Effects of contacts on teart film

Question 1

Soft lenses

Answer 1

Increased tear evaporation & decreased tear film stability

Reduced TBUT (Tear Break-Up Time); tears absorbed into lens

After 3 months of CL wear:
TBUT ↓ by ~3 seconds
DED incidence ↑ from 28% → 68%
TBUT <6 seconds is common in CL wearers

Signs of CL-related Dry Eye:
SEAL (Superior Epithelial Arcuate Lesion)
SMILE (Superior Limbal Epithelial Staining)
Surface desiccation
Conjunctival compression ring

Question 2

RGP

Answer 2

Less impact on the tear film compared to soft contact lenses, as tears don’t soak into the lens matrix.

RGPs promote greater tear exchange.
The lens does not conform to the anterior surface of the eye, potentially causing 3 and 9 o’clock staining.

Foreign bodies (FBs) and film contaminants are more common in RGPs due to higher tear exchange, which can further destabilize the tear film

Question 3

Wearer selection elimionates for RGPs

Answer 3

liminate candidates with:

Marked tear film instability
Prone to deposits
Tear-related intolerance
NITBUT (Non-Invasive Tear Break-Up Time) of <10 seconds (not realistic for RGP use)
History of laser eye surgery, cataract surgery, autoimmune diseases, or certain medications.

Question 4

Managing Dry Eye in Soft Contact Lenses (SCLs)

Answer 4

SiHy (Silicone Hydrogel) lenses have lower water content, reducing moisture loss during dehydration.

Some SiHy lenses are modified to improve wettability and lubricity, enhancing comfort.
The primary goal is to reduce tear film evaporation.

Material: Use ionic lenses for regular replacement, or non-ionic lenses for longer wear.

Thinner lenses are more beneficial for managing dry eye.

Wear schedule: Minimize wear time to
reduce symptoms.
Use unpreserved lubricants to avoid irritation.

As a last resort, high water content hydrogels with minimal wear time can help, as they maintain a stable tear film and stimulate reflex tearing upon blinking.
SiHy daily lenses are preferable, as they are thinner and have a low water content. Dailies Total 1 have a higher water content at the center than the edges, offering high oxygen transmissibility (Dk/t).

Question 5

Managing dry eye with RGPS

Answer 5

Greater tear exchange and mucin resurfacing help maintain tear film stability.
No pervaporation staining due to the lens design.

Higher centration, larger total diameter (TD), and minimal edge thickness promote better fit and comfort.