Central retinal vein occlusion (CRVO) affects one to four percent of Americans older than 40 and very often causes severe vision loss, including "legal blindness" (20/200 vision). While current treatments reduce CRVO symptoms such as macular edema-swelling of the center of the eye's light-sensitive retina-none address the underlying problem, the blocked retinal vein. Ian L. McAllister, MD, Lions Eye Institute, Australia, and his research team took direct aim at the problem, using lasers to create a "bypass" around the constricted retinal vein with the aim of restoring near-normal blood flow to the retina.
In three-quarters of the eyes treated the "bypass" was successful, and patients achieved significant vision gains by the 18 month follow-up. This study was also the first prospective, randomized trial to compare the bypass approach, called laser-induced chorioretinal venous anastomosis (L-CRA), with conventional treatment.
L-CRAs were successfully created in 76.4 percent of the 58 patients in whom the procedure was attempted. Overall, bypass-treated patients achieved significantly better visual acuity and were more likely to gain 20/40 vision (the legal standard for drivers in many countries) than were control group patients. Bypass patients were significantly less likely to have moderate or severe vision loss. While about 18 percent of L-CRA-treated patients developed a significant complication-abnormal blood vessel growth at the surgery site-the researchers report that due to close monitoring and effective management, negative consequences from this and other complications were minimal.
"The risk of complications from L-CRA should be weighed against the substantial vision loss faced by CRVO patients with standard treatments," Dr. McAllister said. "In future studies of L-CRA, optical coherence tomography (not widely available when our study began) would be another useful outcome measure for L-CRA effectiveness," he added.
The research appears in the May issue of Ophthalmology, the journal of the American Academy of Ophthalmology.
- Ian L. McAllister, Mark E. Gillies, Lynne A. Smithies, Elena Rochtchina, Colin A. Harper, Mark D. Daniell, Ian J. Constable, Paul Mitchell. The Central Retinal Vein Bypass Study: A Trial of Laser-induced Chorioretinal Venous Anastomosis for Central Retinal Vein Occlusion. Ophthalmology, 2010; 117 (5): 954 DOI: 10.1016/j.ophtha.2009.10.026
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