A Quantitative Study of Ganglion Cells in the Goat Retina

Abstract

As in a number of mammals, the most prominent feature of the ganglion-cell layer in the retina of the murciano-granadina goat is an increase in the density of ganglion cells in the central area, as well as a concentration along a ridge extending horizontally across the retina, below the optic disc, and in the upper temporal retina. Thus, there is an area of maximum density and two streaks that are known as the 'horizontal' and 'vertical' streak. The isodensity lines of ganglion-cell distribution is toughly concentric, with their values varying from 304 cells/mm2 in the periphery to 3592 cells/mm2 in the central area, with the cells densely packed. There were some individual differences amongst the animal studied, although all of them were purebred animals.

Unusual topographic specializations of retinal ganglion cell density and spatial resolution in a cliff‐dwelling artiodactyl, the Nubian ibex (Capra nubiana)

“…Our findings indicate that the Nubian ibex retina shows general topographic retinal features similar to the findings reported for the goat; however, some notable quantitative differences are found between these closely related species. First, our estimate of a peak ganglion cell density of ~10,000 cells/mm 2 in the temporal area of the Nubian ibex contrasts with the peak ganglion cell density estimates of 3,600 and 14,000 cells/mm 2 reported by two studies on the goat (Gonzalez‐Soriano et al, ; Hughes & Whitteridge, ). Given methodological differences, it is difficult to ascertain whether these contrasting estimates reflect differences in the cytological criteria used to identify retinal ganglion cells, or whether they reflect differences between species or natural biological variation between individuals.…”

“…Our findings demonstrate that the retina of the Nubian ibex contains typical topographic specializations of high ganglion cell density (i.e., a temporal area, a horizontal streak, and a dorsotemporal extension) found in other artiodactyls examined to date (Coimbra et al, ; Coimbra et al, ; Gonzalez‐Soriano, Mayayo‐Vicente, Martinez‐Sainz, Contreras‐Rodriguez, & Rodriguez‐Veiga, ; Hughes & Whitteridge, ; Shinozaki et al, ). Despite a clear need for detailed topographic studies of the retina of other artiodactyls, the consistent presence of these topographic retinal traits suggests that they may represent an artiodactyl retinal blueprint.…”

“…Our mapping of ganglion cell density indicates that the horizontal visual streak of the Nubian ibex runs through the optic disc, which is consistent with the findings reported for the goat by Hughes and Whitteridge (). In contrast, Gonzalez‐Soriano et al () reported a horizontal streak slightly below the optic disc of the goat, but as discussed, it is difficult to make definite conclusions about these differences because of variations in sampling protocols. Interestingly, in other artiodactyls, including the giraffe and the sheep, the horizontal streak is located above the optic disc (Coimbra et al, ; Shinozaki et al, ).…”

“…Moreover, as with other artiodactyls, enhanced visual resolution across the horizon may also be maximized by the horizontally elongated pupil of the Nubian ibex (see Figure ), which probably facilitates the distribution of light onto the horizontal visual streak, creating sharp panoramic images on the retina (Banks, Sprague, Schmoll, Parnell, & Love, ). The relatively loose organization of the horizontal streak of the Nubian ibex contrasts with the well‐developed horizontal visual streaks in the giraffe, sheep, and goat (Coimbra et al, ; Gonzalez‐Soriano et al, ; Hughes & Whitteridge, ; Shinozaki et al, ). These differences may be explained due to lower predation risk in mountainous habitats compared to open savannahs (Hochman & Kotler, ; Iribarren & Kotler, ).…”

Ophthalmic examination findings in adult pygmy goats (Capra hicus)

“…In the field of veterinary ophthalmology, caprine research has been sporadic and is often related to comparative or educational research for human ophthalmology 1–21 . Documentation of ophthalmic examination findings in various species, including normal intraocular pressure estimates and measurements of tear production, helps to establish references for clinical cases as well as investigative research.…”