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Journal of the Optical Society of America

Journal of the Optical Society of America

  • Vol. 37, Iss. 5 — May. 1, 1947
  • pp: 321–334

The Change in Refractive Power of the Human Eye in Dim and Bright Light

GEORGE WALD and DONALD R. GRIFFIN  »View Author Affiliations

JOSA, Vol. 37, Issue 5, pp. 321-334 (1947)

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It has been reported that the human eye behaves as though relatively short-sighted in dim light. Observers tend to compensate for this change by setting optical instruments more negatively in dim than in bright light. New measurements of telescope settings by 21 observers reveal an average increase in power of the eye in dim light of 0.59 diopter (range +1.4 diopters to -3.4 diopters). The dilation of the pupil in dim light does not contribute significantly to this phenomenon. The chromatic aberration of the eye was measured in 14 observers with a specially designed spectral stigmatoscope. The refractive power of the eye increases about 3.2 diopters between 750 and 365 mµ. For this reason the Purkinje shift of maximum visual sensitivity from 560 mµ in bright light to 505 mµ in dim light produces a relative myopia in dim light of 0.35 to 0.40 diopter. Persons who display changes larger or smaller than this do so because of involuntary changes in the accommodation in bright and dim light. In dim light the eye enters a state of relatively fixed focus, little different from its condition when the accommodation is paralyzed with homatropine. In this fixed state the accommodation may be relaxed, or it may add as much as 3 diopters to the refractive power of the eye. Experienced observers focus optical instruments in dim light close to the optimal settings determined objectively. Departures of more than 0.5 diopter in either direction from the optimal focus depress the visual sensitivity and acuity. It is concluded that setting optical instruments about 0.4 diopter more negatively in dim than in bright light is justified on the basis of the chromatic aberration of the eye. Many observers gain a further advantage from individual adjustments of focus in dim light, appropriate to their accommodative behavior.

GEORGE WALD and DONALD R. GRIFFIN, "The Change in Refractive Power of the Human Eye in Dim and Bright Light," J. Opt. Soc. Am. 37, 321-334 (1947)

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  1. The diopter, a unit of refractive power, is the reciprocal of the focal length in meters.
  2. We have had access to restricted reports on this subject from American, British, and French military and governmental sources. Unfortunately these have not to our knowledge been published, and so are not available for specific reference. The reports themselves are on file with the Army-Navy-N.R.C. Vision Committee, Natural Science Building, University of. Michigan, Ann Arbor.
  3. As will appear below, the chromatic aberration of the binoculars themselves introduces a change in focus of about +0.05 diopter in going from bright to dim light. For this reason a more correct value of the average increase in power of the naked eye in dim light is 0.59 diopter.
  4. In an earlier discussion of these experiments (Griffin and Wald, 1946), we included a pair of positive differences in dim light (+1.9 and +2.2 diopters in the two eyes) yielded by an observer who participated in only one trial; and another pair of first settings by another observer (+2.6 and +2.7 diopters) who in a second trial no longer yielded positive settings. These two pairs of unconfirmed first settings, which as it happens also represented the most positive differences in setting in dim light in all our observations, have been discarded in the present report.
  5. Hartridge (1941), p. 412; Duke-Elder (1944), p. 771. Hartridge comments, "We may say, therefore, that in everyday life the effects of spherical aberration are altogether negligible, compared with those of diffraction and chromatic aberration." This was also the conclusion of Matthiessen (1847), one of the earliest workers to attempt to measure the chromatic aberration of the eye accurately: "L'oeil humain est moin achromatique encore que l'on ne pensait; mais, en revanche, il est exempt d'aberration de courbure pour la lumière comprise entre B et G et pour des faisceaux peu obliques, pénétrant à travers u-e pupille peu dilatée; … ."
  6. The focal length of this lens was found to vary less than 0.05 cm between 405 and 750 mµ.
  7. We are much indebted to Dr. Kenneth Ogle of the Dartmouth Eye Institute for advice on the general design and use of stigmatoscopes.
  8. Volume 7, p. 13.
  9. We would expect a more extensive series of settings by homatropinized subjects to yield an average difference of setting in bright and dim light close to the -0.30 to -0.35 diopter accounted for by the combined chromatic aberrations of the eye and of this type of telescope.
  10. The data of Graham and Bartlett (1939), recomputed in terms of total light required to stimulate vision (bright-ness × area), lead to the same conclusion.

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