Lecture 3: Ophthalmology

Question 1

benefits of having an eye within a socket? Bones and fissures of the socket?

Answer 1

1. protection
2. Allows good stereopsis

Question 2

Extra-ocular muscles?

Answer 2

sulphate - SO4 - Superior oblique = CN4

LR6 - lateral rectus = CN6

everything else is CN3

Question 3

Muscles of the eyelids? functions? anatomy of the eyelid?

Answer 3

1. Protection
2. keep the eyes in goo shape

Obicularis oculi - closes the eyelids - CN7

levator palpebral - opens eye lids - CN3

• Tarsal plate provides rigidity
• Conjuctive lines the inside
• fat helps absorbs shocks
• produce the tear film

Question 4

The tear film? Drainage of the tear film?

Answer 4

About 10 microlitres

• Mucin lies agaisnt the epitelium produced by the goblet cells of the conjunctiva
• An aqueous layer from the (accessory) lacrimal glands
• An oil layer from the meibomian glands stopping the aqueous layer from evaporating as well as helping produce a good layer that doesn’t refract light too much.

The tear film aqeuous layer is normally produced by the accessory lacrimal glands and is drained via the puncta into the lacrimal sac and down the lacrimal duct. If the lacrimal glands are stimulated (emotional and protective), then the excess will go down your cheeks.

Question 5

Neurogenic vs sympathetic ptosis?

Answer 5

Neurogenic = large pupil and large ptosis

Sympathetic = Small pupil and small ptosis

Question 6

Focusing structures of the eyes?

Answer 6

2/3 is done at the cornea

The lens does the rest

Cornea:

• Epithelium
• Bowman’s membrane
• Stroma (thick layer)
• Descement’s layer
• endothelium -Constantly pumping water out of the cornea to maintain intralamellar spaces correct.

Question 7

The lens? Common issues? Directly attached structures and fluid surrounding?

Answer 7

Made of fibre cells in layers layed down upon the inner nucleus that you are born with (the lens continues to grow PP)

Cataracts are a common condition in a cortical or nuclear fashion creating visual disturbance.

The lens has an anterior and posterior pole and an equator around its circumference.

Joined to the ciliary muscle (circular muscle) by suspensory ligaments, contracting and decreasing the diameter - increasing the pole to pole distance. Zonules maintain tension when ciliary muscles are relaxed.

The ciliary epithelium is responsible for producing the aqueous humor in the anterior chamber. Flows out pupil to the angle of the anterior chamber and is filtered by the trabecular meshwork.

Question 8

Functions of the Retina?

Answer 8

1. To absorb photons of light and translate them into a biochemical message
2. To translate these biochemical mesages into electrical impulses
3. Finally to transmit these electrical impulses to the brain via ganglion cells

Light travels through the ganglion cells, bipolar and hits the photoreceptors (rods and cones) - the retina is back to front. The photoreceptors sit on the RPE -retinal pigmental epithelium, that provides requirements for turnover and removal of waste.

Question 9

What is the fovea and its function?

Answer 9

It is the centre of our visual acuity and is an area where the bipolar and ganglion cells have moved to the side to allow light to directly hit the photoreceptor cells. Xanthophyll caratenoids absorb UV protecting our foveal cones.

Question 10

The optic nerve? tell me bout dis

Answer 10

There are no photreceptors found here so much like @samleary it appears to be useless. However, it does still have some function acting as the point at which nerves combine to form the optic nerve and head to the brain.

It’s secondary function is to be a point at which blood vessels enter and supply the inner retina.

Question 11

Detection of colours? Colour blindness

Answer 11

Done by 3 different types of cones (blue, green and red)

The absorbancy of red and green is very similar and the opsons within the cones have mutated genes and can not detect maximally a certain light as red or green. There are multiple genes that can be mutated resulting in a spectrum of colour blindness.

Question 12

Glaucoma?

Answer 12

• An optic neuropathy with specific pattern of axonal loss often associated with elevated intraocular pressure.
• Ususally a characteristic pattern of upper and lower visual field loss
• Is extremely common in older age due to perfusion issues (1/10 older people)
• Closed angle - acute increase in pressure and very painful

Open angle - most common and is painless, symptomless and only diagnosed if seen by an optomestrist or opthalmologist.

Question 13

Upcoming technologies?

Answer 13

Gene therapy

RNA interference technology

Stem cell therapy (actually already happening)