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Updated: Jun 10, 2026
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Synthesis of Soft Polysiloxane-urea Elastomers for Intraocular Lens Application
Published on: March 8, 2019
Void volume variations in contact lens polymers
P Sane1, F Tuomisto, J M Holopainen
1Department of Applied Physics, Aalto University, Otakaari 1M, 02150 Espoo, Finland. petri.sane@tkk.fi
Summary
Positron annihilation lifetime spectroscopy (PALS) revealed significant differences in void sizes across contact lens materials. Larger voids in monthly lenses correlate with oxygen diffusion, but decrease with albumin exposure, impacting oxygen permeation.
Area of Science:
- Materials Science
- Polymer Science
- Biotechnology
Background:
- Contact lenses are polymer-based devices requiring specific microstructural properties for safe and effective use.
- Understanding void size and free volume is crucial for predicting oxygen diffusion and material performance.
- Positron annihilation lifetime spectroscopy (PALS) is a sensitive technique for probing nanoscale voids in materials.
Purpose of the Study:
- To investigate void size and free volume properties in hydrated contact lens materials.
- To correlate these microstructural properties with oxygen diffusion and contact lens usage recommendations.
- To evaluate the impact of albumin exposure on void size and oxygen permeation in monthly contact lenses.
Main Methods:
- Positron annihilation lifetime spectroscopy (PALS) was employed to characterize void size distributions.
- Three contact lens materials were analyzed: Balafilcon A, Hilafilcon B, and Polymacon.
- Void size changes were monitored after incubation in artificial aqueous tear (albumin-water solution).
Main Results:
- Significant differences in void volume were observed, with up to a 100% difference between Hilafilcon B and Balafilcon A.
- Larger voids in monthly lenses (Balafilcon A) correlated with higher oxygen diffusion rates, aligning with usage recommendations.
- Albumin exposure reduced void sizes by 25% in Balafilcon A lenses over 4 weeks, decreasing oxygen permeation.
Conclusions:
- PALS is a viable method for quantifying microstructure and void properties in biotechnologically relevant polymers like contact lenses.
- Measured void sizes correlate well with contact lens usage recommendations (daily vs. monthly disposables).
- PALS can be applied to polymer-based intraocular devices where diffusivity is critical, showing potential for future material development.
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