Quantification of grain boundaries in flat-mounted retinae.

From the row tracing of eight retinae, we show the percentage of retinal area analyzed, the number of Y-Junctions identified, and the percentage of Y-Junctions in grain boundaries (see Detection of grain boundaries in flat-mounted, row-traced retinae). Here we assume that the rotation of row orientation about a Y-Junction must be greater than twelve degrees for that Y-Junction to be in a grain boundary, but we systematically scan that (arbitrary) threshold in S2 Table.