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Central Vein Occlusion Study (CVOS)

Purpose | Background | Description | Patient Eligibility | Recruitment Status | Current Status | Results | Publications | Resource Centers | NEI Representative



Central vein occlusion is a common retinal vascular disorder with potentially blinding complications. The two major complications are reduced central vision caused by macular edema and neovascular glaucoma caused by iris neovascularization. Other clinical trials have shown that laser photocoagulation is an effective treatment for complications found in diabetic retinopathy and branch vein occlusion, which have some features in common with CVO: neovascularization and reduced visual acuity caused by macular edema occur in all three disorders. Evidence from small-scale studies suggests that a grid pattern of photocoagulation reduces macular edema in CVO patients, although the associated changes in visual acuity are variable. The CVOS is a detailed investigation of grid pattern photocoagulation in a larger randomized group of patients.


Eligible patients were divided into four groups:

Green argon laser with a slit lamp delivery system was used for all treatments. Photographic documentation of retinal changes was obtained at entry, post-treatment, and at specified followup visits for a period of at least 3 years. The frequency of followup visits varied according to the group to which the CVO patient was assigned. Visual acuity, the primary outcome factor in the group with macular edema, was measured according to a modified Early Treatment Diabetic Retinopathy Study protocol at each visit.

Patient Eligibility

Men and women must have been age 21 or older and willing to return for followup visits for 3 years following assignment into the appropriate group and randomization. Each of the four groups has specific eligibility criteria. Patients with retinal vascular disease other than that specified in the criteria, such as diabetic retinopathy, were ineligible. Patients with macular disease other than that due to CVO were ineligible for that portion of the study.

Patient Recruitment Status

Completed. Recruitment began in August 1988 and ended in July 1992. Followup was completed in February 1994.

Current Status of Study




The Central Vein Occlusion Study Group: Natural history and clinical management of central retinal vein occlusion. Arch Ophthalmol 115: 486-491, 1997.

The Central Vein Occlusion Study Group: Evaluation of grid pattern photocoagulation for macular edema in central vein occlusion. The CVOS Group M Report. Ophthalmol 102: 1425-1433, 1995.

The Central Vein Occlusion Study Group: A randomized clinical trial of early panretinal photocoagulation for ischemic central vein occlusion. The CVOS Group N Report. Ophthalmol 102: 1434-1444, 1995.

Clarkson JG, Central Vein Occlusion Study Group: Central vein occlusion study: Photographic protocol and early natural history. Trans Am Ophthalmol Soc 92: 203-215, 1994.

The Central Vein Occlusion Study Group: Baseline and early natural history report. Arch Ophthalmol 111: 1087-1095, 1993.

Resource Centers

Chairman's Office and Fundus Photograph Reading Center
John G. Clarkson, M.D.
Bascom Palmer Eye Institute
University of Miami School of Medicine
900 Northwest 17th Street
Miami, FL 33101
Telephone: (305) 326-6375

Coordinating Center
Argye Hillis, Ph.D.
Biostatistics Department
Scott and White Hospital
2401 South 31st Street
Temple, TX 76508
Telephone: (817) 724-7748
Fax: (817) 662-3867

NEI Representative

Donald F. Everett, M.A.
National Eye Institute
National Institutes of Health
Executive Plaza South, Suite 350
6120 Executive Boulevard, MSC 7164
Bethesda, MD 20892
Telephone: (301) 496-5983
Fax: (301) 402-0528

Last Updated: 10/21/99

Department of Health and Human Services NIH, the National Institutes of Health