Scleral lenses have gained popularity in the last decade. From a lens with limited viability for over 100 years to the fastest growing segment of the gas permeable lens market, scleral lenses have come a long way.
Mass and Weight. The mass of an object is a fundamental property of the object; a numerical measure of its inertia; a fundamental measure of the amount of matter in the object. Definitions of mass often seem circular because it is such a fundamental quantity that it is hard to define in terms of something else.
Weight refers to the force experienced by an object due to gravity. Mass refers to the amount of matter in an object. An object with a mass of 1 kilogram will weigh approximately 9.81 newtons. (newton is a unit of force) Mass is also an inertial property meaning the tendency of an object to remain at a constant velocity unless acted upon by an outside force.