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Smoothness assessment of corneal stromal surfaces

journal » Cataract
Sébastien Roy , jean-meunier , anca-marian , ossama-nada , francois-legare , francois-vidal , isabelle-brunette , santiago-costantino
Date : 2013-01

Résumé

PURPOSE: To assess the accuracy of the scanning electron microscopy (SEM) and present alternative approaches to quantify surface roughness based on numerical analysis. SETTING: Department of Ophthalmology, Maisonneuve-Rosemont Hospital, University of Montreal, Montreal, Quebec, Canada. DESIGN: Experimental study. METHODS: Lamellar stromal cuts were performed on human corneas using a femtosecond laser or a microkeratome. The photodisrupted stromal surfaces were processed for SEM, and images were acquired at ×1000 magnification. First, images were evaluated by independent observers. Second, images were analyzed based on first-order and second-order statistics of gray-level intensities. Third, 3-dimensional (3-D) surface reconstructions were generated from pairs of SEM images acquired at 2 angles. RESULTS: Results show that traditional assessment of roughness based on evaluating SEM images by independent observers can be replaced by computer-image texture analysis; an algorithm was developed to avoid subjective and time-consuming observations. The 3-D reconstructions allowed additional characterization of surface properties that was not possible with SEM images alone. Significant fluctuations in surface height were lost, although they could be retrieved using 3-D reconstructions. CONCLUSIONS: Image texture analysis allowed objective and repeatable assessment of stromal surface roughness; however, full assessments of surface-height fluctuations required 3-D reconstruction. These complementary methodologies offer a more comprehensive assessment of corneal surface roughness in clinical applications.

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