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Jan Philip Kolb, Thomas Klein, Kathrin J. Mohler, Wolfgang Wieser, Lukas Reznicek, Marcus Kernt, Anselm Kampik, Aljoscha S. Neubauer, Robert Huber; Choroidal, retinal and RPE thickness in diabetic retinopathy measured with widefield MHz-OCT over 60° field of view. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):603.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate changes in thickness of the choroid, RPE and remaining retinal layers in patients diagnosed with diabetic retinopathy over a field of view of 60° (~18mm).
15 consecutive patients diagnosed with diabetic retinopathy (aged 57.4±11.1 years, 41 - 81 years, 3 female and 12 male) were imaged with a wide-field MHz-OCT. This is a custom swept-source OCT device based on a Fourier-domain mode-locked laser source with 1050nm central wavelength and a depth scan rate of 1.68MHz, which is about 16 times faster than the latest commercial OCT devices. Therefore, a densely sampled scan with 2088x1024 A-scans over 60° took only 1.82s total acquisition time. In post processing, the retina was divided into 25 sectors: five circles centered at the macula with diameters of 1mm, 3mm, 6mm, 12mm and 18mm. The second and third one were divided into 4 sectors, the outer two into 8 sectors. Right eyes were mirrored such that the optical nerve head was always in the same sector. A trained observer manually determined the thickness of choroid, RPE and remaining retinal layers at 15 points in each sector. Mean and standard deviation were computed for each sector and layer.
In most patients, segmentation of the top two layers was possible in sectors that were not affected by shadowing, which is also known from other widefield devices. Visibility of the choroid sclera junction was strongly affected by retinal thickness, pigmentation, eye-blinks and saccades. Among all 15 patients, the choroid could be segmented in 5, the RPE in 14 and the remaining layers in 14 cases for at least 20 of the 25 sectors (80%). Results for one patient with the sector overlay are shown in Figure 1. Mean thicknesses of the rings for all patients starting from the center are 249, 248, 229, 208, 202 µm for the choroid. 38, 38, 36, 35, 34 µm for the RPE and 291, 346, 314, 261, 252 µm for the remaining layers.
Layer thicknesses of the posterior eye of diabetic patients over a large area could be measured with OCT for the first time. Based on the mean values, we could not identify any characteristics specific for diabetes regarding layer thicknesses distribution.
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