Related Experiment Video
Updated: Aug 14, 2026
08:28
Development of an In Vitro Ocular Platform to Test Contact Lenses
Published on: April 6, 2016
pH of multipurpose contact lens solutions over time
A López-Alemany1, R Montés i Micó
1Departament d'Optica, Facultat de Fisica, Universitat de València, Burjassot, València, Spain. Antonio.Lopez-alemany@uv.es
Summary
The pH of multipurpose contact lens solutions remained within a comfortable range for eyes, averaging between 6.99 and 7.56. This study monitored pH stability over 32 days after opening bottles.
Area of Science:
- Ophthalmology
- Optometry
- Materials Science
Background:
- Contact lens solutions are crucial for ocular hygiene and comfort.
- Maintaining optimal pH is essential for biocompatibility and preventing eye irritation.
Purpose of the Study:
- To determine the pH stability of multipurpose contact lens solutions.
- To assess if pH fluctuations fall within the range of ocular comfort over time.
Main Methods:
- Nine brands of multipurpose contact lens solutions were tested in Spain.
- pH was measured daily for 32 days using a calibrated pH-meter.
- 10-ml samples were taken from five bottles per brand.
Main Results:
- Observed pH fluctuations over the 32-day period.
- All tested solutions maintained an average pH between 6.99 and 7.56.
- The pH levels were consistently within the range considered comfortable for ocular application.
Conclusions:
- Multipurpose contact lens solutions generally exhibit stable pH within acceptable limits for ocular comfort.
- The tested solutions are likely safe for extended use regarding pH parameters.
Related Concept Videos
01:23Ophthalmic Drug Delivery Systems
Ophthalmic drug delivery faces major limitations due to poor absorption across the corneal membrane. This process is primarily driven by diffusion and is influenced by two main factors: the physicochemical properties of the drug and tear drainage. Most ophthalmic drugs, such as pilocarpine, epinephrine, atropine, and local anesthetics, are weak bases. They are typically formulated at an acidic pH to enhance chemical stability. However, this leads to high ionization, reducing their ability to...
01:19Composition of Polyprotic Acid Solutions as a Function of pH
Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...
01:18Titration of Polyprotic Base with a Strong Acid
The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
02:41pH Scale
Hydronium and hydroxide ions are present both in pure water and in all aqueous solutions, and their concentrations are inversely proportional as determined by the ion product of water (Kw). The concentrations of these ions in a solution are often critical determinants of the solution’s properties and the chemical behaviors of its other solutes. Two different solutions can differ in their hydronium or hydroxide ion concentrations by a million, billion, or even trillion times. A common means of...
03:22Strong Acid and Base Solutions
A strong acid is a compound that dissociates completely in an aqueous solution and produces a concentration of hydronium ions equal to the initial concentration of acid. For example, 0.20 M hydrobromic acid will dissociate completely in water and produces 0.20 M of hydronium ions and 0.20 M of bromide ions.
01:16Focusing of Light in the Eye
Light rays enter the eye through the cornea, a transparent dome-shaped tissue that is the eye's outermost layer. The cornea bends or refracts, light rays traveling to the pupil. The shape of the cornea determines how much of the light is bent and whether the image will be focused correctly on the retina at the back of the eye. Once the light has passed through both refraction layers, it converges into a single focal point onto a small area. This is where photoreceptors start transforming...