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DEP > pharmacology of eye > Flashcards

pharmacology of eye Flashcards

1
Q

routes of administration in eye

A

extraocular - topical the most common

intraocular

peri-oculat

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2
Q

what does the extraocular route target

A

anterior segment

cornea
sclera
conjunctiva
iris
ciliary body
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3
Q

the major route of absorption of the eye when given extraocular

A

cornea

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4
Q

examples of intraocular route meds

A 
Intravitreal injections
e.g. Anti-VEGF
injections
(ranibizumab) for
proliferative diabetic
neuropathy and wet
AMD.
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5
Q

peri-ocular route targets

A

peri-bulbar
retrobulbar injections
subtenons block

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6
Q

which medications in opthamology take the systemic route

A

steroids
carbonic anhydrase inhibitors
ABx

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7
Q

Pts presenting with papilloedema
secondary to raised ICP or acute angle
closure glaucoma are treated with

A

IV acetozolamide to reduce IOP

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8
Q

Patients with severe active thyroid eye

disease can be treated with

A

IV methylprednisolone to reduce inflammation and prevent optic neuritis

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9
Q

advantages of ABx

A
  1. Less invasive mode of delivery
  2. More pleasant for patient
  3. Reduced infection risk compared
    to injections
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10
Q

Disadvantages of ABx

A
  1. Needs to penetrate blood-retinal
    and blood-aqueous barrier
  2. High doses can cause systemic side effects
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11
Q

most common route of administration

A

into the inferior fornix

foreign bodies may be hid in the superior fornix

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12
Q

bioavailability of drug is affected by what

A

corneal and precorneal factors

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13
Q

what are the precorneal factors and how does it affect the bioavailability

A

solution drainage - Once in the fornix the drugs drain through the
nasolacrimal duct to enter the inferior meatus through
the valve of Hasner. Here a substantial amount is
absorbed by the nasal mucosa into the blood stream:

blink rate 15p per minute

tear volume adn tear turnouver rate -> 7/8uL
can be altered by - blink rate and lacrimation

induced lacrimation
- inflammation
- Light
• Temperature
• Additional environmental factors

tear film
- structure of tear film is altered ie meiobian gland dysfunction - reduced drug residency time in fornix

  • pH of tear film ->6.5-7.6 - altered can affect diffusion
  • might bind to tear film proteins - albumin and lysozyme
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14
Q

layers of the cornea are bound by

A

desmosomes

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15
Q

which layer of cornea is hydrophobic and which layer allows ionised water soluble drugs

A

epithelium is hydrophobic - lipid soluble drugs

stroma - type 1 collagen, permites ionised water soluble drugs

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16
Q

endothelium allows aqueous humour how

A

gap junctions

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17
Q

2 major ocular barriers to drugs

A

blood - aqueous barrier

blood - retinal barrier

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18
Q

what is the blood - aqueous barrier

A

Two discrete
cell layers located in the anterior segment of
the eye:

  1. The vascular endothelium of the iris/ciliary
    vessels
  2. The non-pigmented ciliary epithelium

prevent the entry of soutes into the anterior segment

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19
Q

what is the blood-retinal barrier

A

(BRB) restricts the entry of
the drugs from blood into the posterior segment.
It is composed of two types of cells :

  1. The retinal capillary endothelial cells (inner BRB)
  2. The retinal pigment epithelium cells (outer BRB)
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20
Q

what is the outer BRB (RPE)

A

RPE: The outer retinal layers
are nourished by the choroid.

• Nutrients/drugs enter the systemic
circulation and eventually reach the
vascular choroid.

• RPE tight junctions restrict diffusion from
choroid to the outer retinal layers.

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21
Q

what is inner BRB

A

The inner retinal layers are
nourished by the retinal vessels.

• Diffusion from the retinal vessels is
restricted by tight junctions in the
endothelium.

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22
Q

which receptor do acetylcholine bind to in PS Ns

A

Muscarinic receptors located on post-
ganglionic effector organ

Nicotinic receptors located on ganglion
synapses and NMJ

23
Q

The ocular receptor are found where

A

EOM
Levator palpabrae superioris
Iris sphincter

Iris sphincter muscle
Ciliary Body
Lacrimal gland

24
Q

what is choline acetyltrasferase and where is it found

A

responsible for degrading Ach

  1. Corneal epithelium
  2. Ciliary body
  3. Inner plexiform layer of the retina
25
Q

actions of cholinergic agonists

A

reduce IOP - opening trabecular meshwork to allow aqueous drainage

accomodation - stimulate ciliary muscle and open outflow pathway

miosis (pupil constriction) - stimulates iris sphincter muscle

26
Q

examples of direct parasympathomimetic and indirect parasympathomimetic

A

Direct parasympathomimetic: Pilocarpine. Used frequently in the treatment of glaucoma.

Indirect Parasympathomimetic (Inhibit Acetylcholinesterase and prevent breakdown of
Ach): Edrophonium, Physostigmine.
27
Q

how to test for ocular myasthenia

A

made using the Tensilon
Test. IV is edrophonium is administered. Any improvement in ptosis or
diplopia confirms a positive diagnosis.

Longer acting neostigmine can be used for treatment

28
Q

SEs of parasympathomimetics

A

Systemic –salivation, bradycardia

Ocular – cataracts iris cysts, conjunctival toxicity

29
Q

actions of cholinergic antagonists

A

mydriasis (pupil dilatation) - inhibits sphincter pupillae)

cycloplegia - inhibits ciliary muscle contraction - NO ACCOMMODATION

slightly decreased lacrimal secretions

30
Q

how are sympathomimetics used in uveitis and iritis

A

prevent the formation of posterior synaechiae - adhesions between the posterior iris and anterior lens surface

31
Q

uses of cholinergic antagonists

A

Prevent posterior synechiae
• Routine fundal exam
• Provocation of glaucoma (test)

32
Q

types of cholinergic antagonist
time to onset of action
time of effect

A

Atropine
40 mins
7-10 dyas

Cyclopentolate
30 mins
12-24 hours

Tropicamide
20 mins
3-4 hours

33
Q

SEs of cholinergic agonists

A

Systemic – sweating, flushing, tachycardia

Ocular - blurred vision, photophobia, glaucoma,

34
Q

what is the sympathetic outflow trunk

A

T1-L2

35
Q

what is the role of alpha agonists

A

Smooth muscle contraction

• Dilator pupillae muscle
• Ciliary muscle
• Constriction of conjunctival
and episcleral vessels

36
Q

role of beta blockers

A
  • increase aqueous outflow

- decreased aqueous production

37
Q

types of topical alpha agonists

A

apraclonidine

brimonidine

clonidine

38
Q

SEs of alpha agonists

A

Common: allergic conjunctivitis,
conjunctival blanching

Systemic: hypotension, dry mouth

39
Q

types of beta blockers

A

timolol
betacolo
levobunolol

40
Q

where are Beta 2 receptors found

A

ciliary processes

trabecular meshwork

41
Q

MOA of carbonic anhydrase inhibitor

A

Inhibit carbonic anhydrase which is
found in ciliary body epithelium.
It is a key enzyme in aqueous production

42
Q

types of topical CAIS

A

acteozolamide (IV/PO)

dorzolamiode
brinzolamide

topically as have adequate corneal penetration

43
Q

SEs of CAIs

A

Systemic: renal stones, malaise, fatigue

Ocular: stinging, allergic reactions

44
Q

function of the aqueous

A
  1. supply nutrition to the lens, corneal endothelium, corneal stroma BUT NOT CORNEAL ENDOTHELIUM
  2. Maintain IOP -determined bu the rate of aqueous secretion and rate of aqueous outflow 10-21 mmHg
  3. remain transparent
45
Q

aqueous humor pathway

A

secreted by ciliary body epithelium into the posterior chamber

Aqueous flows through the pupil
into the anterior chamber

• Aqueous can be drained through
the trabecular outflow (90%) or
uveoscleral outflow (10%)

• Trabecular: trabecular meshwork,
Schlemm’s canal, episcleral veins

• Uveoscleral: Drained by the
venous circulation in the ciliary
body, choroid and sclera

46
Q

tear film layer and role

A

lipid layer - • Smooth surface for lids to glide over
• Reduces surface tension and draws water into the tear
film
• Prevents evaporation of the

aqueous layer
Antibacterial IgA and lysozyme
• Transfers oxygen to the avascular corneal epithelium
• Abolishes surface irregularities of the cornea

mucous layer
‘Wets’ the cornea and lubricates it. Essentially attaches
the aqueous to the corneal epithelium.

epithelial layer

47
Q

role of orbicularis oculi pump

A

• 70% tears drained by the lower canaliculus. Remainder drained by the
upper.

• With each blink fibres of orbicularis shorten the canaliculi and move the
puncta medially. The lacrimal sac expands creating negative pressure
and drawing in the tears

• When the eyes open and the muscles relax, the sac collapses and tears drain
down the ducts

48
Q

light stimulus pathway

A

• Light stimulus

• EDW nucleus is the
PNS preganglionic
nucleus.

• Fibres travel in CN III
and synapse in the
ciliary ganglion

  • Short ciliary nerve
  • Sphincter pupillae
49
Q

what is accomodation

A

Accommodation occurs when the eyes are directed from a distant object to a near object

50
Q

accommodation reflex

A
  • Convergence of the eyes
  • Pupillary constriction
  • Increased biconvexity of the lens
51
Q

when does accommodation develop and when does ones ability decrease

A

develops at 2 months and is well developed at 8 months

decrease with age and by 60 years is extrememly poor presbyopia

52
Q

how is convergence obtained in accommodation

A

contraction of medial rectus via innervation

by oculomotor nerve

53
Q

how is pupillary constriction achieved in accommodation

A

contraction of sphincter pupillae

54
Q

how is increased lens biconvexity achieved

A 
Circular ciliary muscle contracts,
decreasing tension in zonular fibres,
and allowing the lens capsule to
contact and change the shape of
he lens. The anterior pole moves
forward, the axial width increases
and the diameter of the lens
decreases.

DEP (20 decks)

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