**Core Concept**
Topical beta blockers, such as timolol and betaxolol, are used to reduce intraocular pressure in glaucoma patients by decreasing aqueous humor production. However, their systemic absorption can lead to various side effects due to their action on beta receptors in the body.

**Why the Correct Answer is Right**
Systemic absorption of topical beta blockers can cause a range of side effects, including bradycardia, hypotension, and bronchospasm due to their action on beta-1 and beta-2 receptors in the heart and lungs. Additionally, they can also cause fatigue, dizziness, and changes in taste. However, one notable side effect of topical beta blockers is not a consequence of their systemic absorption, but rather a local effect.

**Why Each Wrong Option is Incorrect**
**Option A:** Bradycardia is a well-documented side effect of systemic absorption of topical beta blockers, as they can decrease heart rate by stimulating beta-2 receptors in the sinoatrial node.
**Option B:** Hypotension is also a side effect of systemic absorption of topical beta blockers, as they can decrease blood pressure by stimulating beta-2 receptors in blood vessels.
**Option C:** Bronchospasm is a side effect of systemic absorption of topical beta blockers, as they can stimulate beta-2 receptors in the lungs, causing airway constriction.

**Clinical Pearl / High-Yield Fact**
A notable exception to the side effects of topical beta blockers is their ability to cause local irritation, such as stinging, burning, or dryness of the eyes, due to their direct action on the ocular surface.

**Correct Answer:** D. Local irritation.