Eye practical Flashcards
What is the iris?
Gives the eye its colour and has a circular diaphragm. Contains the pupil which allow variation in the light entering
What are the two muscles in the iris and what do they do and what is their innervation?
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
What is the name of another muscle of the eye, what does it do and what is its innervation?
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
What is accomodation?
Th adjustment of the eye in order to focus on near vision.
What is tropicamide?
anti cholinergic drug - causes pupil dilation
What is pilocarpine?
cholinergic drug - causes pupil constriction
What are allergies and eye conditions causing cornea/conjunctiva inflammation treated for?
Anti-inflammatory agents like corticosteroids
What are acute eye infections treated with?
Anti-infective preparations (antibacterials, antifungals, antivirals). If severe, systemic treatment
Why is mydriasis (dilation) important?
It allows inspection of the retina and prevents the iris from sticking to the lens during inflammation (irits)
How can mydriasis be achieved?
Anti-muscarinic drugs
Sympathomimetics
Give examples of antimuscarinic agents
atropine
cyclopentalone
tropicamide
Give examples of sympathomimetic agents
phenylephrine
How can constriction of the pupil (miosis) be achieved?
Muscarinic agents
Give an example of a muscarinic agent?
pilocarpine
What can glaucoma be treated with?
Pilocarpine or beta blockers like timolol
What is opacity of the lens called and how can it be treated?
Cataract - systemic steroids or prolonged topical exposure to the eye
What are chronically sore eyes associated with?
reduced tear secretion e.g. from rheumatoid arthritis or Sjogren’s syndrome
Treated with mucolytic agents
Which compounds can be used to detect damage to the cornea from injury or disease?
rose bengal dyes
fluroescein sodium
Where is aqueous humour synthesised?
Epithelium covering the ciliary body, the area of which is greatly increased by the presence of ciliary processes which are heavily vascularised
Describe the structure of the ciliary epithelium
Two layers of ectodermal cells
How is aqueous humour made?
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.
Describe the passage of aqueous humour
- 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
What is normal intraocular pressure?
15mm Hg
What are the two types of glaucoma?
primary and secondary
What is primary glaucoma?
3 types - diagnosed when no evidence of ocular or general cause of secondary glaucoma
What is secondary glaucoma?
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)
What are some glaucoma treatments?
- pilocarpine, physostigmine, timolol, adrenaline and carbonic anhydrase inhibitors
- laser trabecular surgery
