Abstract

The recent development in the use of sinusoidal gratings for the analytical study of optical systems has been applied to the effects of focus and pupil aperture on visual resolution. For an eye with a dilated pupil, the in-focus position is shown to depend upon the spatial frequency of the test target. The effective refractive power of the eye increases for the detection of low-frequency gratings. If the eye is corrected for this change in effective refractive power, an improvement of about 70% in contrast sensitivity occurs for low spatial frequencies. The implications of these findings on the phenomenon of “night myopia” are discussed.

© 1965 Optical Society of America

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References

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  1. M. Koomen, R. Scolnik, and R. Tousey, J. Opt. Soc. Am. 41, 80 (1951).
    [Crossref]
  2. S. Shlaer, J. Gen. Physiol. 21, 165 (1937).
  3. E. L. O’Neill, Introduction to Statistical Optics (Addison-Wesley Publishing Co., Inc., Reading, Massachusetts, 1963).
  4. E. H. Linfoot, Optical Image Evaluation (Focal Press, London, 1964).
  5. F. W. Campbell, J. Physiol. 144, 25P (1958).
  6. O. H. Schade, J. Opt. Soc. Am. 46, 721 (1956).
    [Crossref] [PubMed]
  7. W. S. Stiles and B. H. Crawford, Proc. Roy. Soc. (London) B 112, 428 (1933).
    [Crossref]
  8. F. W. Campbell, J. Physiol. London 123, 357 (1954).

1958 (1)

F. W. Campbell, J. Physiol. 144, 25P (1958).

1956 (1)

1954 (1)

F. W. Campbell, J. Physiol. London 123, 357 (1954).

1951 (1)

1937 (1)

S. Shlaer, J. Gen. Physiol. 21, 165 (1937).

1933 (1)

W. S. Stiles and B. H. Crawford, Proc. Roy. Soc. (London) B 112, 428 (1933).
[Crossref]

Campbell, F. W.

F. W. Campbell, J. Physiol. 144, 25P (1958).

F. W. Campbell, J. Physiol. London 123, 357 (1954).

Crawford, B. H.

W. S. Stiles and B. H. Crawford, Proc. Roy. Soc. (London) B 112, 428 (1933).
[Crossref]

Koomen, M.

Linfoot, E. H.

E. H. Linfoot, Optical Image Evaluation (Focal Press, London, 1964).

O’Neill, E. L.

E. L. O’Neill, Introduction to Statistical Optics (Addison-Wesley Publishing Co., Inc., Reading, Massachusetts, 1963).

Schade, O. H.

Scolnik, R.

Shlaer, S.

S. Shlaer, J. Gen. Physiol. 21, 165 (1937).

Stiles, W. S.

W. S. Stiles and B. H. Crawford, Proc. Roy. Soc. (London) B 112, 428 (1933).
[Crossref]

Tousey, R.

J. Gen. Physiol. (1)

S. Shlaer, J. Gen. Physiol. 21, 165 (1937).

J. Opt. Soc. Am. (2)

J. Physiol. (1)

F. W. Campbell, J. Physiol. 144, 25P (1958).

J. Physiol. London (1)

F. W. Campbell, J. Physiol. London 123, 357 (1954).

Proc. Roy. Soc. (London) B (1)

W. S. Stiles and B. H. Crawford, Proc. Roy. Soc. (London) B 112, 428 (1933).
[Crossref]

Other (2)

E. L. O’Neill, Introduction to Statistical Optics (Addison-Wesley Publishing Co., Inc., Reading, Massachusetts, 1963).

E. H. Linfoot, Optical Image Evaluation (Focal Press, London, 1964).

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Figures (6)

F. 1
F. 1

Photographs of high-contrast grating targets using a simple plano-convex glass lens. Curves of light intensity al the film are superimposed. In the upper photograph the film was placed at the paraxial focus of the lens. In the lower photograph the focus was such that the image of the course grating was at maximum contrast. Here the fine grating is barely resolved (from Koomen, Scolnik, and Tousey1).

F. 2
F. 2

Effect of focus on the contrast sensitivity measured for increasing positive lens power. A 2-mm-diam pupil was used. The eye was in focus for the viewing distance when corrected with +1.5 D lens (closed circles). Each point is the average of three measurements (observer D.G.G.).

F. 3
F. 3

Effect of positive and negative defocus on contrast sensitivity measured with a 2-mm-diam pupil (observer D.G.G.). Each point is the average of three measurements.

F. 4
F. 4

Same as Fig. 3, but for 7-mm pupil.

F. 5
F. 5

Dependency of optimum focus on spatial frequency using a 7-mm-diam pupil on subject D.G.G. ● and F.W.C. ▲ (6-mm pupil). The dotted line is drawn for data from Koomen, Scolnik, and Tousey1 by converting their visual acuity measurements to units of spatial frequency.

F. 6
F. 6

Contrast sensitivity of an eye with a dilated pupil (6 mm). The measurements have been made using a +0.62 ■ and a −0.25 D lens ● (subject F.W.C.). These two lenses were selected because they optimized the threshold contrast of a high-(45 cycle/deg) and a low-(3 cycle/deg) frequency grating, respectively. The curves illustrate the increase in contrast sensitivity which is obtained for low-frequency gratings by defocusing the eye.