Test 206 (Ocular pharmacology)

1. The following are true about latanoprost:

a. it is a prostaglandin F2a analogue

b. it causes conjunctival hyperaemia

c. it causes a break down of the blood ocular barrier

d. it causes miosis

e. it increases the aqueous outflow through the trabecular 
   meshwork

 
Answera.T  b.T  c.T  d.F  e.F
Latanoprost does not affect the pupil size. It increases the uveoscleral outflow.
l
l

2. The following anti-epileptic drugs can cause visual field defect:

a. carbamazepine

b. phenytoin

c. sodium valporate

d. vigabatrin

e. topiramate
 

Answera.F  b.F  c.F  d.T  e.T
Visual field defects can occur with vigabatrin and topiramate. 
 

3. Timolol:

a. has a duration of action of between 12 to 24 hours

b. is excreted unchanged by the kidney

c. reduces intraocular pressure because it is b2 selective

d.  can cause dry eyes

e. should not be used concurrently as latanoprost

 
Answer
a.T   b.F  c.F  d.T  e.F
Timolol is beta 1 selective but because its concentration 
is high in the aqueous following topical administration, it can inhibit beta 2 receptors found in the ciliary body and reduce aqueous production . It is excreted by the liver. It can be used with latanoprost. Dry eye is a known side-effects.

. 4. The effects of muscarinic agonists include:

a. accommodation

b. increases depth of focus

c. mydriasis

d. decreases uveoscleral outflow

e. myopic shift
 

Answer
a.T  b.T  c.F  d.T  e.T
Muscarinic agonists can be direct acting such as pilocarpine or indirect acting such as carbachol an acetyl cholinesterase
inhibitor. They cause accommodation, miosis and increased aqueous outflow through the trabecular meshwork. The
miotic pupil increases the depth of focus and the myopic shift results from the accommodation.

.
.

5. With regard to local anaesthetics:

a. they are either aminoamides or aminoesters

b. they are all removed by hepatic enzymatic degradation

c. the potency of a local anaesthetic can be increased by 
    making the molecule more hydrophilic

d. the action of a local anaesthetic can be prolonged by a
    concurrent use of adrenaline

e. they cause sensory but not motor paralysis

 
Answer
a.T   b.F  c.F  d.T  e.F
Local anaesthetics can be either aminoamides or aminoesters. Aminoamides are removed through hepatic enzymatic degradation whereas aminoesters are inactivated by the plasma cholinesterase. The potency of a local anaesthetic agent can be increased by making the molecule more hydrophobic. Both sensory and motor paralysis occur with local anaesthetics.

 

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