Related Experiment Video
Updated: Feb 12, 2026

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification
Published on: April 7, 2017
Hydrogel Contact Lens Water Content is Dependent on Tearfilm pH
Morris R Lattimore1, Thomas H Harding1, Steven T Williams1,2
1Visual Performance and Protection Division, U.S. Army Aeromedical Research Laboratory, 6901 Farrel Road, Fort Rucker, AL 36362.
Introduction:
Based on clinical inferences, investigators theorized in situ soft lens hydration was linked to the precorneal tearfilm pH.
Methods:
Forty-one myopic subjects at Fort Rucker, AL, USA were fitted with one of two types of extended-wear soft contact lenses, and were followed quarterly for a period of 33 mo. The anterior soft contact lens surface pH was measured in situ, while the in vitro lens water content was measured immediately after lens removal, using a hand-held refractometer on one lens, and a gravimetric means of hydration measurement on the other lens.
Results:
The in situ pH increased logarithmically across extended wearing time, reaching an asymptote at approximately 5 d' wearing time at a pH of 7.45 ± 0.03. Lens water content was shown to similarly decrease at an inversely logarithmic rate, leveling off at 4-5 d' extended wearing time. Both means of hydration assessment correlated well with each other across days' extended wearing time (R = 0.98; p < 0.0001).
Discussion:
A log-log dual conversion yielded significantly different linear slopes (p < 0.001), based on a multifactorial analysis of both lens types, by the pH, and by their water content. The differing ionic status of each material accentuated their varied polar attraction characteristics. Two soft lenses, identical in all patient-based parameters, could provide differing oxygen availability, as well as differing physical fits in patients of identical physical characteristics, as a result of their unique tearfilm pH differences.
Conclusion:
The in situ hydrogel lens water content is directly dependent on the precorneal tearfilm pH.
Related Concept Videos
Contact-dependent Signaling
Gap Junctions
In animal cells, gap junctions are formed...
Body Water Content and Fluid Compartments
Contact Angle
The adhesive force is the molecular force between molecules of different materials, that is, between the molecules of the solid and the liquid. The cohesive...
States of Water
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
Stereotype Content Model
Water and Mineral Acquisition

