Changes with age in the eye of the dog and hog from birth to senility

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

“…11,22,24,37,60,65,104,105 First, the cornea is generally larger in dogs and rabbits compared to humans, while the dimensions are much smaller in mice and rats. 23,[51][52][53][54][55][56][57][58] As such, the relative amount of cornea and conjunctiva exposed on the ocular surface varies among species, an anatomical fact that has important implications in ocular pharmacology and other research fields; for instance, the surface area ratio of conjunctiva to cornea is two times smaller in rabbits (8.6-8.9) than humans (17.2), a finding that could largely explain species differences in drug penetration into the anterior chamber. 37 Second, the corneal thickness varies among mammals and is generally correlated to the size of the animal.…”

“…membrane is present in nearly all primates (including humans) and selected animals (e.g., sheep, deer, and giraffe), 107 but is absent in dogs and common laboratory species. 60,105,107 The number of layers and overall thickness of the corneal epithelium vary among species: humans (5-7 layers, 44-55 µm), 59,108 dogs (6-9 layers, 52-64 µm), 53,61,105 rabbits (5-7 layers, 45-49 µm), 22,59,108 rats (10-14 layers, 26-33 µm), 63,109 and mice (13 layers, 37-46 µm). 55 The corneal stroma, comprising nearly 90% of the total corneal thickness in most mammals, is primarily composed of collagen fibrils arranged in lamellae.…”

“…This discrepancy can be partly explained by the additional secretory tissue in dogs (third eyelid gland) and the larger corneal surface to lubricate in dogs (1.2-2.1 vs. 1.04-1.3 cm 2 ). 37,52,53 The canine tear film may also be thicker than in humans (15.1 vs. 2.3-11.5 µm), although measurements of tear thickness were only obtained in six dogs 123 and the calculation of tear thickness is reportedly highly variable within and between species. 131 • Spontaneous blink rate: The blink action distributes fresh tears on the ocular surface in a uniform layer, promotes secretion of tears from the accessory tear glands, and pumps excess tears (or instilled drop) into the nasolacrimal drainage system.…”

Histomorphometric evaluation of the Göttingen minipig eye

“…Total retinal thickness in the Göttingen minipig [115.35 µm (±12.08); sexes combined] is roughly 0.5× the thickness of the domestic pig retina [237.6 µm (±4.5)]), 0.6× the thickness of the Beagle retina [190 µm (±14)], 1.1× the thickness of the rabbit retina [102.8 µm (±15.5)], and 0.4× the thickness of the human retina [310.92 µm (±34.14)] . Published retinal morphometric data for the Hanford and Sinclair minipigs are lacking and that for the Yucatan minipig is limited to outer nuclear layer thickness in adult males (mean thickness = 24.12 µm).…”

“…This study provides normative histomorphometric data on Göttingen minipig eyes (cornea, retina, and sclera). Additional research is necessary to establish reference data for Göttingen minipigs outside of the 6‐8 month old age range, to document variations in the measured parameters associated with age‐related changes (such as age‐related retinal atrophy and decreased photoreceptor cell numbers as documented in other laboratory animals and domestic pigs), to perform stereological tissue analyses, and to determine if the histomorphometric data correlate well with measurements obtained from in vivo ocular imaging techniques. Establishing ocular anatomic reference data and understanding the anatomic differences between human and Göttingen minipig, ocular anatomy will aid researchers in study design and data interpretation.…”