Contact lenses affect corneal stromal pH

Area of Science:

• Ophthalmology
• Corneal Physiology
• Contact Lens Science

Background:

• Corneal acidosis, a decrease in corneal pH, is increasingly recognized as a factor potentially affecting corneal structure and function.
• Understanding the impact of contact lens parameters on corneal physiology is crucial for safe and effective lens wear.

Purpose of the Study:

• To investigate the relationship between the oxygen transmissibility (Dk/L) of hydrogel contact lenses and changes in corneal stromal pH.
• To assess the effect of both closed-eye and open-eye conditions on lens-induced corneal acidosis.

Main Methods:

• A noninvasive fluorometric technique was employed to measure central corneal stromal pH.
• Subjects wore hydrogel lenses of identical material but varying powers under both open- and closed-eye conditions.

Main Results:

• During closed-eye wear, a significant reduction in central stromal pH was observed, independent of the lens's Dk/L.
• During open-eye wear, central stromal pH also decreased, with the degree of acidosis directly correlated with the lens's Dk/L.
• Corneal pH reductions persisted even after the removal of lenses following extended wear.

Conclusions:

• Extended wear of hydrogel contact lenses can induce significant corneal acidosis.
• The oxygen transmissibility (Dk/L) of hydrogel lenses plays a role in the degree of corneal acidosis during open-eye wear.
• These findings highlight potential risks associated with prolonged hydrogel lens use and underscore the importance of oxygen permeability for corneal health.