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Show Journal of Neuro- Oplillialniology 18( 4): 233- 236, 1998. © 1998 Lippincotl Williams & Wilkins, Philadelphia Retinal Arteriovenous Malformation With Fluctuating Vision and Ischemic Central Retinal Vein Occlusion and Its Sequelae: 25- Year Follow- Up of a Case Thomas G. Hardy, M. D., and Jusdn O'Day, M. D. A patient with a retinal arteriovenous malformation ( AVM) had experienced episodic visual loss with spontaneous recovery for many years, followed by permanent visual loss secondary to central retinal vein occlusion. She subsequently progressed to development of retinal neovascularization extending onto the posterior vitreous face with recurrent vitreous hemorrhage requiring vitrectomy. A brief review of the literature is presented, and the cause of the fluctuations in vision and central retinal vein occlusion are discussed. Key Words: Central retinal vein occlusion- Retinal arteriovenous malformation- Retinal ischemia- Retinal neovascularization- Visual loss. Abnormal arteriovenous communications of the retina, first described by Magnus in 1874 ( 1), are relatively rare findings and have been referred to by many different terms ( 2); the term retinal arteriovenous malformation ( AVM) is used in this article. Visual loss in association with retinal AVM may result from cystic degeneration of the retina ( 3,4), retinal exudation, retinal ischemia with neovascular glaucoma, traction retinal detachment ( 5), and, rarely, retinal hemorrhage ( 6). Other visual problems may arise from involvement of the optic nerve ( 7), chiasm ( 8), optic tract, and other central neural structures. However, these will not be discussed here. This report is of a patient with intermittent visual obscurations in whom a central retinal vein occlusion later developed with retinal neovascularization and vitreous hemorrhage, a complication that has not previously been reported. CLINICAL RECORD A 20- year- old female nurse in 1970 described a history of intermittent blurred vision in the right eye that was present at rest and occasionally worsened with ex- Manuscript received March 5, 1998; accepted July 13, 1998. From the Department of Neuro- Ophthalmology, Melbourne University, Department of Ophthalmology, Royal Victorian Eye & Ear Hospital, East Melbourne, Victoria, Australia. Address correspondence and reprint requests to Dr. Justin O'Day, 55 Victoria Parade, Fitzroy 3065, Victoria, Australia. ercise. The initial clinical findings were reported by Bill-son et al. ( 9) in the Australian Journal of Ophthalmology. Visual acuity at the time was 6/ 6 uncorrected in both eyes. Visual field examination showed small central and paracentral temporal scotomata on the right. A retinal AVM was found arising from the right optic disc and arching across the inferotemporal papillomacular bundle toward the macula. No other ocular abnormalities were found, and results of a general physical examination were normal. Fluorescein angiogram showed early and rapid flow through the AVM with several dilated capillaries and capillary loss between the loops of the AVM, but no leak was visible. There was no angiographic evidence of orbital or intracranial AVM. The patient sought medical attention in July 1986 with a short history of episodic blurring of central vision in the right eye, fluctuating every 15 minutes from extremely dark to clearing; this resolved during the course of a day. Three days later, she again experienced considerable loss of vision, which subsequently improved over a few hours. This visual disturbance was worse at higher altitude while the patient was on a skiing holiday. Visual acuity was 6/ 9 in the right eye and 6/ 4 in the left. FIG. 1. Fundus photograph showing the retinal arteriovenous malformation before development of central retinal vein occlusion ( central retinal vein occlusion). 233 234 T. G. HARDY AND J. O'DAY FIG. 2. Fundus fluorescein angiogram before central retinal vein occlusion. The left eye remained normal throughout the follow- up. Ophthalmodynamometry revealed systolic pressure of 60 mm Hg and diastolic pressure of 10 mm Hg in the right eye, with left eye pressures of 70 mm Hg systolic and 30 mm Hg diastolic. Funduscopic appearances were unchanged, apart from irregularity and slight dilation of the retinal veins ( Fig. 1). A fluorescein angiogram again showed early filling of the AVM, and the capillary loss noted between the AVM loops had extended to the macula ( Fig. 2). The patient sought attention again in July 1993 with further episodic central visual obscurations and episodes of loss of the lower half of her right visual field. Later, persistent reduction of vision developed with visual acuity of 6/ 24. Intraocular pressure remained normal throughout the entire follow- up. A right central retinal vein occlusion was seen, with venous dilation and tortuosity and nerve fiber layer hemorrhages, perivascular sheathing of the AVM, and ischemic changes to the right papillomacular retina. Over the following week the patient described a further decline in vision, with visual FIG. 3. Fundus photograph showing central retinal vein occlusion. ./ Neum- Ophllmlmol, Vol. IS. No. 4. IWH FIG. 4. Early fundus fluorescein angiogram showing capillary loss. acuity now 6/ 60. A right relative afferent pupil defect was present and persisted throughout. There was loss of color vision and the right paracentral scotoma persisted. A florid right central retinal vein occlusion was found, with a swollen optic disc and retinal pallor above the macula ( Fig. 3). Another fluorescein angiogram showed early rapid filling of the AVM with capillary loss within the loops of the AVM also involving the macula ( Fig. 4) and in the midvenous phase showed marked dye leakage from retinal veins and optic disc ( Fig. 5). No hematologic abnormality was detected. During the following months, there was a progressive decline in which vision was finally restricted to finger counting associated with progression of the central retinal vein occlusion and widespread retinal hemorrhages and ischemia ( Fig. 6). In December 1993 there was substantial resolution of the retinal hemorrhages and sheathing of the AVM ( Fig. 7). A fluorescein angiogram showed a poorly vascularized retina with reduced blood supply to the AVM. In March 1994 peripheral retinal neovascularization was noted ( Fig. 8), and 2 months later a vitreous hemorrhage was detected, requiring a course of panretinal photocoagulation. There was no development of rubeosis FIG. 5. Midvenous fundus fluorescein angiogram showing central retinal vein occlusion and dye leakage from retinal veins and disc. RETINAL ARTERIOVENOUS MALFORMATION 235 FIG. 6. Fundus photograph showing progression of central retinal vein occlusion. iridis. Recurrent vitreous hemorrhages over the next 7 months indicated the need for vitrectomy. The final stable visual acuity in May 1996 was 6/ 18. The AVM had regressed dramatically ( Fig. 9). A fluorescein angiogram revealed persistently delayed arm-retina time and macular hypoperfusion with a small amount of residual dye leak from the limbs of the AVM ( Fig. 10). DISCUSSION Retinal arteriovenous malformation ( AVM) is a well-recognized entity with approximately 90 cases described to date. The common finding is one or more abnormal communications between the arterial and venous retinal circulations, although the choroidal circulation has been involved in a minority of occasions ( 1,4,10,11). Cerebral AVMs may be associated with the retinal lesion ( 12,13) and the AVMs are congenital ( 14,15). Onset of symptoms usually occurs in the second to third decade ( 14- 17) and includes visual impairment of varying degrees depending on the location of the AVM and any complications. Predominantly unilateral, there are rare bilateral occurrences ( 18). The natural history may be nonpro- FIG. 7. Fundus photograph showing resolution of central retinal vein occlusion and sheathing of arteriovenous malformation. FIG. 8. Fundus fluorescein angiogram showing dye leakage from arteriovenous malformation and retinal new vessels. gressive ( 15,16), progressive ( 2,5), or occasionally, self-resolving ( 6). Archer et al. ( 2) classified retinal AVMs into three groups. Group 1 is characterized by an arteriolar or abnormal capillary plexus between the major communicating vessels that are usually localized to one sector of retina and are rarely progressive or decompensated. Group 2 AVMs, as exemplified in this case, have direct arteriovenous communications and appear to exhibit hyperdynamic flow through the AVM with resultant increased risk of exudation, hemorrhage, and thrombosis, although these complications are reportedly uncommon. Group 3 AVMs are most often associated with complications because of their large size and extent, displaying large- bore communicating channels vulnerable to hemodynamic stress and its sequelae. The frequency of association with cerebral AVM increases from group 1 to 3 ( 2,19,20). The transient and fluctuating visual loss described in this case is a feature that has not been emphasized previously in reports of retinal AVM and is possibly secondary to a " steal" phenomenon, wherein the hyperdy- FIG. 9. Fundus photograph after panretinal photocoagulation burns showing regression of arteriovenous malformation. ./ Neum- Ophlhulmol, Vol. 18. No. 4, 1998 236 T. G. HARDY AND J. O'DAY FIG. 10. Fundus fluorescein angiogram showing residual dye leak from arteriovenous malformation and macular hypoperfusion. namic nature of the flow through the AVM caused reduction in general retinal blood flow with episodes of ischemia and visual obscurations. Early in the course, the patient noted some exertional alteration in the visual loss that could support the notion of a steal occurring. The worsening with increased altitude would also support this hypothesis, subsequent to relative hypoxia. Several possible mechanisms to explain the retinal ischemia associated with retinal AVM have been described by Tra-boulsi ( 21) and Tomsak ( 22) and other investigators ( 5,23): ischemia resulting from chronic retinal steal and a critical reduction in retinal blood flow; partial thrombosis of the AVM with reduced blood flow to the retina supplied by the AVM, if indeed the AVM supplied some retinal tissue; or obstructed retinal venous outflow at the optic disc from the enlarged afferent or efferent vessels of the AVM. The second option is least likely in this case, given the good flow through the AVM seen on fluorescein angiogram. It is also possible that the ischemia was subsequent to venous hypertension, resulting from arterialization and obstruction downstream and therefore, local hemodynamic disturbance. The permanent visual loss, however, may also be a result of the mechanisms mentioned earlier but is more likely to be consequent to the central retinal vein occlusion that had obvious implications for the macula but also caused widespread retinal ischemia. The most likely cause of the central retinal vein occlusion is compression at the disc by an enlarged venous limb or reduced blood flow secondary to steal by the AVM, with subsequent relative stasis and predisposition to thrombosis. The development of retinal neovascularization is not a common sequel to central retinal vein occlusion, even when the vein occlusion is ischemic. It is possible that the preexisting retinal ischemia resulting from the AVM contributed to new vessel formation in a manner similar to the iris neovascularization described by Bloom et al. ( 5) and Effron et al. ( 23). The subsequent events of vitreous hemorrhage and vitrectomy have not been previously described in the literature regarding retinal AVMs, although rubeotic glaucoma has been described. This case is interesting in view of the fluctuating and then permanent retinal ischemia secondary to the AVM and the subsequent development of retinal neovascularization. The duration of follow- up is also significant, the longest previously documented follow- up had been 17 years ( 24). REFERENCES 1. Magnus H. Ancurysma arteriovenosum relinale. Virchows Arch Pathol Anat 1874; 60: 38. 2. Archer DB, Deutman A, Ernest JT, Krill ARE. Arteriovenous communications of the retina. Am J Ophthalmol 1973; 75: 224- 41. 3. Peyman GA, Sanders DR, Goldberg MF. Principles and practice of ophthalmology. Part 4, Vol. 2. Philadelphia: WB Saunders, 1980: 1312- 24. 4. Gunn R. Direct arteriovenous communication on the retina. Trans Ophthalmol Soc UK 1884; 4: 156. 5. Bloom PA, Laidlaw A, Easty DL. 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