Ocular Pharmacology

Question 1

Requirements for topical administration of drugs to the eyes?

Answer 1

Required to act on the surface

Require corneal penetration

Question 2

Which drugs can effectively penetrate the cornea?

Answer 2

LMW drugs

Question 3

Nature of the epithelium and which drugs can penetrate it?

Answer 3

Epithelium is lipophilic/hydrophobic

Lipid-soluble drugs penetrate the epithelium

Question 4

Nature of the stroma and which drugs can penetrate it?

Answer 4

Stroma is lipophilic/hydrophilic

Water-soluble drugs

Question 5

Which drugs have both lipophilic and hydrophilic properties?

Answer 5

Chloramphenicol; these drugs easily penetrate the cornea

Question 6

How does ocular surface inflammation affect the epithelium?

Answer 6

Often REDUCES the hydrophobic nature of the endothelium

Question 7

So which drugs are limited by which layer of the eye (in terms of penetration)?

Answer 7

Hydrophilic drugs are limited by the epithelium

Hydrophobic drugs are limited by the stroma

Question 8

What chemical modifications can be made to topical steroids to alter their characteristics?

Answer 8

Alcohol or acetate - makes steroid more hydrophobic

Phosphate - makes steroid more hydrophilic

Question 9

Uses of prednisolone acetate?

Answer 9

Hydrophobic and so achieves good penetration in an uninflamed cornea, i.e: it is not washed away by tears

It is used post-operatively

Question 10

Uses of prednisolone phosphate?

Answer 10

Hydrophilic and so only achieves poor penetration in an uninflamed cornea, i.e: it is washed away in the tears

Used for corneal disease or for when low-dose steroids are desired

Question 11

What is benzalkonium?

Answer 11

A preservative in eye products that disrupts the lipid later of tear film, causing dry eyes

It also aids the penetration of some drugs

Question 12

What is Bimatoprost?

Answer 12

Drugs used to lower the intra-ocular pressure in glaucoma

Question 13

How does systemic absorption of topical drugs occur?

Answer 13

Tears are pumped out of the lacrimal sac rapidly but the excess gains systemic absorption at the nasopharynx

Question 14

How can systemic absorption of topical drugs be limited?

Answer 14

By punctal occlusion

Question 15

Routes of administration of drugs

Answer 15

Subconjunctival

Subtenons

Question 16

Routes of administration of ocular injections?

Answer 16

Intravitreal

Intracameral

Question 17

Anti-inflammatory drugs that can be used?

Answer 17

Steroids

Topical NSAIDs (can be used for pain relief, e.g: post-refractive laser)

Anti-histamines (used in allergic conjunctivitis/hayfever)

Mast cell stabilisers

Question 18

When are steroids used topically?

Answer 18

1. Post-operative cataracts
2. Uveitis
3. Prevention of corneal graft injection

Question 19

Local (ocular) side effects of steroids?

Answer 19

Cataract, glaucoma and exacerbation of viral infection

Question 20

Systemic side effects of steroids?

Answer 20

Gastric ulceration

Immunosuppression

Osteoporosis

Weight gain, diabetes

Neuropsychiatric effects, etc

Question 21

Varying strengths of topical steroids?

Answer 21

1. Fluorometholone (FML)
2. Predsol
3. Betamethasone
4. Dexamethasone/prednisolone

Question 22

What is glaucoma?

Answer 22

Group of diseases characterised by progressive optic neuropathy, resulting in characteristic field defects

Cause is intra-ocular pressure

Question 23

Symptoms of glaucoma?

Answer 23

Usually asymptomatic until advanced disease stage

Question 24

How do glaucoma drops occur?

Answer 24

Drugs that either:

1. Decrease aqueous humor production
2. Increase aqueous humor outflow

Question 25

Examples of drugs used in glaucoma treatment?

Answer 25

Prostanoids, e.g: latanoprost β-blockers Carbonic anhydrase inhibitors: • Topical - Dorzolamide • Systemic - Brimonidine Parasympathetic, e.g: pilocarpine Combination drugs (dorzolamide and timolol)

Question 26

Uses of intravitreal injections?

Answer 26

Method of administration of antibiotics in endophthalmitis To deliver intra-ocular steroids Anti-VEGF (anti-vascular endothelial growth factor) - prevents growth of new vessels

Question 27

Advantages and disadvantages of intravitreal injections?

Answer 27

Delivers effective concentration of drug at the target site instantly BUT Many drugs are toxic to the retina

Question 28

Complication of endopthalmitis?

Answer 28

Blindness

Question 29

What is dry macular degeneration?

Answer 29

ATROPHIC type Unknown aetiology

Question 30

What is wet macular degeneration?

Answer 30

New vessel membrane forms over the macula; these haemorrhage and leak, leading to damage of the macula

Question 31

Mechanism of action of local anaesthetic in the eye?

Answer 31

Blocks Na+ channels and impedes nerve conduction

Question 32

Uses of local anaesthetic?

Answer 32

1. Foreign Body (FB) removal 2. Tonometry (IOP measurement) 3. Corneal scraping 4. Comfort

Question 33

Uses of diagnostic dyes?

Answer 33

Most commonly used is fluorescein Uses include: 1. Showing a corneal abrasion 2. Tonometry 3. Diagnosing a nasolacrimal duct obstruction 4. Angiography

Question 34

What are mydriatics?

Answer 34

Cause pupil dilatation by blocking the parasympathetic supply to the iris, e.g: tropicamide and cyclopentolate

Question 35

Side effects of mydriatics?

Answer 35

Blurring AACG (Acute Angle Closure Glaucoma)

Question 36

How do sympathomimetics work?

Answer 36

Act to enhance the sympathetic nervous system, causing the pupils to dilate, e.g: phenylephrine, atropine They do not affect ciliary muscle (accommodation)

Question 37

Example of a drug that constricts the visual fields?

Answer 37

Vigabatrin

Question 38

Example of a drug that can cause a cataract?

Answer 38

Steroids

Question 39

Example of a drug that can cause optic neuropathy?

Answer 39

Ethambutol

Question 40

Example of a drug that can cause maculopathy?

Answer 40

Chloroquine

Question 41

Example of a drug that can cause corneal opacities in the eye?

Answer 41

Amiodarone - appears as a horizontal pigmented line