CHAPTER 31- DRUGS AFFECTING THE EYE

Question 1

Harry, who is 55 years old, visited an optometrist because he was concerned about his worsening vision, particularly when reading small print. The optometrist found that the intraocular pressure in both of Harry’s eye’s was 26mmHg. Harry was referred to an ophthalmologist who confirmed the diagnosis of open angle glaucoma and prescribed Timolol eye-drops 0.25%, one drop twice a daily.

Answer 1

Harry, who is 55 years old, visited an optometrist because he was concerned about his worsening vision, particularly when reading small print. The optometrist found that the intraocular pressure in both of Harry’s eye’s was 26mmHg. Harry was referred to an ophthalmologist who confirmed the diagnosis of open angle glaucoma and prescribed Timolol eye-drops 0.25%, one drop twice a daily.

Question 2

1. What is Timolol and what is its mechanism of action in the treatment of open angle glaucoma?

Answer 2

Timolol is a beta adrenergic blocking agent. It is used optically to lower intraocular pressure in glaucoma and ocular hypertension.

Question 3

After 4 days taking Timolol, Harry felt dizzy on standing. Harry visited his GP who found that Harry’s HR was 60bpm and his BP was 115/67 mmHg. (Harry’s BP measured during previous visit to the GP was 128/76 mmHg). The GP told Harry that his problem was due to Timolol

Answer 3

After 4 days taking Timolol, Harry felt dizzy on standing. Harry visited his GP who found that Harry’s HR was 60bpm and his BP was 115/67 mmHg. (Harry’s BP measured during previous visit to the GP was 128/76 mmHg). The GP told Harry that his problem was due to Timolol

Question 4

2. Are these adverse effects consistent with the pharmacological effects of Timolol?

Answer 4

Adverse effects of Timolol can be:
	blurred vision
	dizziness
	headache
	nausea
	increase tear production
	itching and stinging of the eye
	severe allergic reaction
	fainting

Question 5

3. How could Timolol administered topically to the eye cause adverse effects?

Answer 5

Timolol administered topically depends on the permeability. Direct entry less of a barrier.

Question 6

4. How is Timolol metabolised? Could altered metabolism contribute to the adverse effects?

Answer 6

Timolol is metabolised partially in the liver. The level of beta sympathetic activity varies widely among individuals, and no simple correlation exists between the dose or plasma level.

Question 7

5. What would be an alternative drug to treat Harry’s glaucoma?

Answer 7

Another medication that Harry may choose to use is Latanoprost, travoprost which is a Prostaglandin agonist that also reduces eye pressure by decreasing the production of intraocular fluid and is a 1st line choice of treatment for glaucoma.