Imaging Retinal Microaneurysms in Diabetes using Offset Pinhole Adaptive Optics Scanning Light Ophthalmoscopy: a Quantitative and Qualitative Analysis

Abstract

 

Purpose

 

To investigate the association of retinal microaneurysm (MA) dimension, structural characteristics, and blood flow patterns in diabetes using an offset pinhole adaptive optics scanning light ophthalmoscope (AOSLO)

 

Methods

 

MA imaging was performed on 7 diabetic patients (7 eyes, 3 males, age 50±10years) using an offset pinhole AOSLO with an imaging wavelength centered at 790nm. Image sequences were acquired using 1° or 1.5° field of view at a frame rate of 15Hz. After sinusoidal distortion and eye motion were removed, registered movies and averaged images were obtained for qualitative MA structural characteristic and blood flow pattern assessments. Quantitative measurements of MA total area (TA) and blood filled area (FA) were delineated manually on the averaged images using MATLAB (MathWorks, Natick, MA).

 

Results

 

79 MAs were imaged in 7 eyes. 87% of the MAs showed visible vascular wall structure. Mean±SD (µm2) of MA total area and blood filled area was 2400±2370 and 1500±1700, respectively. The percent of FA/TA was 66±22% (range: 8% - 100%). 4 MA morphologies were observed (focal bulge, 16%; saccular, 57%; fusiform, 19%; irregular, 8%) (Fig. 1). There were significant differences between their mean measurements of TA (p=0.0004), FA (p=0.025), and FA/TA (p=0.038) (ANOVA test). 5 blood flow patterns were recorded (minimum disturbance, 37 %; disturbed laminar flow, 35%; whirlpool, 16%; throbbing, 6%; no flow, 6%) with significant difference between their mean measurements of TA (p<0.0001), FA (p<0.0001), and FA/TA (p=0.04) (ANOVA test). MAs with granular surface and background changes were associated with larger MA TA (p<0.001), larger FA (p<0.001), and smaller FA/TA (p<0.05) (unpaired t test). MAs with lumen clots and reflective wall structure were associated with larger MA TA (p<0.001) and larger FA (p<0.001) (unpaired t test).

 

Conclusions

 

Offset pinhole AOSLO provides noninvasive and direct quantitative assessments of MA structural features and blood flow patterns in patients with diabetic retinopathy. This imaging technique allows for a better understanding of the dynamic interaction between vascular wall and in vivo blood flow.

 

 

Fig 1. Offset pinhole AOSLO imaging of retinal microaneurysms located at 8° superior temporal from the fovea in a 61 yo diabetic female. FB: focal bulge; S: Saccular; F: Fusiform. Scale bar = 25 µm.

 

Keywords: 499 diabetic retinopathy • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 550 imaging/image analysis: clinical