What is a common adverse effect of ocular decongestants and how should they be used?

• A. Systemic hypertension
• B. Rebound redness and tachyphylaxis; use only short term
• C. Improved night vision
• D. Permanent redness

Answer: (B)

Ocular decongestants work by constricting the superficial conjunctival vessels to reduce redness, but their most common adverse effect is rebound redness with tachyphylaxis if used too long. When these vasoconstrictors are used repeatedly, the vessels can become less responsive to the drug, and once the effect wears off, the redness can return and may even be worse than before. This is why the guidance is to use these drops only for a short period, typically a few days, to avoid a cycle of diminishing relief and increasing redness. Some systemic absorption can occur and may affect blood pressure in sensitive individuals, but rebound redness and tachyphylaxis are the hallmark issues driving the short-term use recommendation. The other options—improved night vision or permanent redness—aren’t typical effects, and while systemic hypertension can occur, it’s not the common or primary concern with routine short-term use.