The Repeatability of Automated and Clinician Refraction

Bullimore, Mark A.; Fusaro, Robert E.; Adams, Craig W.

doi:10.1097/00006324-199808000-00028

Cited by 198 publications

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“…As we moved peripherally, the correlation remained high, albeit not as strong as that in the central area. Similarly, other authors have reported an increase in variability in corneal pachymetry measurements from the center to the periphery, particularly in the superior cornea (4,(14)(15)(16)(17) . They attributed this variability to the effects of the superior eyelid (4) .…”

Section: Discussionsupporting

confidence: 55%

Assessment of anterior and posterior corneal indices using two Scheimpflug analyzers

Fahd¹,

Cherfan²,

Raad³

et al. 2014

Arquivos Brasileiros De Oftalmologia

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Purpose: To assess the agreement between the elevation and curvature measurements of the anterior and posterior corneal surfaces obtained using the Galilei Dual Scheimpflug Analyzer and those obtained using the Pentacam single Scheim pflug system. Methods: This prospective, noninterventional, diagnostic study was conducted at the Department of Ophthalmology at the American University of Beirut (Medical Center) and included 60 eyes of 60 consecutive patients. Measurements were obtained using 2 different Scheimpflug analyzers (Galilei and Pentacam). The best-fit sphere was set at 8 mm in both machines. Pachymetry (CCT), anterior elevation (AE) and posterior elevation (PE), and curvature were assessed. Pearson's correlation coefficients, comparison of means, and Bland-Altman plots were used to evaluate agreement between the 2 systems. Results: The average CCT (at the corneal apex) was 533 ± 35 μm and 532 ± 37 μm (p=0.980), the average central AE was 1.25 ± 3.95 μm and 2.

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Section: Discussionsupporting

confidence: 55%

Assessment of anterior and posterior corneal indices using two Scheimpflug analyzers

Fahd¹,

Cherfan²,

Raad³

et al. 2014

Arquivos Brasileiros De Oftalmologia

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“…Assessing the variance in the astigmatic component poses a problem in the conventional clinical notation. 9 Therefore the sphere, cylinder, and axis component were converted into a vector representation for analysis 13 …”

Section: Discussionmentioning

confidence: 99%

“…The validity of autorefractors is traditionally assessed by comparing their results with that of subjective refraction. 9 This is because they are principally designed to assist ophthalmologists and optometrists to reach the end point of subjective refraction as quickly as possible, in a manner similar to that of retinoscopy The PowerRefractor was also compared to another commercially available autorefractor, the Shin-Nippon SRW-5000 in a separate cohort of 150 subjects aged 18-37 years (average 20.1 (SD 4.2) years, median 19.0 years), 45% of whom were male. The Shin-Nippon SRW-5000 is an infrared open view autorefractor found to be valid and repeatable compared to subjective refraction in both adults and children.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of the measurement of refractive error by the PowerRefractor: a remote, continuous and binocular measurement system of oculomotor function

Hunt

Wolffsohn

Gilmartin

2003

British Journal of Ophthalmology

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Background/aim: The technique of photoretinoscopy is unique in being able to measure the dynamics of the oculomotor system (ocular accommodation, vergence, and pupil size) remotely (working distance typically 1 metre) and objectively in both eyes simultaneously. The aim of this study was to evaluate clinically the measurement of refractive error by a recent commercial photoretinoscopic device, the PowerRefractor (PlusOptiX, Germany). Method: The validity and repeatability of the PowerRefractor was compared to: subjective (noncycloplegic) refraction on 100 adult subjects (mean age 23.8 (SD 5.7) years) and objective autorefraction (Shin-Nippon SRW-5000, Japan) on 150 subjects (20.1 (4.2) years). Repeatability was assessed by examining the differences between autorefractor readings taken from each eye and by re-measuring the objective prescription of 100 eyes at a subsequent session. Results: On average the PowerRefractor prescription was not significantly different from the subjective refraction, although quite variable (difference +0.05 (0.63) D, p = 0.41) and more negative than the SRW-5000 prescription (by 20.20 (0.72) D, p,0.001). There was no significant bias in the accuracy of the instrument with regard to the type or magnitude of refractive error. The PowerRefractor was found to be repeatable over the prescription range of 28.75D to +4.00D (mean spherical equivalent) examined. Conclusion: The PowerRefractor is a useful objective screening instrument and because of its remote and rapid measurement of both eyes simultaneously is able to assess the oculomotor response in a variety of unrestricted viewing conditions and patient types.

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“…The mean error between predicted and subjective refraction was about 0.1 ± 0.08 D averaged across 6 eyes of 6 normal subjects whereas their five calculated image-plane metrics did not differ by more than 0.03 D. Similarly, Thibos et al 18 compared 33 metrics calculations to subjective refractions performed to the nearest 0.25 D on 200 normal and healthy eyes from 100 subjects. All the mean predicted values varied from -0.50 D to +0.25 D. The variability between various metrics was always lower than the ± 0.75 D test-retest variability in the measurement of refractive error 19,20 , meaning that the accuracy of metrics to predict subjective image quality should not be assessed this way. Marsack et al 16 used the previous data set to investigate the ability of 31 metrics derived from wave aberrations maps to predict changes in high-contrast logMAR acuity.…”

Section: Introductionmentioning

confidence: 92%

Calculations and Measurements of the Visual Benefit of Correcting the Higher-order Aberrations Using Adaptive Optics Technology

Legras

Rouger

2008

Journal of Optometry

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PURPOSE: Our goal was to examine the accuracy of metrics, calculated using a numerical eye model including the measurement of the monochromatic aberrations of the eye, to predict the contrast sensitivity (CS) and visual acuity (VA) visual benefits (VB) of correcting higher-order aberrations (HO). METHODS: We measured, on the right eyes of 25 subjects (10 myopes and 15 emmetropes) aged 21 to 56 years, the 16 c/deg CS and high-contrast VA in two conditions of aberration corrections: (i) when correcting only the defocus and astigmatism terms and (ii) when dynamically correcting all the monochromatic aberration terms up to the 5 th order. The measured VB was defined as the ratio of the performances between these two conditions of aberration corrections. RESULTS:We measured a VB of 1.25 and 1.64 respectively in term of VA and CS. We did not find any influence of age on the VB and no statistical significant difference between the myopic and emmetropic group. The contrast sensitivity VB was well correlated (r 2 =0.79) with the ratio of the modulation transfer functions calculated at 16 c/deg in both conditions of aberrations corrections (i.e. MTF16c/deg HO /MTF16c/deg SC ). The levels of correlation between various metrics and measured visual acuity VB were lower (r 2 =0.30 in the better case), however the averaged VB was correctly predicted by the ratio of the intersections between the MTF and a typically neural contrast threshold function. CONCLUSIONS: Metrics based on wave aberration measurements are able to predict the impact of monochromatic aberrations on CS.(J Optom 2008;1:22-29 ©2008 Spanish Council of Optometry) KEY WORDS: image quality; adaptive optics; visual benefit; visual performance; monochromatic aberrations. RESUMEN OBJETIVO:Nuestro objetivo era analizar la validez y la precisión de los descriptores numéricos objetivos (calculados a partir de un modelo de ojo existente al que incorporamos las aberraciones monocromáticas del ojo de cada sujeto) a la hora de predecir los beneficios visuales (BV) sobre la sensibilidad al contraste (SC) o sobre la agudeza visual (AV) obtenidos tras corregir las aberraciones de alto orden. MÉTODOS: Medimos la SC a 16 c/grado y la AV de alto contraste en el ojo derecho de 25 sujetos (10 miopes y 15 emétropes) de edades comprendidas entre los 21 y los 56 años. Las medidas se realizaron en dos condiciones distintas de corrección de aberraciones: (i) cuando sólo los términos de desenfoque y de astigmatismo estaban corregidos y (ii) cuando todas las aberraciones monocromáticas hasta 5º orden fueron corregidas dinámicamente.La medida de los BV se definió como la razón de los resultados obtenidos en cada una de estas dos condiciones de corrección de aberraciones. RESULTADOS: Los BV sobre la AV y la SC fueron, respectivamente, de 1,25 y de 1,64. No encontramos ninguna dependencia de los BV con la edad del sujeto, ni ninguna diferencia estadísticamente significativa entre el grupo miope y el emétrope. Se obtuvo una notable correlación (r 2 =0,79) entre los BV sobre la sensi...

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The Repeatability of Automated and Clinician Refraction

Cited by 198 publications

References 0 publications

Assessment of anterior and posterior corneal indices using two Scheimpflug analyzers

Assessment of anterior and posterior corneal indices using two Scheimpflug analyzers

Evaluation of the measurement of refractive error by the PowerRefractor: a remote, continuous and binocular measurement system of oculomotor function

Calculations and Measurements of the Visual Benefit of Correcting the Higher-order Aberrations Using Adaptive Optics Technology

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