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' is a force due to gravity and, therefore, is  measured in newtons in SI. Weight is measured using a spring  balance, calibrated in newtons.Because weight is affected by  gravity, an object of given mass will have a different weight,  according to where it is measured.     'Mass', on the other hand, is measured in kilograms in SI.Mass is  measured by comparing an object of unknown mass with a known mass,  using a scales balance. kilogram is 2.2 lbs, so it is more useful for everyday objects. Things such as â¦ people, furniture, cars, etc. could be measured in kilograms while objects like paper, small amounts of gold, or mail could be measured in grams. 1 kilogram is equal to 1000 grams.