Conversion of Nonischemic Central Retinal Vein Occlusion to Ischemic Occlusion

Most nonischemic CRVOs present relatively good prognosis in visual acuity and spontaneous resolution is relatively common after a certain period of time, but a small portion convert to ischemic CRVOs. The point of conversion from nonischemia to ischemia ranges from few weeks to several years. But because more than half of these conversions occur within the first four months, it requires careful follow-up during this period. The authors retrospectively reviewed 44 patients(47 eyes)who initially showed definite signs of nonischemic CRVO on fundus examination and nonperfusion area less than 10 disc areas proven by fluorescein angiogra-phy. The conversion rate, point of conversion, incidence of anterior segment neovascularization and neovascular glaucoma, predictive factors related to conversion were identified. The average age of the patients was 46. 1 years and 26 patients(59. 0%) were male. 25 patients(56. 8%)had underlying systemic and ocular disorders such as hypertension, chronic renal failure, diabetes mellitus, primary open-angle glaucoma. Final visual acuity was 0.5 or above in 24 eyes(51. 0%)and 0.1 or below in 14 eyes(29. 8%). 7 eyes(14. 9%)converted to ischemic occlusion. The average age of this group of patients was 40.8 years and 4 eyes had underlying systemic disorders. Initial visual acuity showed wide range from 0.15 to 0.7 but final visual acuity was 0.1 or below in all of the cases. The point of the conversion was less than 4 months(average: 9.3 weeks)in all eyes and 5 eyes(71.4%)developed anterior segment neovascularization. All of the eyes that showed definite evidence of anterior segment neovascularization were treated with panretinal photocoagulation but in 2 eyes(28. 6%), regression of neovascularization did not occur and further developed neovascular glaucoma.

Visual Outcome of Central Retinal Vein Occlusion

This study was performed to investigate the visual prognosis in ischemic and nonischemic central retinal vein occlusion(CRVO), to investigate the difference in clinical course of two types, and to identify prognostic factors for poor visual outcome. Fifty seven patients with CRVO were included. Eyes were classified into ischemic or nonischemic type by indirect ophthalmoscopy and fluorescein angiography. Among 58 eyes, 27 eyes(46.6%) were of the nonischemic CRVO and 31 eyes(53.4%) of the ischemic CRVO. Nonischemic CRVO was more common in patients under 45 years and had more benign clinical course than ischemic CRVO. Factors significantly related to visual outcome were initial visual acuity in ischemic CRVO(P<0.01) and the presence of systemic disease in nonischemic CRVO(P<0.01). Hypertension and diabetes were the most commonly associated systemic diseases. The leading causative factors for poor visual outcome were chronic macular edema and neovascular glaucoma in ishemic CRVO, and chronic macular edema in nonischemic CRVO.