PT9: Ocular Pharmacology

Question 1

what are the features of the iris smooth muscle

Answer 1

radial (dilator), sphincteric (constrictor)

regulate pupil size and the amount of light reaching retina

Question 2

what is the function of the ciliary muscle in the eye

Answer 2

changes refractive index of lens, accommodation

Question 3

what parts of the eye are smooth muscle

Answer 3

iris, ciliary

Question 4

what do cranial parasympathetic axons in the iris do

Answer 4

innervate the ciliary ganglion (back of the eye)

Question 5

what do postganglionic fibers do in the iris

Answer 5

innervate the sphincteric constrictor smooth muscle

Question 6

what does high basal tone mean

Answer 6

small pupils at rest

Question 7

what causes pupil constriction

Answer 7

contraction of sphincteric constrictor smooth muscle

Question 8

what causes pupil dilation

Answer 8

contraction of radial dilator smooth muscle

Question 9

what is the smooth muscle response to bright light

Answer 9

miosis

Question 10

what is the smooth muscle response to low light

Answer 10

mydriasis

Question 11

what is consensual pupil response

Answer 11

response in one eye will stimulate same response in the other

Question 12

what is the parasympathetic tone

Answer 12

increase in miosis, ACh acts on M3 muscarinic receptors

Question 13

what is the sympathetic tone

Answer 13

mydriasis, NA acts on alpha1 adrenoceptors

Question 14

what do alpha 1 adrenoreceptors agonists cause

Answer 14

mydriasis

Question 15

what do alpha 1 adrenoreceptor antagonists cause

Answer 15

miosis

Question 16

what is the autonomic action of the eye

Answer 16

calcium/calmodulin binds to myosin light chain kenase (MLCK) which uses ATP to phosphorykate myosin cross bridges; phosphorylated cross bridges bind to actin which produces tension

Question 17

what are two examples of muscarinic antagonists in the eye

Answer 17

mydriatics and cycloplegics

Question 18

what do mydriatics do

Answer 18

block constrictor muscle which causes pupillary dilation

Question 19

what do cycloplegics do

Answer 19

paralyse ciliary muscle which blocks accommodation

Question 20

what are the uses of muscarinic antagonists

Answer 20

anterior uveitis (inflammation), ocular examination, amblyopia (lazy eye)

Question 21

what causes glaucoma

Answer 21

damaged optic nerve, usually a consequence of raised intra-ocular pressure

Question 22

what determines intraocular pressure

Answer 22

determined by rate of formation and rate of drainage of aqueous humour
AH produced by ciliary body epithelium

Question 23

what is the purpose of aqueous humour

Answer 23

maintains intraocular pressure, provides nutrients to the cornea, lens etc, released into posterior chamber

Question 24

how does drainage occur in the eye

Answer 24

through trabecular meshwork and canal of Schlemm

Question 25

what is aqueous humour formation stimulated by

Answer 25

beta agonists

Question 26

what is aqueous humour formulation inhibited by

Answer 26

alpha agonists

Question 27

what are the three inhibitors of aqueous humour formation

Answer 27

alpha1 agonists alpha2 agonists beta adrenoreceptor antagonists

Question 28

what do alpha 1 agonists do

Answer 28

vasoconstrictors that reduce blood supply to ciliary body

Question 29

what do alpha 2 agonists do

Answer 29

reduce cAMP | directly inhibits aqueous humour formation and reduce NA release from sympathetic fibres

Question 30

what do adrenoreceptor agonists do

Answer 30

reduce aqueous humour production

Question 31

what does aqueous humour formation require

Answer 31

active transport of HCO3- out of the ciliary body | carbonic anhydrase catalyses which then dissociates to HCO3-

Question 32

what do carbonic anhydrase inhibitors do

Answer 32

decrease intracellular bicarbonate; decrease carbonic anhydrase which impairs aqueous humour secretion

Question 33

what are the steps of circulation of aqueous humour

Answer 33

AH produced by ciliary body, AH flows from the posterior chamber through the iris into the anterior chamber, trabecular meshwork (canal of Schlemm and into vein), uveoscleral outflow

Question 34

what does drug therapy do in glaucoma

Answer 34

improves drainage of aqueous humour through trabecular network, useful in raised and normal pressure glaucoma (miotics make pupil smaller, muscarinic agonists (carbachol, pilocarpine, ACh) improved drainage through uveoscleral outflow, prostaglandin analogues, latanoprost PGF2alpha analogue

Question 35

what is closed-angle glaucoma

Answer 35

angle between iris and cornea is narrowed, blocks flow of aqueous humour from posterior to anterior chamber, onset can be sudden and result in rapid irreversible damage

Question 36

what is the emergency treatment for closed-angle glaucoma

Answer 36

relieves intra-ocular pressure | increase blood osmolarity; water out of vitreous humour to decrease volume of VH and intra-ocular pressure

Question 37

what are three treatment for glaucoms

Answer 37

laser trabeculoplasty, surgical scleral flap, laser iridectomy

Question 38

what is age-related macular degeneration

Answer 38

'dry' AMD is geographic atrophy with no successful treatments 'wet' AMD is neovascular and has a rapid onset