Test–Retest Reliability of Clinical Shack-Hartmann Measurements

Cheng, Xu; Himebaugh, Nikole; Kollbaum, Pete; Thibos, Larry N.; Bradley, Arthur

doi:10.1167/iovs.03-0265

Cited by 98 publications

(93 citation statements)

References 32 publications

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“…The variability that we measured for higher-order aberrations was only slightly worse that that reported by Cheng et al (2004) They estimated that most of the COAS' variability was attributable to fluctuations in accommodation, the tear film or eye position rather than due to the instrument itself. The COAS may be subject to axial, transverse or angular positioning errors, but they demonstrated that, within the range of misalignments expected for normal clinical use, these caused no significant error.…”

Section: Repeatabilitycontrasting

confidence: 77%

Accuracy, Repeatability and Instrument Myopia Induced by a Clinical Aberrometer - The Complete Ophthalmic Analysis System (COAS)

Salmon¹,

Pol²

2006

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Pubic reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructios, searching existing data sources, gathering and maintaining the date needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, Refractive surgery corrects lower-order refractive aberrations (sphere and astigmatism), but in many cases it inadvertently creates large higher-order aberrations that can degrade vision. This has prompted the development of new instruments, aberrometers, which measure higher-order aberrations. We evaluated a new clinical aberrometer, the Complete Ophthalmic Analysis System (COAS) for accuracy, repeatability and instrument myopia. Methods: We measured 56 normal eyes (28 subjects) using the COAS, with and without cycloplegia and evaluated its lower-order accuracy in comparison to clinical subjective refraction. We also evaluated lower-and higher-order repeatability and instrument myopia. Data were analyzed for a 5.0-mm diameter pupil. For comparison, some of these analyses were also performed on a conventional autorefractor. Results: Mean COAS accuracy for lower-order aberrations (sphere and astigmatism) was at least as good as clinical subjective refraction. Lower-order repeatability was similar to conventional autorefraction. For higher-order aberrations, repeatability, was in the 0.05-0.01-tom range (95% CI). Instrument myopia was small. Conclusions: On average, the COAS provides accurate, repeatable measurements of the lower-order aberrations (sphere and astigmatism) with little instrument myopia. We quantified repeatability for higher-order aberrations and provided recommendations on how to use the COAS in future refractive surgery-related research.

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Section: Repeatabilitycontrasting

confidence: 77%

Accuracy, Repeatability and Instrument Myopia Induced by a Clinical Aberrometer - The Complete Ophthalmic Analysis System (COAS)

Salmon¹,

Pol²

2006

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“…Using retinal IQMs to relate objective measures of visual performance to those subjectively achieved is of particular interest [9][10][11]. Since the optical system of the eye is assumed to be linear, the retinal image quality assessment can be essentially reduced to the comparison of the diffraction limited point spread function (PSF) and the actual aberrated PSF or their respective Fourier transformations, the Optical Transfer Functions (OTFs).…”

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confidence: 99%

“…These metrics were included in the performance analysis as they showed, in several studies [9,11], good correlation with subjective visual performance.…”

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confidence: 99%

A subjective refraction-based assessment of image quality metric

Iskander¹

2011

Photon. Lett. Poland

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“…Both approaches generate accurate and precise measurements of lower and higher order monochromatic aberrations, 29,33,11 and we used both to compare the on-and off-eye aberrations of defocus and spherical aberration observed over a wide dioptric range of three hydrogel and two silicone hydrogel contact lenses. The wet cell provides neutral buoyancy and stable hydration, and thus largely avoids the mechanical forces and hydration fluctuations that might be present when on the eye.…”

Section: Discussionmentioning

confidence: 99%

Comparing the Optical Properties of Soft Contact Lenses On and Off the Eye

Kollbaum¹,

Bradley²,

Thibos³

2013

Optometry and Vision Science

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Purpose-The purpose of the current study was to examine the on-and off-eye optical performance of two types of soft contact lenses (hydrogel and silicone hydrogel).Methods-The monochromatic aberrations (lambda = 850 nm) of contact lenses were measured on-eye using a clinical Shack-Hartmann ocular aberrometer. Additionally, we used an off-eye single-pass contact lens aberrometer (lambda = 540 nm) in which the soft contact lens was placed within a wet cell. Comparison of the lower and higher order aberrations measured with these two methods required compensation for different wavelengths and knowledge of the refractive index of the contact lens materials.Results-The measured on-eye sphere and spherical aberration values were generally similar to those measured off-eye and those specified by the lens manufacturers for both types of soft contact lenses. However, there were notable differences, especially for high plus-powered lenses, which typically exhibited lower sphere power on the eye than expected from the lens specifications and from the off-eye measured powers, both of which were almost identical. Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometrical optics theory. Longitudinal spherical aberration measurements on-and off-eye, however, deviated significantly from that expected of a thin lens with spherical surfaces due to surface asphericities. The difference between on-and off-eye optics can be modeled as a tear lens, or as relative lens thickness changes caused by lens flexure. Conclusions-The results of the current study reveal that the major difference between the oneye lens optics and the manufacturers' specifications are not due to lens errors, but due to eye-lens interactions, which could be either lens flexure or a tear lens forming behind the soft contact lens.Keywords contact lens; spherical aberration; aspheric; flexure; supplemental powerThe paraxial power of a thin lens is proportional to the difference in curvature of its front and back surfaces with a constant of proportionality equal to the difference in refractive index between the lens and surrounding material: P=(Δn)/(1/r 1 − 1/r 2 ). Likewise, a thin conforming soft contact lens (SCL) will change the refracting power of an eye by changing the curvature of the air/eye interface by the difference in curvature of its front and back surfaces. Because of this, the power of a thin SCL in air will approximate its refractive effect on the eye. 1, 2 These two values may not be identical, however, for a combination of several reasons. First, a SCL may fail to conform to the cornea creating an effective "tear Corresponding author: Pete Kollbaum, Indiana University, School of Optometry, 800 East Atwater Ave, Bloomington, IN 47405, kollbaum@indiana.edu. The authors have no financial interest in any of the products or instruments used in this study. lens" between the lens and cornea, as occurs with gas permeable lens fittings. 1,3,4 Second, the lens may change shape and relative thickness w...

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Test–Retest Reliability of Clinical Shack-Hartmann Measurements

Cited by 98 publications

References 32 publications

Accuracy, Repeatability and Instrument Myopia Induced by a Clinical Aberrometer - The Complete Ophthalmic Analysis System (COAS)

Accuracy, Repeatability and Instrument Myopia Induced by a Clinical Aberrometer - The Complete Ophthalmic Analysis System (COAS)

A subjective refraction-based assessment of image quality metric

Comparing the Optical Properties of Soft Contact Lenses On and Off the Eye

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