EVALUATION OF THE INTERNATIONAL STANDARDS ORGANISATION DRAFT INTERNATIONAL STANDARD MODEL EYE FOR USE WITH AUTOMATED INFRARED OPTOMETERS

A recent Draft International Standard describes a method for establish ing the accuracy of automated infra-red optometers, using model eyes. In the present study we evaluate the performance of a series of automa ted infra-red optometers using model eyes constructed to the specifica tions of the Draft International Standard. The results demonstrate sys tematic differences between the values predicted by calculation from t he standard and those found by measurement. These differences were red uced but not eliminated when the effects of non-paraxial refraction th rough the limiting aperture of the model eyes was taken into account. We conclude that the formula used to predict values of refractive powe r from the Draft International Standard is inappropriate because it fa ils to account for higher order aberrations.