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Show Journal of Neuro- Ophthalmology 21( 4): 276- 277, 2001. © 2001 Lippincott Williams & Wilkins, Inc., Philadelphia Photo Essay Nerve Fiber Bundle Visual Field Defect Resulting from a Giant Peripapillary Cotton- Wool Spot Edward Chaum, MD, PhD, Richard D. Drewry, MD, Gerald T. Ware, MD, and Steve Charles, MD Cotton- wool spots are the clinical manifestation of focal infarcts of the retinal nerve fiber layer. They rarely cause significant visual field loss. A large idiopathic cotton- wool spot in a 34- year- old healthy woman caused a nerve fiber bundle visual field defect and an afferent pupillary defect that remained after the cotton- wool spot had disappeared and the retina and optic nerve appeared normal. Key Words: Cotton- wool spots- Visual field defect- Scotoma- Afferent pupillary defect. A 34- year- old healthy woman presented with a 2- day history of an acute, painless, inferior field defect in the right eye. Her medical history was remarkable only for a tick bite 1 year earlier, for which she received prophylactic antibiotics. Visual acuity was 20/ 20 OU with correction. There was a + 1 afferent pupillary defect OD. Hardy- Rand- Rittler color plate testing was 19/ 20 OU. There was no ocular inflammation, and the intraocular pressure was within normal limits. Dilated fundus examination revealed a 1 disk- diameter cotton- wool spot superotempo-rally adjacent to the right optic nerve ( Fig. 1). There were flecks of blood along the temporal rim of the cotton- wool spot. There was no swelling of the optic nerve or evidence of retinal vasculitis or vitreous cells. The left eye was normal. Fluorescein angiography confirmed the clinical findings of a large cotton- wool spot. Focal hy-pofluorescence was seen in the region of retinal swelling owing to blockage of the dye ( not shown). There was late staining of the optic nerve but no dye leakage. From the Department of Ophthalmology, University of Tennessee, Memphis ( EC, RDD, GTW, SC) and Charles Retina Institute, ( GTW and SC), Memphis Tennessee. Address correspondence and reprint requests to Edward Chaum, MD, PhD, Department of Ophthalmology, UT Memphis, 956 Court Avenue, Room D228, Memphis, TN 38163, USA; E- mail: echaum@ mail. eye. utmem. edu The complete blood count was normal ( 6.1 white blood cells, 12.2 hemoglobin, 36.3 hematocrit, 330,000 platelets, and normal differential), The erythrocyte sedimentation rate was elevated at 55. Serology testing was negative for Borrelia burgdorferi and Treponema pallidum IgG and IgM. Antinuclear antibody and rheumatoid factor tests were negative. Cerebral magnetic resonance imaging and magnetic resonance angiography studies were normal. Blood pressure and medical workup were normal. No diagnosis was reached. Visual field testing 5 months later ( Fig. 2) demonstrated a dense inferonasal nerve fiber bundle visual field defect corresponding to the location of the prior cotton- wool spot. Fundus examination now showed only slight nerve fiber layer fibrosis in the region of the prior cotton- wool spot ( Fig. 3). There was no optic disk pallor or excavation. 276 VISUAL FIELD DEFECT AND AFFERENT PUPILLARY DEFECT FROM A COTTON- WOOL SPOT 277 Cotton- wool spots are transient, white, feathery-appearing opacifications, and swellings of the retina resulting from microinfarcts of retinal nerve fiber layer. They are frequently a manifestation of systemic arteriolar disease, most commonly diabetes, hypertension, and collagen vascular disease, but also seen in human immunodeficiency virus and other infections, hematologic disease and coagulopathies, pancreatitis, embolic disease, trauma, pregnancy, and idiopathic conditions ( 1). As many as 95% of patients with cotton- wool spots are identified as having a predisposing systemic condition ( 2). Histopathologic analysis demonstrates retinal infarction from focal arteriolar occlusion. Ischemic injury to the retinal ganglion cells results in disruption of normal axo-plasmic flow and the accumulation of cellular mitochondria and debris in axonal swellings. Our patient presented with a giant cotton- wool spot of idiopathic origin immediately adjacent to the optic nerve. This juxtapapillary location is an anatomic region through which most of the retinal ganglion cell axons from the temporal and superior retina pass to exit the eye. It damaged a significant number of ganglion cell fibers from the superotemporal retina, causing a large visual field defect and an afferent pupillary defect in the eye. The infarct apparently did not involve the optic nerve because the disk itself was not swollen. Interestingly, no disk pallor or pathologic cupping resulted from the loss of nerve fiber bundles even 5 months after presentation. FIG. 2. Humphrey visual field test ( 24- 2) of the right eye performed 5 months after initial presentation. There is a dense, almost absolute inferonasal nerve fiber bundle visual field defect corresponding to the region of the retina where the ganglion cell axons were affected by the cotton- wool spot. FIG. 3. Red- free digital photograph of the right optic nerve and retina taken 5 months after initial presentation ( and at the same time as the visual field shown in Fig. 2). The optic nerve appears normal. Only trace gliosis of the nerve fiber layer can be seen in the region of the prior cotton- wool spot ( arrow). Despite the large visual field defect and the APD, the retina appeared normal apart from mild, barely discernible fibrosis in the nerve fiber layer. It has been axiomatic that visual fields are normal after retinal infarcts manifested by cotton- wool spots. However, nonspecific scotomas and nerve fiber bundle defects have been rarely described ( 3,4). This case serves as a reminder that a previous ( and now vanished) cotton- wool spot could be the cause of a nerve fiber bundle defect, an afferent pupil defect, and a normal-appearing fundus and optic nerve. REFERENCES 1. Brown GC. Retinal arterial obstructive disease. In: Ryan SJ, ed. Retina. St. Louis: Mosby, 1994: 1373- 5. 2. Brown GC, Brown, MM, Hiller T, et al. Cotton- wool spots. Retina 1985; 5: 206- 14. 3. Miller NR, Newman NJ. Topical diagnosis of lesions in the visual sensory pathway. In: Miller NR, Newman NJ, eds. Walsh and Hoyt's Clinical Neuro- ophthalmology. Baltimore: Williams & Wilkins, 1998: 237- 386. 4. Shami MJ, Uy RN. Isolated cotton- wool spots in a 67- year old woman. Surv Ophthalmol 1996; 40: 413- 5. J Neuro- Ophthalmol, Vol. 21, No. 4, 2001 |
