Ocular Pharmacology Flashcards
sub-tenon adminstration
retro-orbital space
intra vitreal injection
delivers concentration at target site instantly
however, many drugs are toxic to the retina
when are intra vitreal injections used
to deliver ABx in endophthalmitis
intra-ocular steroids
anti-VEGF
intra cameral administration
what must drugs be to penetrate the epithelium
lipophilic or hydrophobic
what must drugs be to penetrate the stroma
hydrophilic or lipophobic
what must drugs be to penetrate the cornea, and give an axample
lipophilic and hydrophilic properties eg chloramphenicol
what can ocular surface inflammation do to the properties of the endothelium
make it less hydrophobic
what is also on the surface of the cornea and may impede drug penetration
lipid layer of tear film
what makes steroids more hydrophobic
alcohol and acetate
what makes steroids more hydrophilic
phosphate
when would Prednisolone acetate be used
it is hydrophobic so has good penetration in the uninflamed cornea
often used post-op
when would Prednisolone phosphate be used
it is hydrophilic so will have better penetration in the inflamed cornea
can also be used in the uninflamed cornea for lower dosage
what can be used to enhance corneal penetration
Benzalkonium - preservative that also disrupts the lipid layer of the tear film on the cornea
how can systemic absorption of topical drugs be limited
tears are rapidly pumped out of lacrimal sac into nasolacrimal duct where there is systemic absorption at the nasopharynx
can be limited by punctal occlusion (for 5 minutes)
what local anaesthetic is used
- mechanism
- use
tetracaine 1%
blocks Sodium channels and impedes nerve conduction
used for FB removal, tonometry (IOP measurement),corneal scraping, comfort, opening of eye
what can fluoroscein be use din the diagnosis of (lacrimal ducts)
lacrimal duct obstruction - retained dye in a thickened tear strip is diagnostic
mydriatics
eg tropicamide, cyclopentolate
cause pupillary dilation by blocking the parasympathetic supply to the iris
also cause cycloplegia (stop the lens from focusing)
however, this effect is only noticed in younger people, as in older people the lens is stiffer and not so good at focusing anyway
side effects of mydriatics
cycloplegia (blurring)
very rarely AACG
how do mydriatics (rarely) cause AACG
dilated pupil lessens the corneoscleral angle
- this is why closed angle glaucoma is worse at night, becuase the pupil dilates
- and why pilocarpine is part of the treatment
Sympathomimetics
act on the sympathetic system causing the pupil to dilate
do not affect the ciliary muscle
eg phenylephrine and atropine
what diagnostic tool is phenylephrine used for
differentiate between episcleritis and scleritis
what can ethambutol (TB) cause
optic neuropathy and colour blindness
what can chloroquine (anti-malarial) cause
maculopathy
