When treating diabetic macular edema, focal/grid photocoagulation more effective than intravitreal triamcinolone, results show

August 1, 2009

Intravitreal triamcinolone (IVTA) for treating diabetic macular edema (DME) does not seem to be beneficial over the long term compared with focal/grid photocoagulation, and treatment with IVTA results in a higher chance of developing a cataract compared with treatment with the laser, according to a 3-year comparison study. Focal/grid photocoagulation, therefore, remains the most effective treatment for DME, according to one ophthalmologist.

Key Points

Fort Lauderdale, FL-A study that compared application of focal/grid photocoagulation with two doses of intravitreal triamcinolone (IVTA) to treat diabetic macular edema (DME) found that after 3 years, no real benefit seemed to exist over the long term of treatment with IVTA compared with focal/grid photocoagulation in a subset of patients who completed the 3-year study.

The results of the study were published recently in Archives of Ophthalmology (2009;127:245–251). Dr. Ip

This DRCR.net/ study was a multicenter trial conducted at 88 sites nationally. A total of 693 subjects (840 eyes) participated. The inclusion criteria required a visual acuity (VA) between 20/40 and 20/320 as well as central subfield thickness of 250 μm or greater. Examinations were performed every 4 months for 3 years. The primary outcome was the mean change in VA from baseline to the 2-year time point.

The eyes were randomly assigned to receive one of three treatments: 330 eyes to laser photocoagulation, 256 eyes to 1-mg doses of IVTA, and 254 eyes to 4-mg doses of IVTA, Dr. Ip said. The mean change in VA at 2 years was +1 letter in the patients treated with laser, –2 letters in the 1-mg IVTA group, and –3 letters in the 4-mg IVTA group.

"Three pair-wise comparisons were done, and with respect to the laser versus the 1-mg group, the results significantly favored the laser group. In the comparison of the laser versus the 4-mg group, the results significantly favored the laser group, and in the comparison between the two doses, there was no difference in the VA," Dr. Ip said.

During the third year of the study, few patients required re-treatments; specifically, 75% of the patients who received laser treatment did not require a re-treatment. Fifty-seven of the patients who were treated with the 1-mg IVTA dose and 46% of the patients treated with the 4-mg IVTA dose did not have a re-treatment.

When the investigators evaluated nonrandomized treatments for DME during the 3 years of the study, more patients in the IVTA groups received alternate laser treatment compared with patients randomly assigned to receive laser treatment who received IVTA. Six percent of patients who were randomly assigned to laser treatment received IVTA. In comparison, 23% and 20% of patients treated with 1-mg and 4-mg doses of IVTA, respectively, received laser treatment.

VA changes

The VA results in the study initially favored treatment with the 4-mg dose of IVTA at the 4-month evaluation, he said.

"However, at 12 months, there was no difference among the three treatment groups," Dr. Ip said. "Beginning at 16 months, laser was superior to both doses of IVTA and remained so until the end of the study at 3 years."

The mean changes in VA from baseline to 3 years showed that in the laser group, VA improved by five letters, and in the IVTA groups, no increase in VA occurred. The investigators found a change in VA from 2 to 3 years only in patients whose VA exceeded 20/32.

"The mean change in VA was –2 letters in the laser group, 0 in the 1-mg group, and –4 letters in the 4-mg group," he said.

In the subset of patients whose VA was worse than 20/32 at 2 years, these patients could have had the opportunity for improvement from year two to year three. Dr. Ip said that the mean changes in the VA results in the three treatment groups, however, were very similar, that is, +2 letters in the laser group, +3 in the 1-mg group, and +4 in the 4-mg group.