BackgroundWe needed to validate and calibrate our portable acuity screening tools so amblyopia could be detected quickly and effectively at school entry.MethodsSpiral-bound flip cards and download pdf surround HOTV acuity test box with critical lines were combined with a matching card. Amblyopic patients performed critical line, then threshold acuity which was then compared to patched E-ETDRS acuity. 5 normal subjects wore Bangerter foil goggles to simulate blur for comparative validation.ResultsThe 31 treated amblyopic eyes showed: logMAR HOTV = 0.97(logMAR E-ETDRS)-0.04 r2 = 0.88. All but two (6%) fell less than 2 lines difference. The five showed logMAR HOTV = 1.09 ((logMAR E-ETDRS) + .15 r2 = 0.63. The critical-line, test box was 98% efficient at screening within one line of 20/40.ConclusionThese tools reliably detected acuity in treated amblyopic patients and Bangerter blurred normal subjects.These free and affordable tools provide sensitive screening for amblyopia in children from public, private and home schools. Changing “pass” criteria to 4 out of 5 would improve sensitivity with somewhat slower testing for all students.