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D. M. Marcus, for the Diabetic Retinopathy Clinical Research Network; The Course of Response to Focal/Grid Photocoagulation for Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2078.
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Early DRCR network trials demonstrate that 37% of laser-treated eyes with diabetic macular edema (DME) have OCT central subfield thickening (CST) that has decreased by less than 50%, remaining > 250 microns at 4 months. These eyes with "modest improvement" are often retreated at 4 months. OCT CST and visual acuity (VA) following a single session of focal/grid photocoagulation for DME were assessed over time to determine whether eyes with modest improvement continue to improve if observed rather than being re-treated at 4 months.
Prospective, multi-center, single group focal/grid photocoagulation study of adults with center involved DME (OCT CST ≥250µ). Eyes were treated at baseline and were evaluated for change in VA letter score and OCT CST every 8 weeks until exiting this study or completing the 48 week visit. Beginning at the 16 week visit and continuing every 8 weeks thereafter, eyes were assessed for retreatment and further laser was deferred if the VA letter score improved by ≥5 letters or OCT CST decreased by ≥10% compared with the visit 16 weeks prior. Subjects whose study eye did not improve as described above and received laser re-treatment exited this study.
Between January and June 2007, 26 sites enrolled 128 eyes. Of the 115 eyes that completed the 16-week visit, 53 (46%) improved in OCT CST by ≥10% compared with baseline. Of those, 27 (51%) had a CST ≥250µ at 16 weeks. Of these, 24 had a 24-week visit. Six (25%) of the 24 subjects who completed the 24-week visit improved on OCT from the 16-week visit by ≥10%, 3 with OCT CST <250µ and 3 with OCT CST ≥250µ. One eye improved by a 5-letter VA score and the other 5 changed by less than 5 letters. Compared with the 8-week visit, 10 (42%) of the 24 subjects improved on OCT by ≥10% at 24 weeks.
Based on this small observational study, it appears that four months following focal/grid laser for DME, if there has been modest improvement on OCT, some eyes that remain edematous will continue to improve without additional treatment. Therefore, further investigation on the course of response to focal/grid laser for DME is warranted.
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