c o FIG. 2. Optic disc photographs and Humphrey 60-2 visual fields in twin 2. (A) Right optic disc photograph shows superior segmental optic hypoplasia. (B) Left optic disc showing mild superior segmental optic hypoplasia. (C) See right visual field shows an inferior nonaltitudinal defect that is virtually identical to the right visual field in twin 1. (0) Left visual field shows diffuse peripheral constriction that is worse inferiorly. rior retinal ganglion cells or their axons is unknown. REFERENCES 1. Petersen RA Walton DS. Optic nerve hypoplasia with good visual acuity and visual held defects: a study of children of diabetic mothers. Arch OphthalmoI1977;95:254-8. I C/m Nellro-ophthalmol, Vol. 13, No.2, 1993 2. Nelson M, Lessell S, Sadun AA. Optic nerve hypoplasia and maternal diabetes mellitus. Arch Neurol 1986;43:20-5. 3. Kim RY, Hoyt WF, Lessell S, Narahara MH. Superior segmental optic hypoplasia: a sign of maternal diabetes. Arch OphthalmoI1989;107:1312-15. 4. Petersen RA, Holmes LB. Optic nerve hypoplasia in infants of diabetic mothers. Arch Ophthalmol 1986;104:1587. 5. Hod M, Diamant YZ. The offspring of a diabetic mother: short- and long-range implications. Isr J Med Sci 1992;28: 81---{). |
