Small disparities between imaging devices might not seem important, but when measuring the minutiae of the retinal vasculature, a little difference can be a big issue. Prior research shows that vessel caliber measurements can be used to help evaluate conditions such as diabetic retinopathy, diabetic nephropathy and even hypertension and cardiovascular disease. But, not all imaging techniques are created equal, newly published research shows.

According to a British Journal of Ophthalmology study, the diameter of retinal vessels measured using OCT angiography (OCT-A) were generally wider than those

obtained from an adaptive optics ophthalmoscope. The investigators scanned the eyes of 15 subjects using two different OCT-A protocols (3x3mm2 and 9x9mm2) and two to five different adaptive optics ophthalmoscope scans (1.2x1.2mm2). All scans were then scaled to the same pixel resolution and analyzed by two independent graders.

They found that agreement between the raters was excellent for vessel diameter measurement in both OCT-A protocols and adaptive optics. The measured vessel diameter was widest from the OCT-A 3x3mm2 scans, followed by OCT-A 9x9mm2. It was narrowest when identified from the adaptive optics scans. Measurements obtained from both OCT-A protocols were significantly wider than the adaptive optics scans and, for vessels larger than 45μm, it appeared to be larger in OCT-A 3x3mm2 scans than 9x9mm2 scans, while vessels less than 45μm appeared smaller. 

“Different OCT-A scan protocols may affect the vessel diameter measurements. This needs to be considered when OCT-A measures such as vessel density are calculated,” the study concludes.

Yao X, Ke M, Ho Y, et al. Comparison of retinal vessel diameter measurements from swept-source OCT angiography and adaptive optics ophthalmoscope. Br J Ophthalmol. June 1, 2020. [Epub ahead of print].