Abstract
Purpose :
To characterize the relation between microaneurysms (MAs) identified by fundus fluorescein angiography (FFA) and areas of diabetic macular ischemia (DMI) delineated by optical coherence tomography angiography (OCTA) using a commercially available alignment software.
Methods :
Patients with diabetic retinopathy were recruited from Cairo University clinic. FFA was performed with a TRC 50DX (Topcon, Tokyo, Japan) or Spectralis HRA2 (Heidelberg Engineering, Heidelberg, Germany). OCTA was performed by an Optovue RTvue XR Avanti (Optovue, Fremont, CA) using the 6x6 mm macula scan. All FFA images were automatically cropped and aligned with their respective OCTA image using the i2k Align Retina software (Dual-Align, Clifton Park, NY). All images were de-identified to mask grader. The foveal avascular zone (FAZ) and areas of DMI were manually delineated on OCTA images and MAs marked on the corresponding FFA images then images were overlaid using ImageJ (NIH, Bethesda, MD) and analyzed.
Results :
Nine eyes of 7 patients with DMI were included. The average number of MAs marked in FFA images was 110 ± 29. Only 32.8% of superficial capillary plexus (SCP) was ischemic, yet 61.7% of MAs were associated with such areas, while only 23.4% of the deep capillary plexus (DCP) was ischemic, yet 45.3% of MAs were associated with such areas. As the area of DMI increased so did the total number of MAs associated with both the SCP (R = 0.842, p<0.01) and DCP (R = 0.766, p<0.05) ischemia. About 75% of these MAs bordered ischemic areas (within ±50um); only a minority were localized within ischemic regions. The number of MAs surrounding the FAZ (5.27 ± 3.15 MAs/mm2) was similar to other areas of macular ischemia (5.79 ± 1.04 MAs/mm2 for SCP and 6.53 ± 2.58 MAs/mm2 for DCP, n.s.). As the FAZ increased, so did the number of associated MAs (R = 0.836, p<0.01).
Conclusions :
MAs seen on FFA are strongly associated with the borders of areas of DMI on OCTA including the FAZ. Although more MAs are found in relation to DMI in the SCP, the concentration of MAs associated with DMI in the DCP was greater. Overall, the rate of MA association was twice that expected based on area measurements alone. Few MAs are present inside low-flow regions likely because capillary loss would be associated with regression of MAs.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.