Abstract

A modification of the technique of photoretinoscopy is presented which allows measurement of the refractive state of the eye in noncooperative subjects and in very small eyes. Infrared light provided by high-output infrared LEDs permits measurement at large pupil sizes and thereby better resolution. Arrangement of the IR LEDs at different eccentricities from the optical axis of the video camera markedly increases the range of measurement. The current sensitivity for a measurement distance of 1.5 m in a human eye is ± 0.3 diopter or better over a range of ±5 diopters. Higher amounts of defocus can be better determined at shorter distances.

© 1987 Optical Society of America

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References

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  1. K. Kaakinen, “A Simple Method for Screening of Children with Strabismus, Anisometropia or Ametropia by Simultaneous Photography of the Corneal and the Fundus Reflexes,” Acta Ophthalmol. (Kbl) 57, (1979).
  2. A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).
  3. S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
    [Crossref] [PubMed]
  4. S. H. Day, A. M. Norcia, “Can a Photorefractor Screen for Significant Refractive Errors in Infants?” Invest. Ophthalmol. Vis. Sci. 25 (suppl.), 310 (1984).
  5. S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).
  6. H. C. Howland, “Optics of Photoretinoscopy: Results from Ray Tracing,” Am. J. Optom. Physiol. Opt. 62, 621 (1985).
    [Crossref] [PubMed]
  7. W. R. Bobbier, O. J. Braddick, “Eccentric Photorefraction: Optical Analysis and Empirical Measures,” Am. J. Optom. Physiol. Opt. 62, 614 (1985).
    [Crossref]
  8. F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
    [Crossref]
  9. T. Mandelman, J. G. Sivak, “Longitudinal Chromatic Aberration in the Vertebrate Eye,” Vision Res. 23, 1555 (1983).
    [Crossref] [PubMed]
  10. F. W. Campbell, R. W. Gubisch, “Optical Quality of the Human Eye,” J. Physiol. London 186, 558 (1966).
    [PubMed]
  11. J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
    [Crossref] [PubMed]

1986 (2)

S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).

F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
[Crossref]

1985 (2)

H. C. Howland, “Optics of Photoretinoscopy: Results from Ray Tracing,” Am. J. Optom. Physiol. Opt. 62, 621 (1985).
[Crossref] [PubMed]

W. R. Bobbier, O. J. Braddick, “Eccentric Photorefraction: Optical Analysis and Empirical Measures,” Am. J. Optom. Physiol. Opt. 62, 614 (1985).
[Crossref]

1984 (1)

S. H. Day, A. M. Norcia, “Can a Photorefractor Screen for Significant Refractive Errors in Infants?” Invest. Ophthalmol. Vis. Sci. 25 (suppl.), 310 (1984).

1983 (3)

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

T. Mandelman, J. G. Sivak, “Longitudinal Chromatic Aberration in the Vertebrate Eye,” Vision Res. 23, 1555 (1983).
[Crossref] [PubMed]

1980 (1)

J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
[Crossref] [PubMed]

1979 (1)

K. Kaakinen, “A Simple Method for Screening of Children with Strabismus, Anisometropia or Ametropia by Simultaneous Photography of the Corneal and the Fundus Reflexes,” Acta Ophthalmol. (Kbl) 57, (1979).

1966 (1)

F. W. Campbell, R. W. Gubisch, “Optical Quality of the Human Eye,” J. Physiol. London 186, 558 (1966).
[PubMed]

Allen, D.

S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).

Bobbier, W. R.

W. R. Bobbier, O. J. Braddick, “Eccentric Photorefraction: Optical Analysis and Empirical Measures,” Am. J. Optom. Physiol. Opt. 62, 614 (1985).
[Crossref]

Braddick, O. J.

W. R. Bobbier, O. J. Braddick, “Eccentric Photorefraction: Optical Analysis and Empirical Measures,” Am. J. Optom. Physiol. Opt. 62, 614 (1985).
[Crossref]

Calkins, J. L.

J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
[Crossref] [PubMed]

Campbell, F. W.

F. W. Campbell, R. W. Gubisch, “Optical Quality of the Human Eye,” J. Physiol. London 186, 558 (1966).
[PubMed]

D’Anna, S. A.

J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
[Crossref] [PubMed]

Day, S. H.

S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).

S. H. Day, A. M. Norcia, “Can a Photorefractor Screen for Significant Refractive Errors in Infants?” Invest. Ophthalmol. Vis. Sci. 25 (suppl.), 310 (1984).

Farkas, L.

F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
[Crossref]

Funke, M.

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Gubisch, R. W.

F. W. Campbell, R. W. Gubisch, “Optical Quality of the Human Eye,” J. Physiol. London 186, 558 (1966).
[PubMed]

Hay, S. H.

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Hoare-Nairne, J.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Hochheimer, B. F.

J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
[Crossref] [PubMed]

Hodgkinson, I. J.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Howland, H. C.

F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
[Crossref]

H. C. Howland, “Optics of Photoretinoscopy: Results from Ray Tracing,” Am. J. Optom. Physiol. Opt. 62, 621 (1985).
[Crossref] [PubMed]

Jayroe, R. R.

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Kaakinen, K.

K. Kaakinen, “A Simple Method for Screening of Children with Strabismus, Anisometropia or Ametropia by Simultaneous Photography of the Corneal and the Fundus Reflexes,” Acta Ophthalmol. (Kbl) 57, (1979).

Kerr, J. H.

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Mandelman, T.

T. Mandelman, J. G. Sivak, “Longitudinal Chromatic Aberration in the Vertebrate Eye,” Vision Res. 23, 1555 (1983).
[Crossref] [PubMed]

Molteno, A. C. B.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Norcia, A. M.

S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).

S. H. Day, A. M. Norcia, “Can a Photorefractor Screen for Significant Refractive Errors in Infants?” Invest. Ophthalmol. Vis. Sci. 25 (suppl.), 310 (1984).

O’Brien, N. E.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Parr, J. C.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Schaeffel, F.

F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
[Crossref]

Simpson, A.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Sivak, J. G.

T. Mandelman, J. G. Sivak, “Longitudinal Chromatic Aberration in the Vertebrate Eye,” Vision Res. 23, 1555 (1983).
[Crossref] [PubMed]

Watts, S. D.

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

White, J. C.

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Acta Ophthalmol. (Kbl) (1)

K. Kaakinen, “A Simple Method for Screening of Children with Strabismus, Anisometropia or Ametropia by Simultaneous Photography of the Corneal and the Fundus Reflexes,” Acta Ophthalmol. (Kbl) 57, (1979).

Am. J. Optom. Physiol. Opt. (2)

H. C. Howland, “Optics of Photoretinoscopy: Results from Ray Tracing,” Am. J. Optom. Physiol. Opt. 62, 621 (1985).
[Crossref] [PubMed]

W. R. Bobbier, O. J. Braddick, “Eccentric Photorefraction: Optical Analysis and Empirical Measures,” Am. J. Optom. Physiol. Opt. 62, 614 (1985).
[Crossref]

Invest. Ophthalmol. Vis. Sci. (2)

S. H. Day, A. M. Norcia, “Can a Photorefractor Screen for Significant Refractive Errors in Infants?” Invest. Ophthalmol. Vis. Sci. 25 (suppl.), 310 (1984).

S. H. Day, A. M. Norcia, D. Allen, “Factors Affecting the sensitivity and Specificity of Photorefraction,” Invest. Ophthalmol. Vis. Sci. 27 (suppl.), 1 (1986).

J. Physiol. London (1)

F. W. Campbell, R. W. Gubisch, “Optical Quality of the Human Eye,” J. Physiol. London 186, 558 (1966).
[PubMed]

South. Med. J. (1)

S. H. Hay, J. H. Kerr, R. R. Jayroe, J. C. White, M. Funke, “Retinal Reflex Photometry as a Screening Device for Amblyopia and Preamblyopic States in Children,” South. Med. J. 76, 309 (1983).
[Crossref] [PubMed]

Trans. Ophthalmol. Soc. NZ (1)

A. C. B. Molteno, J. Hoare-Nairne, J. C. Parr, A. Simpson, I. J. Hodgkinson, N. E. O’Brien, S. D. Watts, “The Otago Photoscreener, a Method for the Mass Screening of Infants to Detect Squint and Refractive Errors,” Trans. Ophthalmol. Soc. NZ 35, 43 (1983).

Vision Res. (3)

F. Schaeffel, H. C. Howland, L. Farkas, “Natural Accommodation in the Growing Chicken,” Vision Res. (1986).
[Crossref]

T. Mandelman, J. G. Sivak, “Longitudinal Chromatic Aberration in the Vertebrate Eye,” Vision Res. 23, 1555 (1983).
[Crossref] [PubMed]

J. L. Calkins, B. F. Hochheimer, S. A. D’Anna, “Potential Hazards from Specific Ophthalmic Devices,” Vision Res. 20, 1039 (1980).
[Crossref] [PubMed]

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Figures (7)

Fig. 1
Fig. 1

Optics of photoretinoscopy. In a myopic eye (focal plane at B) a real image of the light source L is created in front of the retina (image plane), whereas a blurred spot appears on the retina. Reflected light entering the pupil from the backside is refocused in the focal plane of the eye B in front of the camera and diverges subsequently. If the lower part of the camera aperture is occluded by a black paper shield S only rays emerging from the bottom of the pupil are detected by the unvignetted part of the aperture. The highest ray above the optical axis in the camera plane is 1. It can be found by tracing a ray from the lowest part of the retinal blur circle which just grazes the edge of the image of paper shield.

Fig. 2
Fig. 2

Infrared photoretinoscope to be placed in front of the video camera. IR LEDs are arranged at five different distances (2, 6.2, 10.5, 14.5, 18.9 mm) from the edge of a black paper shield which occludes about half of the camera aperture. The number of LEDs for every eccentricity is variable to compensate for the intensity drop in fundus reflexes created from higher eccentric light sources.

Fig. 3
Fig. 3

Calibration of the IR photoretinoscope in an artificial eye of known adjustable defocus. The lines represent the theoretically expected defocus [Eq. (1)] for a reflex crescent just to appear in the pupil for a LED of given eccentricity. Circles (A = 0.95 m) and triangles (A = 0.56 m) give the calculated amount of defocus found with the different eccentricities of the IR photoretinoscope.

Fig. 4
Fig. 4

Electronic circuit which flashes the five IR LEDs repeatedly one after another at a current of 90 mA (output 4.5 W/m2 at a distance of 0.1 m). The frequency is adjustable. The number of the visible red LEDs displays the position number of the IR LED just flashing.

Fig. 5
Fig. 5

Spectral distribution of the IR radiation in the LEDs. Lines 1–3 serve as a calibration of the scale. The transmitted light from interference filters (620, 647, and 690 nm) placed in front of a white light source is evaluated by a video camera in front of which a diffraction grating is placed. Line 4 gives the spectral distribution of the IR LED driven at 30 mA. The emission peak is located at 880 nm. Line 5 displays the LED driven at 250 mA. The emission peak is shifted to 911 nm. The intensity was cut down differentially using Wratten ND filters of 1.1, 1.2, 1.5, 1.2, and 2.7 log units for lines 1–5, respectively.

Fig. 6
Fig. 6

(a) Human eye (left) and an artificial eye (right) adjusted to the same amount of defocus are measured at a distance of 0.5 m (eccentricity 2 mm). Note the large amount of scattered light in the pupil of the natural eye. The intensity profile shows that the photoretinoscopic reflex is actually superimposed on the background of scattered light. (b) Refraction at higher eccentricity (10.5 mm) at a distance of 0.5 m. The myopic defocus of 1.4 diopter relative to the camera (left) is not detectable (DF > 100%). After strong accommodation (~7 diopters, right) the photoretinoscopic reflex appears quite clearly.

Fig. 7
Fig. 7

Accommodation in a human subject fixating a target. The multiple images (1–5) are frames grabbed successively with a time interval between each of 200 ms. The eccentricity number of the LEDs in the photoretinoscope which are flashing during the frame grab is identical to the image number. Analysis of the frames shows that the subject’s focus was approximately constant. The subject is myopic with a defocus of 2.7 ± 0.2 diopters relative to the camera as calculated from the dark fractions seen from eccentricities 3, 4, and 5. The subject accommodates 1.5 diopters (refractive state 4.2 ± 0.2 diopters relative to the camera). Note the smaller dark fractions at higher eccentricities if compared to Fig. 7(a).

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