Structural Characteristics of Microaneurysms on Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) and Surrounding Neural Retinal Pathology in Diabetes

Abstract

Purpose: To evaluate if diabetic microaneurysm (MA) features on high resolution AOSLO correlate with local retinal pathology on spectral domain optical coherence tomography (SDOCT).

Methods: Macular MAs were assessed on 1x1.2° AOSLO images (2.5µm resolution limit) for dimension, wall reflectivity, lumen clot, and perfusion pattern. Images were montaged with wider field fundus photos to register MA location. Eyes underwent SDOCT (Spectralis: 49 b scans, 20x20° field, 16 ART Mean, high res). Substacks of 5 b scans centered on each MA were graded within a 500µm box centered on each MA for volume, outer layer disruption/inner layer disorganization, cysts, hyperreflective foci, and ring sign. AOSLO and SDOCT image grading was performed independently in a masked fashion.

Results: 71 MAs from 25 eyes (25 subjects: mean±SD age 45±13 years, DM duration 25±9 years, 60% male, 76% type 1 DM) were imaged. DR severity ranged from mild nonproliferative DR (12%) to proliferative DR (36%). In unadjusted analyses, MAs with wall hyperreflectivity were more likely to be large (longest dimension 110±28µm vs 65±26µm, p<0.0001), have a lumen clot (27% vs 81%, p<0.0001), be partially perfused (40% vs 85%, p=0.001), visible on fundus photos (91% vs 58%, p=0.02) and associated with inner retinal layer disorganization (19% vs 2%, p=0.03) or cysts>250µm (19% vs 2%, p=0.03). MAs with central lumen clots were more likely to have a complete ring sign (47% vs 22%, p=0.01) on SDOCT than MAs without. MAs with a complete ring sign were more often associated with retinal disorganization (31% vs 0%, p=0.003). In a multivariable model adjusting for MA size, clot, and perfusion, only wall hyperreflectivity remained significantly associated with retinal disorganization (p=0.02).

Conclusions: High resolution AOSLO imaging demonstrates that hyperreflectivity of diabetic MAs is associated with adjacent inner layer retinal disorganization and increased cyst burden, both of which have been linked to worse visual acuity. AOSLO also allows imaging of MA’s too small to be seen by traditional fundus photography. Further study of MA structure and neural retina correlates may help elucidate interaction of diabetic vascular and neural pathophysiology and enable novel approaches to assess anatomic and functional outcomes in the diabetic eye.

Keywords: 499 diabetic retinopathy • 498 diabetes • 550 imaging/image analysis: clinical