In people with keratoconus, rigid contact lenses improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the lens, thereby creating the effect of a smoother cornea.
Rockwell Hardness Testing Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation.lick here to learn more about hardness testing basics. The Rockwell hardness test method, as defined in ASTM E-18, is the most commonly used hardness test method.
The Rockwell hardness number is expressed as a combination of the measured numerical hardness value and the scale letter preceded by the letters, HR. For example, a hardness value of 80 on the Rockwell A scale is reported as 80 HRA. Regular Rockwell Hardness Testing- Measures the bulk hardness of the material.