Related Experiment Videos
Tear exchange under hydrogel contact lenses: methodological considerations.
J R Paugh1, F Stapleton, L Keay
1Cornea and Contact Lens Research Unit, School of Optometry and the Cooperative Research Centre for Eye Research and Technology (CRCERT), University of New South Wales, Sydney, Australia.
Investigative Ophthalmology & Visual Science
|November 1, 2001
Summary
This study optimized fluorophotometry to measure tear exchange behind contact lenses. Silicone hydrogel lenses demonstrated superior tear exchange compared to traditional hydrogel lenses.
Area of Science:
- Ophthalmology
- Biomaterials Science
- Optometry
Background:
- Tear exchange behind contact lenses is crucial for ocular health and comfort.
- Quantifying tear exchange kinetics aids in contact lens material development and evaluation.
Purpose of the Study:
- To characterize tear exchange kinetics behind hydrogel contact lenses using fluorophotometry.
- To compare tear exchange between a marketed hydrogel lens and a prototype silicone hydrogel lens.
Main Methods:
- Utilized fluorophotometry with FITC-dextran tracer to measure tear exchange in 11 subjects wearing extended-wear soft contact lenses.
- Modeled tear exchange parameters including tear replenishment rate (TRR), elimination rate (ER), and time for 95% signal elimination (T95).
- Compared ER and T95 under various conditions and between lens types with differing oxygen permeability (Dk).
Main Results:
- Physiological tear elimination rate (ER) was 8.8% per minute, with T95 averaging 31.0 minutes.
- No significant differences in ER or T95 were found between right and left eyes or between habitual and controlled blinking.
- A prototype silicone hydrogel lens (Dk 140) exhibited significantly higher ER than a marketed hydrogel lens (Dk 28).
Conclusions:
- Fluorophotometry provides reliable estimates of postlens tear exchange, comparable to previous studies.
- Tear exchange can be described by ER, TRR, and T95, with double-exponential kinetics best fitting initial fluorescent decay.
- The technique effectively discriminates between contact lens materials with different oxygen permeability.