9 - Dry Eyes

Question 1

Describe 1st gen lubricants
- Pros/cons

Answer 1

Simple lubricants
- e.g. polymers, carbonmer gels, paraffin ointments
Pros:
- Cheap relief, mimics tears
Cons:
- Short residence time
- Ointments blurred vision
- BAK or other preservatives

Question 2

Describe 2nd gen lubricants

Answer 2

Hyaluronic acid:
- Muco-adhesive properties sticks to eye = longer residence time
- Viscoelastic
- Mimics tear film (non-Newtonian)
- Improved epithelial cell health via HA receptors
HP-Guar:
- Similar viscoelasticity
- Improves symptoms

Question 3

DED define

Answer 3

Multifcatoral disease from loss of tear film homeostasis, accompanied by symptoms caused by tear film instability, hyperosmolarity, and ocular surface damage + inflammation.

Question 4

Describe 3rd gen lubricants

Answer 4

• Bioprotection = prevent cell stress/damage/death from hyperosmolarity
• Osmoprotection
• Lipid supplementation restored stability of tear film.

Question 5

5 key principles of lubricating ocular surface?

Answer 5

• Avoid preservatives
• Hyaluronic acid
• Hypotonic formulation
• Protect the ocular surface
• Target the dry eye subtype

Question 6

Describe avoiding preservatives
- What about in glaucoma?

Answer 6

Single most effective change
- COntinous MOno-Dose (COMOD) system prevents backfloew allowing 300 drops per bottle w/o preservatives
- Less harmful preservatives than BAK like Polyquaternium-1, OxyChloro complex, or sodium perborate.

In glaucoma
- BAK as preservative can be used to break down corneal surface for glaucoma drug permeation.
- If ocular surface already damaged from disease, recommend non-preserved drugs

Question 7

Describe Hyaluronic Acid
- Relate viscosity and residence time
- HP-Guar works how?

Answer 7

• Longer lasting than 1st gen due to viscoelastic properties
• Mimics tear film and retains moisture
• Higher viscosity when not blinking much = protection, lower viscosity when blinking more = smooth blinking.
• High H2O binding capacity
• Mimics mucin layer gylcoproteins = higher wettability, binds to cell membranes, even mimics ferning pattern when drying.
• Higher viscosity can increase residence time but variable. Newer drugs avoid too high of viscosity due to temporary blur + reflex tearing/blinking. Unless intended for night use.
• HP-Guar starts as slippery drops so easy to get out of bottle. When react w/ tears, becomes gel-like due to interlinking gel network w/ tears. Makes it stick to eye longer.

Question 8

Describe hypotonic solution

Answer 8

Tears require a balance of electrolytes, cause goblet cells are bad in hyperosmol solutions. In DED, tears evaporate leaving behind hyperosmol solutions. A hypo-osmol drop is therefore required to counteract that, but realistically these types of drops have low residence time
- Bicarbonate (an electrolyte) can promote healing in severe DED

Question 9

What’s protect the ocular surface

Answer 9

• Biocompatible solutes required to help with osmotic stress.

Question 10

Why target the DED subtype?

Answer 10

Otherwise, drops not as effective.
- Lipid sprays can improve lipid layer and allow tear film stability
- Lipid drops offer protection against environmental exposure.
Helps break the vicious cycle of DED

Semi-fluorinated alkanes target EDE
- Perfluorohexyloctane
- Non-preserved
- Small droplet size that rapild spreads
- No blur when instil