The effects of macular ischemia to the response to laser therapy for diabetic macular edema.

Abstract

Purpose: To investigate the effect of diabetic macular ischemia (DMI) on the efficacy of macular laser therapy.

Methods: Consecutive patients who underwent fluorescein angiography, optical coherence tomography, and laser therapy for diabetic macular edema over a 6-month period were included. Parameters quantified included the pre-laser foveal avascular zone (FAZ) area, and the pre- and post- laser central (CMT) and total macular thickness (TMT) measurements. Patients were divided into 2 groups; (1) responders (i.e. thinning of the macular post-laser therapy), and (2) non-responders. Thinning of the macular was defined as a reduction of > 20mm in OCT-derived measurements.

Results: 44 eyes from 44 patients were included. The mean reduction of CMT in the “responders” was 99.7±56.9mm, and the mean increase of CMT in the “non-responders” 65.1±80.7mm (p=0.0001). The mean pre-laser FAZ area of “non-responders” (0.38±0.23mm2) was significantly larger than “responders” (0.29±0.19mm2) (p=0.048). No association between FAZ size and TMT measurements were observed.

Conclusions: We observed that eyes with a large FAZ area, corresponding to early treatment diabetic retinopathy study (ETDRS) grades of moderate to severe diabetic macular ischemia, did not respond to macular laser therapy for diabetic macular edema, irrespectively of pre-treatment retinal thickness measurements. FAZ size may be a useful parameter for assessing the suitability of these patients for alternative treatments for macular oedema.

Keywords: 499 diabetic retinopathy • 505 edema • 578 laser