Glaucoma Pharmacology

Question 1

What is the function of the iris circular muscle?

Answer 1

Constricts pupil to cause miosis; effect is due to activation of M3 receptors (GPCR coupled to Gq); parasympathetic

Question 2

What is the function of the iris radial muscle?

Answer 2

Dilates pupil to cause mydriasis; effect is due to activation of a1 adrenergic receptors (GPCR coupled to Gq protein)

Question 3

What is the function of the ciliary muscle?

Answer 3

Causes accommodation of the eye to near vision; opens up trabecular meshwork to improve outflow of aqueous humor; M3 receptors contract the muscle

Question 4

What is the function of the ciliary epithelium?

Answer 4

Produces aqueous humor; beta adrenergic receptor activation increases humor production (GPCR coupled to Gs); alpha2 adrenergic receptor activation decreases humor production (GPCR coupled to Gi)

Question 5

What is the role of the sympathetic nervous system in production of aqueous humor?

Answer 5

Beta receptor activation will increase production whereas a2 receptor activation will decrease production

Question 6

What is the role of carbonic anhydrase in production of aqueous humor?

Answer 6

Functions to transport Na and HCO3 ions from the ciliary body to aqueous humor; increase in osmotic pressure of the aqueous humor enhances transport of water to the humor to increase its volume

Question 7

What is the role of muscarinic receptors in the outflow of aqueous humor?

Answer 7

Contraction of ciliary muscle improves outflow; contraction of iris circular muscle causes miosis which improves flow

Question 8

What does prostaglandins F2a improve?

Answer 8

Uveoscleral or unconventional outflow of aqueous humor

Question 9

What role does the SNS play in the outflow of aqueous humor?

Answer 9

Contraction of iris radial muscle (a1 receptors) results in mydriasis leading to decreased outflow; relaxation of ciliary muscle (presynaptic a2 receptors) increases uveoscleral outflow)

Question 10

What is glaucoma?

Answer 10

A group of ocular disorders that lead to an optic neuropathy associated with loss of visual sensitivity and field

Question 11

What are the two types of glaucoma?

Answer 11

Primary (genetic, congenital, without apparent causal factor) and secondary (to other diseases, trauma, surgery or drug induced)

Question 12

What are the two types of primary glaucoma?

Answer 12

Open angle and closed angle glaucoma

Question 13

What is open angle glaucoma?

Answer 13

95% of causes; chronic progressive disease with no apparent mechanical blockage of humor outflow

Question 14

What is closed angle glaucoma?

Answer 14

5% of cases; acute intermittent partial or complete blockage of the outflow, may have to be treated as an emergency to avoid vision loss

Question 15

Why is use of beta blockers common?

Answer 15

Convenience of dosing (once or twice daily) and relative lack of local adverse effects

Question 16

Why is Timolol favored over the other beta blockers?

Answer 16

Lacks local anesthetic effects, available as generic and is a full antagonist

Question 17

Why are prostaglandin analogs commonly used?

Answer 17

Given once daily at night time (1 drop daily); more efficiently reduce IOP than beta-blockers

Question 18

What is the nasolacrimal duct occlusion technique?

Answer 18

Apply pressure for about 3 minutes over the nasolacrimal sac after eye drops are applied

Question 19

What are the anatomical predispositions for closed angle glaucoma?

Answer 19

Shallow anterior chamber, narrow angle between cornea and iris, or tight contact between iris and the lens

Question 20

What are the two types of closed angle glaucoma?

Answer 20

With pupillary block and without pupillary block

Question 21

What is closed angle glaucoma with pupillary block?

Answer 21

Tight contact between iris and the lens, the flow of humor into the anterior chamber is blocked, iris moves forward and blocks the outflow

Question 22

What is closed angle glaucoma without pupillary block?

Answer 22

The ciliary processes are located in such a way that they push the iris forward, and the iris blocks the outflow especially during mydriasis

Question 23

Which drugs promote elevation of IOP in pts with open angle glaucoma?

Answer 23

Glucocorticoids (topical, systemic, inhaled) and topical anti muscarinic drugs (including tricyclic antidepressants and serotonin-NE reuptake inhibitors and other drugs with potent anti muscarinic action)

Question 24

In pts with closed angle glaucoma, angle closure may be triggered by what?

Answer 24

Any drug (topically or systemically administered or inhaled) that causes mydriasis such as drugs with alpha-1 adrenomimetic activity + antimuscarinic drugs