Purchase this article with an account.
Young Hyun Kim, Thien Nguyen, Meng C Lin, Cheng-Chun Peng, Clayton J Radke; Effect of Soft-Contact-Lens Wear on Post-Lens Tear-Film Osmolarity. Invest. Ophthalmol. Vis. Sci. 2021;62(8):656.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Despite correlation between tear hyperosmolarity and dry eyes (Tomlinson et al. ), no correlation has been found between tear osmolarity and soft-contact-lens (SCL) wear discomfort. This is likely because clinical instruments measure meniscus osmolarity rather than that in the post-lens tear film (PoLTF) where tear interfaces corneal nerve endings. We quantify the time-periodic differences in osmolarities between various tear-compartment during SCL wear.
Pre-lens tear-film (PrLTF), PoLTF, pre-conjunctival tear-film (PrCjTF) (i.e., the tear film on the bulbar conjunctiva), and meniscus osmolarities are determined based on water and salt conservation balances. The physical model simulates tear-film deposition, black-line formation, interblink period, and eyelid closure following Cerretani and Radke (2014). Lens ion diffusivity (D), ion partition coefficient (k), and thickness are varied to assess the effect of lens properties on various tear-compartment osmolarities. Similarly, tear production and evaporation rates are varied to ascertain the differences in tear osmolarity between normal and dry eyes. All tested parameters are obtained from commercially available SCLs and published studies.
Figure 1 provides various tear-compartment periodic osmolarities during normal eye SCL wear for low and high Ds. Increasing lens thickness, decreasing D, and decreasing k all reduce PoLTF osmolarity. However, the effect of k is small for commercially available SCLs. For hypertonic dry eyes, osmolarities of all compartments are elevated depending on the severity of the dry eye. Tested parameters show PoLTF and meniscus osmolarities vary between 303 to 340 mOsM and 310 to 325 mOsM, respectively. Meniscus osmolarity depends on dry-eye conditions and not on lens parameters.
We devised a numerical tool to determine PoLTF osmolarity during SCL wear for the first time. PoLTF osmolarity changes significantly with lens parameters but not the meniscus osmolarity. Tear osmolarity of dry eye is more sensitive to changes in lens parameters than the normal eye. Understanding correlation between SCL wear discomfort and PoLTF osmolarity requires further investigation as the corneal nerves interact with the PoLTF and not with meniscus tear.
This is a 2021 ARVO Annual Meeting abstract.
Figure 1: Osmolarity of various tear compartments during soft-contact-lens wear with low (a) and high (b) ion diffusivities for normal eye.
This PDF is available to Subscribers Only