Abstract
Purpose :
Atomic Force Microscopy (AFM) has proven to be a useful method for characterizing corneal mechanical properties ex vivo. However, traditional setups are bulky and cannot be used in vivo. Self-sensing cantilevers (SSCs) are an alternative technology that can be used to replace the traditional AFM cantilever and optical lever system to perform biomechanical measurements. In this study, we compared the performance of a SSC system to a traditional AFM optical lever system in measuring the Young’s Modulus of elasticity of the full-thickness cornea.
Methods :
To avoid variability associated with cadaver tissue, experiments were conducted on a realistic corneal model designed to practice corneal dissection (Cordelia, Bioniko Models). To restore hydration of the corneal model, it was placed in deionized water at room temperature for 30 minutes. After this, it was adhered to a Petri dish and placed in a custom AFM system that has been optimized for biomechanical studies (Ziebarth et al. Mol Vis 2007 Apr; 13:504-510). Traditional AFM cantilevers (1.75N/m, 50mm diameter, sQUBE) were used to measure Young’s modulus of the corneal model in 2 different locations on 3 different days, with at least 10 scans recorded in each location each day. A piezoresistive, self-sensing AFM cantilever (Agar Scientific, Ltd., Essex, UK) was then used to measure the mechanical response of the same sample. A total of 14 measurements were performed at 4 different speeds (7.5mm/s, 10mm/s, 15mm/s, and 30mm/s). All data was analyzed using custom software written in MATLAB.
Results :
Using the traditional AFM system, Young’s modulus of elasticity of the corneal model was 25.8±4.3kPa. Using the SSC, we were able to record a consistent linear response during indentation of the corneal model. The slope (voltage/displacement) and change in voltage were consistent, independent of speed of indentation or day of measurement. The slope was 0.50±0.06N/m, and the change in voltage was 7.85±0.81mN. These values are directly correlated to the Young’s modulus of elasticity of the sample.
Conclusions :
SSC technology can be used to measure biomechanical properties of the cornea, similar to traditional AFM systems. However, due to its small form factor, it has the capability of being applied in in instances of large and geometrically complex samples.
This is a 2021 ARVO Annual Meeting abstract.