ABO Practical broken down based on the ABO-NCLE practical Exam Candidate HandbookPractical Test Specifications sheet Questions and Answers

Single Vision - corrects for one distance Multifocal - Corrects with two or more prescriptions (or 'powers') Bifocal - lens having two focus strengths Trifocal - pertaining to having three focus strengths Calculating Prismatic Effects - obtained at the center of an optical lens by producing a difference in edge thickness, either by grinding the back surface at an angle to the front surface during lens surfacing or, if the lens has sufficient power, de-centering the optical center of the lens Compounding Prism - BI & BI BO & BO BU & BD Cancelling Prism - BI & BO BD & BD BU & BU Prentice's Rule - P=hcm x D P=amount of prism created h= number of cm OC moved cm= centimeters (convert to mm, divide by 10) D= power in meridian with error Vertical Imbalance - The difference in vertical prism power at the reading level in a pair of lenses. OC Height's by lens - SV = 1/2 of B Progressive = Fitting cross FT = 5mm above segment Vertex Compensation - A plus lens when moved farther from the eye gains in plus power Distance is 0 with CL because they are on the eye Vertex compensation Formula - De= Dl/(1 + d xDl) De= diopter effective value of error created D/= lens power (given power) d= amount in METERS lens moved from refracted position to position lens is worn Keep sign for what it is (+/-) - to d means moves away Horizontal Centration - PD Vertical Centration - OC Horizontal & Vertical Centration Formula - Given PD/OC - Human PD/OC= mm moved Frame PD is found by adding A+DBL Power in Oblique Meridians - Dt= (sina)²x Dc +Ds Dt= Total Power we need (sina)²= degree we have degree we need Dc= cylinder power Ds= sphere power Lensmeter - is an ophthalmic instrument. It is mainly used by optometrists and opticians to verify the correct prescription in a pair of eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames. (also known as a focimeter or vertometer) Lens Measurement Devices - lens clock, calipers, millimeter ruler, circumference gauge Lens Clock - is used to measure the surface powers base curve of a lens Lens Calipers - Measures thickness of lenses in mm Millimeter ruler - measures interpupillary distance, or seg heights, or OC heights Circumference gauge - For quick and accurate measurements of lenses or patterns. Corneal reflex Pupilometer - for precisely measuring and digitally recording pupillary distances. Used for measuring of monocular and binocular Hand Tools - Screwdrivers, needle-nose pliers, tweezers, files scratchless screwdriver - for working on drill mount or facetted lenses pickup screwdriver - jaws with spring tension to hold screws while you put them in place, available with either type blade Big Brass screwdriver - unscrew most screw, with a large brass handle plastic top screwdriver - most popular and most dangerous Pad Popper - used to remove snap-in nosepads without changing the alignment of the adjustable guard arms. the prongs are inserted behind the nosepad and in front of the nosepad box. a simple twist removes the pad Rimless mounting tool - the hook is started at the hinge side of the nylon line that pulls around the lens. use caution, easy to chip lens eyewire sizing pliers - used to check the size of the lens without damaging the barrels of the frame