ACCURACY OF POWER MEASUREMENT WITH AN OPTICAL PROJECTION FOCIMETER

Title ACCURACY OF POWER MEASUREMENT WITH AN OPTICAL PROJECTION FOCIMETER
Author, Co-Author Pierre O.D., Jacques O.D., Marie O.D., Sylvie O.D.
Topic
Year
1992
Day
Sunday
Program Number
Poster 53
Room
Great Hall
Affiliation
Abstract This study was designed to determine the accuracy of power measurement performed with an optical projection focimeter by focussing the target instrument. Measurements were performed with an Essilor Axil optical projection focimeter with a diaphragm aperture of 7.5 mm and for power reading at 0.01D. Experimental procedures included zero setting, measurement of a +10D precision lens (Melles Griot, 01LP017) and assessment of cylindrical and spherical trial lenses with nominal powers of -0.12, -0,25 and -0,50 D. Focusing the target was performed without knowledge of power display. In experiment 1, each student of first and second year of optometry program (inexperienced observers, n=81) performed the measurement in each experimental condition. In experiment 2, three optometrists involved in ophthalmic optics (experimented observers) performed 20 repeated measurements for each condition. Experiment 1 shows that the standard deviation (SD) of power measurement varies from 0.02 to 0.08 D depending on the condition. The sensitivity of astigmatism detection is 45% for the 0.12D cylinder and 93% for the 0.25D one. In experiment 2, SD is not more than 0.03D for sphere and 0.04D for cylinder. Sensitivity of astigmatism detection is 88% and 100% for 0.12 and 0.25D cylinders respectively. For trained observers, the accuracy of the instrument is equivalent to that obtained with automatic electronic focimeters.
Affiliation of Co-Authors
Outline