Several of these eyelets together form the strepsipteran compound eye, which is similar to the 'schizochroal' compound eyes of some trilobites.

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Being part of the outermost (fibrous) layer of the eye the cornea also has a protective role, protecting the eye's delicate components from foreign particles. A third often-quoted explanation is related to the age-dependent decrease of tear secretion, particularly among women after 40 years of age. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals. The function of the iris is to control the size of the pupil through the actions of the sphincter and dilator pupillae muscles. Hence multiple eye types and subtypes developed in parallel (except those of groups, such as the vertebrates, that were only forced into the photopic environment at a late stage).

Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being ciliated (as in the vertebrates) or rhabdomeric. Many small organisms such as rotifers, copepods and flatworms use such organs, but these are too small to produce usable images. The layers 1-6 of retina are supplied by the branches of the central

EYEBALL | English meaning - Cambridge Dictionary EYEBALL | English meaning - Cambridge Dictionary

Results from multivariate logistic regression analysis suggest that current smokers tended to be less sensitive to the exposure to airborne sodium borate dust. The sclera is an opaque, white, outer layer that surrounds the posterior five-sixths of the eyeball.This type of compound eye, for which a minimal size exists below which effective superposition cannot occur, [23] is normally found in nocturnal insects, because it can create images up to 1000 times brighter than equivalent apposition eyes, though at the cost of reduced resolution.