October 18, 2010

Q&A: Concerning Anatomy Of The Eye

Structures in the eye bend the light rays entering the eye so that when they reach the retina they are focused. The cornea and lens both help to do this. The cornea gives the initial bend to the light but the lens is the fine tuner.

This article is for Medical Students & Professionals
This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Anatomy Of The Eye article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
The lens of the eye
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

The lens of the eye

The lens can change shape with the help of the ciliary body which contains fine muscle fibres that pull on it. Depending on the angle of the light coming into it, the lens becomes more or less curved (convex). This alters its strength and allows it to focus the light correctly on to the back of the eye. This is very similar to the action of a lens in a camera which focuses the light on to the film.

Firstly, light passes through the transparent cornea. Most bending of light occurs here. Light then travels through the pupil and hits the lens. The lens also bends light, increasing the amount focused on the highly specialised cells of the retina.

MCQ: clinical scenario

What suspensory ligaments connect the outer edge of the lens of the eye with the ciliary processes?

a) zonnules of Zinn
b) zonnules of Schlemm
c) cruciate ligaments
d) ligaments of Treitz
e) ciliary ligaments

MCQ questions & answers on medicalnotes.info

MCQ: answer

The correct answer is A

MCQ: explanation

Also known as the suspensory ligament, the Zonnules of Zinn comprise a network of collagen fibres which connect the outer edge of the lens with the ciliary processes. In this hammock of fine fibres lies the lens. To the right is the margin of the vitreous humour, to the left is the posterior chamber, which lies between the zonnules and the iris. Below in the ciliary processes lie cells which are excreting aqueous humour, which flows to the pupil.

See also the separate article, Anatomy of the Eye, for more information.

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