To determine the number of wide-field, monostratified
ganglion cell classes present in the human retina, we analyzed
a large sample of ganglion cells by intracellular staining
in an in vitro, whole-mount preparation of the
retina. Over 1000 cells were labeled by horseradish peroxidase
or Neurobiotin; some 200 cells had wide dendritic trees
narrowly or broadly stratified within either the inner
(ON) or outer (OFF) portion of the inner plexiform layer.
Based on dendritic-field size and the pattern and extent
of dendritic branching, we have distinguished six wide-field
cell groups. The giant very sparse ganglion cells included
both inner and outer stratifying cells and were unique
both for their extremely large dendritic field (mean diameter
= 1077 μm) and extremely sparsely branched dendrites.
Four of the cell groups had similarly large dendritic fields,
ranging in mean diameter from 737 to 791 μm, but differed
in the pattern and extent of dendritic branching, with
the number of dendritic branch points ranging from a mean
of 33 to 129. Of these four groups, the large very sparse
group and the large dense group included both inner and
outer stratifying cells, while the large sparse and large
moderate groups consisted of inner stratifying cells only.
The thorny monostratified ganglion cells were distinct
from the other cells in having medium size dendritic fields
(mean diameter = 517 μm) and moderately branched, inner
stratifying dendritic trees with many thin, spiny, twig-like
branchlets. All six groups had medium-size cell bodies,
with mean soma diameters ranging from 17 to 21 μm.
Though the physiological properties and central projections
of human wide-field, monostratified ganglion cells are
not known, some of the cells resemble macaque ganglion
cells known to project to the lateral geniculate nucleus,
the pretectum, or the superior colliculus.