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Contractile Morning Glory Disc Causing Transient Monocular Blindness in a Child
Michael C. Brodsky, MD
Arch Ophthalmol. 2006;124:1199-1201.
Transient monocular visual loss is a rare complaint in children since they lack the vascular risk factors found in the elderly population. I recently examined a boy who experienced numerous daily episodes of intermittent monocular visual loss that corresponded to contraction of a morning glory disc anomaly in the involved eye.
Report of a Case
A 10-year-old boy complained of multiple daily episodes of sudden and complete monocular visual loss that lasted from 10 to 40 seconds and were followed by complete visual recovery. These episodes often occurred without any apparent stimulus or warning but were sometimes precipitated by turning his head abruptly, heat, and exercise. He had a history of migraine headaches but was otherwise healthy and taking no medications. Results of magnetic resonance imaging and magnetic resonance angiography were normal.
On examination, visual acuity was 20/20 OU. Both pupils reacted briskly to light and there was no afferent pupillary defect. Titmus testing showed 40 seconds/arc. Extraocular movements were full. There was no strabismus, nystagmus, or microphthalmos. Results of slitlamp examination were normal. Retinoscopy disclosed a mildly myopic refractive error in both eyes. Retinal examination results were normal in the right eye but disclosed a morning glory disc anomaly in the left eye (Figure 1A).
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Figure 1. Retinal photographs. A, Morning glory optic disc when the vision is normal. B, Morning glory optic disc during an amaurotic episode. Note reduced optic disc diameter, dilation of the peripapillary retinal veins, and increased hyperemia of the optic disc.
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At the onset of the visual loss, the left optic disc became smaller and hyperemic, with dilation of the retinal veins (Figure 1B). When these episodes of visual loss occurred, the patient's left pupil became unreactive to light, and he developed a left afferent pupillary defect. Treatment with oral Benadryl, pseudoephedrine, and verapamil hydrochloride (60 mg twice daily for 1 week) yielded no improvement in symptoms. The patient has experienced no residual visual deficits from these episodes over 2 years of follow-up.
Comment
Optic disc contractility has been associated with the morning glory disc anomaly, optic disc coloboma, and peripapillary staphyloma.1 The posterior sclera and choroid of humans and monkeys normally contain nonvascular contractile cells with adjacent nerve terminals, suggesting active neural control.2 Histologically, the majority of optic nerve head colobomas have heterotopic intrascleral and choroidal smooth muscle fibers oriented concentrically around the distal optic nerve.3-4 Functional smooth muscle in this heterotopic location would explain the observed contractility in some of these excavated optic discs. Pollock1 attributed optic disc contractility to a passive flux of peripapillary subretinal fluid in his patient with morning glory disc anomaly and peripapillary retinal detachment. However, no peripapillary subretinal fluid was visible in the present case.
The rarity of transient monocular visual loss in association with contractile optic discs probably reflects the generally poor vision in the involved eye. However, Graether5 described similar symptoms in a 34- year-old man who had experienced complete loss of vision in his left eye as long as he could remember (Figure 2). The patient had no family history of migraine headache or other neurologic disease. The episodes of amaurosis came without apparent stimulus or associated symptoms of any kind. If the patient closed his right eye, he recognized that his vision was dimmed or absent in the left eye. The visual loss occurred several times a day and lasted from 30 to 60 seconds. Retinal examination disclosed a morning glory disc anomaly in the left eye. During the episodes of visual loss, the optic disc became hyperemic, the major retinal veins dilated, and contraction of the central glial tuft could be observed (Figure 2).
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Figure 2. Retinal photographs from the article by Graether.5 A, Morning glory optic disc (not recognized as such at the time) prior to an episode of visual loss. B, Morning glory optic disc during an amaurotic episode. Note reduced diameter of the central glial tuft, dilation of the peripapillary retinal veins, and increased hyperemia of the optic disc.
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The retinal venous dilation in these 2 cases probably resulted from constriction of the retinal veins near the scleral canal by heterotopic smooth muscle tissue. If the transient visual loss were caused by reduced arterial perfusion, as from vasospasm, the retinal veins would not have as much blood to evacuate and would not dilate. While increased retinal venous pressure would secondarily decrease arterial perfusion, the magnitude of the venous distention was not commensurate with the instantaneous monocular blindness that both patients experienced. The observed retinal venous distention was mild compared with the severe venous engorgement that accompanies papilledema in patients who retain normal visual acuity. This instantaneous visual loss and rapid recovery in both patients suggests that intermittent contraction of heterotopic smooth muscle can directly constrict the distal optic nerve to produce an axonal conduction block. The retinal venous dilation and optic disc hyperemia are probably epiphenomena that arise when increased intraneural pressure is transmitted to the vasa nervorum.
AUTHOR INFORMATION
Correspondence: Dr Brodsky, Arkansas Children's Hospital, 800 Marshall, Slot 111, Little Rock, AR 72202 (brodskymichaelc{at}uams.edu).
Financial Disclosure: None reported.
Funding/Support: This study was supported by a grant from Research to Prevent Blindness Inc.
REFERENCES
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1. Pollock S. The morning glory disc anomaly: contractile movement, classification, and embryogenesis. Doc Ophthalmol. 1987;65:439-460.
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2. Poukens V, Glasgow BJ, Demer JL. Nonvascular contractile cells in sclera and choroid of humans and monkeys. Invest Ophthalmol Vis Sci. 1998;39:1765-1774.
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3. Font RL, Zimmerman LE. Intrascleral smooth muscle in coloboma of the optic disk: electron microscopic verification. Am J Ophthalmol. 1971;72:452-457.
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4. Willis F, Zimmerman LE, O’Grady R, et al. Heterotopic adipose tissue and smooth muscle in the optic disc: association with isolated colobomas. Arch Ophthalmol. 1972;88:139-146.
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5. Graether JM. Transient amaurosis in one eye with subsequent dilatation of retinal veins. Arch Ophthalmol. 1963;70:342-345.
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SECTION EDITOR: W. RICHARD GREEN, MD
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