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Blindness in animals can be caused be the result of environmental adaptations over time, or due to various conditions of the eyes. [1] Many blind species have been able to adapt, [2] navigate and survive in their environment by relying on their other senses. Some species are born without eyes such as the kauaŹ»i cave wolf spider, olm and the ...
Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, [3] dilated pupils. Pupillary light reflexes are usually reduced but present; the slow phase mediated by melanopsin in retinal ganglion cells is retained.
Progressive retinal atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. Similar to retinitis pigmentosa in humans, [1] it is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness.
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Retinal dysplasia is an eye disease affecting the retina of animals and, less commonly, humans. It is usually a nonprogressive disease and can be caused by viral infections, drugs, vitamin A deficiency, or genetic defects. Retinal dysplasia is characterized by folds or rosettes (round clumps) of the retinal tissue.
There are many diseases known to cause ocular or visual changes. Diabetes , for example, is the leading cause of new cases of blindness in those aged 20–74, with ocular manifestations such as diabetic retinopathy and macular edema affecting up to 80% of those who have had the disease for 15 years or more.
The light available in an animal's habitat is a significant determiner of a mammal's color vision. Marine, nocturnal or burrowing mammals, which experience less light, have less evolutionary pressure to preserve dichromacy, so often evolve monochromacy. [citation needed]
The long-term failure of this strategy has been due to natural selective pressures on both the rabbit and virus populations, which resulted in the emergence of myxomatosis-resistant animals and attenuated virus variants. The process is regarded as a classical example of host–pathogen coevolution following cross-species transmission of a pathogen.