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Fang Zheng, Qinqin Zhang, Andrew R Miller, Joao Rafael Dias, Elie Motulsky, Guanghui Liu, Zhongdi Chu, Chieh-Li Chen, Sophie Kubach, Luis De Sisternes, William J Feuer, Giovanni Gregori, Mary K Durbin, Ruikang K Wang, Philip J Rosenfeld; Comparing Area Measurements of Choroidal Neovascularization Obtained using Different Swept Source OCT Angiographic Scan Patterns in Neovascular Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2017;58(8):50.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the sizes of choroidal neovascularization (CNV) imaged using different scan patterns from the same swept source optical coherence tomography angiography (SS-OCTA) instrument.
Patients diagnosed with neovascular age-related macular degeneration (AMD) were imaged using a 100-kHz SS-OCTA instrument (PLEX Elite 900, Carl Zeiss Meditec, Dublin, CA). The scanning protocols used to image CNV included the 3mm × 3mm and 6mm × 6mm field of view (FOV). The 3mm × 3mm FOV consisted of 300 A-scans per B-scan (repeated four times at each of the 300 B-scan positions), resulting in each A-scan and each B-scan being separated by 10 microns. The 6mm × 6mm FOV consisted of 500 A-scans per B-scan repeated twice at each of the 500 B-scan locations, resulting in a spacing of 12 microns between each adjacent A-scan and B-scan. Neovascular lesions were excluded if they were not fully contained within the 3mm × 3mm FOV. The en face slab used to detect the CNV extended from the outer retina to the choriocapillaris (ORCC slab), and projection artifacts were removed using a proprietary algorithm on each of the scan patterns. A validated automated algorithm was used to measure the area of the CNV.
Thirty-five eyes of 31 patients were enrolled in this comparison study. Seventeen eyes were chosen randomly and have been analyzed thus far. The mean lesion areas were 1.09mm2 (SD=0.74; range: 0.13-2.59) and 1.13 mm2 (SD=0.76; range: 0.17-2.70) for the 3mm x 3mm and 6mm x 6mm FOVs respectively (p=0.34). Differences between area measurements using the two FOVs were not correlated with the lesion size (r=0.15, p=0.56).
The area measurements of CNV were comparable when comparing 3mm x 3mm and 6mm x 6mm SS-OCTA FOVs. Since it might be necessary to increase the SS-OCTA scan area as CNV grows to adequately quantitate the size of the CNV and determine when retreatment might be necessary, it is reassuring to know that different FOVs from the same instrument provide comparable area measurements for the CNV.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
An example of CNV bigger than 2.5mm2. Top: ORCC slab with projection artifacts removed. Bottom: ORCC slab with the outlines of the CNV.
An example of CNV smaller than 0.5mm2. Top: ORCC slab with projection artifacts removed. Bottom: ORCC slab with the outlines of the CNV.
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