Anatomy of the eye

Question 1

What is the eye position of predators?

Answer 1

Eyes are set forward and have large binocular vision.

Question 2

What is the eye position of prey?

Answer 2

Eyes are set laterally and large field of monocular vision.

Question 3

What is the anterior pole of the eyeball?

Answer 3

Highest point on the cornea

Question 4

What is the posterior pole of the eyeball?

Answer 4

Highest point on the posterior surface

Question 5

What is the optic axis?

Answer 5

Straight line passing through the anterior and posterior poles.

Question 6

What is the equator?

Answer 6

Equal distance between the poles.

Question 7

What is the meridian?

Answer 7

Line passing from pole to pole

Question 8

What is the limbus?

Answer 8

Junction between the cornea and the sclera

Question 9

What is a descemetocele?

Answer 9

Deep corneal ulcer in which most/all of the corneal stroma is absent

Question 10

What is the function and structures of the external fibrous tunic?

Answer 10

Provides form and offers protection.
Cornea
Sclera
Limbus

Question 11

What is the structure of the sclera?

Answer 11

Dense collagen with blood vessels

Cribiform area is where the optic nerve passes

Question 12

What is the function and structures of the middle vascular tunic (uvea)?

Answer 12

Pigmented and found immediately inside of the sclera.
Provides nutrients to the eyeball.
Regulates size of the pupil and shape of the lens.
Choroid.
Ciliary body.
Iris.

Question 13

What is the location of the choroid?

Answer 13

Lines the sclera from the optic nerve

Question 14

What is the function of the ciliary body?

Answer 14

Thick area opposite to the limbus.

Allows for accomodation of the lens in primates

Question 15

What are the blood vessels associated with the sclera?

Answer 15

Anterior ciliary arteries
Long posterior ciliary arteries
Short posterior ciliary arteries.

Vorticose veins emerge near the sclera

Question 16

What is the function of the choroid?

Answer 16

Forms a light reflected layer in the dorsal fundus.

Loss of visual acuity when light hits the retina a second time, as the images are superimposed.

Question 17

Where does the aqueous humour leave the eye?

Answer 17

Pectinate ligament.

Drains into scleral venous sinus.

Question 18

How does the angle of filtration of the aqueous humour affect the eye?

Answer 18

This is provided by the pectinate ligament.
Iridocorneal angle.
Wide = increased intraocular pressure.

Question 19

What is the sympathetic innervation of the middle vascular tunic (uvea)?

Answer 19

Cranial cervical stellate ganglion.
Follows ophthalmic nerves to the orbit.
Innervates dilator of the pupil

Question 20

What is the parasympathetic innervation of the middle vascular tunic (uvea)?

Answer 20

Pre-synaptic fibres run to orbit in oculomotor nerve.

Post-synaptic fibres innervate ciliary muscle and constrictor of the pupil.

Question 21

What is the function of iridic granules? What type of animals are they found in?

Answer 21

Reduces glare and eye strain in bright light.

Found in ungulates.

Question 22

What is the function of the outer pigmented layer (pars ceca retina)?

Answer 22

Makes the posterior eye dark.
Absorbs reflected light.
Prevents blurred vision.
Not photsensitive.

Question 23

Where can the pars ceca retina be found?

Answer 23

From the optic nerve to the pupillary margin

Question 24

Where can the pars ceca optica be found?

Answer 24

Optic nerve to the ora serrata

Question 25

What is the structure of the lens?

Answer 25

Outer capsule under constant tension by zonular fibres. Hard nucleus composed of many fibres. Zonular fibres attach the lens to ciliary bodies.

Question 26

Where is the site of cataracts in the lens?

Answer 26

Y-shaped suture

Question 27

What is the location of the optic disc?

Answer 27

Point at which nerve fibres converge to form the optic nerve.

Question 28

What is the macula?

Answer 28

Area of maximum optimal resolution. Found dorsolateral to the optic disc. Light focussed here leads to greater visual acuity.

Question 29

What is the cause of diabetic cataracts?

Answer 29

High blood glucose concentration leads to a high intralenticular sorbitol level. This increases osmotic forces within the eye, so water is drawn in. Eventually this causes swelling of the fibres and cell death.

Question 30

What is the hyaloid canal?

Answer 30

Found in the vitreous body, which is posterior to the lens. Runs from the back of the lens to the optic disc. Contains the hyaloid artery and primary vitreous in the embryo.

Question 31

Where can the aqueous humour be found in the eye?

Answer 31

Between the cornea and iris. | Between the iris and the lens.

Question 32

What is enucleation?

Answer 32

Removal of the globe and it's contents. Including the 3rd eyelid and conjunctival sac. Orbit and ocular muscles are left intact. Implant inserted into the socket.

Question 33

What is evisceration?

Answer 33

Removal of the iris, cornea and contents | Leaves the sclera intact.

Question 34

What is exenteration?

Answer 34

Removes adnexal structures including the eyelids, muscles and fat.

Question 35

What is epiphora?

Answer 35

Overflow of tears running down the face, which can cause irritation, which can irritate the skin and predispose to infection. Often caused by blocked nasolacrimal ducts.