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The pH of multi-purpose soft contact lens solutions
1Morton D. Sarver Laboratory for Contact Lens and Corneal Research, University of California, Berkeley, School of Optometry, USA.
Summary
Multi-purpose contact lens solutions were tested for pH levels. All solutions maintained pH within the ocular comfort zone, suggesting pH-induced discomfort is unlikely for soft contact lens wearers.
Area of Science:
- Ophthalmology
- Optometry
- Biomedical Engineering
Background:
- Contact lens discomfort is often associated with pH variations in lens care solutions compared to natural tear pH.
- Understanding the pH of multi-purpose solutions is crucial for preventing ocular irritation.
Purpose of the Study:
- To evaluate the pH stability of three common multi-purpose soft contact lens solutions.
- To determine if the pH of these solutions falls within the range of ocular comfort.
Main Methods:
- A Fisher Scientific Accumet 950 pH/ion meter was used to measure the pH of three multi-purpose solutions over 23-36 days.
- Daily measurements were taken using 15-ml increments to simulate typical usage.
- pH values were compared against the ocular awareness threshold (outside 6.6-7.8) and tear pH (7.45).
Main Results:
- The average pH values were: ReNu (7.18 ± 0.02), Opti-One (6.97 ± 0.02), and Complete (7.55 ± 0.02).
- All tested solutions consistently remained within the established zone of ocular comfort (6.6-7.8).
- pH values exhibited minimal fluctuation throughout the testing period.
Conclusions:
- The pH of the evaluated multi-purpose contact lens solutions is unlikely to cause patient discomfort.
- While pH appears stable, eye care practitioners should still exercise care in selecting appropriate lens care products for individual patient needs.