Scleral lens landing zone toricity and tear exchange

To quantify the effect of landing zone toricity on tear exchange during short-term scleral lens wear using a profilometry based method.

Nine healthy participants wore scleral lenses (KATT™, Capricornia) with a spherical and 150 μm toric landing zone in a randomised order on separate days, with other lens parameters held constant. Following the instillation of 10 µl of 2 % sodium fluorescein, Eye Surface Profiler images were captured over 100 min of lens wear. A second dose of 10 µl of 2 % sodium fluorescein was instilled after 90 min of lens wear. Fluorescence intensity data were extracted and analysed over central (5 mm diameter, coincident with the centre of the horizontal visible iris diameter [HVID]) and peripheral regions (1 mm annulus, with the HVID as the outer border).

Fluorescence intensity varied throughout lens wear, with the toric lens design displaying greater fluorescence intensity than the spherical design at 0, 60, and 100 min (all p < 0.05), when averaged across both regions. The ingress of sodium fluorescein was evident with the toric lens design in both central and peripheral regions during the first 30 min of wear, followed by a gradual decline, while the spherical design stabilised after 5-10 min. The toric lens design displayed tear exchange following the reapplication of sodium fluorescein after 90 min of lens wear, while the spherical design did not.

Scleral lenses with a toric landing zone facilitated greater central and peripheral tear exchange than a spherical lens design. Alterations to the scleral landing zone which enhance tear exchange may have clinical implications for reducing peripheral corneal oedema during lens wear.