Upload
corine
View
34
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
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
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.
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
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
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)
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.
Self-refraction
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
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
Histogram of Subjective Endpoints
Actuator
2(19) 1.398, 0.178 0.0933t p
AdSpec
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