Quantifying Retinal Layer Thickness in Murine Alzheimer's Models

P301S, P301L mice and age- and strain-matched WT mice were examined by OCT before sacrifice. Briefly, mice were anesthetized via intraperitoneal injection with a combination of ketamine (100 mg/kg) and xylazine (10 mg/kg). Mouse eyes were topically dilated with one drop of tropicamide and phenylephrine. Eyes were imaged using Spectral Domain Ophthalmic Imaging System (Envisu R2200, Bioptigen Inc., NC) as described previously [41 (link)–43 (link)]. Annular scans consisted of 1000 A-scans × 100 B-scans covering a donut-shaped area centered at the optic nerve disc were performed in order to remove variance of optic nerve head measurement. The inner and outer radiuses of the donut-shaped area were 200 and 700 μm from the center of the optic nerve disc, respectively. Then OCT depth thickness report and analysis were generated from Bioptigen’s automated segmentation algorithm developed for the murine eye. The thickness of each retinal layer presented in the report for each eye was an average of 100,000 measurements (A-scans) in the donut-shaped area, which accurately measured retinal thickness and excluded the necessity to register and quantify the same anatomical landmark between different animals. The ganglion cell complex (GCC) includes all three innermost layers: the nerve fiber layer (NFL), the ganglion cell layer (GCL) and the inner plexiform layer (IPL).