8/17/2019 Iris and Pupil

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IRIS AND PUPIL

1. Iris is muscle that contracts and dilates to determine the pupil size .

Iris is brightly colored, and this is the “color” of the eye. The pupil is the

opening where the light enters.

LENS

2. Eye lens is located just ehind the iris! The eye lens is made o"

transparent #ers encased in a clear memrane! The lens is suspended

by a suspensory ligament, which attaches to muscle known as ciliary muscle.

 The eye lens is quite e!ible unlike a lens made out of glass. The ciliary

muscle can actually change the shape o" the ac$ o" the lens y

%e&ing' and this is how the lens is used to "ocus etween near and

"ar ojects! In addition, the inde! of refraction of the lens is di"erent from

the middle of the lens to the edge of the lens.

A(()*)DA+I)N

#. The process in which the eye "ocuses is called accommodation. The

muscle contracts, the shape of the lens deforms. The back of the lens bulges

out to increase the power of the lens $decreasing the focal length% so that the

eye can focus on a near ob&ect. 'hen the ciliary muscle rela!es, the ligament

tightens up, decreasing the cur(ature of the back of the lens.

A,UE)US -U*)R AND .I+RE)US -U*)R

/!  The ca(ities in the eye are not empty. They are instead )lled with transparent

gelatinous liquid. The space etween the cornea and the eye lens is

#lled with the a0ueous humor, and the space etween the eye lens

and the ac$ o" the eye is #lled with 1itreous humor . +hey pro1idenutrients to the cornea and the lens* since these elements must be

clear, they do not ha(e any blood (essels which is the normal mean of

transporting nutrients and wastes. +he 2%oaters3 we o"ten see are the

dead red lood cells %oating inside the 1itreous humor! In addition4

the pressure o" the humors pro1ide to maintain the round shape o"

the eye!

RE+INA

+. +he retina is the photosensiti1e detector o" the eye. It consists of two

types of receptors -ods, which is sensiti(e to low light le(el, and conses,

which is sensiti(e to high light le(el and also responsible for color (ision . little depression "ound at the center o" the retina is called a "o1ea4

where it contains a greater concentration o" cones! This is where the

part o" the 1isual #eld which is the most sharpest! The signals from the

receptors are carried out by ner(e network which lea(es the eye through the

optic ner(e to the brain.