A 58-year-old airline captain comes to the office after he was found to have abnormal vision testing during a pilot medical certification examination. The patient feels well and has no ocular symptoms. Vision testing shows normal visual acuity but moderate loss of peripheral vision in both eyes. Results of the funduscopic examination are shown in the image below. Other neurologic and cardiopulmonary examination findings are unremarkable. He is started on latanoprost eyedrops. The medication is most likely to improve this patient's condition through which of the following mechanisms?

Question

A 58-year-old airline captain comes to the office after he was found to have abnormal vision testing during a pilot medical certification examination.  The patient feels well and has no ocular symptoms.  Vision testing shows normal visual acuity but moderate loss of peripheral vision in both eyes.  Results of the funduscopic examination are shown in the image below.  Other neurologic and cardiopulmonary examination findings are unremarkable.  He is started on latanoprost eyedrops.  The medication is most likely to improve this patient's condition through which of the following mechanisms?

Quizplus · Accepted Answer

11ec160b_3c22_fd6b_9249_c13f9dbef347_MD0001_00 Aqueous humor is secreted by epithelial cells of the ciliary body into the posterior eye chamber. The fluid then flows through the pupil into the anterior chamber to the iridocorneal angle. Here, it diffuses through a trabecular network into Schlemm's canal (scleral venous sinus) and subsequently drains into episcleral and conjunctival veins. A small amount of aqueous can also diffuse through the ciliary muscle and adjacent sclera (uveoscleral pathway). Open-angle glaucoma is characterized by increased intraocular pressure due to increased secretion or decreased outflow of aqueous humor. It is a form of optic neuropathy and causes progressive loss of ganglion cell axons, which may be visualized as a pale optic disc and enlarged optic cup (compared to normal retina). Symptoms evolve over decades, with progressive loss of peripheral visual fields. Glaucoma is managed with agents that either decrease production or increase outflow of aqueous humor. Latanoprost is a topical prostaglandin used in the treatment of glaucoma. It is applied as a prodrug and converted to the active form by esterases in the cornea. Prostaglandins are the preferred first-line agents for the treatment of glaucoma, and although the exact mechanism of action is uncertain, they have been found to decrease the collagen content in the uveoscleral outflow pathway and increase outflow of aqueous humor. They are also known to cause increased pigmentation in the iris and eyelashes. (Choices A, C, and E) Carbonic anhydrase inhibitors (eg, dorzolamide) decrease formation of bicarbonate in the ciliary body, leading to decreased sodium and fluid transport and subsequently decreased production of aqueous humor. Alpha-adrenergic agonists (eg, brimonidine) inhibit production of aqueous humor due to vasoconstriction in the ciliary body. Beta blockers (eg, timolol) also decrease production of aqueous humor. Prostaglandins do not affect production of aqueous humor but are often used in combination with these other agents. (Choice B) Increased formation of new blood vessels at the optic disc is the characteristic feature of proliferative diabetic retinopathy. Strict control of diabetes will reduce the risk of diabetic retinopathy, but it is not affected by topical prostaglandins. Educational objective: Glaucoma is a form of optic neuropathy characterized by increased intraocular pressure associated with increased production or decreased outflow of aqueous humor. Topical prostaglandins (eg, latanoprost) increase outflow of aqueous via the uveoscleral pathway and are the preferred treatment for open-angle glaucoma. __________ References: Latanoprost ophthalmic solution in the treatment of open angle glaucoma or raised intraocular pressure: a review. (http://www.ncbi.nlm.nih.gov/pubmed/19668444)

A 58-Year-Old Airline Captain Comes to the Office After He