Eye practical

Question 1

What is the iris?

Answer 1

Gives the eye its colour and has a circular diaphragm. Contains the pupil which allow variation in the light entering

Question 2

What are the two muscles in the iris and what do they do and what is their innervation?

Answer 2

Circular muscle around pupil called sphincter pupillae causing constriction of pupil - innervated by PNS (third cranial nerve)

Radial muscle called dilator pupillae (radial as lines that go out from the centre like spokes) causes pupil dilation and is innervated by sympathetic nerves

Question 3

What is the name of another muscle of the eye, what does it do and what is its innervation?

Answer 3

Ciliary muscle which suspends the lens to alter its shape. When ciliary muscle contracts the lens can bulge and is used for near vision (accomodation). PNS innervation and SNS

Question 4

What is accomodation?

Answer 4

Th adjustment of the eye in order to focus on near vision.

Question 5

What is tropicamide?

Answer 5

anti cholinergic drug - causes pupil dilation

Question 6

What is pilocarpine?

Answer 6

cholinergic drug - causes pupil constriction

Question 7

What are allergies and eye conditions causing cornea/conjunctiva inflammation treated for?

Answer 7

Anti-inflammatory agents like corticosteroids

Question 8

What are acute eye infections treated with?

Answer 8

Anti-infective preparations (antibacterials, antifungals, antivirals). If severe, systemic treatment

Question 9

Why is mydriasis (dilation) important?

Answer 9

It allows inspection of the retina and prevents the iris from sticking to the lens during inflammation (irits)

Question 10

How can mydriasis be achieved?

Answer 10

Anti-muscarinic drugs

Sympathomimetics

Question 11

Give examples of antimuscarinic agents

Answer 11

atropine
cyclopentalone
tropicamide

Question 12

Give examples of sympathomimetic agents

Answer 12

phenylephrine

Question 13

How can constriction of the pupil (miosis) be achieved?

Answer 13

Muscarinic agents

Question 14

Give an example of a muscarinic agent?

Answer 14

pilocarpine

Question 15

What can glaucoma be treated with?

Answer 15

Pilocarpine or beta blockers like timolol

Question 16

What is opacity of the lens called and how can it be treated?

Answer 16

Cataract - systemic steroids or prolonged topical exposure to the eye

Question 17

What are chronically sore eyes associated with?

Answer 17

reduced tear secretion e.g. from rheumatoid arthritis or Sjogren’s syndrome
Treated with mucolytic agents

Question 18

Which compounds can be used to detect damage to the cornea from injury or disease?

Answer 18

rose bengal dyes

fluroescein sodium

Question 19

Where is aqueous humour synthesised?

Answer 19

Epithelium covering the ciliary body, the area of which is greatly increased by the presence of ciliary processes which are heavily vascularised

Question 20

Describe the structure of the ciliary epithelium

Answer 20

Two layers of ectodermal cells

Question 21

How is aqueous humour made?

Answer 21

The ectodermal cells contain ATPase and carbonic anhydrase. Na+ is selectively absorbed from the stroma into intracellular clefts. The AH passes through the space between the iris and the lens into the anterior chamber.

Question 22

Describe the passage of aqueous humour

Answer 22

• AH passes between the iris and the lens into the anterior chamber
• It returns to the venous circulation through the pores of the corneo-scleral trabeculum in the antero-lateral wall of the anterior chamber and through the endothelium of the canal of Schlemm
• The hyperosmolality in the cleft causes water flow from the stroma producing continuous flow of aqueous humour

Question 23

What is normal intraocular pressure?

Answer 23

15mm Hg

Question 24

What are the two types of glaucoma?

Answer 24

primary and secondary

Question 25

What is primary glaucoma?

Answer 25

3 types - diagnosed when no evidence of ocular or general cause of secondary glaucoma

Question 26

What is secondary glaucoma?

Answer 26

Present when an intraocular pressure of more than 20mm-Hg is found in the presence of an ocular disturbance which can reasonably be expected to lead to a raised pressure (e.g. trauma, intraocular neoplasms, neovascular formation, steroid administration)

Question 27

What are some glaucoma treatments?

Answer 27

• pilocarpine, physostigmine, timolol, adrenaline and carbonic anhydrase inhibitors
• laser trabecular surgery