Abstract

An instrument is described which automatically measures the radius of curvature of the cornea and other spherical surfaces. The principle involves moving a light pattern across the face of a cathode-ray tube. After being imaged by a lens and reflected off the cornea, the light strikes two photocells. The placement of the photocells and the lens and the geometry of the cornea determine the positions on the cathode-ray tube face from which light must issue for its reflection off the cornea to reach the photocells. The measurement is in the form of an electronic signal and the accuracy is comparable to that of an optical keratometer.

© 1966 Optical Society of America

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References

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  1. G. Westheimer, Am. J. Optom. 34, 339 (1957).
    [Crossref]
  2. H. H. Emsley, Visual Optics (Hatton Press, London, 1939), 2 nd ed., Chap. IX.
  3. G. Westheimer, Am. J. Optom. 42, 315 (1965).
    [Crossref]

1965 (1)

G. Westheimer, Am. J. Optom. 42, 315 (1965).
[Crossref]

1957 (1)

G. Westheimer, Am. J. Optom. 34, 339 (1957).
[Crossref]

Emsley, H. H.

H. H. Emsley, Visual Optics (Hatton Press, London, 1939), 2 nd ed., Chap. IX.

Westheimer, G.

G. Westheimer, Am. J. Optom. 42, 315 (1965).
[Crossref]

G. Westheimer, Am. J. Optom. 34, 339 (1957).
[Crossref]

Am. J. Optom. (2)

G. Westheimer, Am. J. Optom. 34, 339 (1957).
[Crossref]

G. Westheimer, Am. J. Optom. 42, 315 (1965).
[Crossref]

Other (1)

H. H. Emsley, Visual Optics (Hatton Press, London, 1939), 2 nd ed., Chap. IX.

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Figures (3)

F. 1
F. 1

Basic arrangement of the automatic photoelectric keratometer. Light emitted on the face of a cathode-ray tube is imaged by lens L and the cornea. The separation y of the two places on the cathode-ray tube from which light must come for it to fall on two photocells, P1 and P2, is measured. For a given geometrical arrangement of cathode-ray tube, lens and photocells, y is uniquely related to r, the radius of curvature of the cornea.

F. 2
F. 2

Block diagram of a model of the automatic photoelectric keratometer showing the interconnection of the various basic electronic stages.

F. 3
F. 3

Curve relating output of the automatic photoelectric keratometer (sweeps per second counted digitally) to the radiu-scope in diopters (0.3375/r) for a series of calibrated surfaces.