Free ABO Ocular Pharmacology and Therapeutics Questions and Answers — Questions and Answers
Question 1: What is the primary mechanism of action by which prostaglandin analogs, such as latanoprost, lower intraocular pressure (IOP)?
- Decreasing aqueous humor production by the ciliary body.
- Increasing aqueous humor outflow through the trabecular meshwork.
- Increasing aqueous humor outflow through the uveoscleral pathway. (Correct answer)
- Constricting the pupil to increase outflow (miosis).
Correct answer: Increasing aqueous humor outflow through the uveoscleral pathway.
Prostaglandin analogs are first-line therapy for open-angle glaucoma. Their primary mechanism is to increase the outflow of aqueous humor through the uveoscleral (or unconventional) pathway by remodeling the extracellular matrix in the ciliary muscle.
Question 2: A patient has been using topical prednisolone acetate 1% four times daily for several months for chronic uveitis. Which of the following is the most common and significant ocular side effect associated with long-term use?
- Corneal melt
- Miosis
- Elevated intraocular pressure and cataract formation. (Correct answer)
- Optic nerve atrophy
Correct answer: Elevated intraocular pressure and cataract formation.
The two most common and clinically significant side effects of long-term topical corticosteroid use are the development of steroid-induced glaucoma (elevated IOP) and posterior subcapsular cataracts. Regular monitoring of IOP and lens status is crucial for any patient on chronic topical steroid therapy.
Question 3: A patient presents with a classic dendritic ulcer on the cornea, which is pathognomonic for herpes simplex virus (HSV) keratitis. What is the standard-of-care first-line treatment?
- Topical corticosteroids
- Oral acyclovir
- Topical ganciclovir or trifluridine (Correct answer)
- Intravenous ceftriaxone
Correct answer: Topical ganciclovir or trifluridine
For active epithelial HSV keratitis (dendritic or geographic ulcers), the standard of care is to use a topical antiviral agent like ganciclovir gel or trifluridine solution. Oral antivirals (acyclovir, valacyclovir) are also highly effective and are often used as an alternative or adjunct.
Question 4: Which of the following cycloplegic/mydriatic agents has the longest duration of action, often lasting for one to two weeks?
- Tropicamide
- Cyclopentolate
- Atropine (Correct answer)
- Phenylephrine
Correct answer: Atropine
Atropine is the most potent and longest-acting cycloplegic agent available. Its effects on accommodation and pupillary dilation can last for 7 to 14 days, making it useful for treating severe uveitis and for amblyopia therapy but less ideal for routine dilated fundus exams.
Question 5: The bactericidal action of fourth-generation fluoroquinolones, such as moxifloxacin, is achieved by inhibiting which two bacterial enzymes?
- Beta-lactamase and penicillin-binding protein
- Dihydropteroate synthase and dihydrofolate reductase
- DNA gyrase and topoisomerase IV (Correct answer)
- RNA polymerase and reverse transcriptase
Correct answer: DNA gyrase and topoisomerase IV
Fluoroquinolones exert their bactericidal effect by inhibiting two essential bacterial enzymes involved in DNA synthesis: DNA gyrase (topoisomerase II) and topoisomerase IV. This dual-target mechanism is a key feature of later-generation fluoroquinolones, providing a broad spectrum of activity.
Question 6: A contact lens wearer presents with severe eye pain out of proportion to clinical signs and a ring infiltrate. Acanthamoeba keratitis is suspected. Effective treatment typically requires:
- Monotherapy with a topical fourth-generation fluoroquinolone.
- Intensive topical corticosteroids.
- Combination therapy with a biguanide and a diamidine. (Correct answer)
- Oral antifungal agents like fluconazole.
Correct answer: Combination therapy with a biguanide and a diamidine.
Treatment of Acanthamoeba keratitis is challenging and requires long-term therapy targeting both the active trophozoite and the dormant cyst forms. The standard of care involves combination therapy with a biguanide (e.g., PHMB) and a diamidine (e.g., propamidine), often administered hourly initially.
Question 7: A glaucoma patient is started on oral acetazolamide. Which of the following is a common systemic side effect that the patient should be warned about?
- Paresthesias of fingers and toes (Correct answer)
- Bronchodilation
- Hypertension
- Hyperkalemia
Correct answer: Paresthesias of fingers and toes
Oral carbonic anhydrase inhibitors like acetazolamide frequently cause systemic side effects. Among the most common are paresthesias (a tingling or "pins and needles" sensation) in the extremities, a metallic taste, fatigue, and metabolic acidosis.
Free ABO Ocular Pharmacology and Therapeutics Questions and Answers
What is the primary mechanism of action by which prostaglandin analogs, such as latanoprost, lower intraocular pressure (IOP)?