Abstract
Purpose :
We compared microvascular changes of diabetic subjects in several modes of a custom adaptive optics scanning laser ophthalmoscope (AOSLO) to cone distribution models. We analyzed vascular features that show increasing stages of response to ischemia: 1) microaneurysms of sufficient size to include a build-up of epithelial cells; 2) capillary bends or loops that indicate vessel tubule formation and initial elongation, and 3) doubled or collateral vessels or complex tangles that indicate extensive elongation and alteration of direction of growth.
Methods :
Cone density and retinal vessels were imaged for 10 diabetic subjects (29-79 yr, 54.5 +/- 12.7 yr. All subjects were consented and tested in a manner approved by the Indiana University Institutional Review Board, which adhered to the Declaration of Helsinki. We performed OCT and OCTA (Heidelberg Spectralis II), then imaged cones and then retinal microcirculation with AOSLO in about 1.5 hr. We simultaneously acquired confocal and multiply scattered light images, using a roughly 100 micron diameter confocal aperture and 3 offset apertures of about 500 microns diameter and offset by 300 microns that differed in direction or wavelength. We used both reflectance mode and motion (variance) mapping for vessels, montaging images for the 6 x 6 deg central retina and temporal retina to 7 deg. To assess the response to retinal ischemia for stages 1-3, we graded all AOSLO imaging modes. Cone density modelling used a 2 parameter exponential model: ln(cone density) = a * microns eccentricity + b and the deviation from our published norms.
Results :
This sample of diabetic subjects had a widely varying response to ischemia. A minimal ischemic response was 1) few microaneurysms, no 2) no capillary bends or 3) doubled vessels. Some eyes with a strong ischemic response had significantly low cone density parameter (b=10.3 or 10.4 vs. 10.8 +/-.222) and 1) many microaneurysms, some overlapping; 2) capillary bends, loops and vessels of varying diameter; and 3) doubled/collateral vessels, some a tangled mass. Vascular lesions differed for imaging modes, e.g. fine gauge tangles better seen in reflectance mode, but some microaneurysms better with motion mapping while others in a reflectance image.
Conclusions :
Diabetic subjects have numerous lesions detectably small with clinical means that can be associated with low cone density decrease, which may imply neural damage.
This is a 2021 ARVO Annual Meeting abstract.