The MPDL-treated group showed a trend toward better vision 12 months later, compared with the CGL group, though this did not reach statistical significance. Fewer patients had laser scars after MPDL.

Macular edema is the most frequent cause of blindness in patients who have diabetes for 20 years or longer. In patients with clinically significant macular edema, laser photocoagulation can reduce the incidence of visual loss by about half for at least three years after treatment.

The new study, conducted by Dr. Victor Chong of Oxford Eye Hospital, UK, and colleagues, included 53 patients with Type 2 diabetes and clinically significant macular edema (84 eyes) at centers in Portugal and London. Their ages ranged from 34 to 78 years and the average duration of diabetes was 12.4 years.

Forty eyes received CGL and the other 44 received MPDL; patients with bilateral clinically significant macular edema received CGL in one eye and MPDL in the other. Retreatments were performed as needed at or after 4 months.

Following treatment, no significant differences were seen between the two groups in contrast vision sensitivity or in central macular thickness.

At the end of 12 months, average visual acuity and best corrected visual acuity were not significantly different between the two groups. Laser scars were found in 59% of the eyes in the CGL group, but only 13.9% of the MPDL group.

The clinical significance of the reduction in visible scarring caused by MPDL compared to CGL "is yet to be determined," the researchers cautioned. In theory, less scarring should result in better vision, though a longer follow-up would likely be needed to demonstrate that.

Br J Ophthalmol. Oct. 2009;93:1341-1344.