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The pH of aerosol saline solution
M G Harris1, C K Higa, L L Lacey
1Morton D. Sarver Laboratory for Contact Lens and Corneal Research, School of Optometry, University of California, Berkeley.
Summary
Buffered aerosol saline solutions maintain a pH suitable for ocular comfort, unlike unbuffered solutions. This study indicates all aerosol saline should be buffered for safe soft contact lens wear.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Materials Science
Background:
- Aerosol saline solutions are commonly used by soft contact lens wearers.
- The pH stability and ocular compatibility of these solutions during use are critical.
- Previous research has not extensively evaluated pH changes in aerosol saline during normal usage.
Purpose of the Study:
- To assess the pH stability of aerosol saline solutions during typical usage.
- To compare the pH of buffered versus unbuffered aerosol saline solutions.
- To determine the suitability of aerosol saline pH for ocular comfort.
Main Methods:
- Eight brands of aerosol saline solution were tested.
- pH measurements were recorded daily for 14 to 24 days using a calibrated pH meter.
- Saline was dispensed in 15-ml increments, simulating daily use by soft lens wearers.
Main Results:
- No significant pH change was observed within individual aerosol saline brands over the study period.
- A statistically significant difference in median pH was found between buffered and unbuffered solutions.
- Buffered solutions averaged a pH of 7.30 (within ocular comfort range), while unbuffered solutions averaged 5.79 (outside ocular comfort range).
Conclusions:
- Buffered aerosol saline solutions maintain a pH conducive to ocular comfort.
- Unbuffered aerosol saline solutions exhibit a pH outside the ocular comfort range.
- It is recommended that all aerosol saline solutions intended for ophthalmic use be buffered.