Variables Affecting Ocular Vessel Density Measurements

Abstract

Purpose : To examine the effect of co-variables commonly used in ocular structure models on ocular vessel density (VD) measurements provided by OCT angiography (OCTA)

Methods : Healthy subjects with a normal comprehensive ophthalmic examination, axial length (AL) measurements, qualified visual fields (VF; Humphrey Field Analyzer; Zeiss, Dublin, CA), and optic nerve head (ONH) and macula OCT and OCTA scans (Cirrus HD-OCT 200x200 cube scans and 3x3 mm/ 6x6 mm Angioplex; Zeiss) were included. Subjects with comorbidities affecting the systemic or local micro or macro vasculature and subjects taking medications that modify vessel diameter were excluded. Peripapillary, ONH, and macular VD were calculated using the device's native software. Mixed-effects models were used accounting for age, gender, signal strength, AL, and inter- and intra-subject correlation.

Results : 72 eyes (46 subjects) with a mean age of 45.1 (±13.9) years, mean AL of 23.82 (±1.03) mm, and mean signal strength of 8.32 (±1.04) were included in the study for ONH analysis and a subset of 33 eyes were included for macular analysis. The 3x3 and 6x6 ONH inner VD measurements decrease as age advances (-0.1 ±0.02 mm/mm2, p=0.005; -0.07 ±0.02 mm/mm2, p=0.0026, respectively). The central and inner measurements in the 3x3 macular scans decrease with age (-0.14 ±0.03 mm/mm2, p=0.0006; -0.06 ±0.01mm/mm2, p=0.0003, respectively). ONH and macula VD in both scanning sizes were not associated with AL, except for the macula 6x6 outer region (0.41 ±0.05 mm/mm2, p=0.05). Only macular VD measurements were associated with signal strength.

Conclusions : When analyzing ocular VD, the variables of age, AL, and image quality, should be considered.

This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.