Opthamology

Question 1

What are the layers of the tear film, what are their functions and what produces them?

Answer 1

An outer oil layer, functions to prevent seals the tear film and helps to prevent evaporation. Produced by the tarsal glands.

The middle aqueous layer is produced by the lacramal glands and functions to lubricate the eye and to remove particles to prevent infection.

The inner mucus layer is produced by goblet cells in the conjunctiva. It functions to lubricate to help the eyelids to move.

Question 2

What are two neurogenic causes of ptosis?

Answer 2

Cranial nerve III palsy - LPS upper lid palsy, extraocular muscles, pupil parasympathetic.
Horners syndrome: Sympathetic innervation of mullers muscle - subtle ptosis and subtle miosis (small pupil)

Question 3

What is a blowout fracture?

Answer 3

Fracture to the maxilla (medial wall or orbital floor), from a punch to the eye or ball hit to the eye etc.

Signs: black eye, infra-orbital nerve anaesthesia, double vision (eye can’t look all the way down or up) - muscle is trapped

Question 4

What are the features of thyroid eye disease?

Answer 4

Huge extraoccular muscles - compression, push things forward etc.

eye lid retraction, lid lag, lagophthalmos,
Occular surface inflammation becayse of exposure,
Proptosis of the globe muscles are big and push the eye forward,
Myopathy, muscles are so big they can’t work - skuint
Optic neuropathy (blindness), big muscles press on the nerve

May require surgical intervention, lubricating of the eyes/ taping them shut

Question 5

What does the refracting of light that hits the eye?

Answer 5

The cornea does most of the refracting (2/3) and the lens (1/3)

Question 6

What is hyperopia?

Answer 6

Long sight, the light is refracted to a point behind the retina

Question 7

What is myopia?

Answer 7

Short sight, light is refracted in front of the retina.

Question 8

What is astigmatism?

Answer 8

The cornea curvature is different at different places which causes the light to be reflected differently in different places.

Question 9

What are the layers of the cornea?

Answer 9

Epithelium, bowman’s membrane (acellular), stroma (largest layer, gap between the keratocytes is important to allow light through), descement’s layer, endothelium

Question 10

What is the slit lamp assessment for?

Answer 10

To look at the inner eye. Thickness of the cornea. Can also use in vivo confocal microscope to look at the cornea in a living person.

Question 11

What does the cornea need to function?

Answer 11

In needs clarity (not cloudy etc), regular curvature and controlled thickness.
Endothelial cells pump liquid from the cornea to keep it dry.

Question 12

What is koratoconus?

Answer 12

A disorder of the eye which results in progressive thinning of the cornea. It results in an irregular cornea causing distorted (blurred) vision.

Multifactoral causes, definitely a genetic component, probably an environmental component also (two hit hypothesis)

Usualy beings a puberity and continues at varying speens between ages 10-40.

15-20% result in transplant.

Question 13

What is Desecemet’s membrane endothelial keratoplsty?

Answer 13

Removal of host cornea Decremet’s layer and unhealthy endothelium. Tissue replaced with donors Decemet;s layer and endothelium secured n place with only air.

Question 14

Where do cataracts form?

Answer 14

In the lens, either the lens cortex (cortical cataracts) or in the lens nucleus (nuclear cataract)

Question 15

What is the lens made of?

Answer 15

Fibre cells

Question 16

Where is the cilliary muscle?

Answer 16

Circularly around the lens with zonules attaching it to the lens, enabling it to expand the lens (dilated cillary muscle) and dilate (contracted cilliary muscle) the lens, this increases the width of the lens in the middle and increasing the curve

Question 17

What is accommodation of the lens?

Answer 17

The ability to change the curvature of the lens to increase or decrease where our vision is focused.

Question 18

What cells in the eye produce aqueous humour?

Answer 18

The epithelium of the cilliary body. It goes to the anterior chamber (in front of the iris). It is filtered by trabecular mesh work. If blocked or non-functional then the liquid can’t flow away. Then the pressure will increase.

Question 19

What are the features of cataracts?

Answer 19

Reduced visual acuity.
Significant lens opacity.
No other lens ocular pathalogies.

Can be congenital, acquired, age related, metabolic (diabetes), toxic (corticosteroids), trauma (poke in he eye), secondary (inflammation)

Surgery for cataracts.
intra-capsular, extra-capsular, phacoemulsification (ultrasound), femto-laser assisted.

Question 20

What is the function of the retina?

Answer 20

To translate light into a biochemical signal,to translate that signal into an electrical impulse, to translate the electrical impulse to the brain via ganglion cells.

Question 21

What happens when light hits the retina?

Answer 21

It stimulates the photoreceptors which stimulate the bipolar cells which stimulate the ganglion cells, which transmit the stimulation to the brain.

Question 22

What causes the blindspot in your eye?

Answer 22

The fact that there are no photo receptors in where the optic nerve hits the eye.

Question 23

What is the pattern of rods and cones in the different parts of the eye?

Answer 23

Mostly cones in the fovea, which gives visual acuity and colour vision. Mostly rods in the periphery, which gives detection of movement. Periphery is quite poor at detecting detail.

Question 24

What causes colour blindness?

Answer 24

Something about opsons

Question 25

What is glaucoma?

Answer 25

An optic neuropathy with axon loss pattern. It is associated with increased introccular pressure because of lower perfusion.

Characteristic pattern of visual field loss. Upper and lower and peripheral loss before central loss.

Common in the older population.

There are two types, open angle and closed angle. Acute closed angle is an emergency.

Cup to disc ratio used to (0.5 normal). Can identify increased ICP

Question 26

What is the normal intraoccular pressure?

Answer 26

11-22 mmHg

Question 27

What are common retinal disorders?

Answer 27

Diabetic retanopathy
etinal detachment
Age related macular degeneration