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Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie , JD Silver †† , DN Crosby †† , MJA Newbery , AK Robertson Vision for the Developing World, Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford. OX2 6AW England †† Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, England Conflict of interest JD Silver: developer of the AdSpec GE MacKenzie: employed by JD Silver ICEE 2007 The Inaugural World Congress on Refractive Error and Service Development WCRE 2007 14-16 March, 2007 Durban, South Africa

Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

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Page 1: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes

GE MacKenzie†, JD Silver††, DN Crosby††, MJA Newbery†, AK Robertson†

†Vision for the Developing World, Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford. OX2 6AW England

†† Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, England

Conflict of interestJD Silver: developer of the AdSpecGE MacKenzie: employed by JD Silver

ICEE 2007The Inaugural World Congress on Refractive Error and Service Development

WCRE 2007 14-16 March, 2007 Durban, South Africa

Page 2: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Variability

Reproducibility conditions*

“conditions where test results are obtained with the same method on

identical test items in different laboratories with different operators using different

equipment”

Minimum Variability Maximum Variability

Repeatability conditions*

“conditions where independent test results are obtained with the same

method on identical test items in the same laboratory by the same operator

using the same equipment”

Implementation of ISO 5725-1:1994. Accuracy (trueness and precision) of measurement methods and results. Part 1: general principles and definitions. BS ISO.

Page 3: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

The 0.50D Rule

Study Examiners SubjectsMeasurements

Harvey et al. (1997) 1 47 1

Repeatability Studies

1201McKendrick, Brennan (1995)

1402Johnson et al. (1996)

2401Walline et al. (1999)

1125unspecifiedSalchow et al. (1999)

2401Raasch et al. (2001)

11171Choong et al. (2006)

31001Dave et al. (2004)

2301Elliott et al. (1997)

1862Bullimore et al. (1998)

11001Trusit, Yasufumi (2004)

2602Sheedy et al. (2004)

11901Pesudovs, Weisinger (2004)

2992Leinonen et al. (2006)

1213Sloan et al. (1954)

2402Zadnik et al. (1992)

5121Rosenfield, Chiu (1995)*

MeasurementsSubjectsExaminersStudy

* SD = 0.14 D, 95% Range 0.55D

Reproducibility Studies

Page 4: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Reproducibility of Subjective Refraction amongst Qualified

Optometrists

Purpose: To evaluate the reproducibility of subjective refraction

Sampling: 40 randomly selected optometric practices - Oxford and the City of

Westminster, United Kingdom

Measurement independence

Trial frame refractions

Page 5: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

95% Limits for Residuals over mean refraction

Reproducibility SD = 0.28 D, 95% Range 1.10 D

(Repeatability SD = 0.14 D, 95% Range 0.55 D)

Page 6: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

0.5 I

0.5 K

0.5 J

0.5 I

0.5 K

0.5 J

Software courtesy of Harris, Malan, Rubin. Optometric Science Research GroupDepartment of Optometry, University of Johannesburg, P.O. Box 524, Auckland Park 2006

Distribution of Refractive State. Reproducibility Data.

2

40

0.8281 D, 0.2336 D, 0.1449 D

0.55 / 0.55 106

norm = 1.2340 D

0.0822 0.0000 0.0101

0.0000 0.0082 0.0034 D

0.0101 0.0034 0.0074

I J K

vc

n

F I F J F K

S

W. F. Harris (2005) . Reduction of artefact in scatter plots of spherocylindrical data. Ophthalmic and Physiological Optics 25 (1), 13–17.

Page 7: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Self-refraction

Page 8: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

0 5 10 15 20 25-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

Time (s)

Stig

mat

ic P

ower

(D

)

Stigmatic Self-refraction

Image degrades

Subjective endpoint

Additional lens power change leads to no

improvement in image quality

As lens power decreases image quality increases

Subject fogged. Image severely degraded

The anatomy of a stigmatic self-refraction

Page 9: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Dynamics of 20 repeated measures of self-refraction

0 5 10 15 20 25 30 35 40 45-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

Time (s)

Stigm

atic P

ow

er

(D)

Repeatability of Stigmatic Self-refraction

Page 10: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Histogram of Subjective Endpoints

Actuator

2(19) 1.398, 0.178 0.0933t p

AdSpec

Page 11: Repeatability and reproducibility of self-refraction using continuously adjustable fluid-filled spectacle lenses in pre-presbyopes GE MacKenzie †, JD Silver

Future Directions

• Similar studies in with large samples of children, pre-presbyopic adults and presbyopic adultsEmmetropes, hyperopes and myopesVarious degrees of astigmatism

• Evaluate feedback control systems used during self-refraction

• Study image blur detection, image size, vergence interactions

• Optimization of self-refraction protocol