From Karadeniz Technical University, School of Medicine, Department of Ophthalmology, Trabzon, Turkey.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Adem Turk, MD, Karadeniz Technical University, School of Medicine, Department of Ophthalmology, 61080 Trabzon, Turkey.
Optic nerve aplasia is an uncommon congenital defect of the optic nerve and retina. The condition most often presents unilaterally and rarely bilaterally. Unilateral optic nerve aplasia may be associated with normal brain development in otherwise healthy individuals. Bilateral optic nerve aplasia is frequently accompanied by severe central nervous system abnormalities.1–4 This report describes bilateral optic nerve aplasia in an otherwise healthy infant.
A 3-month-old female infant was referred to the authors’ clinic from the pediatrics clinic for ophthalmologic evaluation. She was born at 7.5 months’ gestation with a birth weight of 2.8 kg. Physical development was within normal limits. Ophthalmologic examination showed poor vision with negative pupil reactions. The pupils were mydriatic and afferent pupillary defects were present in both eyes. Cycloplegic refraction was −2.00 diopters in the right eye and −2.50 diopters in the left eye. The eyes were in the down gaze position, and the right eye was smaller than the left eye.
Significant nystagmus was not found. The corneal diameter was 6.5 mm in the right eye and 8 mm in the left eye. On dilated fundus examination, the heads of the optic nerves were not detected in either eye, and there was severe retinal pigment epithelial atrophy. No normal retinal vessels were observed in either eye (Fig. 1).
Figure 1. Fundus Appearance of a Child with Optic Nerve Aplasia.
Magnetic resonance imaging of the eye, orbit, and brain was performed at 3 months of age and repeated at 9 months of age. Radiologic findings were remarkable for the rudimentary appearance of the intraorbital portions of both optic nerves. Magnetic resonance imaging did not show the optic chiasm at either 3 or 9 months of age. Other tissues around the chiasm appeared normal. The brain ventricles were normal in size and position (Fig. 2). On electrophysiological examination, flash visual evoked potential did not show any spike.
Figure 2. (A) T1-Weighted and (B) T2-Weighted Magnetic Resonance Imaging of the Cranium Showing the Intraorbital Portions of Both Optic Nerves and the Abnormal Optic Chiasm.
B-scan echography showed a small right globe (axial length: 16.83 mm) and a left globe that was nearly normal in size (axial length: 17.60 mm). As with magnetic resonance imaging, ultrasonography did not show optic nerves. There was no similar anomaly in the patient’s siblings or parents.
Optic nerve aplasia is the complete absence of the optic nerve and disc, retinal ganglion cells and nerve fiber layer, and retinal vessels. The pathogenesis of optic nerve aplasia is unknown. One report attributed it to defective formation of the embryonic fissure, failure of the mesenchymal inlay of the hyaloid system to enter the embryonic fissure, or primary agenesis of the retinal ganglion cells.4
Optic disc aplasia is a rare anomaly of the optic nerve that has been reported several times in the literature.1–4 In humans, only unrelated cases of achiasmatism have been described. Jansonius et al.5 reported a patient with optic nerve defect. The patient’s siblings were unaffected.
Bilateral cases are rare and are usually associated with severe abnormalities of the central nervous system. There are few reports of bilateral optic nerve aplasia in the English literature.1,2,4,5 Scott et al.6 described isolated bilateral aplasia of the optic nerves, chiasm, and tracts in an otherwise healthy 2-month-old female infant. Sanjari et al.3 described an otherwise healthy patient with aplasia of the chiasm, bilateral optic nerves, and tractus. Similarly, Pomeranz at al.7 described an 18-month-old boy with achiasma and unilateral optic nerve hypoplasia. The first report of achiasma as nondecussating retinal–fugal fiber syndrome (achiasma) was presented by Apkarian et al.8 In the current case, in addition to bilateral optic nerve aplasia, the chiasm could not be detected clearly.
The most important findings associated with optic nerve aplasia are microphthalmos, albinism, and aniridia.9–12 In the current case, microphthalmos was prominent in the right eye but the left eye was nearly normal in size. The irides were blue-gray in the current patient, but there were no other findings associated with albinism. In addition, the patient had mild iris coloboma in the left eye. Ginsberg et al.9 described a patient with optic disc agenesis associated with aniridia and extraocular anomalies. These authors stated that there might be a developmental relationship between aniridia and optic disc agenesis. Golnik10 and Blanco et al.11 emphasized that optic nerve anomalies might be associated with other central nervous system and systemic abnormalities. Likewise, Storm and PeBenito12 described a patient with optic nerve aplasia associated with hydrencephaly.
Several reports described electrophysiologic tests as being useful for detecting optic disc and chiasm anomalies.5,7 Jansonius et al.5 showed the absence of crossing optic nerve fibers with electrophysiological tests and magnetic resonance imaging in a 15-year-old girl without a chiasm. In the current case, no wave was detected on flash visual evoked potential.
Optic nerve aplasia should be considered in a patient with microphthalmos, coloboma, and light-colored irides. The current case will contribute to the literature because these abnormalities are rare.
- Brodsky MC. Anomalies of the optic disc. In: Miller NR, Newman NJ, eds. Walsh and Hoyt’s Clinical Neuro-Ophthalmology, vol. 1, 5th ed. Baltimore: Williams & Wilkins; 1998:799–800.
- Brodsky MC. Congenital optic disc anomalies. In: Taylor D, Hoyt G, eds. Pediatric Ophthalmology and Strabismus, 3rd ed. Philadelphia: Elsevier-Saunders, 2005:637–638.
- Sanjari MS, Ghasemi Falavarjani K, Parvaresh MM, Kharazi HH, Kashkooli MB. Bilateral aplasia of the optic nerve, chiasm, and tracts in an otherwise healthy infant. Br J Ophthalmol. 2006;90:513–514. doi:10.1136/bjo.2005.088229 [CrossRef]
- Margo CE, Hamed LM, Fang E, Dawson WW. Optic nerve aplasia. Arch Ophthalmol. 1992;110:1610–1613.
- Jansonius NM, van der Vliet TM, Cornelissen FW, Pott JW, Kooijman AC. A girl without a chiasm: electrophysiologic and MRI evidence for the absence of crossing optic nerve fibers in a girl with a congenital nystagmus. J Neuroophthalmol. 2001;21:26–29.
- Scott IU, Warman R, Altman N. Bilateral aplasia of the optic nerves, chiasm and tracts in an otherwise healthy infant. Am J Ophthalmol. 1997;124:409–410.
- Pomeranz HD, Agadzi AK, Ekesten B. Achiasma and unilateral optic nerve hypoplasia in an otherwise healthy infant. Acta Ophthalmol Scand. 2006;84:140–144. doi:10.1111/j.1600-0420.2005.00523.x [CrossRef]
- Apkarian P, Bour LJ, Barth PG. A unique achiasmatic anomaly detected in non-albinos with misrouted retinal-fugal projections. Eur J Neurosci. 1994;6:501–507. doi:10.1111/j.1460-9568.1994.tb00293.x [CrossRef]
- Ginsberg J, Bove KE, Cuesta MG. Aplasia of the optic nerve with aniridia. Ann Ophthalmol. 1980;12:433–439.
- Golnik KC. Congenital optic nerve anomalies. Curr Opin Ophthalmol. 1998;9:18–26. doi:10.1097/00055735-199812000-00004 [CrossRef]
- Blanco R, Salvador F, Galan A, Gil-Gibernau JJ. Aplasia of the optic nerve: report of three cases. J Pediatr Ophthalmol Strabismus. 1992;29:228–231.
- Storm RL, PeBenito R. Bilateral optic nerve aplasia associated with hydranencephaly. Ann Ophthalmol. 1984;16:988–992.