The Effect of Optical Defocus on the Test–Retest Variability of Visual Acuity Measurements

Rosser, D A; Murdoch, Ian

doi:10.1167/iovs.03-1320

Cited by 49 publications

(56 citation statements)

References 26 publications

(35 reference statements)

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“…However, it can also be used to test the stand-alone question whether k samples have equal or different variances. Here we used Levene’s test in a within-participants design (i.e., ignoring the matching) due to a lack of simple alternatives, as has been done in previous studies on the test-retest variability of visual acuity measurements [52].…”

Section: Resultsmentioning

confidence: 99%

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

et al. 2014

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For assessing tactile spatial resolution it has recently been recommended to use tactile acuity charts which follow the design principles of the Snellen letter charts for visual acuity and involve active touch. However, it is currently unknown whether acuity thresholds obtained with this newly developed psychophysical procedure are in accordance with established measures of tactile acuity that involve passive contact with fixed duration and control of contact force. Here we directly compared tactile acuity thresholds obtained with the acuity charts to traditional two-point and grating orientation thresholds in a group of young healthy adults. For this purpose, two types of charts, using either Braille-like dot patterns or embossed Landolt rings with different orientations, were adapted from previous studies. Measurements with the two types of charts were equivalent, but generally more reliable with the dot pattern chart. A comparison with the two-point and grating orientation task data showed that the test-retest reliability of the acuity chart measurements after one week was superior to that of the passive methods. Individual thresholds obtained with the acuity charts agreed reasonably with the grating orientation threshold, but less so with the two-point threshold that yielded relatively distinct acuity estimates compared to the other methods. This potentially considerable amount of mismatch between different measures of tactile acuity suggests that tactile spatial resolution is a complex entity that should ideally be measured with different methods in parallel. The simple test procedure and high reliability of the acuity charts makes them a promising complement and alternative to the traditional two-point and grating orientation thresholds.

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Section: Resultsmentioning

confidence: 99%

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

et al. 2014

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“…That is the mean VA error anticipated by using these linear models will be 0.1 logMAR. Interestingly, when the retinal image is degraded by defocus, test-retest differences in VA are on average about 0.1 logMAR 65. Therefore, although the above image quality metrics are not perfect at predicting VA, they are about as good at predicting VA in the presence of image blur as a standard clinical VA measure, and as such may qualify as an effective substitute for actual VA measurements and thus may be employed as an objective substitute for subjective refractions 52.…”

Section: Discussionmentioning

confidence: 99%

Visual Impact of Zernike and Seidel Forms of Monochromatic Aberrations

Cheng¹,

Bradley²,

Ravikumar³

et al. 2010

Optometry and Vision Science

102

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Purpose To examine the impact on visual acuity of different aberrations modes (e.g. coma, astigmatism, spherical aberration (SA)) and different aberration basis functions (Zernike or Seidel). Methods Computational optics was used to generate retinal images degraded by either the Zernike or Seidel forms of 2nd through 4th order aberrations for an eye with a 5mm pupil diameter. High contrast, photopic visual acuity was measured using method of constant stimuli for letters displayed on a computer-controlled, linearized, quasi-monochromatic (λ=556 nm) display. Results Minimum angle of resolution (MAR) varied linearly with the magnitude (root mean square error, RMS) of all modes of aberration. The impact of individual Zernike lower and higher order aberrations (HOAs) varied significantly with mode, e.g. arc minutes of MAR/micron of RMS slopes varied from 7 (spherical defocus) to 0.5 (quadrafoil). Seidel forms of these aberrations always had a smaller visual impact. Notably, Seidel spherical aberration (SA) had 1/17th the impact of Zernike SA with the same wavefront variance, and about 1/4th the impact of Zernike SA with matching levels of r4 wavefront error. With lower order components removed, HOAs near the center of the Zernike pyramid do not have a large visual impact. Conclusions The majority of the visual impact of high levels of 4th order Zernike aberrations can be attributed to the 2nd order terms within these polynomials. Therefore, the impact of SA can be minimized by balancing it with a defocus term that flattens the central wavefront (paraxial focus) or maximizes the area of the pupil with a flat wavefront. Over this wide range of aberration types and levels, image quality metrics based upon the PSF and OTF can predict VA as reliably as VA measures can predict retests of VA, and thus such metrics may become valuable predictors of both VA and, via optimization, refractions.

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“…the test-retest variability, of the test used [30,31]. Unlike logMAR charts, the Snellen chart, which we had to rely on in this nationwide primary care study, has a large-scale increment resulting in a relatively high measurement error.…”

Section: Discussionmentioning

confidence: 99%

Prevalence and progression of visual impairment in patients newly diagnosed with clinical type 2 diabetes: a 6-year follow up study

et al. 2011

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BackgroundMany diabetic patients fear visual loss as the worst consequence of diabetes. In most studies the main eye pathology is assigned as the cause of visual impairment. This study analysed a broad range of possible ocular and non-ocular predictors of visual impairment prospectively in patients newly diagnosed with clinical type 2 diabetes.MethodsData were from a population-based cohort of 1,241 persons newly diagnosed with clinical, often symptomatic type 2 diabetes aged ≥ 40 years. After 6 years, 807 patients were followed up. Standard eye examinations were done by practising ophthalmologists.ResultsAt diabetes diagnosis median age was 65.5 years. Over 6 years, the prevalence of blindness (visual acuity of best seeing eye ≤ 0.1) rose from 0.9% (11/1,241) to 2.4% (19/807) and the prevalence of moderate visual impairment (> 0.1; < 0.5) rose from 5.4% (67/1,241) to 6.7% (54/807). The incidence (95% confidence interval) of blindness was 40.2 (25.3-63.8) per 10,000 patient-years. Baseline predictors of level of visual acuity (age, age-related macular degeneration (AMD), cataract, living alone, low self-rated health, and sedentary life-style) and speed of continued visual loss (age, AMD, diabetic retinopathy (DR), cataract, living alone, and high fasting triglycerides) were identified.ConclusionsIn a comprehensive assessment of predictors of visual impairment, even in a health care system allowing self-referral to free eye examinations, treatable eye pathologies such as DR and cataract emerge together with age as the most notable predictors of continued visual loss after diabetes diagnosis. Our results underline the importance of eliminating barriers to efficient eye care by increasing patients' and primary care practitioners' awareness of the necessity of regular eye examinations and timely surgical treatment.

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The Effect of Optical Defocus on the Test–Retest Variability of Visual Acuity Measurements

Cited by 49 publications

References 26 publications

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

Visual Impact of Zernike and Seidel Forms of Monochromatic Aberrations

Prevalence and progression of visual impairment in patients newly diagnosed with clinical type 2 diabetes: a 6-year follow up study

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