How to Model the
Human Eye in Zemax
Introduction

Accurate simulation and modeling of the
human eye can be tricky. Entire volumes
have been written on the subject, and it is a
subject that continues to spur new
developments. In this study, we will create
model of a human eye in Zemax using the
Liou & Brennan 1997 eye model.
Human Eye Model

set the System|General|Units Lens Units to
“Millimeters”. Next you’ll want to set the
Wavelengths (found in the System section)
to “F, d, C (Visible)” as shown below:

Next, go to System|General|Aperture and set
the Aperture Type to “Float By Stop Size”
and then go to System|General|Glass
Catalogs and add the catalog “MISC” to your
Glass Catalogs. Set just one Field, of Type
“Angle(Deg)” with an X-Field value of 5:

Now insert 3 surfaces before the STOP and
insert another 3 surfaces after the STOP.
Below is a step-by-step guide to setting up
all the surfaces, one at a time.

Surface 0
This surface is not actually labeled Surface 0 in the Zemax Lens
Data Editor, it’s labeled “OBJ” and it’s the object surface. Below
are the settings for Surface 0 (note that any settings not
mentioned here should be left with their default values):
Surf:Type = Standard
Comment = Object
Radius = Infinity
Thickness = 1.00E+009

Surface 1
The first surface (after the Object) is just a dummy plane, and we
use it to make our layout drawings easier to understand. Below
are the settings for Surface 1:
Surf:Type = Standard
Comment = Input Beam
Radius = Infinity
Thickness = 50.0

Surface 2
This is the outer cornea surface. Below are the settings for Surface 2:
Surf:Type = Standard
Comment = Cornea
Radius = 7.77
Thickness = 0.55
Glass = Model; 1.376, 50.23
Semi-Diameter = 5.00
Conic = -0.18
Note: to set these glass parameters you will need to right-click the Glass cell, select “Model” as
the Solve Type from the drop down list, and then type in the values like this:

Surface 3
This is the interface between the cornea and the aqueous humor. Below are the
settings for Surface 3:
Surf:Type = Standard
Comment = Aqueous
Radius = 6.4
Thickness = 3.16
Glass = Model; 1.336, 50.23
Semi-Diameter = 5.00
Conic = -0.60

Surface 4
This surface is not actually labeled Surface 4 in the Zemax Lens Data
Editor, it’s labeled “STO” and it’s the aperture stop of the system. This is
our eyemodel’s pupil plane. Below are the settings for Surface 4:
Surf:Type = Standard
Comment = Pupil
Radius = Infinity
Thickness = 0.00
Glass = Model; 1.336, 50.23
Semi-Diameter = 1.25

Surface 5
This is the anterior (front) portion of our model’s crystalline lens. Below are the settings for
Surface 5:
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

Surface 6
This is the posterior (rear) portion of our model’s crystalline lens. Below are
the settings for Surface 6:
Surf:Type = Gradient 3
Comment = Lens-back
Radius = Infinity
Thickness = 2.43
Semi-Diameter = 5.00
n0 = 1.407
Nr2 = -1.978E-003
Nz2 = -6.605E-003

Surface 7
This is the rear surface of the crystalline lens (that is, it is the interface between the crystalline
lens and the vitreous body of the eye). Below are the settings for:
Surface 7:
Surf:Type = Standard
Comment = Vitreous
Radius = -8.1
Thickness = 16.23883
Glass = Model; 1.336, 50.23
Semi-Diameter = 5.00
Conic = 0.96

Surface 8
This surface is not actually labeled Surface 8 in the Zemax Lens
Data Editor, it’s labeled “IMA” and it’s the image surface. This is
the retina of our model. Below are the settings for Surface 8:
Surf:Type = Standard
Comment = Retina
Radius = -12.0
Semi-Diameter = 5.00

This is the Liou & Brennan (1997) eye model. At
this point, your Lens Data Editor should look like
this:

Change the Settings on the 3D Layout so
that Rotation Z = 90, and set it so that the
First Surface is Surface 1 (input beam) and
you’ll see the top-down view of the model,
complete with offset pupil and off-axis field

Here is the resulting Diffraction Image Analysis diagram:

You’ll see below that the thickness from the back
of the eyeglass lens to the coordinate break (at
the eyeball’s center) is 28mm (that’s 15mm from
eyeglass to cornea plus 13mm from cornea to
center of eyeball). Then, after the coordinate break,
there is a thickness of negative 13mm, to get back
to the cornea surface.

Surface 2
This is the front surface of the eyeglass lens.
Surf:Type = Even Asphere
Comment = glasses-front
Radius = 100.0
Thickness = 3.0
Glass = POLYCARB
Semi-Diameter = 20.0

Surface 3
This is the rear surface of the eyeglass lens.
Surf:Type = Extended Polynomial
Comment = glasses-back
Radius = 100.0
Thickness = 28.0
Semi-Diameter = 20.0

Surface 4
This is the coordinate break located at the center
of the eyeball.
Surf:Type = Coordinate Break
Comment = center of eye
Thickness = -13.0

Here is a 3D Layout plot showing the system from
a side view for the 3 configurations
Prepare to Optimize

Insert two new operands at the beginning of
the Merit Function. Below are the settings to
use for these two new operands:

First new operand
Type = XNEG
Surf1 = 2
Surf2 = 3
Zone = 0
Target = 1
Weight = 1

Second new operand
Type = XXEG
Surf1 = 2
Surf2 = 3
Zone = 0
Target = 6
Weight = 1
Optimizing The PAL
Summary

We used Zemax to model a human eye using
realistic parameters, including a gradient
refractive-index crystalline lens, pupil,
curved retina, and off-axis field angle. We
then provided for a realistic rotation of this
model and used this rotating eye model to
design a progressive addition lens (PAL)