Topography of ganglion cells in the retina of the horse.

Topography of ganglion cells in the retina of the horse (Thoroughbred) was analyzed in the wholemount retina stained with cresyl violet, and a total number of ganglion cells were estimated. Sizes of ganglion cells were also measured and size spectra were analysed. The main results showed that: (1) a common point in 4 wholemount retinae, based on cell densities and retinal locations, was that a retina could be divided into 5 regions, namely visual streak, nasal, temporal, dorsal and ventral region to the visual streak. A maximum cell density of 4,000 cells/mm2 was found in the visual streak. And a total number of ganglion cells was estimated in a range of 398 x 10(3) - 469 x 10(3), with a mean of 441 x 10(3) +/- 31 x 10(3) (n=4). (2) cell sizes were measured as the mean lengths of the major and minor axes of the somas, and were in a range of 5-53.8 microm. The lowest mean diameter was 14.0 microm (+/- 3.7) in the visual streak and the highest was 25.9 microm (+/- 7.6) in the ventral region. Cell size spectra were unimodal and positively skewed. It is expected that these analyses will provide an anatomical and physiological background for further study of the visual system in the horse.