ACCOMMODATION (LENS)
Illustration of both relaxed and accommodated orientations of the lens
of the eye. Source: Dortonne I. Biomechanical response of the in situ
primate lens. THURJ 2011 (Biological Science, Public Health and
Medicine), 2:1.
Accommodation is the means by which the eye makes adjustments for seeing objects at different distances. Accommodation primarily is accomplished by the action of ciliary muscle changing the convexity of the eye's lens and adjusting its focusing power.
When viewing an object at a distance, the ciliary muscle relaxes. This causes the Zonules of Zinn and other suspensory ligaments to pull on the lens, which makes it flatter and thinner. When a near object is viewed, the ciliary muscle contracts. This causes the Zonules of Zinn to become slack, which enables the lens to return to a thicker and more convex orientation.
For this reason, reading or using the computer for prolonged periods, or engaging in other types of close work, without frequent rest periods can result in eye fatigue. This is because prolonged near vision requires that the ciliary muscle remains contracted, resulting in exhaustion of the muscle fibers.
Additional information about Accommodation
Accommodation of the Eye from Thinkquest.org
Eye Pain Following Pupillary Dilation from glaucoma-eye-info.com
Related Topics
Diplopia
Hyperopia
Myopia
Ocular Convergence
Presbyopia
Return from Accommodation to Medical Terms Aa-Az