Steady-state accommodation response to different Snellen letter sizes

The steady-state accommodation response to Snellen letters of different sizes was measured with a laser-Badal optometer. It was found that the accommodation response was least when viewing the 6/9 letter size for both monocular and binocular observation at 6 m and increased when the letter size got smaller or larger. The mean accommodation response for the monocular viewing state was significantly higher than the binocular state for Snellen letter sizes between 6/4.7 and 6/12. At 40 cm the accommodation response for different letter sizes showed no obvious trend. However, the lag in binocular accommodation was significantly less than the monocular lag.