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Question 1

Describe the path of the light reflex

Answer 1

Light activates optic nerve and AP passes alongAxons pass though the LGN and some decussateAxons synapse at the pretectal nucleusAP passes to Edinger-Westphal nucleus and stimulates CN3 fibres of ciliary ganglionStimulate constrictor pupillae

Question 2

Describe the corneal reflex pathway

Answer 2

Closes eye in response to stimulation of the cornea- AP generated when cornea is stimulated (nasociliary branch)- Stimulates temporal and zygomatic branches of the facial nerve, causing constriction of orbicularis oculi.

Question 3

Define the vestibulo-ocular reflex

Answer 3

Reflex eye movement that stabilises images on the retina during head movement by producing eye movement in the direction opposite to the head movement

Question 4

Describe Horner’s Syndrome

Answer 4

Lack of sympathetic innervation to the ipsilateral side of the head. MiosisAnhydrosisFlushingPtosis

Question 5

Describe retinal detachment

Answer 5

Blow to the eye can cause the layers of the retina to become separated. Pigment cell layer is not firmly attached to the neural layer (it is however firmly attached to the choroid)- complain of flashes of light/speck floating in their vision

Question 6

Define exopthalmos

Answer 6

Protrusion of the eye- eyelids part more than normal- sclera are visible all around the cornea and the iris.

Question 7

Causes of exopthalmos

Answer 7

unilateral = aneurysm or haematomabilateral = Grave’s disease

Question 8

Why do you get papilloedema with raised ICP?

Answer 8

Optic nerve is surrounded my meninges, CSF in subarachnoid spaceIncrease CSF pressure can compress the optic nerve, blood vessels supplying retina which can lead to blindness. Papilloedema is because the vein is occluded before the artery, leading to the oedema of the retina.

Question 9

Give some different types of strabismus

Answer 9

Extropia = eye turned outEsotropia = eye turned inHypertropia = one eye higher than the otherHypotropia = one eye lower than the other

Question 10

Where do you find the lateral geniculate nucleus?

Answer 10

Thalamus

Question 11

Describe the primary visual cortex

Answer 11

Found posteriorly in the occipital lobe2mm thickMade up of 6 layersContains prominent strips of white matter - myelinated axons

Question 12

Define the focal length of the eye

Answer 12

The distance from the lens to the point of focus

Question 13

Describe how the strength of a lens is measured

Answer 13

Dioptric strength- the reciprocal of its focal length in metresstrength = 1 / focal length (metres)

Question 14

What is normal intraocular pressure?

Answer 14

20-25mmHg

Question 15

How is the intraocular pressure maintained?

Answer 15

The aqueous humour has a greater osmotic strength than the blood, therefore fluid is drawn into the ciliary body. The fluid can escape via the canal of Schlemm

Question 16

What defines why someone is short-sighted?

Answer 16

The strength of their eye lens system is too strong- axial length of the eye is too long - focus lies in front of the retina

Question 17

What defines why someone is long sighted?

Answer 17

The strength of their eye lens system is too weak- too short axial length- focus lies behind the retina

Question 18

Define presbyopia

Answer 18

Age related degeneration of the eyesight- get progressively more long-sighted with age

Question 19

Define myopic

Answer 19

Short-sighted

Question 20

Define hyperopic

Answer 20

Long-sighted

Question 21

Describe accommodation of the eye

Answer 21

The ciliary muscle contracts in order to increase the convexity of the lens, which will add to the dioptric strength of the eye

Question 22

Why does accommodation occur?

Answer 22

As an object approaches the eyes, the light rays will diverge. The focal point moves backwards as a result and the eye needs to accommodate, by adding to the dioptric strength so that the object can remain in focus.

Question 23

Define near point

Answer 23

The shortest distance in front of the eye where an object can be maintained in focus.

Question 24

Define visual acuity

Answer 24

The ability to distinguish between two separate sources of light.

Question 25

What does visual acuity depend on?

Answer 25

Density of light receptorsSize of receptive field of the receptors in the retina.

Question 26

Define a cataract

Answer 26

An opacity in the lens, so that light cannot pass through

Question 27

Give some causes of cataracts

Answer 27

SenilityTraumaMetabolic disturbance e.g. diabetes Congenital

Question 28

Define scotoma

Answer 28

Pathological blind area