Envisu uhr2200

An ultrahigh resolution 850 nm (bandwidth 160 nm) OCT system with an axial resolution of 1.6 μm in tissue (Envisu UHR2200; Bioptigen, Durham, NC, USA) operating in EDI mode was used to obtain optical sections of the retina. Mice were anesthetized with ketamine (100 mg/kg) and xylazine (6 mg/kg). Eye position was adjusted to place the optic nerve head in the center of the OCT scan. For imaging LA animals, all procedures were done under normal procedure room illumination (500 lux). For long-term (∼5 hours) LA, mice were placed in regular animal housing (50 lux), and kept in the procedure room (500 lux) for short-term (15 minutes and 2 hours) LA. For DA animals, all procedures were performed under dim red light. Optical coherence tomography images were analyzed using ImageJ (NIH) and Diver 2.4 software (Bioptigen). Data are presented as mean ± SD.

Mice were anesthetized with ketamine (100 mg/kg) and xylazine (6 mg/kg). OCT images were captured using either Envisu UHR2200 (Bioptigen, Durham, NC, USA) or Spectralis (Heidelberg Engineering, Franklin, MA, USA). Whereas Envisu system employs a wider bandwidth (160 nm) for OCT beam and provides a higher axial resolution (1.6 μm in tissue), the Spectralis instrument combines simultaneous reflectance fundus imaging with OCT imaging, which allows for precise and repeatable scanning at the same retinal region during follow-up studies. Light-adapted animals were imaged in the procedure room under standard illumination conditions (500lux). Dark-adapted animals were prepared under dim red light and imaged in darkness. For Bioptigen Envisu system with a 50-degree OCT field, mouse eye was positioned with the optic nerve head (ONH) in the center of the OCT scan. Full field volume scans (1.4 mm × 1.4 mm at 1000 A-scan × 100 B-scan × 5) were captured. In addition, two radial scans were acquired at horizontal and vertical position and averaged 40 times. For Heidelberg Spectralis system with a 30-degree OCT field, volume scans of nasal and temporal side of ONH were captured with each B-scan averaged 30 times.

The procedure used for OCT imaging of mouse retina followed a published protocol.^{5 (link),27 (link)} Briefly, after mice were anesthetized with ketamine (100 mg/kg) and xylazine (6 mg/kg), retina OCT images were captured with Envisu UHR2200 (Bioptigen, Durham, NC, USA). The mouse eye was positioned with the ONH in the center of the OCT scan. Full field volume scans (1.4 mm × 1.4 mm at 1000 A-scan × 100 B-scan × 5) and two radial scans (at horizontal and vertical position and averaged 40 times) were captured. Mice retina were first imaged after ∼20 minutes of adaptation to room light (500 lux) in the procedure room under standard illumination conditions, and again in darkness after overnight dark adaptation. Averaged radial scan images were used for retinal thickness measurement. For each eye, measurements were performed on 4 spots (450 μm from center of ONH at both horizontal and vertical directions) by using the vendor-provided Reader program (Bioptigen), and an averaged number was used as the measurement for the eye. Outer retina length was measured from the outer limiting membrane to the RPE-choroid boundary.