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34 EW GLAUCOMA February 2011 April 2012 SLT rising to the pseudophakic occasion by Maxine Lipner Senior EyeWorld Contributing Editor more appropriate to give them more time to show the full response to SLT up to 3 months," Dr. Shazly said. He acknowledged that in more advanced cases, practitioners may not have the luxury to wait to see a full response to SLT. Source: Lifesize/Thomas Northcut/Getty Images How use of the technology fares after cataract surgery P seudophakic glaucoma and ocular hypertension patients who underwent selective laser trabeculo- plasty (SLT) experienced treatment delays when compared to their phakic counterparts, according to Tarek A. Shazly, M.D. Results e- published in Clinical Ophthalmology in 2011 indicated that while long- term results were equivalent, IOP reduction at the 2-week mark was 7.6% greater in phakic patients. "The point of the study was to evaluate and to determine if pseudophakia affects the outcome of SLT because there's a common concept that SLT doesn't work in pseudophakic patients as well as phakic patients," said Dr. Shazly, fellow at the time of study publica- tion, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. Investigators wanted to eval- uate whether this was true or not. Included in the study were 94 consecutive eyes of 75 ocular hyper- tension and primary open-angle glaucoma patients who received SLT as a primary treatment. Patients' IOP was checked at 3, 6, 12, 18, and 30 months. Delayed reaction While pseudophakic status did not affect long-term results, early results were not as strong in the pseudophakic group. At the 2-week post-op mark, IOP reduction for those in the pseudophakic group was just 19.8% compared with 29.8% for phakic patients. However, by the 3-month mark this had climbed to a 26.5% reduction in the pseudophakic group versus a 29.8% reduction in the phakic group. "We found no statistically significant dif- ference between the amplitude of pressure reduction following SLT at the different time points that we checked, starting from 2 weeks until the end of the 30 months, between the pseudophakic and the phakic patients, apart from the 2-week pe- riod where the pseudophakic pa- tients showed a significantly lower percentage of IOP reduction," Dr. Shazly said. "Starting from 3 months until 30 months, the amplitude of pressure reduction of SLT success was equivalent between the two groups." Investigators theorized that the delay in pressure reduction may re- sult from use of a common pressure reduction pathway. "The hypothesis that we have is that SLT and cataract surgery share some common steps in the pressure reduction pathway— probably interleukins and prostaglandin release," Dr. Shazly said. "So the pathway is already being utilized by the time that SLT is done, and that may make it less re- sponsive to the procedure, at least initially." One point of investigators' on- going research is to see if the pres- sure reduction effect of cataract surgery interacts with pressure re- duction from SLT. "Prior studies showed some common mechanism between first response in the trabec- ular meshwork in response to ultrasound injury, laser, and prostaglandin analogues," Dr. Shazly said. He sees the study as having im- portant clinical implications for practitioners who use SLT for this pseudophakic population. "Some glaucoma specialists and general ophthalmologists may decide a little earlier on, like at the 2-week period, if SLT is successful or not," Dr. Shazly said. "Obviously if we used this kind of judgment in pseudopha- kic patients we may prematurely put them on drops, repeat the laser, or do glaucoma surgery." This, however, may short-change some pseudophakic patients. "Based on the results of this study it may be Clinical perspective Barbara A. Smit, M.D., consultant, Spokane Eye Clinic, Wash., and clin- ical instructor, University of Wash- ington, Spokane, sees the results as mirroring her clinical experience. "Early on in my use of SLT, I checked the patients' pressure every week for a while to try to figure out at what point I could determine whether or not they had a useful effect from the laser," she said. "At that time, I discovered that it wasn't until about 6 weeks post-operatively that it became clear whether or not there was a significant effect on IOP," she said. "So it became my practice at that time to check pa- tients at 6 weeks post-laser to decide whether or not further therapy was necessary based on the response to the laser treatment." While Dr. Smit did not at the time differentiate between the pa- tients who were pseudophakic and those who were phakic, she thinks that there's a possibility that lens status played a role. "It may have been that some of the patients who had a more delayed reaction, where the IOP didn't stabilize until about 6 weeks, were pseudophakes and that was why—but I didn't look at the numbers to be able to determine that," she said. As a rule, she finds the SLT procedure easier to perform in this pseudophakic population. "Once you remove the lens of the eye, you open up space in the anterior cham- ber," Dr. Smit said. "So in patients who have a somewhat narrow or crowded angle, access to the angle is better after lens removal, and there- fore it's easier to apply the laser." Dr. Smit sees the SLT procedure as particularly beneficial in virgin glaucoma eyes. "It's my impression that patients who have not been treated previously with glaucoma medications oftentimes get a good result," she said. "The other popula- tion that I find I get particularly good results in is patients who have elevated pressures due to steroids."