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Arch Ophthalmol. 2004;122:408-409.

Congenital retinal arteriovenous malformation¹ is a rare, unilateral, nonhereditary disorder with variable visual impairment depending on the severity of the vascular anomaly. Most cases do not show any anatomical progression.² Venous occlusion, intraretinal or vitreal hemorrhage,³ or optic atrophy² are rare causes of sudden or gradual visual loss. We describe the case of a child with visual loss caused by slow progression of a foveal vascular loop and relative amblyopia.

Report of a Case
A 6-year-old boy had deteriorating vision 1 year after the incidental detection of a retinal arteriovenous malformation in his right eye (Figure 1). At the time of the initial detection, his visual acuity was 20/20 OU. One year later, his visual acuity was 20/60 OD and 20/20 OS. Multiple dilated and tortuous vessels emerged from the right optic disc (Figure 2) with 1 superotemporal loop reaching the fovea. No retinal thickening, exudates, bleeding, or relative afferent pupillary defects were present. Scanning laser ophthalmoscope–fundus perimetry showed an absolute scotoma overlying the foveal vascular loop. Fixation was unstable and 5° inferotemporal to the fovea (Figure 2). Comparison with the fundus photograph taken 1 year earlier showed some advancement of the loop.

View larger version (145K): [in this window] [in a new window] Figure 1. Fundus photograph taken in 1998. The central vascular loop was well separated from the foveola, and visual acuity reached 20/20 OU.

View larger version (92K): [in this window] [in a new window] Figure 2. Fundus photograph taken in November 1999. The loop has reached the foveola. The overlay shows the retinal fixation areas when first seen in our clinic (March 1999; visual acuity of 20/60 OD), after successful occlusion therapy (November 1999; visual acuity of 20/30 OD), and at the final visit after therapy had been discontinued (October 2000; visual acuity 20/400 OD).

The left eye was healthy. There was no strabismus, and stereopsis (Lang test) was normal. Cycloplegic refraction was +2.00 diopters spherical OU. The medical history, systemic history, and examination results were unremarkable. Recent magnetic resonance tomography results did not show any intracranial anomaly of Bonnet-Dechamp-Blanc or Wyburn–Mason syndrome.

Because the location of the loop itself did not account for the total amount of visual acuity loss, we suspected relative amblyopia and recommended occlusion of the left eye for 4 hours per day.

Eight months later, visual acuity had improved to 20/30 OD and scanning laser ophthalmoscope– fundus perimetry showed a definite central shift of the retinal fixation area (Figure 2). Esotropia of +10° without correction and +3° with correction was now present.

Afterward, occlusion therapy was difficult and finally abandoned by the parents. One year later, visual acuity was 20/400 OD. A further progression of the vascular loop and a 13° temporal shift of the fixation area were present (Figure 2). Because of that and the lack of success to maintain useful vision, we stopped any treatment.

Comment
The initial drop in visual acuity may have been due to 2 factors, a slow progression of the loop approaching the fovea and relative amblyopia. The progression of the loop toward the fovea was gradual and totaled 500 µm in 33 months (180 µm/y). Although most cases of arteriovenous malformation are thought to be stable,² anatomical changes of arteriovenous malformations have previously been described⁴ but not linked to visual loss.

On the other hand, relative amblyopia is likely to have been a contributing factor. It is defined as a reversible functional deficit superimposed on a congenital organic abnormality or pathologic changes acquired in early childhood. Our hypothesis was supported by the increase in visual acuity with patching and the shift of fixation. When manifest esotropia was present, strabismic amblyopia may have contributed to the final visual loss.

Not all retinal AV malformations are stationary, and small changes can induce a visual loss that may be amplified by relative amblyopia in patients during their sensitive period of visual development. Unlike this patient, most cases do not progress. A trial of occlusion therapy may be warranted in young children if visual acuity is worse than expected from the location of a central loop.

The author has no relevant financial interest in this article.

AUTHOR INFORMATION

Oliver Ehrt, MD
Munich, Germany

Corresponding author: Oliver Ehrt, MD, Department of Ophthalmology, Ludwig Maximilians University, Mathildenstr 8, D-80336 Munich, Germany (e-mail: oliver.ehrt{at}med.uni-muenchen.de).

REFERENCES
1. Archer DB, Deutman A, Ernest JT, Krill AE. Arteriovenous communications of the retina. Am J Ophthalmol. 1973;75:224-241. WEB OF SCIENCE | PUBMED 2. Baurmann H, Meyer F, Oberhoff P. Komplikationen der Arteriovenösen Anastomosen der Netzhaut. Klin Monatsbl Augenheilkd. 1968;153:562-571. PUBMED 3. Mansour AM, Wells CG, Jampol LM, Kalina RE. Ocular complications of arteriovenous communications of the retina. Arch Ophthalmol. 1989;107:232-236. FREE FULL TEXT 4. Augsburger JJ, Goldberg RE, Shields JA, Mulberger RD, Magargal LE. Changing appearance of retinal arteriovenous malformation. Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1980;215:65-70. FULL TEXT | WEB OF SCIENCE | PUBMED

SECTION EDITOR: W. RICHARD GREEN, MD

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