7 - Tear Subs & Preservatives

Question 1

Tear substitutes

-brief description

Answer 1

Synthetic water-based solutions

Lubricate eye and replace aqueous portion of tears

Several types of substances used to enhance lubrication

• cellulose esters (carboxymethylcellulose + hydroxymethylcellulose)
• polyvinyl alcohol (PVA)

Commonly used 3-4x/day
-if more, use preservative free

Question 2

Tear substitutes

-main disadvantage

Answer 2

90% is eliminated w/in the first minute or two

Methylcellulose incr viscosity, allowing more contact time with cornea
-PVA is not as viscous

Question 3

Restasis

-MOA

Answer 3

Inhibits T-cell activation by stopping IL-2 production
(IL-2 activates T-cells)

Takes 3mo to work

Question 4

Benzalkonium chloride

Answer 4

Very common

Corneal toxicity = SPK!

Question 5

Thimerosal

Answer 5

Rarely used anymore
-used in trifluridine (viroptic, herpes tx 9x/day)

Sensitivity to mercury component
Prolonged use (3+ weeks) not recommended due to toxicity

Question 6

Ethylenediaminetetraacetic acid (EDTA)

Answer 6

Chelating agent, sequester Ca2+

Band keratopathy

Question 7

Purite/sodium perborate

Answer 7

Oxidative preservative in Refresh/GenTeal, respectively

Effective + less toxic

Question 8

Findings in pts with toxic reaction to preservative

Answer 8

Diffuse SPK

Follicles (chaT)