Intro to Ophthalmology

Question 1

Where is light mainly refracted in the eye?

Answer 1

the cornea

and a little bit at the lens

Question 2

What are the 3 layers of the tear film?

Answer 2

upper/outermost
LIPID: sealant to prevent evaporation of tear film
WATER: provides moisture and dissolves O2 to the exterior to the cornea
MUCIN: contains enzymes and electrolytes

Question 3

How does accommodation by the lens change for a distant object?

Answer 3

ciliary muscle relaxes
suspensory ligaments are tense
lens flattens and elongates

Question 4

How does accommodation by the lens change for a close object?

Answer 4

ciliary muscle contracts
suspensory ligaments relax
lens become fat and spherical

Question 5

What is hypermetropia (hyperopia)?

Answer 5

refraction error: far-sightedness
ocular globe is too long
image is focused behind the retina

corrected with convex lens

Question 6

What is myopia?

Answer 6

refraction error: short-sightedness
ocular globe is too short
image focused in front of the retina

corrected with concave lens

Question 7

What is presbyopia?

Answer 7

age-related vision loss 
loss of elasticity in the lens
inability to focus 
weakened accommodation 
"reading glasses"

Question 8

What proportion of the refraction does the cornea do?

Answer 8

2/3 of total refraction

Question 9

What is the function of the sympathetic innervation to the eye?

Answer 9

• dilates pupil

- arousal/fear

Question 10

What are the sympathetic nerves suppling the eye?

Answer 10

• ophthalmic division of trigeminal nerve (V1)

- long ciliary nerve

Question 11

What is the function of the parasympathetic innervation to the eye?

Answer 11

• constricts pupil

- focusing of lens (accommodation)

Question 12

What are the 2 pupil reflexes?

Answer 12

• light reflex

- near reflex

Question 13

What is the near reflex of the pupil?

Answer 13

"triple reflex"
causes:
- miosis (constricted pupils)
- accommodation of lens (small and fat)
- convergence of eyes

PNS controlled

Question 14

What is the light reflex of pupil?

Answer 14

reflex controlling pupil diameter in response to light intensity

PNS controlled

Question 15

What is the clinical importance of pupils?

Answer 15

tested as part of neurotransmitters exam

• provides info on pre-chiasmal afferent visual pathways (retinal and optic nerve)
• window into function of CN III (oculomotor)

Question 16

How does the sympathetic innervation to the eye travel?

Answer 16

travels down via the spinal cord
and then comes back up the neck
to the internal capsule

Question 17

How does the PNS innervation to the eye travel?

Answer 17

travels from the midbrain with CN III (oculomotor)

Question 18

What is the main function of the SNS in the eye?

Answer 18

DILATION of pupil

Question 19

What is the main function of the PNS in the eye?

Answer 19

near pupil reflex

light reflex

Question 20

What is aqueous humour?

Answer 20

• fluid produced by ciliary body
• fills the anterior chamber and hydrates the vitreous
• supplies O2 an nutrients to the posterior cornea
• maintains into-ocular pressure and so shape of eyeball
• disorders of drainage: glaucoma

Question 21

What is glaucoma?

Answer 21

disease of optic nerve/retinal ganglion cells

can cause blindness
generally asymptomatic

3 key signs

• raised intra-ocular pressure
• optic disc cupping
• visual field loss

main risk factor: AGE

Question 22

What is the normal intra-ocular pressure?

Answer 22

10-21 mmHg

Question 23

What is the Rx for glaucoma?

Answer 23

MEDICATION (eye drops)

1) Beta blockers: reduced aqueous production
2) PG analogues: increase outflow

SURGERY
trabeculectomy

Question 24

What are the main causes of eye disease worldwide?

Answer 24

• cataract (50%)
• glaucoma
• macular degeneration
• corneal scars
• diabetic retinopathy
• childhood blindness
• trachoma
• onchocerciasis

Question 25

What are the biggest causes of eye disease in the UK?

Answer 25

• age-related macular degeneration
• glaucoma
• diabetic retinopathy

Question 26

What are cataracts?

Answer 26

• loss of clarity of the lens
• risk factors: age, smoking, DM, steroids
• congenital (rare)
• Sx: blurring, glare, monocular double vision
• Clinical signs: reduced acuity, normal fields, normal pupils, dim red reflex, hazy view of fundus

Question 27

What is the Rx for cataracts?

Answer 27

surgery

replace with plastic lens