Image Quality Metrics Quantify Changes inRetinal Image Quality in the Chick Eye during

Emmetropization and Lens Induction of Myopia

Jennifer J. Hunter1, Melanie C.W. Campbell2,3,4, Marsha L. Kisilak2,3,Elizabeth L. Irving2

Center for Visual Science1, University of Rochester, USASchool of Optometry2, Department of Physics& Astronomy3, University of Waterloo,

CanadaGuelph-Waterloo Physics Institute4, Canada

Emmetropization

Growth towards emmetropia

Usually occurs during childhood

In general, humans exhibit:• ↓ in mean ocular refraction

• ↓ in range of refraction

• ↓ in astigmatism

Guiding optical signal is unknown. Wide interest in monochromatic aberrations and their

variation with age & refractive error

ocular refraction (D)

num

ber

15 10 5 0 5 10 151

0.5

0

0.5

1

1.51.5

1−

f x( )

g x( )

1515− x

0myopic hyperopic

Chick Model of Myopia

The chick is commonly used as a model of oculardevelopment & myopia

16 chicksgoggled -15D OD; control OS

(Kisilak, 2005)

Refractive Error Measurement

Age (days)0 2 4 6 8 10 12 14

Hartm

ann-Shack MO

R (D

)

-15

-10

-5

0

5

control eye -15D goggle eye

Research Objectives

In chicks:

How does image quality change as a function of normalgrowth?

Does image quality on the retina differ during thedevelopment of lens-induced myopia?

Which metrics best quantify these changes?

Hartmann-Shack Image Acquisition

Aberrometry on awake chicks with goggles removed(Kisilak et al., 2006).

Image Quality

RMSA plots showed no difference with age but adifference between goggle and control eyes acrossgrowing pupils (Kisilak et al., 2006).

Equal amounts of different aberration types affectretinal image quality to different magnitudes(Applegate, 2002).

Necessary to quantify retinal image quality

Angular PSF: HOA, Defocus &Astigmatism

243.6 arcmin

Day 7Day 0 Day 2 Day 4 Day 9 Day 10 Day 14

Control

Goggle

Angular PSF: HOA alone

Day 7Day 0 Day 2 Day 4 Day 9 Day 10 Day 14

13.6 arcmin Control

Goggle

Image Quality Metrics

Define image quality metrics which would quantify• small changes in retinal image quality due to aberrations

during normal and abnormal growth• larger changes due primarily to defocus• the presence of an optical signal to the direction of defocus (not

discussed here)

Three categories• Relative to the diffraction limit• Absolute blur or spatial frequency dimensions• Orientation measures (not discussed here)

Relative Image Quality Metrics:PSF Correlation

2nd order & up

3rd & 4th order

Control

Goggle

Age (days)0 2 4 6 8 10 12 14

PSF Correlation

0.0

0.2

0.4

0.6

0.8

1.0

Day p = 0.008Eye p = 0.041

Eye p < 0.001

Relative Image Quality Metrics:MTF Correlation

2nd order & up

3rd & 4th order

Control

Goggle

Age (days)0 2 4 6 8 10 12 14

MTF C

orrelation

0.0

0.2

0.4

0.6

0.8

1.0

Day p = 0.004

Day p < 0.001Eye p < 0.001

Absolute Image Quality Metrics:PSF √2nd Moment

2nd order & up

Control

Goggle

Age (days)0 2 4 6 8 10 12 14

PSF sqrt [2nd

mom

ent] (arcmin)

0

10

20

30

40

50

Day * Eye p < 0.001

Absolute Image Quality Metrics:PSF √2nd Moment

3rd & 4th order

Control

Goggle

Age (days)0 2 4 6 8 10 12 14

PSF sqrt [2nd

mom

ent] (arcmin)

6

7

8

9

10

Day p = 0.002Eye p = 0.036

Conclusions:Normal Ocular Development

From hatching, retinal image quality (both overall andHOA alone) improves with growth in control eyes, bothrelative to diffraction-limit & absolute image quality.

This is quantified by metrics of retinal image quality.

Conclusions:Myopic Ocular Development

When defocus, astigmatism and HOA are considered,image quality improves with age but remains poorerthan in normal eyes.

There appears to be an initial effect of goggling on theimage quality due to HOA.

With age, it is overcome and image quality improves,such that by day 14, it is not different from normaleyes.

Different metrics best quantify the image quality withand without defocus.

Acknowledgements

Our appreciation is extended toA. Casey, C. Cookson, L. Epps

and D. King.

This research was supported byNSERC Canada,

CRC Program, PREA, OGS & CFI.

Absolute Image Quality Metrics:MTF Entropy

2nd order & up

3rd & 4th order

Control

Goggle

0 2 4 6 8 10 12 14

Age (Days)

MTF Entropy (x10

8)

0

1

2

3

4

5

6

Day p < 0.001

Day * Eye p = 0.038

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8R1

R2

R3

R4

R5

R6

R7

R8

R9

R10

R11

R12

R13

R2 R4 R6 R8 R10 R12R1 R3 R5 R7 R9 R11 R13

Relative Image Quality Metrics

Absolute Image Quality Metrics

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8A1

A2

A3

A4

A5

A6

A7

A8

A9

A2 A4 A6 A8A1 A3 A5 A7 A9

Signals to Defocus Direction

Astigmatism & Higher-orderAberrations

Higher-orderAberrations

HyperopicViewing

MyopicViewing

MyopicViewing

HyperopicViewing

Mean Ocular Refraction

Age (days)0 5 10 15 20

MO

R (D

)

-30

-20

-10

0

10

control eye-30D goggle-15D goggle (Kisilak et al 2006)-10D goggle (Irving et al. 1992)

JCC0

Age (days)0 5 10 15 20

JCC

0 (D)

-1.5

-1.0

-0.5

0.0

0.5

1.0

control eyegoggle eye

**

* Control & goggled eyes significantly different