Clinical Report: Midday Removal and Reinsertion of Soft Contact Lens Cannot Prevent Post-lens Tear-film Hyperosmolarity

SIGNIFICANCE Our analysis shows that post-lens tear-film (PoLTF) hyperosmolarity is not preventable with midday removal and reinsertion of soft contact lenses. However, low lens-salt diffusivity can prevent the PoLTF from becoming hyperosmotic. Lens-salt diffusivity should be lowered to minimize PoLTF osmolarity while also avoiding lens adhesion. PURPOSE Soft contact lenses with high lens-salt diffusivity result in hyperosmotic PoLTFs. If the time it takes for PoLTF osmolarity to reach periodic steady state is multiple hours, simple midday lens removal and reinsertion can prevent the PoLTF from becoming hyperosmotic. We investigate whether midday removal and reinsertion of a soft contact lens can prevent the PoLTF from becoming hyperosmotic. METHODS Time to periodic steady state for PoLTF osmolarity upon soft-contact-lens wear is determined with a previously developed transient tear-dynamics continuum model. Interblink period, lens-salt diffusivity, and lens thickness was varied to assess their effects on time to periodic steady state for PoLTF osmolarity. Time to periodic steady states were assessed for both normal and dry eyes. RESULTS Within the physically realistic ranges of lens-salt diffusivity, lens thickness, and interblink period, PoLTF osmolarity reaches the periodic steady state well within the first hour of lens wear for both normal and dry eyes. Time to periodic steady state for PoLTF osmolarity is predominately dictated by the salt transport across the contact lens between the PoLTF and the pre-lens tear film and water transport from the ocular surface to the PoLTF. CONCLUSIONS Since the time to periodic steady state is less than 1 hour for physically realistic ranges of lens-salt diffusivity, interblink period, and lens thickness, midday lens removal and reinsertion cannot prevent PoLTF hyperosmolarity. Instead, focus should be on using soft contact lenses with low salt diffusivity to prevent PoLTF hyperosmolarity.

Automated summary

Our analysis suggests that midday removal and reinsertion of soft contact lenses cannot prevent hyperosmolarity in the post-lens tear film. However, using soft contact lenses with low salt diffusivity can prevent hyperosmotic post-lens tear films.