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Laser photocoagulation seems to be associated with stable rates of visual acuity up to 2 years after treatment for diabetic retinopathy.
"A substantial percentage of patients with diabetes have diabetic retinopathy, and between 11% and 17% have sight-threatening retinopathy," he said. "We aimed to determine the visual outcomes, the changes in VA over time, and to identify the characteristics of patients with poor visual outcomes following laser photocoagulation for diabetic retinopathy."
Dr. Tham and colleagues conducted a retrospective analysis of 503 consecutive eyes of 356 patients who underwent laser photocoagulation during a 1-year period and followed those patients for 2 years after treatment.
"Overall, 7% of patients had VA worse than 20/200 1 year after laser treatment, while at the 2-year follow-up, 4.3% of patients had VA worse than 20/200," Dr. Tham said. "For all subgroups of patients, there was a decrease in the percentage of patients with VA of 20/200 or worse 2 years after treatment. However, there was a higher percentage of patients with poor VA in the group with combined pathologies (14% and 9% at 1 and 2 years, respectively). About 8% of patients lost more than three lines of Snellen acuity at 1 and 2 years after treatment, but the percentage was higher (10.3%) among those with combined pathologies."
Evaluations at three points
The investigators evaluated the changes in the VA at baseline and at 1 and 2 years after treatment. Dr. Tham provided some examples of the findings.
In the range of 20/20 to 20/40, 84% of patients were in that range at 1 year, and about 15% had a decrease in VA to 20/40 to 20/150. For the patients in the worst VA range of 20/200 or worse, 58% of patients still were in that range at 1 year, whereas 42% had an improvement in VA.
"Generally, the majority of patients tend to remain in the same VA range over the course of the study. That was also true for the patients with clinically significant macular edema," he said. "However, for those with combined pathologies who had a baseline VA of 20/40 to 20/150, only 45% remained within that range, and 38% had improvements in VA at 1 year.
"For those with combined pathologies, less than half of the patients with retinopathy had stable vision 1 and 2 years after treatment; about half had improved VA at the 1-and 2-year time points," Dr. Tham continued. "Of those in the lowest VA range, 83% had improvement in VA into the middle range at the 1-year examination, and 17% improved to the highest range at 1 year."
Primary risk factor
The primary risk factor for poor visual outcomes is a low VA level, i.e., 20/200, at baseline. The finding was similar to that of previously reported studies.
"The most important finding of this study is that we are now able to counsel patients with actual data with regards to visual outcomes post-laser photocoagulation," Dr. Tham concluded. "As patients are generally concerned with their visual outcomes after laser treatment, based on this study we can now tell them with confidence that, in general, the VA at baseline will remain the same after laser treatment. In fact, their VA may even improve for certain conditions."