# US 8,540,370 B2 · Devices and methods for selecting intraocular lenses

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- Number: US 8,540,370 B2
- Document ID: US8540370B2
- Status: Granted
- Kind: B2
- Application number: 13/340,998
- Filed: 2011-12-30
- Published: 2012-06-28
- Granted: 2013-09-24
- Earliest claimed: 2004-11-12
- Assignees: AMO Groningen B.V.
- Applicants: Sverker Norrby
- Inventors: Sverker Norrby
- Web page: https://patentgrep.com/patent/US8540370B2

## CPC

- A61F 2/1613: {having special lens configurations, e.g. multipart lenses; having particular optical properties, e.g. pseudo-accommodative lenses, lenses having aberration corrections, diffractive lenses, lenses for variably absorbing electromagnetic radiation, lenses having variable focus}
- A61B 3/0025: {characterised by electronic signal processing, e.g. eye models}
- A61F 2240/002: Designing or making customized prostheses
- A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

The invention relates to devices and methods for selecting IOLs for implantation and eye models useful with the methods. One method comprises the steps of determining the axial eye length, the pupil size at a desired light level; the desired postoperative refraction; determining an aspheric representation of the corneal curvature and determining the location of the plane of fixation of the IOL following implantation.

## Claims

### Claim 1

A method of selecting an IOL to be implanted in the eye of a subject comprising:
a) determining an axial eye length and a pupil size at a desired light level and determining at least one of a desired postoperative refraction and a desired postoperative spherical aberration;
b) determining an aspheric representation of a corneal curvature;
c) selecting an IOL with predetermined power and asphericity, and determining a location of the lens haptic plane (LHP);
d) employing the results of previous sections to establish an eye model for the eye of the subject, the eye model including the axial eye length, the pupil size, the aspheric representation of the corneal curvature, and the LHP;
e) computing with a ray tracing routine and the axial eye length, the pupil size, the aspheric representation of the corneal curvature, and the LHP of said eye model, an expected at least one of a postoperative refraction and postoperative spherical aberration;
f) in the case that the at least one of the expected postoperative refraction and postoperative spherical aberration is not within a predetermined criteria, selecting another IOL with different power and/or asphericity and repeating steps d) and e) until the at least one of the expected postoperative refraction and postoperative spherical aberrations is within the at least one of the desired postoperative refraction and desired postoperative spherical aberration; and
g) selecting, for implantation, an implantable IOL of the nearest power and asphericity available.

### Claim 2 (depends on 1)

The method of to claim 1 wherein the determining the axial eye length comprises transforming a measured axial eye length to a human population average scale by addition of a transformation constant.

### Claim 3 (depends on 1)

The method of claim 1, wherein the selected implantable IOL has at least one aspheric curvature.

### Claim 4 (depends on 1)

The method of claim 1, wherein the selected implantable IOL has spherical curvatures.

### Claim 5 (depends on 1)

The method of claim 1, wherein the determining the aspheric representation of the cornea curvature comprises corneal topography and/or tomography.

### Claim 6 (depends on 5)

The method of claim 5, wherein the aspheric representation of the cornea includes a k value for at least one corneal surface in combination with additional modifying terms.

### Claim 7 (depends on 5)

The method of claim 5, wherein the aspheric representation of the cornea includes a k value for both anterior and posterior corneal surfaces.

### Claim 8 (depends on 1)

The method of claim 1, wherein the computing with the ray tracing routine includes utilizing a focusing ray entering the pupil at 1/√{square root over (2)} an entrance pupil height.

### Claim 9 (depends on 1)

The method of claim 1, wherein the computing with the ray tracing routine includes tracing a marginal ray and a paraxial ray to determine the midpoint between a foci of the marginal ray and a foci of the paraxial ray, as best focus of the eye model.

### Claim 10 (depends on 1)

The method of claim 1, wherein the computing with the ray tracing routine includes tracing a marginal ray and a paraxial ray to determine the distance between a foci of the marginal ray and a foci of the paraxial ray as a metric for image quality.

### Claim 11 (depends on 3)

The method of claim 3, wherein the selected implantable IOL is described as having at least one surface described as modified conicoid according to the following formula:
x
=
(
1
R
)
⁢
y
2
1
+
1
-
k
⁡
(
1
R
)
2
⁢
y
2
+
a
4
⁢
y
4
+
a
6
⁢
y
6
+
…
wherein R is the radius of curvature at the apex, k is the conic constant, y is the radial distance from the optical axis and x is the sag in the direction of light propagation.

### Claim 12 (depends on 4)

The method of claim 4, wherein the eye of the subject has an oblate anterior corneal surface with a k value >1, or wherein the eye of the subject has a hyperboloid corneal surface with a k value <0.

### Claim 13 (depends on 1)

The method of claim 1, further comprising measuring an anterior corneal apex radius, and wherein the determining the location of the lens haptic plane (LHP) comprises utilizing the corneal apex radius.

### Claim 14 (depends on 1)

The method of claim 1 further comprising measuring both anterior and posterior corneal apex radii, and wherein the determining the location of the lens haptic plane (LHP) comprises utilizing the anterior and posterior corneal apex radii.

### Claim 15 (depends on 1)

The method of claim 1, wherein, the location of the lens haptic plane is determined with a prediction algorithm that comprises input values of measured axial eye length and at least one of the measured corneal radius and a corneal power (K).

### Claim 16 (depends on 15)

The method of claim 15, wherein the prediction algorithm is of the type
LHP=a+b×AL+c×ACD+d×LT+e×CR+f×AL2+g×ACD2+h×LT2+i×CR2+j×AL×ACD+k×AL×LT+l×AL×CR +m×ACD×LT+n×ACD×CR+o×LT×CR
wherein AL is the axial eye length, CR the corneal radius, or alternatively corneal power (K), ACD the anterior chamber depth, and LT the crystalline lens thickness.

### Claim 17 (depends on 15)

The method of claim 15, wherein said prediction algorithm for the determining the location of the lens haptic plane in millimeters is
LHP=2.486+0.2174×(AL+ΔAL)−0.4213×CR
wherein AL is the measured axial eye length, ΔAL is a transformation constant, which is specific for the equipment used to measure AL, and CR is the measured corneal radius.

### Claim 18 (depends on 1)

The method of claim 1, wherein the location of the lens haptic plane is directly determined.

### Claim 19 (depends on 18)

The method of claim 18, wherein the location of the lens haptic plane is determined by ultrasound biomicroscopy.

### Claim 20 (depends on 18)

The method of claim 18, wherein the location of the lens haptic plane is determined by optical coherence tomography.

### Claim 21 (depends on 18)

The method of claim 18, wherein the location of the lens haptic plane is determined by Scheimpflug photography.

### Claim 22 (depends on 1)

The method of claim 1, wherein the eye of the subject has undergone refractive corneal surgery thereby obtaining an oblate corneal surface.

### Claim 23 (depends on 1)

The method of claim 1, wherein the eye of the subject has undergone refractive corneal surgery thereby obtaining a hyperbolic corneal surface.

### Claim 24 (depends on 1)

The method of claim 1 wherein the selecting the implantable IOL comprises designing the implantable IOL to result in the at least one of the desired postoperative refraction and the desired postoperative spherical aberration.

### Claim 25 (depends on 1)

The method of claim 1, wherein the desired light level comprises mesopic light conditions.

### Claim 26

An eye model suitable for selecting at least one combination of power and asphericity of an intraocular lens to be implanted in an eye of a subject, comprising:
an axial eye length based on a measured axial eye length transformed to a human population average scale by addition of a transformation constant;
a pupil size at a desired light level;
an aspheric representation of at least one corneal curvature;
a lens haptic plane location for fixation of the intraocular lens following implantation; and
a ray tracing routine configured to calculate an expected at least one of a postoperative refraction and postoperative spherical aberration based at least in part on the axial eye length, the pupil size, the aspheric representation of the at least one corneal curvature, and the lens haptic plane location; and
wherein the eye model is stored on a tangible computer readable memory.

### Claim 27 (depends on 26)

An eye model according to claim 26, wherein the aspheric representation of the at least one corneal curvature is derived from corneal topography and/or tomography.

### Claim 28 (depends on 27)

An eye model according to claim 27, wherein the aspheric representation of the at least one cornea curvature includes a k value for at least one corneal surface in combination with additional modifying terms.

### Claim 29 (depends on 27)

An eye model according to claim 27, wherein the aspheric representation of the at least one cornea curvature includes a k value for both anterior and posterior corneal surfaces.

### Claim 30 (depends on 28)

An eye model according to claim 28, wherein the aspheric representation of the at least one cornea curvature includes a k value >1 referring to a corneal oblate anterior corneal surface.

### Claim 31 (depends on 26)

An eye model according to claim 26, wherein, the lens haptic plane location is obtained with a prediction algorithm that includes input values of measured axial eye length and at least one of a measured corneal radius and a corneal power (K).

### Claim 32 (depends on 31)

An eye model according to claim 31, wherein the prediction algorithm is of the type
LHP=a+b×AL+c×ACD+d×LT+e×CR +f×AL2+g×ACD2+h×LT2+i×CR2+j×AL×ACD+k×AL×LT+l×AL×CR +m×ACD×LT+n×ACD×CR+o×LT×CR
wherein AL is the axial eye length, CR the corneal radius, or alternatively corneal power (K), ACD the anterior chamber depth, and LT the crystalline lens thickness.

### Claim 33 (depends on 31)

An eye model according to claim 31, wherein said prediction algorithm for the obtaining the lens haptic plane location in millimeters is
LHP=2.486+0.2174×(AL+ΔAL)−0.4213×CR
wherein AL is the measured axial eye length, ΔAL is a transformation constant, which is specific for the equipment used to measure AL, and CR is the measured corneal radius.

### Claim 34 (depends on 26)

An eye model according to claim 26, wherein the lens haptic plane location is directly determined.

### Claim 35 (depends on 34)

An eye model according to claim 34, wherein the lens haptic plane location is determined by means of ultrasound biomicroscopy.

### Claim 36 (depends on 34)

An eye model according to claim 34, wherein the lens haptic plane location is determined by means of optical coherence tomography.

### Claim 37 (depends on 34)

An eye model according to claim 34, wherein the lens haptic plane location is determined by means of Scheimpflug photography.

### Claim 38

A method of selecting an IOL to be implanted in the eye of a subject comprising:
a) determining an axial eye length, a pupil size at a desired light level;
b) determining an aspheric representation at least one corneal surface;
c) selecting a first IOL and determining a location of a plane of fixation of the first IOL following implantation;
d) establishing an eye model;
e) based on the eye model, the first selected IOL, the axial eye length, the pupil size, the aspheric representation of the corneal curvature, and the plane of fixation, calculating an amount of postoperative spherical aberration using a ray tracing routine;
f) based on e), selecting an implantation IOL to provide a selected amount of postoperative spherical aberration.

### Claim 39 (depends on 38)

The method of claim 38, wherein the selecting the implantation IOL further comprises:
selecting a second IOL to replace the first IOL and repeating e) and f) until the calculated amount of postoperative spherical aberration is sufficiently close to the selected amount.

### Claim 40

A method of selecting an IOL to be implanted in the eye of a subject, comprising:
determining one or more ocular dimensions based on one or more measurements of at least one eye;
selecting a desired postoperative refractive outcome;
selecting first IOL having at least one of a power, an aspheric profile, and a lens plane;
establishing an eye model based on the one or more characteristics of the at least one eye;
determining a location of the lens plane;
performing a calculation to determine a predicted postoperative refractive outcome based on the eye model, a ray tracing algorithm, the location of the lens plane, and the selected first IOL;
comparing the predicted postoperative refractive outcome to the desired refractive outcome;
based on the comparison, repeating the calculation with at least a second selected IOL having at least one of a different power, a different aspheric profile, and a different lens plane; and
selecting an implantable IOL configured for implantation into the eye of a subject based at least in part on the repeated calculation.

### Claim 41 (depends on 40)

The method of claim 40, wherein the desired postoperative refractive outcome comprises providing distant vision.

### Claim 42 (depends on 40)

The method of claim 40, wherein the desired postoperative refractive outcome comprises reducing an optical aberration of the eye.

### Claim 43 (depends on 40)

The method of claim 40, wherein the lens plane is a lens haptic plane.

### Claim 44 (depends on 40)

The method of claim 40, wherein the selected implantable has an aspheric surface with a predetermined aspheric surface profile.

### Claim 45 (depends on 40)

The method of claim 40, wherein the one or more characteristics of the at least one eye comprises an ocular pupil size.

### Claim 46

A computer system for selecting an IOL for placement into an eye of a subject, comprising:
a processor; and
a computer readable memory coupled to the processor, the memory having stored therein:
an array of ordered values, including:
one or more ocular dimensions;
a desired refractive outcome;
at least one of a power, an aspheric profile, and a lens plane of one or more IOLs;
parameters of an eye model based on one or more characteristics of at least one eye;
sequences of instructions which, when executed by the processor, cause the processor to select an implantable IOL configured for implantation into the eye of the subject, the sequences of instructions configured to:
determine a location of the lens plane;
perform a calculation to determine a predicted postoperative refractive outcome based on the eye model, the location of the lens plane, and a ray tracing algorithm;
compare the predicted postoperative refractive outcome to the desired refractive outcome;
based on the comparison, repeat the calculation with an IOL having at least one of a different power, a different aspheric profile, and a different lens plane.