Walsh & Hoyt: Methods of Measuring Accommodation

The principal difficulties encountered in the clinical quantitation of accommodation are the subjective nature of the end points and the number of variables that must be controlled if meaningful information is to be obtained. The accommodative amplitude of an eye is visually estimated by bringing fine print toward it and recording the distance at which the print blurs. However, when the near point of accommodation is measured in this manner, the end point (blurring of the print) is often indistinct because the patient is required to make a judgment of the quality of the image. Egan suggested the use of a cross cylinder in front of the eye with a series of horizontal and vertical lines to replace the fine print. Suddenly seeing the vertical lines blur while the horizontal lines remain sharp should result in an accurate and reproducible near point of accommodation. However, fine print may well represent a better accommodative stimulus than nonspecific lines.