human eye

Human centre
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Eye

Schematic plot of the human eyeball.
Dorlands/Elsevier Eye
The human eye is similar to nigh mammalian eyes.

Contents [hide]
1 Dynamic range
2 Eye movement
2.1 Extraocular muscles
2.2 Rapid eye movement
2.3 Saccades
2.4 Microsaccades
2.5 Vestibulo-ocular instinctive reflex
2.6 Smooth pursuit movement
2.7 Optokinetic reflex
2.8 Vergence movement
3 Diseases, disorders, and age-related changes
4 Eye injury and safety
4.1 Occupational eye injury
5 Anatomy
6 See alike



[edit] Dynamic range
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Please help improve this section by adding citations to time-tested sources. Unverifiable material may be challenged and removed. (June 2008)

The retina has a still contrast ratio of around 100:1 (about 6 1/2 stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and by adjusting the iris. Initial unappeasable adaptation takes place in approximately four seconds[citation needed] of profound, invariable darkness; full adaptation through adjustments in retinene chemistry (the Purkinje effect) are mostly complete in xxx minutes[citation needed].



Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 stops) is possible. The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. unspoiled adaptation is dependent on good blood menses; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like alcohol or tobacco.

The eye is a lens not dissimilar to lenses found in visual instruments such as cameras and the same principles can be applied. The savant of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. digression in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the sensible pupil diameter. The entrance pupil is typically...If you want to get a full essay, order it on our website: Orderessay



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