Abstract

The cone prism introduced is mainly used in applanation tonometers to act as an applanation prism for linear measurement of the applanation diameter or the applanation area of the cornea. Its principles of optical design and linear measurement are expounded in detail. The measuring body, which comprises the cone prism and other optical and electronic parts, is also briefly introduced.

© 1999 Optical Society of America

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References

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  1. R. A. Moses, “The Goldmann applanation tonometer,” Am. J. Ophthalmol. 46, 865–869 (1958).
    [PubMed]
  2. E. S. Perkins, “Hand-held applanation tonometer,” Br. Ophthalmol. 49, 591–593 (1965).
    [CrossRef]
  3. J. Dreager, “Applanation tonometer,” U.S. patent5,203,331A (20April1993).
  4. R. C. Zeimer, J. T. Wilensky, “An instrument for self-measurement of intraocular pressure,” IEEE Trans. Biomed. Eng. 29, 178–183 (1982).
    [CrossRef] [PubMed]

1982 (1)

R. C. Zeimer, J. T. Wilensky, “An instrument for self-measurement of intraocular pressure,” IEEE Trans. Biomed. Eng. 29, 178–183 (1982).
[CrossRef] [PubMed]

1965 (1)

E. S. Perkins, “Hand-held applanation tonometer,” Br. Ophthalmol. 49, 591–593 (1965).
[CrossRef]

1958 (1)

R. A. Moses, “The Goldmann applanation tonometer,” Am. J. Ophthalmol. 46, 865–869 (1958).
[PubMed]

Dreager, J.

J. Dreager, “Applanation tonometer,” U.S. patent5,203,331A (20April1993).

Moses, R. A.

R. A. Moses, “The Goldmann applanation tonometer,” Am. J. Ophthalmol. 46, 865–869 (1958).
[PubMed]

Perkins, E. S.

E. S. Perkins, “Hand-held applanation tonometer,” Br. Ophthalmol. 49, 591–593 (1965).
[CrossRef]

Wilensky, J. T.

R. C. Zeimer, J. T. Wilensky, “An instrument for self-measurement of intraocular pressure,” IEEE Trans. Biomed. Eng. 29, 178–183 (1982).
[CrossRef] [PubMed]

Zeimer, R. C.

R. C. Zeimer, J. T. Wilensky, “An instrument for self-measurement of intraocular pressure,” IEEE Trans. Biomed. Eng. 29, 178–183 (1982).
[CrossRef] [PubMed]

Am. J. Ophthalmol. (1)

R. A. Moses, “The Goldmann applanation tonometer,” Am. J. Ophthalmol. 46, 865–869 (1958).
[PubMed]

Br. Ophthalmol. (1)

E. S. Perkins, “Hand-held applanation tonometer,” Br. Ophthalmol. 49, 591–593 (1965).
[CrossRef]

IEEE Trans. Biomed. Eng. (1)

R. C. Zeimer, J. T. Wilensky, “An instrument for self-measurement of intraocular pressure,” IEEE Trans. Biomed. Eng. 29, 178–183 (1982).
[CrossRef] [PubMed]

Other (1)

J. Dreager, “Applanation tonometer,” U.S. patent5,203,331A (20April1993).

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Figures (7)

Fig. 1
Fig. 1

Schematic configuration of the prism and optical paths.

Fig. 2
Fig. 2

Illustration of the relationship among R 1, R 2, and r.

Fig. 3
Fig. 3

Cone prism in contact with the eye and the applanation diameter of the cornea d.

Fig. 4
Fig. 4

Modulating flake of light intensity V is inserted into the optical path.

Fig. 5
Fig. 5

Functional curve that the modulation function V(R) will follow.

Fig. 6
Fig. 6

Schematic configurations of two types of the measuring body that comprises the cone prism.

Fig. 7
Fig. 7

Schematic configurations of two types of the measuring body that comprises the triangular prism.

Equations (30)

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dφ1=-E02πR1dR1  D1/2R1R0,
dφ2=E02πR2dR2  R0R2D2/2.
R1=r0+r0-rsin α;
dR1=-sin α dr.
R2=r0+r0+rsin α;
dR2=sin α dr.
dφ1=2πE0r0+r0-rsin αsin α dr,
dφ2=2πE0r0+r0+rsin αsin α dr;
dφ=dφ1+dφ2=4πr0E0 sin α1+sin αdr,
dφ=K dr.
φ0φdφ=K 0rdr,
φr=Kr+φ0,
φ=Φ-φ+Rnφ
φ=Φ-Rtφ.
Δφ=Rtφ.
r=ΔφKRt-φ0K.
d=2γ=2KRt Δφ-2φ0K,
VR=0  0R<D1/2,
VR1=a1R1+b1VR0=0D1/2R1R0VD1/2=1,
VR2=a2R2+b2VR0=0R0R2D2/2VD2/2=1,
VR1=4D2-D1R0-R1  D1/2R1R0;
E0R1=E0VR1=4E0D2-D1R0-R1.
VR2=4D2-D1R2-R0  R0R2D2/2;
E0R2=E0VR2=4E0D2-D1R2-R0.
dφ=dφ1+dφ2=2 π-E0R1R1dR1+E0R2R2dR2.
dφ=K0 2πrdr=K0ds,
E=dφds=K0.
φ=K0s,
Δφ=K0RtS
S=1K0Rt Δφ.

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