Spectralis sd oct

Spectral-domain optical coherence tomography (SD-OCT) analysis was performed 2 months following blast TBI or sham procedure using a Spectralis SD-OCT (Heidelberg Engineering, Vista, CA, USA) imaging system coupled with a 25 D lens for mouse ocular imaging (Heidelberg Engineering). Anesthetized mice were placed on a temperature-controlled platform and pupils were dilated using a 1% tropicamide solution. The cornea was moisturized with a saline solution applied every 20 to 30 seconds during the procedure. Volume scans (49-line dense array) positioned directly over the optic nerve head were performed to quantify the RGC complex (inner plexiform layer + ganglion cell layer + retinal nerve fiber layer) thickness. Scans were analyzed by an individual masked to the treatment of the mouse in the superior and inferior central retina, approximately 150 μm from the peripapillary region. All scans were analyzed by excluding blood vessels from the thickness calculation. Baseline measurements were obtained 1 week prior to blast exposure, with follow-up analysis occurring 2 months post blast exposure.

Subjects received SD-OCT of both eyes using a Spectralis SD-OCT (Heidelberg Engineering, Vista, CA, USA) imaging system (Heidelberg Engineering). Rats were anesthetized (as described above), pupils were dilated using a 1% tropicamide solution, and the cornea was moisturized with a saline solution. Volume scans (49-line dense array, 15 A-scans per B-scan, 20° scan angle, 20° × 25° scan area) positioned directly over the optic nerve head were taken for each eye. The retinal ganglion cell complex (RGCC) thickness + the retinal nerve fiber layer (RNFL) was quantified as the sum of the thickness of the retinal nerve fiber, ganglion cell, and inner plexiform layers. Using unlabeled data, two B-scans per eye were analyzed by two experimenters by measuring the overall thickness at five equidistant points along the scan and excluding blood vessels from the calculation.

Each subject was required to have at least one good-quality Spectralis SD-OCT (Heidelberg Engineering Inc., Heidelberg, Germany) circular scan, SD-OCT ONH cube scan, SD-OCT ONH radial scan, and SD-OCT macular cube scan acquired on the same day. Spectralis OCT uses a dual-beam SD OCT, a confocal laser-scanning ophthalmoscope with a wavelength of 870 nm, and an infrared reference image to obtain images of ocular microstructures. The instrument has an acquisition rate of 40,000 A-scans per second. Spectralis OCT incorporates a real-time eye-tracking system that couples confocal laser-scanning ophthalmoscope and SD OCT scanners to adjust for eye movements and to ensure that the same location of the retina is scanned over time. The image acquisition protocols included (1) high-resolution RNFL circle scan, which consists of 1536 A-scan points from a 3.45-mm circle centered on the optic disc, (2) high-resolution cube scan centered on the optic disc (73 B-scans with 768 A-scans each), (3) enhanced depth imaging (EDI) scan centered on the optic disc (48 B-scans with 1024 A-scans each), and (4) high-resolution cubic scan centered on the fovea (73 B-scans with 768 A-scans each). Quality assessment of OCT scans was evaluated by Imaging Data Evaluation and Assessment (IDEA) Center experienced examiners masked to the subject's results of the other tests.

SD-OCT was performed using Cirrus HD-OCT (Carl Zeiss Meditec AG, Jena, Germany) or Spectralis SD-OCT (Heidelberg Engineering GmbH, Heidelberg, Germany) pre-operatively and post-operative on day 1, week 1, months 1, 3, 6, 12 and 24. ETDRS BCVA was measured on the respective follow-up dates and converted to the logarithm of the minimum angle of resolution (logMAR) for statistical analysis. Outcomes included anatomical changes based on CMT and functional changes based on BCVA. Proportional early CMT and BCVA changes form the pre-operative baseline values were also evaluated as a percentage of the final respective values at 24 months follow-up and as a percentage of the healthy fellow eye CMT and BCVA.