eye care

Question 1

Describe the MOA of CMC, HPMC (and other cellulose derivatives) in eye drops

Answer 1

Cross links upon contact with tear film due to pH difference to increase viscosity.

Note: they are too viscous to instill easily alone

Question 2

Describe the MOA of PEG and propylethylene glycol in eye drops

Answer 2

• Forms a protective layer over mucous membrane, relieving inflammation
• Increases viscosity

Question 3

What are the 3 functions of glycerin in eye drops

Answer 3

1. Demulcent
2. Humectant
3. Lubricant

Question 4

Does glycerin lower tear osmolarity?

Answer 4

Yes

Question 5

What are emollients?

Answer 5

They are usually oily or fat-based agents that soften and protect tissues from drying or cracking

Question 6

What do demulcents do in eye drops?

Answer 6

To relieve pain in irritated or inflamed mucous membranes

Question 7

Can cellulose derivative ingredients (e.g. HPMC, CMC) be instilled alone in eye drops?

Answer 7

No. They are too viscous to be instilled alone

Question 8

Which 2 emollients found in eye drops are also lubricants?

Answer 8

1. White petrolatum

2. Lanolin

Question 9

What is the function of sorbitol in eye drops?

Answer 9

Lowers viscosity of gelling agents such as HP guar and HPMC, which are too viscous to be directly instilled in the eye.

Once instilled on the eye, sorbitol dissipates quickly which allows the solution to be more viscous than it is in the bottle.

Question 10

Name 3 functions of sodium hyaluronate in eye drops

Answer 10

1. Controls localised inflammation
2. Protects and promotes healing of corneal epithelium
3. Lowers tear osmolarity (better than glycerin)

Question 11

Which preservative found in eye drops is notorious for causing eye irritation upon instillation?

Answer 11

Benzalkonium chloride (BAK)

Question 12

What is sodium cromoglycate?

Answer 12

A mast cell stabiliser

Question 13

What is the MOA of olopatadine in eye drops?

Answer 13

A selective histamine H1-antagonist that inhibits release of histamine from mast cells

Question 14

List at least 5 drug classes/ drugs that may worsen dry eyes

Answer 14

1. Antihistamines
2. Anticholinergics
3. Beta blockers
4. Retinoids (e.g. isotretinoin)
5. SSRIs
6. Amiodarone
7. Diuretics
8. Contraceptives

Question 15

Name 3 medical conditions that may contribute to the development of dry eyes

Answer 15

1. Uncontrolled diabetes
2. Parkinson’s
3. Sjögren’s syndrome