Pharmacology

Question 1

Which layers of the cornea are permeable to water and lipid drugs?

Answer 1

• Good for LMW drugs
• Lipid : water : lipid sandwich
• Epithelium is lipophilic/hydrophobic
• Stroma is lipophobic/hydrophilic
• Lipid soluble drugs penetrate epithelium
• Water soluble drugs penetrate stroma
• Some drugs have both lipophilic and hydrophilic properties and penetrate the cornea easily e.g. Chloramphenicol.
• Ocular surface inflammation can often reduce the hydrophobic nature of the endothelium

Question 2

Are hydrophilic/phobic drugs limited by corneal stroma/epithelium?

Answer 2

• Hydrophilic drugs limited by epithelium

- Hydrophobic drugs limited by stroma

Question 3

Which chemicals make steroids more hyprophobic and which make it more hydrophilic?

Answer 3

• Alcohol or acetate makes steroid more hydrophobic

- Phosphate makes it more hydrophilic

Question 4

Give some features of prednisolone acetate and prednisolone phosphate

Answer 4

Prednisolone Acetate 
- Hydrophobic
- Good penetration in uninflamed cornea
- Used post-operatively
Prednisolone phosphate
- Hydrophilic
- Poor penetration in uninflamed cornea
- Used for cornea disease or when want low dose steroids

Question 5

What is Bimatoprost 0.03% used to treat?

Answer 5

Glaucoma

Question 6

What is punctal occlusion?

Answer 6

Inserting silicone things into the lacrimal ducts to stop them draining

Question 7

Give two possible sites for ocular injections

Answer 7

Intravitreal – go behind the limbus and inject into the vitreous
Intracameral – go into anterior chamber

Question 8

Give six uses for ophthalmic drugs

Answer 8

1. Treatment of Infections – Chloramphenicol drops/ointment
2. Treatment of Inflammation – steroid drops (five different strengths)
3. Treatment of Glaucoma
4. Diagnostic eye drops
5. Intraocular injectionw
6. Ocular toxicity

Question 9

Give four anti-inflammatory agents used in the eye

Answer 9

• Steroids
• Topical NSAIDs
• Anti-histamines
• Mast cell stabilisers

Question 10

Give three topical uses of steroids

Answer 10

1. Post op cataracts
2. Uveitis
3. To prevent corneal graft rejection
   Steroids can also be used to treat choroiditis, temporal arteritis, anterior ischaemic neuropathy

Question 11

Give three local side effects of steroids

Answer 11

Cataract
Glaucoma
Exacerbation of viral infection

Question 12

Give six systemic side effects of steroids

Answer 12

1. Gastric ulceration
2. Immunosuppression
3. Osteoporosis
4. Weight gain
5. Diabetes
6. Neuropsychiatric effects

Question 13

When can NSAIDs be used?

Answer 13

NSAIDS can be used for pain relief e.g. post refractive laser

Question 14

What are the principles of treatment of glaucoma?

Answer 14

Either reduce aqueous production or open up the drainage for it.

Question 15

Name two drugs which turn down aq production in glaucoma

Answer 15

1. Carbonic anhydrase inhibitors e.g. topical e.g. Dorzolamide (‘Trusopt’) or systemic – acetazolamide (Diamox)
2. Alpha2 adrenergic agonist Brimonidine (‘Alphagan’)

Question 16

Give two examples of diagnostic eye drops and two of dilating eye drops

Answer 16

Diagnostic drops
- Pyoxymetacaine hydrochloride
- Fluorescein sodium
Dilating drops
- Phenylephrine hydrochloride
- Tropicamide

Question 17

Give four uses for Fluorescein

Answer 17

1. Shows corneal abrasion
2. Tonometry
3. Diagnosing nasolacrimal duct obstruction
4. Angiography

Question 18

Mydriatic drugs

• Examples
• How do they work?
• Side effects?

Answer 18

• E.g. tropicamide, cyclopentolate
• Cause pupil dilation by blocking parasympathetic supply to iris
• Side effects – blurring, AACG

Question 19

Sympathomimetics

• How do they work
• What do they do?
• Examples?

Answer 19

• Acts on sympathetic system
• Causes pupil to dilate
• Do not affect the ciliary muscle (accomodation)
• E.g phenylephrine, atropine

Question 20

Give the eye side effect that each of the following drugs gives:

• Vigabatrin
• Steroids
• Ethambutol
• Chloroquine

Answer 20

Vigabatrin constricts fields.
Steroids cause cataract.
Ethambutol can cause optic neuropathy.
Chloroquine can cause maculopathy.