Researchers recently reported a higher detection rate of proliferative diabetic retinopathy (PDR) with widefield OCT angiography (OCT-A) when compared with clinical examination.1 While this suggests that widefield OCT-A could be used noninvasively for the early detection and characterization of neovascularization, the question then becomes which scan protocol is the best.1 Looking to answer this, one team found that angio 12x12mm images focusing on the fovea and the optic disc may achieve the best balance between speed and efficacy in detecting DR lesions.2
The first of two studies on the subject included 79 eyes of 46 patients—57 eyes had PDR and 22 had severe non-proliferative DR (NPDR). A pair of graders identified neovascularization on widefield OCT-A imaging using 12x12mm montage scans and compared their findings with clinical examination outcomes.1
The investigators detected neovascularization at the disc in the form of preretinal hyperreflective material on OCT-A B-scans in 39 eyes with evident flow signals in 79.5% compared with 51.3% when detected clinically. When they classified disc neovascularization on OCT-A into four subtypes, they found that subtypes one and two could not be seen on clinical examination alone.1
Beyond the disc, the team noted that OCT-A detected neovascularization in 81.0% of cases compared with 55.7% detected clinically. They added that widefield OCT-A resulted in a higher percentage of PDR grading (88.6%) than on clinical examination (72.2%). Ultra-widefield fluorescein angiography confirmed the OCT-A diagnoses in the majority of cases.1
Building on these results, another observational study imaged 176 eyes of 119 PDR, NPDR or non-DR patients with widefield swept-source OCT-A using the following scan protocols: angio 3x3mm centered on the fovea, angio 6x6mm centered on the fovea and the optic disc, montage 15x9mm and angio 12x12mm centered on the fovea and the optic disc. Two graders independently evaluated and compared the images for DR lesions.2
The team discovered that angio 6x6mm images centered on the fovea detected neovascularization at about half the rate of montage 15x9mm images. They noted that angio 6x6mm images centered on both the fovea and the optic disc increased this rate to about two thirds. They observed comparable detection rates between angio 12x12mm images and montage 15x9mm images for all DR lesions. In terms of microaneurysms, the investigators found that angio 6x6mm images performed better than montage 15x9mm images.2
1. Khalid H, Schwartz R, Nicholson L, et al. Widefield optical coherence tomography angiography for early detection and objective evaluation of proliferative diabetic retinopathy. Br J Ophthalmol. March 19, 2020. [Epub ahead of print].
2. Zhu Y, Cui Y, Wang JC, et al. Different scan protocols affect the detection rates of diabetic retinopathy lesions by wide-field swept-source optical coherence tomography angiography. Am J Ophthalmol. March 20, 2020. [Epub ahead of print].