Novel Rodent Models for Macular Research

BACKGROUND: Many disabling human retinal disorders involve the central retina, particularly the macula. However, the commonly used rodent models in research, mouse and rat, do not possess a macula. The purpose of this study was to identify small laboratory rodents with a significant central region as potential new models for macular research. METHODOLOGY/PRINCIPAL FINDINGS: Gerbillus perpallidus, Meriones unguiculatus and Phodopus campbelli, laboratory rodents less commonly used in retinal research, were subjected to confocal scanning laser ophthalmoscopy (cSLO), fluorescein and indocyanine green angiography, and spectral-domain optical coherence tomography (SD-OCT) using standard equipment (Heidelberg Engineering HRA1 and Spectralis™) adapted to small rodent eyes. The existence of a visual streak-like pattern was assessed on the basis of vascular topography, retinal thickness, and the topography of retinal ganglion cells and cone photoreceptors. All three species examined showed evidence of a significant horizontal streak-like specialization. cSLO angiography and retinal wholemounts revealed that superficial retinal blood vessels typically ramify and narrow into a sparse capillary net at the border of the respective area located dorsal to the optic nerve. Similar to the macular region, there was an absence of larger blood vessels in the streak region. Furthermore, the thickness of the photoreceptor layer and the population density of neurons in the ganglion cell layer were markedly increased in the visual streak region. CONCLUSIONS/SIGNIFICANCE: The retinal specializations of Gerbillus perpallidus, Meriones unguiculatus and Phodopus campbelli resemble features of the primate macula. Hence, the rodents reported here may serve to study aspects of macular development and diseases like age-related macular degeneration and diabetic macular edema, and the preclinical assessment of therapeutic strategies

Morphologic and fluorangiographic study of the feline retina

The microvasculature of the feline retina was studied using the techniques of histology, vascular corrosion casts and fluorescein angiography. The feline retina is holangiotic. It is irrigated by several large retinal arterioles and venules which are situated in the nerve fibre layer and ganglion cell layer of the retina and usually do not bulge into the vitreous body. The smaller arterioles, capillaries and venules are organized into an inner plexus, located in the ganglion cell layer, and an outer plexus, located between the inner nuclear layer and the outer plexiform layer. At the level of the area centralis retinae there are no large blood vessels but only capillaries, small arterioles and venules. On fluorescein angiography, the fluorescence in the retinal arterioles occurs nearly simultaneously with that in the choriocapillaris. The retinal arterio-venous phase is characterized by a complex filling of the smaller arterioles and capillaries which show the most pronounced contrast at the level of the non-tapetal area. In the early-venous phase, fluorescence starts in the smaller retinal venules which drain the area centralis region, followed by filling of the largest venules, whereby lamination of fluorescence can be observed. During the late-venous phase, these venules are homogeneously and completely filled

Morphologic and clinical study of the retinal circulation in the miniature pig. Part A: Morphology of the retinal microvasculature. Exp. Eye Res., 1992, 54, 965 - 973, 16 figg.

The microvasculature of the retina was studied in 20 miniature pigs by means of vascular corrosion casts and semithin histological sections. These techniques provided information useful for a better understanding of retinal fluoangiography. Various characteristics of the porcine retinal vessels, which are similar in the human retinal vasculature, were demonstrated in this study: the holangiotic retina, the trilaminar organization of the retinal capillaries and the presence of particular avascular zones, radial peridiscal capillaries and initial annular constrictions of certain arteriolar side-branches. The intrinsic retinal vasculature also shows some dissimilarities between both species. The major retinal blood vessels of the pig lie very superficially in the nerve fibre layer, in contrast to their deeper location in man. The streak-shaped macular area of the pig contains no major vessels but, unlike the central fovea in the human eye, it is not completely avascular. Another interesting finding is the presence of a large anterior border venule in the porcine retina

Comparative morphology of the pectinate ligament in the domestic animals

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