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Optical Models of Eye
Reporter:曾千芳
Date:2011/12/15
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大綱
 Introduction
 Method(cornea/lens)
 aspheric surface
 Index of refraction
 Schematic eye models
 Model the human eye in ZEMAX
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Introduction
 Develop a model eye that
1.Represent the ocular anatomy as closely as possible.
2.Presdicts spherical and chromatic aberrations as close to
empirical as possible.
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Method
Schematic drawing of the new schematic eye
小窩:
感知視覺
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Surface 4:imaginary plane dividing the lens
Surface1:air-cornea.
Surface2:cornea-anterior chamber. into anterior and posterior sections.
Surface5:lens-viterous
Surface3:anterior chamber-lens .
(pupil aperture decentered 0.5mm)
Cornea/Lens
 To describing an aspheric surface. A common method is to use a
conicoid in the form:
R: the radius at the apex ;
Q:asphericity parameter(specifies the type of conicoid);
 Cornea:
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Index of refraction -lens
 The distribution of the gradient index :
z:along the optical axis; ω:radial distance
(𝜔2 = 𝑥 2 + 𝑦 2 ) ; 𝑛00 𝑛01 𝑛02 𝑛10 :coefficients for a parabolic gradient-index
distribution
 To predict the chromatic aberration of the eye, we assumed
the ocular media to have dispersive properties similar to those
of water.(n=1.3335 at 0.555μm)
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Schematic eye models
 n(cornea)=1.376 ; n(aqueous) , n(vitreous) are similar to water~1.33
 n(anterior lens) – Grad A ; n(posterior lens)-Grad P
 Pupil decentration~0.5mm ; Angle alpha~5°
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Model the human eye in ZEMAX
 Setup the surface
 EX:
Surface1(cornea)
Surf:Type = Standard
Comment = Cornea
Radius = 7.77
Thickness = 0.55
Glass = Model; 1.376
Semi-Diameter = 5.00
Conic = -0.18
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Surfance3 (lens front)
Surf:Type = Gradient 3
Comment = Lens-front
Radius = 12.4
Thickness = 1.59
Semi-Diameter = 5.00
n0 = 1.368
Nr2 = -1.978E-003
Nz1 = 0.049057
Nz2 = -0.015427
Discussion
 The anatomical accuracy of a schematic eye is very important
for the purpose of modeling vision in refractive procedures.
 A lens with a gradient-index (GRIN) structure was
introduced in this new model to represent the anatomical
structure of the human crystalline lens. Most previous finite
schematic eyes either had aspheric refracting surfaces and a
homogeneous lens or a GRIN lens structure with spherical
surfaces but not both.
 Effect to Aberration: posterior corneal aspheric surface ,
modification of the parameters of GRIN lens…etc.
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Future work
 The present model does not yet account for changes with age
or individual variability. Further research on the changes of
ocular biometry with age is required for incorporation of this
factor into the eye model.
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