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.
Aptitude test. Aptitude test, examination that attempts to determine and measure a personâs ability to acquire, through future training, some specific set of skills (intellectual, motor, and so on). The tests assume that people differ in their special abilities and that these differences can be useful in predicting future achievements.