Comparison of four technics of surface roughness assessment of corneal lamellar cuts

Abstract

PurposeSurface roughness of corneal lamellar cuts is a crucial quality criterion, because smother is the cutting plan, better will be the visual recovery. Nevertheless, despite several studies published in the last years, it remains difficult to reliably quantify the differences between a microkeratome (MKT) and a femtosecond laser (FSL). A possible reason could be that the different studies employed different technics to assess surface roughness. AimTo directly compare 4 microscopy technics of surface roughness assessment of corneal lamellar cuts.MethodsStromal lamellae were cut in organ cultured human corneas with a Moria MKT or a FSL. Environmental scanning electron microscopy (eSEM), standard SEM and chromatic confocal microscopy (CCM) were first used to verify that dehydration and metallization of samples did not artefactually alter the surface state. Three 3 quantitative methods (Atomic Force Microscopy (AFM), CCM and Focus‐Variation Microscopy (FVM)) were then compared using the same stromal lamellae. Lamellae with low or high surface roughness were selected with sSEM. The Bowman membrane was used as a smooth control. Roughness quantification was done with Mountains, a validated software.ResultsCompared to eSEM, sSEM provided better image contrast allowing better visualization of the surface roughness. Dehydration and metallization did not change the surface appearance with eSEM and sSEM, and did not modify the roughnesses measured by CCM. Only CCM and FVM were able to reveal significant differences between lamellae of different roughness. CCM allowed acquisition of larger areas, allowing a better characterization of heterogeneous surfaces.ConclusionsCCM seems to be particularly suitable for quantifying the roughness of cutting plans obtained in the cornea.