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.
The mass of an object is how much matter is contained within that object. The SI unit of measure for mass is the kilogram. The word mass should be used instead of the term 'weight', which suggests the force of gravity acting upon the object. The mass of an object is how much matter is contained within that object. The SI unit of measure for mass is the kilogram.