Ocular Pharmacology

Question 1

What is required of topical preparations?

Answer 1

Required to act on a surface = need corneal penetration

Question 2

What drug class are good for corneal penetration?

Answer 2

Low molecular weight drugs

Question 3

How is the cornea structured?

Answer 3

Lipid : water : lipid sandwich = epithelium is lipophilic/hydrophilic, stroma is lipophobic/hydrophilic

Question 4

How does the structure of the cornea affect where drugs can be absorbed?

Answer 4

Lipid soluble drugs penetrate the epithelium, water soluble drugs penetrate the stroma

Question 5

What is an example of a drug that crosses the cornea easily?

Answer 5

Chloramphenicol = has both lipophilic and hydrophilic properties

Question 6

What effect may the tear film have on drug penetration?

Answer 6

May impeded drug penetration (lipid layer)

Question 7

How does the structure of the cornea impact what drugs have limited absorption?

Answer 7

Hydrophilic drugs are limited by the epithelium, hydrophobic drugs are limited by the stroma

Question 8

What properties do topical steroids need to have?

Answer 8

Need to be both hydrophobic and hydrophilic = chemical modification may be needed

Question 9

What are some ways that steroids can be modified?

Answer 9

Alcohol or acetate may be added to make steroid more hydrophobic, phosphate may be added to make steroid more hydrophilic

Question 10

What are some features of prednisolone acetate?

Answer 10

Hydrophobic, good penetration in uninflamed cornea, used post-operatively

Question 11

What are some features of prednisolone phosphate?

Answer 11

Hydrophilic , poor penetration in uninflamed cornea, used for corneal disease or when low dose steroids are needed

Question 12

What are the common uses of benzalkonium chloride?

Answer 12

Surfactant and antibacterial agent = commonly found in household cleaning products

Question 13

How may corneal penetration be enhanced?

Answer 13

By adding benzalkonium as a preservative = disrupts lipid layer of tear film and aids penetration of some drugs

Question 14

What are some features of bimatoprost 0.03%?

Answer 14

Drug used to lower intra-ocular pressure in glaucoma, has benzalkonium concentration of 0.05 mg/ml

Question 15

What is the benzalkonium concentration in bimatoprost 0.01%?

Answer 15

0.2 mg/ml

Question 16

What are some features of the systemic absorption of drugs?

Answer 16

Tears are pumped out of the lacrimal sac rapidly, excess gains systemic absorption at nasopharynx, limited by punctal occlusion

Question 17

What are some routes of administration?

Answer 17

Subconjunctival, subtenons

Question 18

What are the types of intra-ocular injection?

Answer 18

Intravitreal, intracameral

Question 19

What are some uses of ophthalmic drugs?

Answer 19

Treatment of infection, treatment of inflammation, treatment of glaucoma, diagnostic eye drops, intra-ocular injections, ocular toxicity

Question 20

What are some common anti-inflammatory agents used?

Answer 20

Steroids, topical NSAIDs, antihistamines, mast cell stabilisers

Question 21

What are the actions of steroids?

Answer 21

Suppress inflammation, allergy and immune response

Question 22

What are steroids commonly used topically for in the eye?

Answer 22

Post-operative cataracts, uveitis and to prevent corneal graft rejection

Question 23

What are the local effects of steroids?

Answer 23

Cataracts, glaucoma, exacerbation of viral infection

Question 24

What are some systemic effects of steroids?

Answer 24

Gastric ulceration, immunosuppression, osteoporosis, weight gain, diabetes

Question 25

What are some different strengths of steroids?

Answer 25

FML, predsol (prednisolone phosphate), betamethasone, dexamethasone/prednisolone acetate

Question 26

What are antihistamines and mast cell stabilisers used for?

Answer 26

Hayfever and allergic conjunctivitis

Question 27

What are NSAIDs mainly used for?

Answer 27

Pain relief (i.e post-refractive laser)

Question 28

What is glaucoma?

Answer 28

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

Question 29

What is the only modifiable risk factor for glaucoma?

Answer 29

Raised intra-ocular pressure

Question 30

What are some features of glaucoma?

Answer 30

Usually asymptomatic, screened for by optometrist, chronic disease, usually slowly progressive, incidence increases with age

Question 31

What are some treatments for glaucoma?

Answer 31

Prostanoids = latanoprost Beta blockers = timolol, betaxolol, levobunolol cartelol Carbonic anhydrase inhibitors = topical (dorzolamide) or systemic (acetazolamide) Alpha 2 adrenergic antagonists = brimonidine (contraindicated in children as it causes sleep apnoea) Parasympathomimetic = pilocarpine Cosopt = combo of dorzolamide and timolol

Question 32

What is the benefit of intravitreal delivery?

Answer 32

Delivers effective concentration of drug at the target site instantly

Question 33

What is an issue with intravitreal delivery?

Answer 33

Many drugs are toxic to the retina

Question 34

What is intravitreal delivery used for?

Answer 34

Delivery of antibiotics in endophthalmitis and intra-ocular steroids

Question 35

How does local anaesthetic work?

Answer 35

Blocks sodium channels and impedes nerve conduction

Question 36

What is local anaesthetic used for?

Answer 36

FB removal, tonometry (intra-ocular pressure measurement), corneal scraping, comfort, cataract surgery

Question 37

What is the most common diagnostic dye?

Answer 37

Fluorescein

Question 38

What is fluorescein used for?

Answer 38

Showing corneal abrasion and dendritic ulcers Identifying leaks and nasolacrimal duct obstruction Tonometry and angiography

Question 39

What are some examples of mydriatics?

Answer 39

Tropicamide, cyclopentolate

Question 40

What do mydriatics do?

Answer 40

Cause pupil dilation by blocking parasympathetic supply to iris = cause cycloplegia (stop lens from focusing)

Question 41

What are some side effects of mydriatics?

Answer 41

Blurring of vision, acute angle closure glaucoma

Question 42

What type of drug should never be used to treat herpetic keratitis?

Answer 42

Steroids

Question 43

What do sympathomimetics do?

Answer 43

Act on sympathetic system to cause pupil dilation

Question 44

What can some sympathomimetics cause?

Answer 44

Cycloplegia = some can (atropine) and some cannot (phenylephrine)