Aberrometer

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James S. Wolffsohn - One of the best experts on this subject based on the ideXlab platform.

  • Validity of a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Poster Purpose: A study to validate a prototype Hartmann-Shack (HS) wavefront Aberrometer. Methods: The dynamic range was assessed using a calibrated model eye. It was validated against a conventional HS-Aberrometer (Topcon KR1W) in 75 eyes using both instruments in random order. Additionally, intra-sessional repeatability was tested. Results: The Aberrometer showed a large dynamic range of +21.0 D to −25.0 D. It was comparable to a conventional HS Aberrometer for spherical-equivalent SE (MD ± 95% CI: 0.02 ± 0.49D; correlation: r = 0.995, p 

  • validity of a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Poster Purpose: A study to validate a prototype Hartmann-Shack (HS) wavefront Aberrometer. Methods: The dynamic range was assessed using a calibrated model eye. It was validated against a conventional HS-Aberrometer (Topcon KR1W) in 75 eyes using both instruments in random order. Additionally, intra-sessional repeatability was tested. Results: The Aberrometer showed a large dynamic range of +21.0 D to −25.0 D. It was comparable to a conventional HS Aberrometer for spherical-equivalent SE (MD ± 95% CI: 0.02 ± 0.49D; correlation: r = 0.995, p < 0.001), astigmatic components (J0: 0.02 ± 0.15D; r = 0.977, p < 0.001; J45: 0.03 ± 0.28; r = 0.666, p < 0.001) and HOAs RMS (0.02 ± 0.20D; r = 0.620, p < 0.001). Intra-sessional repeatability correlation was also excellent (SE = 1.000, p < 0.001; astigmatic-components J0 = 0.998, p < 0.001, J45 = 0.980, p < 0.01; HOAs RMS = 0.961, p < 0.001). Conclusions: This study confirms the validity of the prototype Aberrometer. The prototype Aberrometer can measure continuously to provide direct feedback of the optical status of the eye during surgery.

  • intraoperative prediction of refractive error using a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Purpose: To ascertain the agreement level between intra-operative refraction using a prototype surgical Hartmann-Shack Aberrometer and subjective refraction a month later. Methods: Fifty-four consecutive patients had their pseudophakic refractive measured with the Aberrometer intra-operatively at the end of their cataract surgery. A masked optometrist performed subjective refraction 4 weeks later. The two sets of data were then analysed for correlation. Results: The mean spherical equivalent was −0.14 ± 0.37 D (Range: −1.41 to +1.72 D) with the prototype Aberrometer and −0.34 ± 0.32 (−1.64 to +1.88 D) with subjective refraction. The measurements positively correlated to a very high degree (r =+0.81, p < 0.01). In 84.3% of cases the two measurements were within 0.50D of each other. Conclusion: The Aberrometer can verify the aimed refractive status of the eye intraoperatively to avoid a refractive surprise. The Aberrometer is a useful tool for real time assessment of the ocular refractive status.

  • design and validity of a miniaturized open field Aberrometer
    Journal of Cataract and Refractive Surgery, 2013
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p<0.001), astigmatic components (J0: 0.02 ± 0.15D; r=0.977, p<0.001; J45: 0.03 ± 0.28; r=0.666, p<0.001) and higher order aberrations RMS (0.02 ± 0.20D; r=0.620, p<0.001). Intraclass correlation coefficient assessments of intra-sessional repeatability for the Aston Aberrometer were excellent (spherical equivalent =1.000, p<0.001; astigmatic components J0 =0.998, p<0.001, J45=0.980, p<0.01; higher order aberrations RMS =0.961, p<0.001). CONCLUSIONS: The Aston Aberrometer gives valid and repeatable measures of refractive error and higher order aberrations over a large range. As it is able to measure continuously, it can provide direct feedback to surgeons during intraocular lens implantations and corneal surgery as to the optical status of the visual system.

  • Design and validity of a miniaturized open-field Aberrometer.
    Journal of cataract and refractive surgery, 2012
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p

Uday K. Bhatt - One of the best experts on this subject based on the ideXlab platform.

  • Validity of a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Poster Purpose: A study to validate a prototype Hartmann-Shack (HS) wavefront Aberrometer. Methods: The dynamic range was assessed using a calibrated model eye. It was validated against a conventional HS-Aberrometer (Topcon KR1W) in 75 eyes using both instruments in random order. Additionally, intra-sessional repeatability was tested. Results: The Aberrometer showed a large dynamic range of +21.0 D to −25.0 D. It was comparable to a conventional HS Aberrometer for spherical-equivalent SE (MD ± 95% CI: 0.02 ± 0.49D; correlation: r = 0.995, p 

  • validity of a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Poster Purpose: A study to validate a prototype Hartmann-Shack (HS) wavefront Aberrometer. Methods: The dynamic range was assessed using a calibrated model eye. It was validated against a conventional HS-Aberrometer (Topcon KR1W) in 75 eyes using both instruments in random order. Additionally, intra-sessional repeatability was tested. Results: The Aberrometer showed a large dynamic range of +21.0 D to −25.0 D. It was comparable to a conventional HS Aberrometer for spherical-equivalent SE (MD ± 95% CI: 0.02 ± 0.49D; correlation: r = 0.995, p < 0.001), astigmatic components (J0: 0.02 ± 0.15D; r = 0.977, p < 0.001; J45: 0.03 ± 0.28; r = 0.666, p < 0.001) and HOAs RMS (0.02 ± 0.20D; r = 0.620, p < 0.001). Intra-sessional repeatability correlation was also excellent (SE = 1.000, p < 0.001; astigmatic-components J0 = 0.998, p < 0.001, J45 = 0.980, p < 0.01; HOAs RMS = 0.961, p < 0.001). Conclusions: This study confirms the validity of the prototype Aberrometer. The prototype Aberrometer can measure continuously to provide direct feedback of the optical status of the eye during surgery.

  • intraoperative prediction of refractive error using a prototype surgical Aberrometer
    Clinical and Experimental Ophthalmology, 2014
    Co-Authors: Uday K. Bhatt, Sunil Shah, Harminder S Dua, James S. Wolffsohn
    Abstract:

    Purpose: To ascertain the agreement level between intra-operative refraction using a prototype surgical Hartmann-Shack Aberrometer and subjective refraction a month later. Methods: Fifty-four consecutive patients had their pseudophakic refractive measured with the Aberrometer intra-operatively at the end of their cataract surgery. A masked optometrist performed subjective refraction 4 weeks later. The two sets of data were then analysed for correlation. Results: The mean spherical equivalent was −0.14 ± 0.37 D (Range: −1.41 to +1.72 D) with the prototype Aberrometer and −0.34 ± 0.32 (−1.64 to +1.88 D) with subjective refraction. The measurements positively correlated to a very high degree (r =+0.81, p < 0.01). In 84.3% of cases the two measurements were within 0.50D of each other. Conclusion: The Aberrometer can verify the aimed refractive status of the eye intraoperatively to avoid a refractive surprise. The Aberrometer is a useful tool for real time assessment of the ocular refractive status.

  • design and validity of a miniaturized open field Aberrometer
    Journal of Cataract and Refractive Surgery, 2013
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p<0.001), astigmatic components (J0: 0.02 ± 0.15D; r=0.977, p<0.001; J45: 0.03 ± 0.28; r=0.666, p<0.001) and higher order aberrations RMS (0.02 ± 0.20D; r=0.620, p<0.001). Intraclass correlation coefficient assessments of intra-sessional repeatability for the Aston Aberrometer were excellent (spherical equivalent =1.000, p<0.001; astigmatic components J0 =0.998, p<0.001, J45=0.980, p<0.01; higher order aberrations RMS =0.961, p<0.001). CONCLUSIONS: The Aston Aberrometer gives valid and repeatable measures of refractive error and higher order aberrations over a large range. As it is able to measure continuously, it can provide direct feedback to surgeons during intraocular lens implantations and corneal surgery as to the optical status of the visual system.

  • Design and validity of a miniaturized open-field Aberrometer.
    Journal of cataract and refractive surgery, 2012
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p

Rudy M.m.a. Nuijts - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of the Comparability and Repeatability of Four Wavefront Aberrometers
    Investigative ophthalmology & visual science, 2011
    Co-Authors: Nienke Visser, Tos T. J. M. Berendschot, Frenne Verbakel, Annelie N. Tan, John De Brabander, Rudy M.m.a. Nuijts
    Abstract:

    PURPOSE To compare total ocular aberrations and corneal aberrations identified with four different Aberrometers and to determine the repeatability and interobserver variability. METHODS In this prospective comparative study, 23 healthy subjects underwent bilateral examination with four Aberrometers: the Irx3 (Hartmann-Shack; Imagine Eyes, Orsay, France), Keratron (Hartmann-Shack; Optikon, Rome Italy), iTrace (ray-tracing; Tracey Technologies, Houston, TX), and OPD-Scan (Automated Retinoscopy; Nidek, Gamagori, Japan). Six images per eye were obtained. Second-, third- and fourth-order spherical aberrations were exported for 5.0-mm pupils. RESULTS Significant differences in measurements were found for several total ocular aberrations (defocus [2,0], astigmatism [2,2], trefoil [3,-3], trefoil [3,3], and spherical aberration [4,0]) and corneal aberrations (defocus [2,0] and astigmatism [2,2]). The Irx3 showed the highest repeatability in measuring total ocular aberrations, followed by the Keratron, OPD-Scan, and iTrace. The repeatability of the corneal aberration measurements was highest for the iTrace, followed by the Keratron and OPD-Scan. The OPD-Scan showed a lower interobserver variability, compared with the Irx3, Keratron, and iTrace. CONCLUSIONS Total ocular and corneal aberrations are not comparable when measured with different Aberrometers. Hartmann-Shack Aberrometers showed the best repeatability for total ocular aberrations and iTrace for corneal aberrations. It would be worthwhile in the future to evaluate Aberrometers in patients with more aberrant eyes.

  • Repeatability and validity of Zywave Aberrometer measurements
    Journal of cataract and refractive surgery, 2002
    Co-Authors: Willem J Hament, Vaisjaly A Nabar, Rudy M.m.a. Nuijts
    Abstract:

    Abstract Purpose To study the repeatability of Zywave Aberrometer (Bausch & Lomb) measurements and compare the measurements with those of subjective refraction and noncycloplegic and cycloplegic autorefractions in a clinical setting. Setting Department of Ophthalmology, University Hospital Maastricht, Maastricht, The Netherlands. Methods Subjective manifest refraction, noncycloplegic autorefraction, cycloplegic autorefraction, and Zywave Aberrometer measurements were performed in 20 eyes of 20 myopic patients. Three consecutive Zywave measurements were performed with and without dilation of the pupil. The mean difference and 95% limits of agreement among the measurement methods were determined for dilated and 3.5 mm pupils. The repeatability coefficient of the Zywave Aberrometer measurements was determined. Results The mean differences in spherical equivalent (SE), sphere, and cylinder between subjective refraction and Zywave predicted phoropter refraction (PPR) with a dilated pupil were −1.10 diopters (D) ± 0.46 (SD) (P Conclusions Subjective refraction measurements are slightly more myopic than cycloplegic autorefraction measurements. With a dilated pupil, the Zywave measurements were significantly more myopic than subjective refractions and even more myopic than cycloplegic autorefractions. Zywave measurements and subjective refractions were in better agreement with a 3.5 mm pupil. The repeatability of Zywave Aberrometer measurements is adequate for lower-order aberrations.

Toshifumi Mihashi - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of paraxial forward scattering from intraocular lens with increased surface light scattering using goniophotometry and Hartmann-Shack wavefront aberrometry
    Japanese Journal of Ophthalmology, 2017
    Co-Authors: Keiichiro Minami, Toshifumi Mihashi, Yoko Maruyama, Kazunori Miyata, Tetsuro Oshika
    Abstract:

    Purpose To evaluate the influence of increases in light scattering on intraocular lens (IOL) surfaces on paraxial forward scattering using goniophotometry and Hartmann-Shack wavefront aberrometry. Methods Surface light scattering was reproduced experimentally by acceleratedly aging 4 intraocular lenses by 0, 3, 5, and 10 years each. Light scattering from both IOL surfaces was measured using Scheimpflug photography. The paraxial forward scattering from the aged IOLs was measured using a goniophotometer with a halogen light source (wavelength: 350–850 nm) and telecentric optics, and changes in the maximum intensity and full width at 10% of maximum intensity (FW10%) were evaluated. The influences on the retina image were examined using a Hartmann-Shack Aberrometer (wavelength: 840 nm). The contrast and difference from the point spread function of the central centroids were evaluated. Results The mean surface light scattering from both IOL surfaces ranged from 30.0 to 118.3 computer compatible tape (CCT) and increased with each aging year. Evaluations using the goniophotometer and the Hartmann-Shack Aberrometer showed no significant change in the paraxial forward scattering with the aging year ( P  > .45, Kruskal–Wallis test), and no association with the surface light scattering intensity was found ( P  > .75, Spearman rank correlation). Conclusion This experimental study using aged IOLs demonstrated that surface light scattering does not influence paraxial forward scattering.

  • design and validity of a miniaturized open field Aberrometer
    Journal of Cataract and Refractive Surgery, 2013
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p<0.001), astigmatic components (J0: 0.02 ± 0.15D; r=0.977, p<0.001; J45: 0.03 ± 0.28; r=0.666, p<0.001) and higher order aberrations RMS (0.02 ± 0.20D; r=0.620, p<0.001). Intraclass correlation coefficient assessments of intra-sessional repeatability for the Aston Aberrometer were excellent (spherical equivalent =1.000, p<0.001; astigmatic components J0 =0.998, p<0.001, J45=0.980, p<0.01; higher order aberrations RMS =0.961, p<0.001). CONCLUSIONS: The Aston Aberrometer gives valid and repeatable measures of refractive error and higher order aberrations over a large range. As it is able to measure continuously, it can provide direct feedback to surgeons during intraocular lens implantations and corneal surgery as to the optical status of the visual system.

  • Serial measurements of accommodation by open-field Hartmann–Shack wavefront Aberrometer in eyes with accommodative spasm
    Japanese Journal of Ophthalmology, 2012
    Co-Authors: Hiroyuki Kanda, Toshifumi Mihashi, Mariko Kobayashi, Takeshi Morimoto, Kohji Nishida, Takashi Fujikado
    Abstract:

    Purpose To investigate the serial changes of accommodation and spherical aberration in eyes with accommodative spasm. Methods Four patients with accommodative spasm and ten healthy subjects were studied. The ocular refractive power (spherical equivalent) and spherical aberration were measured serially with an open-field, binocular Hartmann–Shack wavefront Aberrometer. Patients and subjects wore full-correction lenses and were instructed to fixate a target set at 50 cm from the eye. The time-average of the refractive power, spherical aberration, and fluctuations of accommodation analyzed by the fast Fourier transform (FFT) of the two groups were compared. Results The average ± standard deviation refractive power in the patients was significantly more negative than that in the healthy subject (−3.12 ± 1.06 vs. −1.49 ± 0.17 D). The integrated intensity of the FFT from 1 to 4 Hz was significantly higher in the patients than in the healthy subjects. The spherical aberration in patients was more negative than that in the healthy subjects (−0.033 ± 0.048 μm vs. 0.002 ± 0.027 μm). Conclusions Eyes with accommodative spasm are characterized by a lead of accommodation with greater fluctuations and negative spherical aberrations. Excessive accommodation can be measured objectively in such eyes with a binocular wavefront Aberrometer without cycloplegics.

  • Design and validity of a miniaturized open-field Aberrometer.
    Journal of cataract and refractive surgery, 2012
    Co-Authors: Uday K. Bhatt, Toshifumi Mihashi, Amy L. Sheppard, Sunil Shah, Hs Dua, T. Yamaguchi, James S. Wolffsohn
    Abstract:

    PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann Aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional Aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p

  • Tear Film Break-up Time Evaluated by Real-Time Hartmann-Shack Wavefront Sensing
    Japanese Journal of Ophthalmology, 2006
    Co-Authors: Toshifumi Mihashi, Shizuka Koh, Sayuri Ninomiya, Naoyuki Maeda, Yoko Hirohara, Takashi Fujikado
    Abstract:

    PurposeTo develop a novel method for measuring tear break-up time (BUT) by continuously measuring higher order wavefront aberrations using a Hartmann-Shack (H-S) Aberrometer.MethodsWavefront aberrations up to the sixth order for a 4-mm pupil were measured in six eyes of six normal subjects using an H-S Aberrometer. The aberrometry was performed once every second for up to 50 s under topical anesthesia. The sequence of the points was divided into two stages, and the BUT was defined as the wavefront border of the stages (WFBUT). The WFBUT was compared with the BUT by the conventional fluorescein method (FLBUT) or by the disruption of placid-ring images (PLBUT).ResultsIn three eyes, the WFBUT (average, 10.9 ± 1.1 s) was shorter than the PLBUT (average, 17.5 ± 2.5 s), while in the other three eyes the WFBUT (average, 21.5 ± 2.2 s) was longer than PLBUT (average, 8.1 ± 2.2 s). The FLBUT was shorter than WFBUT or PLBUT in most cases.ConclusionsThe tear break-up time measured by H-S Aberrometer may be used as a practical measure of tear break-up.  Jpn J Ophthalmol 2006;50:85–89 © Japanese Ophthalmological Society 2006

Larry N. Thibos - One of the best experts on this subject based on the ideXlab platform.

  • differences between wavefront and subjective refraction for infrared light
    Optometry and Vision Science, 2014
    Co-Authors: Danielle F W Teel, Robert J Jacobs, James Copland, Daniel R Neal, Larry N. Thibos
    Abstract:

    ABSTRACTPurposeTo determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light.MethodsObjective refractions were obtained with a commercial wavefront Aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 3

  • Importance of fixation, pupil center, and reference axis in ocular wavefront sensing, videokeratography, and retinal image quality.
    Journal of cataract and refractive surgery, 2009
    Co-Authors: Raymond A. Applegate, Larry N. Thibos, Michael D. Twa, Edwin J. Sarver
    Abstract:

    Purpose To examine the impact of the location of the fixation target, pupil center, and reference axis of ophthalmic Aberrometers and videokeratographers on the measurement of corneal aberrations relevant to vision. Setting Clinical Research, Visual Optics Institute, College of Optometry, University of Houston, Houston, Texas, USA. Methods The design features of a generic Aberrometer and videokeratographer and their interaction with the eye were examined. The results provided a theoretical framework for experimental assessment of pupil translation errors on corneal aberrations relevant to vision and their correction in 129 eyes. Results Two key principles emerged. First, the Aberrometer's measurement axis must coincide with the eye's line-of-sight (LoS). Second, the videokeratographer's measurement axis (the vertex normal) must be parallel with the eye's LoS. When these principles are satisfied, the eye will be in the same state of angular rotation and direct comparison of measurements is justified, provided any translation of the pupil from the vertex normal is taken into account. The error incurred by ignoring pupil displacement in videokeratography varies between eyes and depends on the type of aberration and amount of displacement, with the largest residual correction root-mean-square wavefront error being 1.26 μm over a 6.0 mm pupil, which markedly decreases retinal image quality. Conclusion Translation of the pupil center with respect to the vertex normal in videokeratography should not be ignored in the calculation of the corneal first-surface, internal aberrations of the eye relevant to vision, or the design of refractive corrections based on videokeratography.

  • Measuring ocular aberrations and image quality in peripheral vision with a clinical wavefront Aberrometer.
    Clinical & experimental optometry, 2009
    Co-Authors: J. Shen, Larry N. Thibos
    Abstract:

    Background:  Clinical Aberrometers are accurate, robust instruments for measuring wavefront aberrations for foveal vision but several practical concerns arise when performing aberrometry of the peripheral field. The purpose of this study was to evaluate these concerns experimentally using a physical eye model. Methods:  A physical model eye was constructed to provide a stable test case that resembled a human eye. Aberrations were measured with a commercial Shack-Hartmann Aberrometer along lines-of-sight ranging from zero to 45° of eccentricity. Commercial software for wavefront reconstruction and Zernike analysis was adapted for use with elliptical entrance pupils encountered off-axis. Results:  Pupil dimensions estimated from the array of Shack-Hartmann spots captured by the wavefront sensor followed geometrical optics predictions up to 30° eccentricity. With careful attention to detail, aberration analysis over an elliptical pupil was verified with alternative software. Retinal image quality declined slowly as eccentricity increased due to the eye model's spherical aberration. The total RMS computed from Zernike coefficients overestimated the total RMS computed based on the wavefront error of the elliptical pupil. Conclusion:  Measurement of off-axis wavefront aberrations of a model eye over a restricted range of eccentricities is possible with the COAS clinical wavefront Aberrometer and auxiliary lenses to correct astigmatism. When central image quality is good, the off-axis aberrations will have a powerful effect on peripheral image quality. When central image quality is poor, the additional effect of off-axis aberrations will be minor.

  • Validation of a combined corneal topographer and Aberrometer based on Shack–Hartmann wave-front sensing
    Journal of the Optical Society of America. A Optics image science and vision, 2004
    Co-Authors: Fan Zhou, Larry N. Thibos, Xin Hong, Donald T. Miller, Arthur Bradley
    Abstract:

    A corneal Aberrometer based on Shack-Hartmann wave-front sensing was developed and validated by using calibrated aspheric surfaces. The Aberrometer was found to accurately measure corneal reflective aberrations, from which corneal topography and corneal refractive aberrations were derived. Measurements of reflective aberrations correlated well with theory (R2 = 0.964 to 0.994). The sag error root mean square (RMS) was small, ranging from 0.1 to 0.17 microm for four of the five calibrated surfaces with the fifth at 0.36 microm as a result of residual defocus. Measured refractive aberrations matched with theory and whole-eye aberrometry to within a small fraction of a wavelength. Measurements on three human corneas revealed very large refractive astigmatism (0.65-1.2 microm) and appreciable levels of trefoil (0.08-0.47 microm), coma (0.14-0.19 microm), and spherical aberration (0.18-0.25 microm). The mean values of these aberrations were significantly larger than the RMS in repeated measurements.

  • validation of a combined corneal topographer and Aberrometer based on shack hartmann wave front sensing
    Journal of The Optical Society of America A-optics Image Science and Vision, 2004
    Co-Authors: Fan Zhou, Larry N. Thibos, Xin Hong, Donald T. Miller, Arthur Bradley
    Abstract:

    A corneal Aberrometer based on Shack-Hartmann wave-front sensing was developed and validated by using calibrated aspheric surfaces. The Aberrometer was found to accurately measure corneal reflective aberrations, from which corneal topography and corneal refractive aberrations were derived. Measurements of reflective aberrations correlated well with theory (R2 = 0.964 to 0.994). The sag error root mean square (RMS) was small, ranging from 0.1 to 0.17 microm for four of the five calibrated surfaces with the fifth at 0.36 microm as a result of residual defocus. Measured refractive aberrations matched with theory and whole-eye aberrometry to within a small fraction of a wavelength. Measurements on three human corneas revealed very large refractive astigmatism (0.65-1.2 microm) and appreciable levels of trefoil (0.08-0.47 microm), coma (0.14-0.19 microm), and spherical aberration (0.18-0.25 microm). The mean values of these aberrations were significantly larger than the RMS in repeated measurements.