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Steven C. Dakin - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vision screening of 5 15 year old children in three tongan schools comparison of the auckland Optotypes and lea symbols
Clinical and Experimental Optometry, 2020Co-Authors: Lisa M Hamm, Nicola Anstice, Fiona Langridge, Joanna M Black, Mele Vuki, Toakase Fakakovikaetau, Cameron C Grant, Steven C. DakinAbstract:BACKGROUND: Comprehensive vision screening programmes for children are an important part of public health strategy, but do not exist in many countries, including Tonga. This project set out to assess: (1) the functional vision of children attending primary schools in Tonga and (2) how a new recognition acuity test (The Auckland Optotypes displayed on a tablet computer) compares to use of a standardised eye chart in this setting. METHODS: Children from three Tongan primary schools were invited to participate. Acuity testing was conducted using a standardised recognition acuity chart (Lea symbols) and the tablet test displaying two formats of The Auckland Optotypes. Measures of ocular alignment, stereo acuity and non-cycloplegic photorefraction were also taken. RESULTS: Parents of 249 children consented to participate. One child was untestable. Only 2.8 per cent of testable children achieved visual acuity worse than 0.3 logMAR in the weaker eye. Results from the Spot Photoscreener suggested that no children had myopia or hyperopia, but that some children had astigmatism. The tablet test was practical in a community setting, and showed ±0.2 logMAR limits of agreement with the Lea symbols chart. CONCLUSION: The sample of children in Tongan primary schools had good functional vision. A modified version of the tablet acuity test is a promising option for vision screening in this context.
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recognition acuity in children measured using the auckland Optotypes
Ophthalmic and Physiological Optics, 2018Co-Authors: Lisa M Hamm, Steven C. Dakin, Nicola Anstice, Joanna M BlackAbstract:PURPOSE: Sloan letters displayed by the Electronic Visual Acuity (EVA) system are the gold standard for recognition acuity measurement in research settings. However, letters are not always appropriate for children. The Auckland Optotypes (TAO) are a new, open-access set of 10 pictograms available in regular and vanishing formats. We sought to assess feasibility of using both formats of TAO for measuring visual acuity (VA) in children using a Bayesian adaptive staircase, in a community setting. METHODS: We tested 121 children (5-12 years old) with both formats of TAO, a handheld flipchart vision screener (Parr vision test), as well as the gold standard EVA. We measured feasibility of the three comparison tests in three ways. First, using limits of agreement (LoA) with EVA, second, calculating area under the receiver operating characteristic curve (AUC), and finally, investigating trial-by-trial responses. RESULTS: Agreement between tests was within test-retest reliability of EVA measures (LoATAOregular = ±0.14, LoATAOvanishing = ±0.15, LoAParr = ±0.16 logMAR). TAO tests were highly effective at identifying children with vision impairment (AUCTAOregular = 0.96, AUCTAOvanishing = 0.95), whereas Parr was less effective (AUCParr = 0.82). In 5-6 year old children there was an enhanced advantage of TAO (AUCTAOregular = 0.97, AUCTAOvanishing = 0.98) over Parr (AUCParr = 0.75). Although each child completed 16 trials, approximately 10 trials were sufficient to achieve excellent LoA, and six trials sufficient for accurate screening. CONCLUSION: Threshold VA assessment and vision screening are feasible using both vanishing and regular formats of TAO.
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the auckland Optotypes an open access pictogram set for measuring recognition acuity
Journal of Vision, 2018Co-Authors: Lisa M Hamm, Steven C. Dakin, Janice Yeoman, Nicola AnsticeAbstract:: When measuring recognition acuity in a research setting, the most widely used symbols are the Early Treatment of Diabetic Retinopathy Study (ETDRS) set of 10 Sloan letters. However, the symbols are not appropriate for patients unfamiliar with letters, and acuity for individual letters is variable. Alternative pictogram sets are available, but are generally comprised of fewer items. We set out to develop an open-access set of 10 pictograms that would elicit more consistent estimates of acuity across items than the ETDRS letters from visually normal adults. We measured monocular acuity for individual uncrowded Optotypes within a newly designed set (The Auckland Optotype [TAO]), the ETDRS set, and Landolt Cs. Eleven visually normal adults were assessed on regular and vanishing formats of each set. Inter-optotype reliability and ability to detect subtle differences between participants were assessed using intraclass correlations (ICC) and fractional rank precision (FRP). The TAO vanishing set showed the strongest performance (ICC = 0.97, FRP = 0.90), followed by the other vanishing sets (Sloan ICC = 0.88, FRP = 0.74; Landolt ICC = 0.86, FRP = 0.80). Within the regular format, TAO again outperformed the existing sets (TAO ICC = 0.77, FRP = 0.75; Sloan ICC = 0.65, FRP = 0.64; Landolt ICC = 0.48, FRP = 0.63). For adults with normal visual acuity, the new Optotypes (in both regular and vanishing formats) are more equally legible and sensitive to subtle individual differences than their Sloan counterparts. As this set does not require observers to be able to name Roman letters, and is freely available to use and modify, it may have wide application for measurement of acuity.
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Vanishing Optotype acuity: repeatability and effect of the number of alternatives
Ophthalmic and Physiological Optics, 2010Co-Authors: Nilpa Shah, Steven C. Dakin, Tony Redmond, Roger S. AndersonAbstract:PURPOSE: Vanishing Optotype letters have a pseudo high-pass design so that the mean luminance of the target is the same as the background and the letters thus 'vanish' soon after the resolution threshold is reached. We wished to determine the variability of acuity measurements using these letters compared to conventional letters, and in particular how acuity is affected by the number of alternatives available to the subject. METHODS: Acuity was measured using high contrast letters of both conventional and Vanishing Optotype design for three experienced normal subjects. Thresholds were determined for central vision in a forced choice paradigm for two alternatives (2AFC; AU and OQ), 4AFC (AQUO), 6AFC (QUANGO) and 26AFC (whole alphabet) using a QUEST procedure. Three measurements were made for each condition. RESULTS: Threshold letter size was always larger for the Vanishing Optotypes than conventional letters, although the size of this difference (0.11-0.34 logMAR) depended on the number of alternatives and what they were. The effect of the number of AFC, and the individual letters employed, was smaller for the Vanishing Optotypes, implying that they are more equally legible than conventional Optotypes. Variability was also lower for the Vanishing Optotype sets (0.01-0.03 logMAR) than the conventional letter sets (0.03-0.06). CONCLUSIONS: The smaller effect of the number of letter alternatives, combined with more equal discriminability and lower threshold variability, implies that Vanishing Optotypes may be appropriate targets from which to design letter charts to measure small clinical changes in acuity.
Gabriela Diendorfer - One of the best experts on this subject based on the ideXlab platform.
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integrating a novel concept of sentence Optotypes into the radner reading charts
British Journal of Ophthalmology, 2016Co-Authors: Wolfgang Radner, Stephan Radner, Gabriela DiendorferAbstract:Purpose To add a new set of 24 sentence Optotypes to the German version of the RADNER reading charts and to investigate whether sentences constructed based upon an optimised concept of sentence Optotypes can be used together with the original 38 sentences. Methods Twenty-eight optimised sentence Optotypes were constructed based upon the concept of sentence Optotypes as established for the RADNER Reading Charts, with words having the same number of characters and syllables being placed in the same positions. The best comparable sentences were statistically selected in 30 volunteers. Reading speed and the number of errors were determined. Validity was analysed in comparison to a 111-word long standardised paragraph and 7 of the 38 original sentence Optotypes. Results The mean reading speed obtained with the 28 sentences was 192.30±26.69 words per minute (wpm), as compared with 192.47±25.32 wpm for the 7 original sentence Optotypes and 165.28±20.82 wpm for the long paragraph; 24 of the 28 optimised sentences met our selection criteria for reading speed/time (mean reading speed: 192.41±26.58). The mean number of reading errors was 0.10±0.30. The correlation between the 24 optimised sentence Optotypes and the long paragraph was r=0.90. Reliability analyses yielded an overall Cronbach9s α coefficient of 0.992. Conclusion The 24 new sentence Optotypes can be integrated into the existing set of 38 original sentences. Since all the statistical results obtained were similar to those of the original sentences, the best possible reliability had apparently already been achieved with the original sentence Optotypes.
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english sentence Optotypes for measuring reading acuity and speed the english version of the radner reading charts
Graefes Archive for Clinical and Experimental Ophthalmology, 2014Co-Authors: Wolfgang Radner, Gabriela DiendorferAbstract:Purpose To develop 28 short sentence Optotypes for the English version of the Radner Reading Charts that are as comparable as possible in number and length of words, as well as in difficulty and syntactical construction.
Nicola Anstice - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vision screening of 5 15 year old children in three tongan schools comparison of the auckland Optotypes and lea symbols
Clinical and Experimental Optometry, 2020Co-Authors: Lisa M Hamm, Nicola Anstice, Fiona Langridge, Joanna M Black, Mele Vuki, Toakase Fakakovikaetau, Cameron C Grant, Steven C. DakinAbstract:BACKGROUND: Comprehensive vision screening programmes for children are an important part of public health strategy, but do not exist in many countries, including Tonga. This project set out to assess: (1) the functional vision of children attending primary schools in Tonga and (2) how a new recognition acuity test (The Auckland Optotypes displayed on a tablet computer) compares to use of a standardised eye chart in this setting. METHODS: Children from three Tongan primary schools were invited to participate. Acuity testing was conducted using a standardised recognition acuity chart (Lea symbols) and the tablet test displaying two formats of The Auckland Optotypes. Measures of ocular alignment, stereo acuity and non-cycloplegic photorefraction were also taken. RESULTS: Parents of 249 children consented to participate. One child was untestable. Only 2.8 per cent of testable children achieved visual acuity worse than 0.3 logMAR in the weaker eye. Results from the Spot Photoscreener suggested that no children had myopia or hyperopia, but that some children had astigmatism. The tablet test was practical in a community setting, and showed ±0.2 logMAR limits of agreement with the Lea symbols chart. CONCLUSION: The sample of children in Tongan primary schools had good functional vision. A modified version of the tablet acuity test is a promising option for vision screening in this context.
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recognition acuity in children measured using the auckland Optotypes
Ophthalmic and Physiological Optics, 2018Co-Authors: Lisa M Hamm, Steven C. Dakin, Nicola Anstice, Joanna M BlackAbstract:PURPOSE: Sloan letters displayed by the Electronic Visual Acuity (EVA) system are the gold standard for recognition acuity measurement in research settings. However, letters are not always appropriate for children. The Auckland Optotypes (TAO) are a new, open-access set of 10 pictograms available in regular and vanishing formats. We sought to assess feasibility of using both formats of TAO for measuring visual acuity (VA) in children using a Bayesian adaptive staircase, in a community setting. METHODS: We tested 121 children (5-12 years old) with both formats of TAO, a handheld flipchart vision screener (Parr vision test), as well as the gold standard EVA. We measured feasibility of the three comparison tests in three ways. First, using limits of agreement (LoA) with EVA, second, calculating area under the receiver operating characteristic curve (AUC), and finally, investigating trial-by-trial responses. RESULTS: Agreement between tests was within test-retest reliability of EVA measures (LoATAOregular = ±0.14, LoATAOvanishing = ±0.15, LoAParr = ±0.16 logMAR). TAO tests were highly effective at identifying children with vision impairment (AUCTAOregular = 0.96, AUCTAOvanishing = 0.95), whereas Parr was less effective (AUCParr = 0.82). In 5-6 year old children there was an enhanced advantage of TAO (AUCTAOregular = 0.97, AUCTAOvanishing = 0.98) over Parr (AUCParr = 0.75). Although each child completed 16 trials, approximately 10 trials were sufficient to achieve excellent LoA, and six trials sufficient for accurate screening. CONCLUSION: Threshold VA assessment and vision screening are feasible using both vanishing and regular formats of TAO.
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the auckland Optotypes an open access pictogram set for measuring recognition acuity
Journal of Vision, 2018Co-Authors: Lisa M Hamm, Steven C. Dakin, Janice Yeoman, Nicola AnsticeAbstract:: When measuring recognition acuity in a research setting, the most widely used symbols are the Early Treatment of Diabetic Retinopathy Study (ETDRS) set of 10 Sloan letters. However, the symbols are not appropriate for patients unfamiliar with letters, and acuity for individual letters is variable. Alternative pictogram sets are available, but are generally comprised of fewer items. We set out to develop an open-access set of 10 pictograms that would elicit more consistent estimates of acuity across items than the ETDRS letters from visually normal adults. We measured monocular acuity for individual uncrowded Optotypes within a newly designed set (The Auckland Optotype [TAO]), the ETDRS set, and Landolt Cs. Eleven visually normal adults were assessed on regular and vanishing formats of each set. Inter-optotype reliability and ability to detect subtle differences between participants were assessed using intraclass correlations (ICC) and fractional rank precision (FRP). The TAO vanishing set showed the strongest performance (ICC = 0.97, FRP = 0.90), followed by the other vanishing sets (Sloan ICC = 0.88, FRP = 0.74; Landolt ICC = 0.86, FRP = 0.80). Within the regular format, TAO again outperformed the existing sets (TAO ICC = 0.77, FRP = 0.75; Sloan ICC = 0.65, FRP = 0.64; Landolt ICC = 0.48, FRP = 0.63). For adults with normal visual acuity, the new Optotypes (in both regular and vanishing formats) are more equally legible and sensitive to subtle individual differences than their Sloan counterparts. As this set does not require observers to be able to name Roman letters, and is freely available to use and modify, it may have wide application for measurement of acuity.
Michael Bach - One of the best experts on this subject based on the ideXlab platform.
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Imitating the effect of amblyopia on VEP-based acuity estimates
Documenta Ophthalmologica, 2016Co-Authors: Sven P. Heinrich, Celia M. Bock, Michael BachAbstract:Purpose Acuity testing based on visual evoked potentials (VEPs) overestimates acuity in patients with amblyopia. We hypothesized that distortion and fragmentation of the stimulus in amblyopia impede recognition of Optotypes, while it leaves the pattern onset response in the VEP mostly unaffected, resulting in overestimation of acuity. Methods Acuity VEPs were recorded in visually normal participants with the stimulus degraded by patterned polymethyl methacrylate panes, which induce distortion and fragmentation. For comparison, frosted panes were used to induce blur through wide-angle scattering. Standard psychophysical optotype acuity was recorded under the same conditions. Results With the distorted and fragmented stimuli, the VEP consistently overestimated acuity relative to psychophysical optotype acuity. With blurred stimuli, both measures were in good agreement. Conclusions The data support the assumption that stimulus distortion and fragmentation leave VEP-based measures of acuity relatively unaffected, resulting in a discrepancy between measures of acuity that are based on checkerboard VEPs on one hand and psychophysical optotype recognition on the other hand. The technique of stimulus degradation described here provides a simple and efficient way of imitating effects that are known from amblyopia and may thus serve as a tool in the evaluation of vision tests.
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Event-Related Potentials Allow for Optotype-Based Objective Acuity Estimation.
Investigative Ophthalmology & Visual Science, 2015Co-Authors: Sven P. Heinrich, Isabel Lüth, Michael BachAbstract:PURPOSE: The event-related potential P300 has been proposed for objective acuity estimation. In contrast to the acuity VEP, which relies on grating or checkerboard stimuli, the P300 can be recorded to small stimulus differences, making it suitable to use optotype stimuli. This may result in a better agreement with subjective measures of acuity than that found with VEP-based estimates. We tested the feasibility of using Landolt C Optotypes with a P300 acuity paradigm and assessed the relationship between subjective and objective acuity estimates for both optotype and grating stimuli. METHODS: Dioptric blur (+1, +2, and +4 diopters) was used to degrade vision. Separate oddball sequences with Landolt Cs and with gratings, respectively, were used to record the P300. Thresholds were estimated by fitting a sigmoid curve to P300 amplitudes as a function of Landolt C size or grating coarseness, respectively. Psychophysical thresholds were also obtained for both stimulus types. RESULTS: There was a sizable discrepancy in psychophysical acuity estimates between Landolt C and grating stimuli, probably due to spurious resolution with gratings. With both stimulus types, reliable P300 acuity estimates were obtained. These reflected the psychophysical discrepancy. Conversion factors (Landolt C, 2.3; grating, 1.5) allowed for translating P300-based acuity to psychophysical acuity. CONCLUSIONS: We demonstrate, to our knowledge for the first time, that objective acuity estimation with Landolt C Optotypes is feasible. Both psychophysical and P300-based estimates share the same stimulus-type dependence. P300-based acuity estimation with Optotypes may thus be particularly useful with visual impairments that differentially affect grating and optotype acuity.
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resolution acuity versus recognition acuity with landolt style Optotypes
Graefes Archive for Clinical and Experimental Ophthalmology, 2013Co-Authors: Sven P. Heinrich, Michael BachAbstract:Background International standards define acuity as the reciprocal of the threshold gap size of a Landolt C optotype. However, the literature is inconsistent as to what type of acuity is measured with Landolt Cs. The present study addresses this question more directly than previous studies by quantifying the effect of an inherent luminance artifact in Landolt-style Optotypes.
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The dynamics of practice effects in an optotype acuity task.
Graefes Archive for Clinical and Experimental Ophthalmology, 2011Co-Authors: Sven P. Heinrich, Katja Krüger, Michael BachAbstract:Background Practice-related improvements of performance are common in many areas of visual processing. There is preliminary evidence that this is also the case for standard optotype acuity tasks. The present study was designed to confirm and quantify the effect of practice under different feedback conditions and to track the dynamics of practice over several sessions.
Wolfgang Radner - One of the best experts on this subject based on the ideXlab platform.
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integrating a novel concept of sentence Optotypes into the radner reading charts
British Journal of Ophthalmology, 2016Co-Authors: Wolfgang Radner, Stephan Radner, Gabriela DiendorferAbstract:Purpose To add a new set of 24 sentence Optotypes to the German version of the RADNER reading charts and to investigate whether sentences constructed based upon an optimised concept of sentence Optotypes can be used together with the original 38 sentences. Methods Twenty-eight optimised sentence Optotypes were constructed based upon the concept of sentence Optotypes as established for the RADNER Reading Charts, with words having the same number of characters and syllables being placed in the same positions. The best comparable sentences were statistically selected in 30 volunteers. Reading speed and the number of errors were determined. Validity was analysed in comparison to a 111-word long standardised paragraph and 7 of the 38 original sentence Optotypes. Results The mean reading speed obtained with the 28 sentences was 192.30±26.69 words per minute (wpm), as compared with 192.47±25.32 wpm for the 7 original sentence Optotypes and 165.28±20.82 wpm for the long paragraph; 24 of the 28 optimised sentences met our selection criteria for reading speed/time (mean reading speed: 192.41±26.58). The mean number of reading errors was 0.10±0.30. The correlation between the 24 optimised sentence Optotypes and the long paragraph was r=0.90. Reliability analyses yielded an overall Cronbach9s α coefficient of 0.992. Conclusion The 24 new sentence Optotypes can be integrated into the existing set of 38 original sentences. Since all the statistical results obtained were similar to those of the original sentences, the best possible reliability had apparently already been achieved with the original sentence Optotypes.
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english sentence Optotypes for measuring reading acuity and speed the english version of the radner reading charts
Graefes Archive for Clinical and Experimental Ophthalmology, 2014Co-Authors: Wolfgang Radner, Gabriela DiendorferAbstract:Purpose To develop 28 short sentence Optotypes for the English version of the Radner Reading Charts that are as comparable as possible in number and length of words, as well as in difficulty and syntactical construction.
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The Dutch version of the Radner Reading Chart for assessing vision function
Nederlands Tijdschrift voor Geneeskunde, 2007Co-Authors: Kristel Johanna Maria Maaijwee, Wolfgang Radner, C. F. M. Meulendijks, J. C. Van Meurs, C. B. HoyngAbstract:A chart for measuring visual acuity is a better functional test than the routine distance visual acuity testing with single Optotypes. The characteristics of a good reading chart are: logarithmically diminishing print size, simultaneous measurement of reading acuity and reading speed, and the calculation of one score for reading acuity corrected for the number of reading errors. The original German-language Radner Reading Chart meets all these requirements, and above all emphasizes the principle of 'sentence Optotypes' i.e. highly standardized sentences, because sentence complexity also influences reading performance. Sentence Optotypes were created in the Dutch language and tested according to Radner's strict principles. The most equally matched sentence Optotypes in terms of reading speed and number of reading errors were selected for the introduction and printing of the first Dutch version of the Radner Reading Chart. The Dutch Radner Reading Chart is precise and practical and therefore useful for research and daily practice.