[Osmogenic causes of reversible changes in light scattering power and refraction of hydrophilic intraocular lens in the early postoperative period].

Abstract

Recently, hydrophilic acrylic intraocular lenses (IOLs) have become the most widely used in clinical practice due to simpler manufacturing process and known optical disadvantages of hydrophobic lenses (e.g., dysphotopsia effect). Acrylic hydrophilic lenses, similar to polymethylmethacrylate and silicone IOLs, are susceptible to both reversible and irreversible optical changes intraoperatively and in the early postoperative period. The optical properties of the IOL may be affected by its transfer from one medium to another with a short-term shock effect on the lens polymer followed by chemical relaxation within the IOL-medium system.

Purpose: This study evaluated potential changes in the optical power and light-scattering properties of the IOL material resulting from rapid changes in the osmolarity of the surrounding medium.

Material and methods: Physical models based on a commercially available hydrophilic IOL were created to assess changes in the refractive index of the polymer and the quality of light transmission in response to the change of bathing solution. An original photometer and a series of test saline solutions with varying osmolarities were prepared for this purpose.

Results: The most pronounced refractive effect was observed when the bathing solution was switched from isotonic to hypertonic. The increase in the refractive index of the IOL material amounted to Δn = +0.0038, which could translate into clinically significant changes of 0.25-0.6 diopters depending on the initial IOL power. Returning the IOL to isotonic conditions after prolonged exposure to hypo- or hyperosmolar environments led to reversible opacification of the lens material. Optical destabilization effects were observed within the first hours (refraction) and could persist for up to 24 hours.

Conclusion: The conducted experiments model potential violations of IOL storage and transportation guidelines prior to implantation. The findings provide insights into certain reversible optical phenomena in hydrophilic IOLs, and can help explain the results of clinical assessments in the early postoperative period.