Exam 2: Case Study Questions

A 61-year-old man is noted to have increased intraocular pressure on a routine eye examination. The visual acuity is normal in both eyes. The dilated eye examination reveals no evidence of optic nerve damage. Visual field testing shows mild loss of peripheral vision. He is diagnosed with primary open-angle glaucoma.

1. What is the action of pilocarpine on the muscles of the iris and ciliaris?

2. What receptor mediates this action?

3. How does pilocarpine lower intraocular pressure (IOP) in this patient?

4. What causes the headache and blurred vision?

5. What other side effects may be associated with pilocarpine?

6. Is pilocarpine the appropriate first-line drug for the treatment of primary open-angle glaucoma?

1. Iris: miotic (contraction of the circular muscles); Ciliaris: contraction resulting in a globular lens and accommodation

2. M3

3. Pilocarpine eye drops cause contraction of the ciliary muscle, which opens the trabecular meshwork spaces to increase the outflow of aqueous humor through the canal of Schlemm, thereby lowering IOP. Pilocarpine also causes miosis by contracting the iris sphincter muscle, which in turn lowers IOP (this mechanism is beneficial in treating closed-angle glaucoma).

4. Pilocarpine is a tertiary amine that can cross the blood-brain barrier and cause headaches; cycloplegia causes blurred vision.

5. Cholinergic adverse effects (SLUDGE).

6. No. Topical medications for glaucoma work either by increasing aqueous outflow (prostaglandins, cholinergic agonists) or by decreasing production of the aqueous humor (alpha adrenergic agonists, beta blockers, carbonic anhydrase inhibitors). The topical prostaglandins are increasingly chosen over topical beta-blockers and other medications as initial therapy in open-angle glaucoma, partly due to their low side-effect profile. Beta-blockers are also used as initial therapy.

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