Opthamalic Flashcards
The optokinetic response (OKR)
Using black and white stripes that rotate to find blind participants
dry eye symptoms
-redness
-stigning
-burning or scratchy
stringy mucus
causes of dry eye
reduced tears or composition
-turns into keratitis(chronic)
-treat with artificial tears
Blepharitis symptoms
-inflammation of the eyelid
-discharge/crusting on lid margins/eyelashes
-strongly mucus
Blepharitis causes
-staphylococcus infection
-treat with antibiotic and anti-inflammatory drug
conjunctivitis symptoms
-pink discoloration
-burning or itching
-discharge
Causes of conjuctivitis
-inflammation of the conjunctiva (bacterial or viral)
-allergic reaction
-reduce the course of infection or inflammation
-prevent spread
Keratitis symptoms
-decreased vision
-ocular pain
-cloudy/opaque cornea
causes of keratitis
-inflammation of cornea(bacterial, viral, or fungal
-treat with antibiotic and anti-inflammatory drug
Glaucoma
-buildup of aqueous humor
-increases occular pressure
-eventually can cause blindness
advantages of topical eye delivery
-easy access
-localized effect of drug action
-avoid first pass metabolism and systemic side effects
Barriers to topical delivery
-efficient clearance mechanisms
-blood ocular barriers
-posterior eye diseases harder to treat
goals of topical drug delivery
-target of site of action
-prolong residence time
-decrease frequency
-improve patient compliance
barriers to topical drug delivery: cornea
-major barrier
-outermost layer
-70% of refractive power
-protects eyes from dust
-5 layers
barriers to topical drug delivery: iris
-melanin binds drugs
barriers to topical drug delivery: tear duct
-nasolacrimal clearence
barriers to topical drug delivery: conjenctiva
-vascular
-increased clearance
barriers to topical drug delivery: Ciliary body
-produce aqueous humor
layers of cornea
-epithelium: barrier to hydrophilic drugs, tight junctions
-bowman’s layer
-stroma: barrier to lipophilic drugs
-Descemet’s membrane
-endothelium
tear film
-lipid layer: protective
-aqueous layer: anti bacterial
-mucous layer: adherence
-corneal epithelia
osmolarity and pH of saline
neutral
nasolacrimal drainage
-drain from tear duct into nasal cavity
-when you blink, fluid forced nasally
steps of nasolacrimal drainage
-inferior puncta
-lacrimal canaliculi
-lacrimal sac
-nasolacrimal duct
-nasal cavity
aqueous humor
-secreted by ciliary body
-drained by trabecular meshwork and Schlemm’s canal
-removes metabolites like lactate
-200-300 microL
-maintains ocular pressure
Vitreous humor
-hydrogel with fills cavity b/w lens and retina
-high water content
–no flow through vitreous, only diffusion
The conjuctiva
-high vascular
-goblet cells produce mucin
-large SA is more permeable to drugs
0major route to enter circulation: major factor in pre-cornea drug loss
Choroid
-highly vascularized
-fenestrated capillaries
Sclera
-outermost tunic of the eye
-protects inner structures and cornea
-made of collagen and proteoglycans in an extracellular matrix
uptake and bioavailability: physiological factors
-tear film and nasolacrimal drainage
-eyelid movements, blinking
-protein binding
-metabolism and efflux
-conjunctival loss
protein binding
-drug and protein binging can inactivate drugs
-wait 5-10 mins if applying more than one eye drop
metabolism
-lipophilic prodrugs to cross corneal epithelium
-esterase and hydroxylases convert prodrug to active form
Efflux
-drug transporters on corneal and conjunctival epithelia cells
-amino acid and organic anion transporters may increase conc in the eye
-efflux pumps
