ABO advanced A+ Compiled Revision Questions and Certified Answers 2024

Base Curve - Curvature of the front of the lens How is Cyl ground on a minus cyl lens? - Single curve on the front. Cyl ground on the back How is cyl ground on a plus cyl lens? - Flattest curve on the front. Old way of doing it do to cosmetics What is Vogels formula used for? - Creating best form and n standard surfacing Vogel's Formula (+ lenses) - Spherical equivalent + 6.00 Vogel's Formula (- lenses) - Spherical equivalent + 6.00 / 2 Corrected Curve Theory rules: - #1 ocular curves (minus side) that fall between -4.00 - - 7.00 are best for delivering non abbe rated vision #2 -as minus increases BC should flatten - as plus increases BC should steepen What are the 2 base curves every lens has? - Nominal - general category (ex. 4.25 or 6.00) Actual/True curve- real measured curve/sag depth Index of refracting formula - Speed of light in air/speed of light in material Speed of light in air? - 186,000 miles per second Flint glass index of refraction and abbe value - 1.58-1.69 & 30-40 Barium glass index of refraction and abbe value - 1.51-1.616 & 55-59 Highlite glass index of refraction and abbe value - 1.70 & 32 CR39 index of refraction and abbe value - 1.49 & 58 Poly index of refraction and abbe value - 1.59 & 30-32 Trivex index of refraction and abbe value - 1.53 & 43-45 5 categories of absorptive lenses - 1- tinted solid glass 2- glass w/surface coatings 3- tinted plastic 4- photochromic 5- polarized Absorption definition - Reduction of transmission of radiant energy through a medium Transmission definitions - Transit or passing if radiant energy through a medium Grey tint characteristics - Most popular Least amount of color change Brown tint characteristics - Uses yellow to increase contrast Good for hazy days Yellow tint characteristics - Can be added to any color to increase contrast Filters out blue light Green tint characteristics - Good color balance w/better contrast than grey Transmission curve closes to the human eye Pink/rose tint characteristics - Reduces glare and softens bright light situations Blue tint characteristics - Causes glare by promoting blue spectrum Vaccum coatings used for: - Mirrors and depositing uniform color on glass lenses Term for snow blindness - Photokeratitis What are polar filters made of? - Thin sheets of polyvinyl alcohol being stretched in one meridian Who released photochromic lenses - Corning When we're photochromic lenses released - 1964 What molecule changes in photochromic lenses - Silver halide crystals Methods used for creating photochromics - Imbibing, extrusion, injection molded, cast, or mixed in monomer What method of creating photochromics does transitions use? - Imbibing How does imbibing work? - A high pressure spray is deposited on the lens then exposed to high temps to assist the solution in permeating the surface