In Vitro Repeatability and Inter-Device Agreement of Higher-Order Aberration Measurements in Scleral Lenses Using Two...

Scleral lenses (SLs) are increasingly incorporating complex optical designs, including front surface eccentricity (FSE) optimisation and wavefront-guided (WFG) corrections, to address residual higher-order aberrations (HOAs) in eyes with irregular corneas. Accurate in vitro optical verification of these surfaces relies on Hartmann-Shack (HS) metrology systems, yet commercially available devices differ substantially in lenslet array spatial sampling density, raising questions about their interchangeability for quality control purposes. This study evaluated the repeatability and inter-device agreement of HOA measurements in SLs obtained with two HS metrology systems with substantially different spatial sampling resolution. Sixteen SLs (four symmetric spherical, four spherical with toric periphery, four symmetric aspherical, four aspherical with toric periphery) were measured three times each using the SHSOphthalmic Cito (54 × 54 lenslet array) and SHSInspect Prio (157 × 157 lenslet array). Sphere (D) and Zernike coefficients from third to fifth radial orders were extracted for three aperture diameters (3.00, 5.00, and 7.00 mm) and analysed as root-mean-square (RMS) values by radial order and as Total HOA RMS. Both devices demonstrated excellent within-device repeatability for Sphere, RMS4, and Total HOA RMS (ICC: 0.994-1.000, CV ≤ 4%), while RMS3 and RMS5 showed moderate repeatability (ICC: 0.591-0.964, CV: 7-21%). Inter-device agreement was excellent at 5.00 and 7.00 mm (ICC: 0.950-1.000, mean bias < 0.006 μm), with a significant difference only for RMS3 at 7.00 mm aperture (p = 0.034). At 3.00 mm, significant systematic bias was detected for RMS4 (bias = -0.00102 μm, p < 0.001) and Total HOA RMS (bias = -0.00092 μm, p < 0.001), with the Cito underestimating values relative to the Prio. FSE design did not significantly influence inter-device differences. HS spatial sampling density influences HOA measurement accuracy in SLs at small apertures, and standardised high-resolution metrology protocols are essential to ensure accurate HOA characterisation.