The Function of This Recess Is to -P-Yvl-E-Ct V-Ta- - Lxje

a. Each eye lies in a bony recess of the skull. Palpate the ridges of the cranium which form the orbit.

The function of this recess is to -P-Yvl-e-ct v-tA-,,- @Lxje-

3,. BEEF EYE DISSECTION Procedure

a. Examine the extrinsic eye muscles and the optic nerve (these

were described in.preceding sections).

b. Note the shape of the pupil, it is -(describe si Identify the cornea.

c. Holding the eyeball, make an incision into the ceat with a sharp scalper about one-quarter of an in-ch posterior to the cornea. In-sert the scissors into the incision and carefully cut all the way around $'.he cornea, taking care no-I". to squeeze the fluid out of the eye.

Why do you suppose it is so difficult to penetrate the sclera?- -T@a_ -5,C&PVL k

What is the fluid which escaped'from the eye while you were cutti'ng? A7 Q u t-bLL rilua@) A -

Describe the color and consistency of this fluid

d. Ge.ntly 1-ift,the front portion of' the eye and place it on the tray with the inner surface upward. The LENS usually rema-ins attached to the VITREOUS BODY.

Describe the color and consistency of the vitreous body..

e. Looking at the inner surface of the anterior portion of the eye, identify the thickened, black circular CILIARY BODY.

khat function does the black pigment perform?

e-Y z

f. Examine the iris carefully (use a dissecting microscope). Can you distinguish circular and radial-nuscle fibers?

g. With a dissecting needle separate the LENS from the vitreous

body.

(describe shape oil lens)

kg) What property of the lens is essential for accommodation? JE-@ L*-S'7 ic @-TZ

(h) Describe the changes which occu- in the eye during accommodation

NEAR POINT ACCOMMODATION (con't) (i) Name the receptor and effector

for the accommodation reflex.

1. PUPILLARY REFLEXES

The size of the pupil is affected by two factors; light intensity and proximity of the object being viewed.

a. Light Intensity

The intensity of light which s-rikes the retina is the

effective stimulus for initiating the light reflex. If the light proves too strong for optimal visual acuity, impulses

pass over the optic nerve and autonomic nervous system neurons. As a result, -It-.he pupil constricts thereby decreasing the

amount of liaht which enters the eye. Conversely, a decrease in illumination through a comparable reflex mechanism causes the pupils to enlarge. When the eye is exposed to intense light the pupil can contract to approximately 1.5 mm. and

in complete darkness the pupil may enlarge to almost 10 mm. in diameter. This approximates a total difference,in pupillary area of about 4OX.

if li ght is shone into only one eye, both pupils constrict. This is the CONSENSUAL LIGHT RERLEX.

Procedure

(1) Observe the size of the pupils of your subject in the normal light of the lab.

(2) thine a bright light into only ONE of the subject's eyes. (This may be done by having the subject hold a paper perpendicular to his face - extending down the bridge of his nose)

Record any change in size of each pupil.-Pight pupil Left pupil

(3) Remove the light and record any subsequent change 4in pupil size. Right pupil

Left pupil 4;@l, Azle4