Abstract

A fundus camera is a complex optical system for imaging the retina of the eye. Designing a fundus camera requires the combination of an imaging system and an illumination system to share common optics. This combination of systems results in the need to find an optimal balance between imaging and illuminating the retina. We present a series of parameters and methods used to optimize the illumination system of a fundus camera while maintaining excellent image quality.

© 2008 Optical Society of America

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References

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  1. A. Bennett and J. Francis, “Retinoscopy and ophthalmoscopy,” in The Eye: Visual Optics and the Optical Spatial Sense, H. Davson, ed. (Academic, 1962), Vol. 4, pp. 181-208.
  2. N. Shibata and M. Torii, “Fundus camera,” U.S. Patent 6,654,553 (2003).
  3. N. Kishida and S. Ono, “Eye fundus examination apparatus,” U.S. Patent 7,055,955 (2006).
  4. N. Ichikawa, “Fundus camera,” U.S. Patent 7,219,996 (2007).
  5. N. Shibata, “Fundus camera,” U.S. Patent 6,755,526 (2004).
  6. H. A. Knoll, “Ophthalmic instruments,” in Applied Optics and Optical Engineering, Volume 5, Optical Instruments, Part 2, R. Kingslake, ed. (Academic, 1969), pp. 281-304.
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    [CrossRef] [PubMed]
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    [CrossRef]
  9. D. A. Atchison and G. Smith, Optics of the Human Eye (Butterworth-Heinemann, 2000).
  10. E. DeHoog and J. Schweigerling, Ophthalmic Optics Laboratory, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA, “Fundus camera systems: a comparative analysis,” Appl. Opt. (to be published).
  11. I. Escudero-Sanz and R. Navarro, “Off-axis aberrations of a wide angle schematic eye model,” J. Opt. Soc. Am. A 16, 1881-1891 (1999).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]

2008 (1)

2005 (1)

2002 (1)

M. Hammer and D. Schweitzer, “Quantitative reflection spectroscopy at the human,” Phys. Med. Biol. 47, 179-191 (2002).
[CrossRef] [PubMed]

1999 (1)

1998 (2)

D. Atchison, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 85(1998).
[CrossRef]

G. Smith, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 83-84(1998).
[CrossRef]

1997 (2)

1989 (1)

F. C. Delori and K. P. Pflibsen, “Spectral reflectance of the human ocular fundus,” Appl. Opt. 28, 1065-1077 (1989).
[CrossRef]

1966 (1)

F. W. Campbell and R. W. Gubisch, “Optical quality of the human eye,” J. Physiol. 186, 558-578 (1966).
[PubMed]

Bennett, A.

A. Bennett and J. Francis, “Retinoscopy and ophthalmoscopy,” in The Eye: Visual Optics and the Optical Spatial Sense, H. Davson, ed. (Academic, 1962), Vol. 4, pp. 181-208.

Arasa, J.

Atchison, D.

D. Atchison, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 85(1998).
[CrossRef]

Atchison, D. A.

Brennan, N. A.

Campbell, F. W.

F. W. Campbell and R. W. Gubisch, “Optical quality of the human eye,” J. Physiol. 186, 558-578 (1966).
[PubMed]

DeHoog, E.

E. DeHoog and J. Schweigerling, Ophthalmic Optics Laboratory, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA, “Fundus camera systems: a comparative analysis,” Appl. Opt. (to be published).

Delori, F. C.

F. C. Delori and K. P. Pflibsen, “Spectral reflectance of the human ocular fundus,” Appl. Opt. 28, 1065-1077 (1989).
[CrossRef]

Diaz, J. A.

Escudero-Sanz, I.

Francis, J.

A. Bennett and J. Francis, “Retinoscopy and ophthalmoscopy,” in The Eye: Visual Optics and the Optical Spatial Sense, H. Davson, ed. (Academic, 1962), Vol. 4, pp. 181-208.

Gubisch, R. W.

F. W. Campbell and R. W. Gubisch, “Optical quality of the human eye,” J. Physiol. 186, 558-578 (1966).
[PubMed]

Hammer, M.

M. Hammer and D. Schweitzer, “Quantitative reflection spectroscopy at the human,” Phys. Med. Biol. 47, 179-191 (2002).
[CrossRef] [PubMed]

Ichikawa, N.

N. Ichikawa, “Fundus camera,” U.S. Patent 7,219,996 (2007).

Kishida, N.

N. Kishida and S. Ono, “Eye fundus examination apparatus,” U.S. Patent 7,055,955 (2006).

Knoll, H. A.

H. A. Knoll, “Ophthalmic instruments,” in Applied Optics and Optical Engineering, Volume 5, Optical Instruments, Part 2, R. Kingslake, ed. (Academic, 1969), pp. 281-304.

Liang, J.

Liou, H. L.

Mahajan, V.

V. Mahajan, Aberration Theory Made Simple (SPIE Press, 1991).
[CrossRef]

Navarro, R.

Ono, S.

N. Kishida and S. Ono, “Eye fundus examination apparatus,” U.S. Patent 7,055,955 (2006).

Pflibsen, K. P.

F. C. Delori and K. P. Pflibsen, “Spectral reflectance of the human ocular fundus,” Appl. Opt. 28, 1065-1077 (1989).
[CrossRef]

Pizarro, C.

Schweigerling, J.

E. DeHoog and J. Schweigerling, Ophthalmic Optics Laboratory, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA, “Fundus camera systems: a comparative analysis,” Appl. Opt. (to be published).

Schweitzer, D.

M. Hammer and D. Schweitzer, “Quantitative reflection spectroscopy at the human,” Phys. Med. Biol. 47, 179-191 (2002).
[CrossRef] [PubMed]

Shibata, N.

N. Shibata, “Fundus camera,” U.S. Patent 6,755,526 (2004).

N. Shibata and M. Torii, “Fundus camera,” U.S. Patent 6,654,553 (2003).

Smith, G.

D. A. Atchison and G. Smith, “Chromatic dispersions of the ocular media of the human eyes,” J. Opt. Soc. Am. A 22, 29-37 (2005).
[CrossRef]

G. Smith, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 83-84(1998).
[CrossRef]

D. A. Atchison and G. Smith, Optics of the Human Eye (Butterworth-Heinemann, 2000).

Torii, M.

N. Shibata and M. Torii, “Fundus camera,” U.S. Patent 6,654,553 (2003).

Williams, D. R.

Appl. Opt. (1)

F. C. Delori and K. P. Pflibsen, “Spectral reflectance of the human ocular fundus,” Appl. Opt. 28, 1065-1077 (1989).
[CrossRef]

J. Opt. Soc. Am. A (5)

J. Physiol. (1)

F. W. Campbell and R. W. Gubisch, “Optical quality of the human eye,” J. Physiol. 186, 558-578 (1966).
[PubMed]

Ophthal. Physiol. Opt. (2)

D. Atchison, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 85(1998).
[CrossRef]

G. Smith, “H. L. Liou and N. A. Brennan (1996) prediction of spherical aberration with schematic eyes. Ophthal. Physiol. Opt. 16(4), 348-354,” Ophthal. Physiol. Opt. 18, 83-84(1998).
[CrossRef]

Phys. Med. Biol. (1)

M. Hammer and D. Schweitzer, “Quantitative reflection spectroscopy at the human,” Phys. Med. Biol. 47, 179-191 (2002).
[CrossRef] [PubMed]

Other (10)

Calculation of setting areas equal results in √(2) * Ri=Rpupil, where Rpupil=3.75 mm.

V. Mahajan, Aberration Theory Made Simple (SPIE Press, 1991).
[CrossRef]

D. A. Atchison and G. Smith, Optics of the Human Eye (Butterworth-Heinemann, 2000).

E. DeHoog and J. Schweigerling, Ophthalmic Optics Laboratory, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA, “Fundus camera systems: a comparative analysis,” Appl. Opt. (to be published).

A. Bennett and J. Francis, “Retinoscopy and ophthalmoscopy,” in The Eye: Visual Optics and the Optical Spatial Sense, H. Davson, ed. (Academic, 1962), Vol. 4, pp. 181-208.

N. Shibata and M. Torii, “Fundus camera,” U.S. Patent 6,654,553 (2003).

N. Kishida and S. Ono, “Eye fundus examination apparatus,” U.S. Patent 7,055,955 (2006).

N. Ichikawa, “Fundus camera,” U.S. Patent 7,219,996 (2007).

N. Shibata, “Fundus camera,” U.S. Patent 6,755,526 (2004).

H. A. Knoll, “Ophthalmic instruments,” in Applied Optics and Optical Engineering, Volume 5, Optical Instruments, Part 2, R. Kingslake, ed. (Academic, 1969), pp. 281-304.

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Figures (13)

Fig. 1
Fig. 1

Design schematic of a fundus camera from a patent filed in 2003 [2]. The imaging path is shown with solid rays. The illumination path is shown with dashed rays. The annular illumination pattern is created at the iris of the eye by the center of the illumination path using an annulus, 16, and a mirror with a central hole, 21, located at the conjugate planes of the iris. A plate with a black dot, 19, is placed conjugate to the objective, 20, to remove backreflections from the objective.

Fig. 2
Fig. 2

Simplified retinal illumination system consisting of a model eye, an objective, and a holed mirror. The holed mirror, 21, reflects the image of source object.

Fig. 3
Fig. 3

Illumination annulus and imaging pupil located at the pupil of the eye. R i designates the radius of the imaging pupil. R L designates the inside radius of the annular illumination pattern at the pupil. The white annulus between R L and R i is space needed between parameters to prevent corneal backreflections.

Fig. 4
Fig. 4

Simplified fundus camera with the pupil of the eye displaced from the objective focal point.

Fig. 5
Fig. 5

Strehl ratio of the eye as a function of pupil diameter.

Fig. 6
Fig. 6

Effects of the source angle on retinal illumination for a WF#1 system: (a) uniformity versus percent of aperture filled and (b) illumination patterns on the retina for different sources angles. For (b) the top left plot corresponds to 100% of the aperture filled, while the bottom right plot corresponds to 8% of the aperture filled. Intermediate plots range between 8% to 100% of the objective’s aperture filled.

Fig. 7
Fig. 7

Diagram showing the minimum angle, α, of illuminating optics necessary for full illumination of the retina. R L is the inner radius of the illumination annulus, and β is the angle subtended by the illumination path focused on the pupil of the eye.

Fig. 8
Fig. 8

(a) Illumination annulus at the decentered pupil. (b), (c) Profiles of illumination distribution on the retina for various source angles using a Gaussian angular source. Power and x axis are normalized for comparison of eye models. Percentages refer to the percentage of the objective aperture filled. (b) Escudero and Navarro eye model. (c) Decentered eye model.

Fig. 9
Fig. 9

Illumination pattern on the detector as a result of corneal backreflections for a WF#1 with a 2 - mm imaging pupil at the following illumination ratios: (a) 1.0, (b) 1.2, and (c) 1.4. Higher IR to eliminate backreflections results in lower efficiency.

Fig. 10
Fig. 10

Illumination ratio versus pupil diameter for different WF# systems.

Fig. 11
Fig. 11

(a) Efficiency versus pupil diameter for varying WF#s. (b) Normalized detector irradiance versus pupil diameter for varying WF#s.

Fig. 12
Fig. 12

(a) Illumination versus pupil position for a WF#1 system. (b) Normalized detector irradiance pupil position for a WF#1.

Fig. 13
Fig. 13

Effects of moving the pupil from the objective focus on retinal illumination uniformity. (a) Plot of uniformity versus pupil position. (b) Illumination patterns at the retina top left correspond to the objective focus 5 mm behind the pupil; bottom right corresponds to the objective focus at the pupil. Intermediate images are taken at 1 mm intervals between 5 and 0 mm behind the pupil.

Tables (1)

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Table 1 Simplified Camera Prescription

Equations (6)

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IR = R L R i ,
NDI = Φ d Φ s A d ,
η = Φ d Φ s * 100 % .
U = 1 | Φ center Φ 85 % | Φ max .
s = exp ( σ 2 ) ,
P = ( d × tan ( θ 2 ) D L 2 ) 2 ,

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