Correction of empty-field myopia on the basis of the dark-focus of accommodation.

The influence of negative spherical corrections on the detection of a small increment flash presented in a uniform field or Ganzfeld were determined. The range investigated included each observer's normal correction as well as values based on the focus assumed by each observer in total darkness (dark-focus of accomodation). A correction equivalent to the dark-focus resulted in maximum sensitivity. The results suggest a convenient technique for the determination of optimal correction for empty-field viewing conditions.