TUBB3 and glaucoma: Therefore, to determine the extent of RGC somal loss in D2.C5B6 mice, retinal flat mounts from D2.C5B6 and D2 eyes with no detectable glaucoma (NOE) and severe glaucoma were labeled with TUBB3, and the TUBB3-positive cells in the ganglion cell layer were counted (see Methods).