Alpha 2-agonists allow for an additional _________ mmHg IOP reduction when added to PGAs.

• A. 3.5
• B. 1.5
• C. 2.0
• D. 4.0

Answer: (A)

When you add an alpha-2 adrenergic agonist to a prostaglandin analog, you get an extra drop in intraocular pressure beyond what the PGA alone provides. This add-on effect comes from complementary actions: the PGA mainly increases outflow through the uveoscleral pathway, while the alpha-2 agonist reduces aqueous humor production and can modestly enhance outflow as well. The combined result is typically about a 3.5 mmHg additional decrease in IOP, a value that sits in the common range reported for this combination. So, 3.5 mmHg is the best choice because it reflects the well-established additive effect seen with this drug pairing. In contrast, smaller add-on reductions like 1.5 or 2.0 mmHg underestimate the usual benefit, and a 4.0 mmHg add-on, while possible in some patients, is less representative of the typical average.