Silicone Hydrogel and Rigid Gas-Permeable Scleral Lens Tear Exchange.

Area of Science:

• Ophthalmology
• Biomaterials Science
• Corneal Physiology

Background:

• Contact lens wear can alter the natural tear film dynamics.
• Understanding tear elimination rate (ER) is crucial for assessing contact lens-induced ocular surface changes.
• Silicone hydrogel (Si-Hy) and scleral gas permeable (GP) contact lenses represent distinct categories of modern contact lens materials.

Purpose of the Study:

• To quantitatively compare the tear elimination rate (ER) under silicone hydrogel (Si-Hy) and scleral gas permeable (GP) contact lenses (CLs).
• To evaluate the impact of different CL types on tear film dynamics in wearers.
• To investigate potential correlations between CL design and tear exchange efficiency.

Main Methods:

• Recruitment of subjects successfully wearing well-fitting Si-Hy CLs or scleral GP CLs, many with irregular corneas.
• Objective measurement of tear ER using a fluorometer to track fluorescein isothiocyanate dextran dye signal decay.
• Calculation of ER in %/min from 5 to 30 minutes to mitigate reflex tearing effects, with specific measurements for scleral GP lenses during settling and later wear periods.

Main Results:

• Scleral GP CL wearers exhibited significantly lower average ER (0.57%/min and 0.42%/min) compared to non-CL wear (34.17%/min).
• Si-Hy CL wearers demonstrated a higher average ER of 6.09%/min.
• The ER under scleral GP lenses was significantly lower than under Si-Hy lenses for both settling and later wear periods (P < 0.001).

Conclusions:

• Well-fitted scleral GP contact lenses result in significantly reduced tear elimination rates compared to soft Si-Hy contact lenses.
• The observed lower ER under scleral GP lenses suggests improved tear film stability and reduced tear turnover.
• A slight increase in tear exchange during the initial settling period of scleral GP lenses may indicate dynamic changes in tear vault thickness.