Discussion by

Discussion by Sharon Fekrat, MD Initial widespread excitement about creating anastomoses has been dampened by the risk of significant complications, the most devastating of which is choroidovitreal neovascularization that, if not treated early, can lead to marked visual loss despite aggressive efforts to contain it. Because of significant potential complications and low success rates and the recent introduction of other novel therapeutic options, retina specialists rarely or no longer perform this procedure. The technique to create reliably a laser anastomosis while minimizing complications has not yet been agreed on. Before attempting this procedure again in a widespread fashion, we need to know more, such as what laser wavelength and power to use and where to place the laser applications relative to a branch vein. A 50-␮m spot and 0.1-second duration generally have been agreed on, as well as treating nasal to the disc. The power to use is usually dictated by the degree of lens opacity and retinal edema. Work in our laboratory has demonstrated that at least 2.5 W of argon green ruptures Bruch’s and at least 3.0 W ruptures a branch vein 100% of the time in pig eyes without lens opacity or retinal edema. The original technique was pioneered by McAllister et al and involved repeated applications of argon laser directly to a vein and underlying Bruch’s membrane, with successful anastomoses in 33%. Similar rates were reported by others. This technique has been modified further by McAllister et al after histologic analysis showed that the vein itself is difficult to rupture with argon laser alone and also absorbs considerable amounts of laser energy, preventing sufficient penetration to rupture underlying Bruch’s membrane.

From the Duke Eye Center, Duke University Medical Center, Durham, North Carolina. Address correspondence to Sharon Fekrat, MD, Duke Eye Center, Duke University Medical Center, Erwin Road, P.O. Box 3802, Durham, NC 27710.

© 2003 by the American Academy of Ophthalmology Published by Elsevier Science Inc.

The current recommended technique is to use 50 ␮m, 0.1 seconds, and powers up to 6 W. The initial argon laser application is adjacent to the chosen vein wall. The second laser spot is placed adjacent to this on the vein wall itself. If no rupture of the vein is seen, a Nd-yttrium–aluminum– garnet laser (YAG) may be used. This new technique has increased success rates according to McAllister et al; however, this requires the use of a YAG laser, which is not readily available to most retina specialists, and using two different lasers for one procedure is cumbersome. McAllister had documented in dog eyes that it appears to be essential to breach both of these anatomic barriers to allow a venous connection. However, Leonard et al report the formation of at least one anastomosis that developed in all 19 eyes, giving a success rate of 100% by rupturing only Bruch’s. The maximum number of attempts in each of these 19 was four. Consequently, if the success rate were calculated based on the number of attempts and the presence of success at each site, the mean visual improvement of five lines in 84% is not likely the result of natural history alone, since the mean duration of central vein occlusion before first treatment attempt was 11 months. Surgical techniques largely have been abandoned. In summary, Dr. Leonard’s proposed technique merits further investigation and may be the answer we have been searching for. Even if our success rates increase, vision does not improve in all eyes and likely depends on patient selection as well as other poorly understood factors. Patient selection is critical to minimize the risk of choroidovitreal neovascularization. Follow-up at 2-week intervals for 8 weeks is mandatory to detect this neovascularization for early and prompt management. References 1. Haupert CL, Grossniklaus HE, Sharara N, Davidson MG, Syed A, Fekrat S: Optimal laser power to rupture Bruch’s membrane and the retinal vein in the pig. Ophth Surg Lasers Imaging 2003;34: (in press).

ISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(02)01996-6

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