Ophthalmic Agents Flashcards
Name and describe the three proposed routes for systemic absorption of topical ophthalmic agents.
Transconjunctival/scleral - travels through the cornea, sclera, and ciliary body to systemic circulation
Transcorneal - through cornea, aqueous humor, and iris
Nasolacrimal - Drains through nasal lacrimal duct to nasal mucosa, where first-pass metabolism is bypassed; this is the most active of the three
Describe how the composition of the cornea influences transcorneal absorption.
The cornea is trilamellar - Fat (epithelium) - Water (stroma) - Fat (endothelium). Effectively absorbed drugs will posses both hydrophillic and hydrophobic properties.
Describe the PANS innervation of the eye.
Preganglionic neurons have somas in the Edinger-Westphal nucleus. The axons of these neurons run with those of the occulomotor nucleus until reaching the orbit and branch from the inferior division of the occulomotor cord to form the parasympathetic root of the ciliary ganglion. These preganglionic nerves synapse at the ciliary ganglion.
Short ciliary nerves are the post-ganglionic fibers. They enter the posterior eye to innervate the sphincter pupillae and ciliaris muscles
Describe the SANS innervation of the eye.
The preganglionic cell bodies lie in the IMLCC of T1-2. They ascend the sympathetic chain to the superior cervical ganglion and synapse.
Postganglionic cell bodies project axons superiorly along the carotid to form the internal carotid plexus in the cavernous sinus. Branches of this plexus extend to the ciliary ganglion, nasociliary division of opthalmic nerve, and, occulomotor nerve.
Short ciliary nerves - extend from the ciliary ganglion to enter the eye posterioly; provide some sympathetic innervation to dilator pupillae and ciliary muscles
Long ciliary nerves - extend from the nasociliary n. to enter the eye and travel between the sclera and choroid; provides majority of the innervation to dilator pupillae and ciliary muscles.
Superior div. Occulomotor - carries sympathetic fibers which innervate the superior tarsal muscle
What are the adrenergic and muscarinic receptors of the dilator pupillae, sphincter pupillae, and ciliary muscles.
Dilator pupillae - alpha 1
Sphincter Pupillae - M3
Ciliary body - M3 and Beta 2
What is aniscoria?
Discrepancy between pupil diameters
Describe the algorithm for the analysis of aniscoria with bilateral light reflexes preserved.
Begin with “cocaine” test. If dilation occurs, horner’s syndrome is not present. Therefore, simple aniscoria. If there is no dilation, evaluation with hydroxyamphetamine will determine post- versus pre-ganglionic (dilation) horner’s.
Note: Cocaine prevents resorption of NE from the synapse; hydroxyamphetamine is sympathomimetic.
Describe the algorithm for the analysis of aniscoria with unilateral light reflexes.
Evaluate for denervation cholinergic supersensitivity with hypoconcentrated methacholine or pilocarpine. If there is a constriction, Adie’s pupil is present. If there is no response, administer higher dose of pilocarpine. Constriction indicates CN III palsy.
How will muscarinic agonists and antagonists effect pupil size, accomodation, and IOP?
Agonists - miosis, allow accomodation, increase outflow
Antagonists - mydriasis, blurred vision, may initiate acute close-angle glaucoma
How will adrenergic agonists and antagonists effect pupil size, accomodation, and IOP?
Agonists - mydriasis, no effect on accomodation, increase aqueous outflow and decrease production
Antagonist - reverse mydriasis, no effect on accomodation, beta-blockers decrease humor production
Describe the clinical course of closed-angle glaucoma?
Often initiated by the use of anti-histamines, anti-muscarinics, or alpha-1 agonists. This is a clinical emerbency requiring surgery for iridectomy. In the short-term IOP can be managed with muscarinics or AChE inhibitors.
Describe the clinical course of open-angle glaucoma?
Occurs mainly in african-americans. Increase IOP is biggest risk factor. Tx may relieve IOP, but doesn’t always slow the progression.
Describe the prototype, MOA, and ADRs of prostaglandins used for glaucoma.
Prototype = Latanoprost
MOA = Increased uveoscleral outflow
ADR = hyperemia, increased number/length of lashes, pigmentation of lashes and iris
Note: These are now first-line treatment, unless pt. cant afford.
Describe the MOA and ADR of beta-blockers used for glaucoma.
MOA = Decreased humor production, thought to be secondary to decreased blood flow
ADR = well-tolerated aside from possible systemic side effects on the airways and heart (CI in dysrhythmias and bronchospasm)
Note: Non-selective are more efficacious than Beta-1; remember they all end in olol.
Name the alpha-2 agonist drugs used for glaucoma. Describe their MOA and ADR.
Apraclonidine and Brimonidine
MOA = increase uveoscleral outflow and decrease humor production
ADR = hyperemia and discomfort of the eye, headaches, xerostomia, and increased BP
