A 68-year-old man comes to the ophthalmology clinic for a routine follow-up. He has no acute vision changes, but he notes that he sometimes bumps into furniture while walking at night. He has a history of type 2 diabetes mellitus and hypertension. Physical examination reveals an intraocular pressure of 26 mmHg in the right eye and 27 mmHg in the left eye. Funduscopic examination shows an increased cup-to-disc ratio of 0.7 bilaterally with thinning of the neural rim. Automated visual field testing demonstrates bilateral arcuate scotomas in the peripheral visual fields. The anterior chamber angles are open on gonioscopy.
Which of the following is the most appropriate initial pharmacologic therapy for this patient?
The correct answer is:
C) Topical latanoprost
The patient is presenting with chronic open-angle glaucoma (COAG), characterized by elevated intraocular pressure, optic nerve "cupping," and peripheral visual field loss (scotomas) in the setting of open anterior chamber angles. Topical prostaglandin analogs, such as latanoprost, are considered first-line pharmacologic therapy for COAG. They work by increasing the drainage of aqueous humor through the uveoscleral pathway. They are preferred due to their once-daily dosing and high efficacy in lowering intraocular pressure with a favorable systemic safety profile.
Answer choice A: Laser trabeculoplasty, is incorrect. Laser trabeculoplasty is an effective procedure to increase aqueous outflow and is often used in patients who are non-adherent with or intolerant to medical therapy. However, topical medications like prostaglandin analogs are typically initiated first in the management of COAG. The question also specifically asks for "pharmacologic" therapy.
Answer choice B: Oral acetazolamide, is incorrect. While carbonic anhydrase inhibitors can lower intraocular pressure by decreasing aqueous humor production, the oral form is generally reserved for the acute management of angle-closure glaucoma or as adjunctive therapy in refractory cases of COAG due to its significant systemic side effects such as paresthesias and metabolic acidosis.
Answer choice D: Topical pilocarpine, is incorrect. Pilocarpine is a cholinergic agonist (miotic) that increases aqueous outflow through the trabecular meshwork. While historically used for COAG, it is rarely used today as a first-line agent because it requires frequent dosing and causes significant side effects, including miosis, limiting night vision, and accommodative spasm.
Answer choice E: Topical timolol, is incorrect. Topical beta-blockers like timolol were formerly the first-line treatment for COAG. They work by decreasing aqueous humor production from the ciliary body. While still widely used, they are generally considered second-line or adjunctive to prostaglandin analogs because they are slightly less effective at lowering IOP and carry risks of systemic side effects, such as bradycardia and bronchospasm.
Key Learning Point
Topical prostaglandin analogs, such as latanoprost and bimatoprost, are the first-line pharmacologic treatment for chronic open-angle glaucoma. They function by increasing uveoscleral outflow and are preferred for their high efficacy and once-daily dosing.
