By David Douglas
NEW YORK (Reuters Health) Oct 01 - In patients with diabetic macular edema, laser treatment at the start of intravitreal ranibizumab therapy shows no benefit, according to a new paper.
"Focal/grid laser treatment at initiation of intravitreal ranibizumab is no better, and possibly worse, than deferral of laser treatment for 24 weeks or more in eyes with diabetic macular edema involving the fovea with vision impairment," coauthor Adam Glassman of the Jaeb Center for Health Research, Tampa, Florida told Reuters Health by email.
Glassman's team had earlier showed that intravitreal ranibizumab every four weeks with prompt or deferred laser treatment was more effective through at least two years compared with prompt laser treatment alone.
Now, in a September 20th online paper in Ophthalmology, they update the data at three years, but only for eyes originally randomized to ranibizumab plus prompt or deferred laser treatment.
All "prompt" patients received laser treatment but 54% of the deferred group did not receive laser treatment during the trial. All told, they compared 144 patients with prompt laser treatment and 147 with deferred laser treatment.
The approximate Snellen equivalent visual acuity ranged from 20/32 to 20/320.
The estimated mean change in visual acuity letter score from baseline through the three-year visit was 2.9 letters more in the deferred than in the prompt laser treatment group (9.7 versus 6.8).
In addition, say the investigators, "These mean changes were associated with a greater chance of at least moderate improvement and a smaller chance of substantial loss in visual acuity from baseline in eyes assigned to ranibizumab plus deferred laser treatment compared with ranibizumab plus prompt laser treatment."
The median number of injections was 12 in the prompt group and 15 in the deferral group. The investigators say this may account for some of the differences in visual acuity.
It is possible, they add, that "the investigator was biased to believe that if laser treatment had been administered, then perhaps an injection could be withheld at visits that allowed discretion."
"The potentially destructive effects of the laser treatment also may be related to some of the visual acuity differences between groups," they said.
They also point out that the results are based on outcomes of a group, and "individual patients may benefit from other strategies based on individual decisions by the patient and physician."
Follow-up will continue through five years.
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