Abstract

A photographic method, eccentric photorefraction has been developed which allows measurement of accommodation. The method was designed for the testing of infants and young children where traditional methods such as retinoscopy are difficult to deliver since the child's attention cannot always be sustained. Eccentric photorefraction shares a common principle with previous photorefractive methods in that a small flash source illuminates the eyes of a subject some distance (eg 150cm) from the camera. In this method, the source is placed eccentrically to the limiting aperture of the camera. The camera is focussed on the subject. Depending upon the accommodation of the subject, a "crescent" of light can be photographed in the pupil margin. The position of the crescent is dependent upon whether the eye is defocussed in front or behind the camera. For a given pupil size, the width of the crescent will vary with the magnitude of the eye's defocus. The optical analysis of the method has been described.^2,3 When the source is placed at specific eccentricities from the camera aperture, distinct working ranges are defined². Measurement of a large range of accommodative responses is possible. Accurate measures of accommodation require that a calibration be made from human eyes placed at known degrees of defocus. Once the adjustment has been made the method is suitable for clinical measures of accommodation.⁴

© 1988 Optical Society of America