Math for ABO test Questions and Answers I ABO (American Board of Opticianry)

Math for ABO test Questions and Answers I ABO (American Board of Opticianry) A Box: 53 DBL: 15 ED: 55 PD: 30/32 OD: 68/2 =34 OS: 68/2=34 What is the MBS for the rt and left lens? (Ans: - OD: 68/2 =34 OS: 68/2=34 Decentration: Frame PD- PT PD OD: 34-30=4 decentered OS: 34-32= 2 decentered OD: MBS=ED+(2xDecenter)+2 MBS=55+ 8 (2x4)+2=65mm OS: MBS=ED+(2x decenter)+2 MBS=55+4 (2x2)+2=61mm OD-65mm blank OS: 61MM blank What is Prentice rule used for? (Ans: - To (Power x distance in mm) /10find prismatic effect What is the formula for Prentice Rule? (Ans: - (Power x distance in mm) /10 How do you find Minimum blank size? (MBS) (Ans: - MBS= ED + (2xdecenter)+2 What is image jump? (Ans: - The sudden displacement of am image as the bifocal line is crossed. The amount of image jump for a given style of bifocal is independent of the power in the distance portion. Can image jump be calculated? and if so how is it done? (Ans: - Yes. Use Prentice Rule.