Researchers suggest that decreasing the center thickness of a high Dk, low modulus miniscleral lens from 350μm to 150μm results in less than a 0.25D increase in lens flexure.
The team came to this conclusion after evaluating nine healthy patients who ranged from 21 to 29 years of age. The participants had normal corneas and were fit with ICD 16.5 miniscleral lenses (hexafocon B material) with center thicknesses of 150μm, 250μm and 350μm.
On average, lens flexure increased as center thickness decreased, but remained below 0.50D. The study also notes that scleral toricity was positively correlated with in vivo flexure for the 150μm and 250μm lenses, and eyes with greater than 200μm of scleral toricity exhibited greater in vivo flexure than eyes with less than 200μm, on average. The researchers found that this effect was greatest for the 150μm lens.
They conclude that “when intentionally reducing scleral lens center thickness to enhance oxygen transmissibility, customized back surface designs may be required to minimize in vivo flexure in eyes with >200μm scleral toricity at a 15mm chord.”
|Vincent SJ, Kowalski LP, Alonso-Caneiro D, et al. Importance of decreasing the center thickness on miniscleral lens flexure. Cont Lens Anterior Eye. July 12, 2018. [Epub ahead of print].|