Test 15 (pharmacology)

1. Direct-acting cholinergic agonists include:

a. pilocarpine

b. echothiophate iodide

c. carbachol

d. tropicamide

e. atropine

Answera.T   b.F   c.T   d.F   e.F
Atropine and tropicamide are cholinergic antagonists
Echothiophate iodide is an irreversible cholinesterase inhibitor.
 

2. The ocular effects of prostaglandins include:

a. breakdown of blood-aqueous barrier

b. miosis

c. conjunctival hyperaemia

d. eyelid retraction

e. ocular hypertension

Answera.T   b.T   c.T   d.F   e.T
Prostaglandins are ubiquitous local hormones involved in many body functions. The ocular responses of higher doses of prostaglandins comprise hyperaemia, breakdown of blood-aqueous-barrier, hypertension and miosis. 

3. True statements about carbonic anhydrase inhibitors include:

a. at least 50% of the carbonic anhydrase needs to be inhibited before the 
    intraocular pressure shows a significant drop

b. they inhibits carbonic anhydrase found in the non-pigmentary ciliary 
    epithelium.

c. shallowing of the anterior chamber is a feature

d. transient hypermetropia is a feature

e. it can cause thinning of the cornea if given topically

Answera.F   b.T   c.T   d.F   e.F
At least 90% of the carbonic anhydrase needs to be inhibited before the intraocular pressure shows a significant drop.
They cause shallowing of the anterior chamber and therefore transient myopia.
When given topically, it can lead to thickening of the cornea in patients with diseased endothelium
 

4. The effect of pilocarpine include:

a. increased incidence of retinal tear

b. increased tension in the zonules

c. contraction of the ciliary body

d. increased thickness of the lens

e. increased permeability of the iris vessels

Answera.T   b.F   c.T   d.T   e.T

Pilocarpine causes contraction of the ciliary body and can lead to retinal tear.

The contraction decreases the tension of the zonules and lead to increased thickness of the lens.
It should be avoided in anterior chamber inflammation because it increases permeability of the blood vessels.
 

5. Phenylephrine:

a. directly stimulates the alpha-adrenergic receptors

b. affects the accommodation

c. stops the pupil response to bright light

d. causes mydriasis which does not respond to pilocarpine

e. causes rebound miosis

Answera.T   b.F   c.F   d.F   e.T
Phenylephrine causes mydriasis through alpha-adrenergic stimulation. However, unlike anticholinergic drugs, the mydriasis is relatively weak and the dilated pupil reacts to light. Pilocarpine stimulates the cholinergic pathway and therefore will constrict the pupil dilated with phenylephrine.
Rebound miosis is a feature and can last a few days.
 
 
 

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