Ocular Pharmacology and Therapeutics Flashcards

In the HEDS trial, oral acyclovir 400 mg twice daily for one year produced which result?

Answer: It reduced recurrence of ocular HSV disease by about half

HEDS showed that prophylactic oral acyclovir cut recurrences of any ocular HSV disease by about 45%, with the largest benefit in patients with prior stromal keratitis.

What is the main dose-limiting systemic toxicity of IV foscarnet used for CMV retinitis?

Answer: Nephrotoxicity

Foscarnet is mainly nephrotoxic and also causes electrolyte problems such as hypocalcemia and hypomagnesemia, while ganciclovir mainly causes myelosuppression.

Which cycloplegic agent has the longest duration of action?

Answer: Atropine

Atropine's mydriatic and cycloplegic effects can last 7 to 14 days.

A child develops ataxia, hallucinations, and incoherent speech after dilating drops. Which agent is most likely responsible?

Answer: Cyclopentolate 2%

Cyclopentolate, especially at higher concentrations, causes CNS anticholinergic toxicity in children, including psychosis and ataxia.

How does topical apraclonidine confirm a diagnosis of Horner syndrome?

Answer: It dilates the Horner pupil through denervation supersensitivity of alpha-1 receptors

Apraclonidine is a weak alpha-1 agonist that dilates the upregulated, supersensitive Horner pupil, so the anisocoria reverses.

Why does a Horner pupil fail to dilate with topical cocaine?

Answer: Too little norepinephrine is released into the synapse for reuptake blockade to work

Cocaine blocks norepinephrine reuptake, and it has no effect when sympathetic denervation means little norepinephrine is released.

A Horner pupil does not dilate after hydroxyamphetamine. Where is the lesion?

Answer: Postganglionic (third-order) neuron

Hydroxyamphetamine releases norepinephrine from intact third-order neurons, so a pupil that does not dilate means a postganglionic lesion.