Development of Phonemically Balanced Word List in Tamil for Speech Audiometry and Evaluation of Its Effectiveness in Adults.

Speech audiometry has become an essential component of the audiological test battery. Various speech audiometry materials have been developed in different languages and also revised later to meet criteria such as familiarity of the words, phonetic/phonemic balance, number of test items, and dialectal variations. The current study focused on developing a PB word list in Tamil for adults. The study was carried out in two phases. Phase I involved the development of a PB word list in Tamil. Phase II included evaluating the effectiveness of the developed word lists on adults with normal hearing sensitivity and hearing impairment. A total of 500 bisyllabic words were used in creating a master list. The collected words were subjected to familiarity testing with 40 native Tamil speakers. From the master list of 500 words, 90% of the participants rated 320 words as most familiar, and those words were included in the study. The 320 words were validated by eight experts working in the fields of audiology, speech-language pathology, linguistics, and psychology. The disagreed-with words were excluded from the list, and only 270 words that were agreed upon by all the experts were included in the final list. The final lists comprised four-word lists with 25 phonetically balanced (PB) words per list. The final word lists were recorded and tested for goodness. These final words were then administered to find SIS scores for two groups. Group I consisted of adults with 120 normal hearing sensitivity, and Group II consisted of 130 adults with hearing impairment. The results were analysed using SPSS software. The mean SIS in adults with normal hearing sensitivity ranged from 99.4 to 99.8%. The SIS of adults with normal hearing sensitivity revealed no significant difference (p > .05) with respect to gender, ears, or across the four-word lists. All four-word lists provided similar scores, establishing the equivalency of word lists in individuals with normal hearing sensitivity as well as hearing impairment. A psychometric curve of performance intensity function in adults with normal hearing sensitivity revealed that the SIS score increased as the sensation level increased from 10 to 40 dB SL. There is a linear increase in SIS scores from 10 to 20 dB SL. A plateau was attained at 40 dB SL with 100% SIS scores. Thus, the present study recommends the use of 40 dB SL for SIS testing. Mean SIS scores for adults with mild, moderate, and severe hearing loss were found to be 90.1%, 65.4%, and 41.8%, respectively. A significant decrease in SIS was observed as the degree of hearing loss increased.

Easy, bias-free Bayesian hierarchical modeling of the psychometric function using the Palamedes Toolbox.

A hierarchical Bayesian method is proposed that can be used to fit multiple psychometric functions (PFs) simultaneously across conditions and subjects. The method incorporates the generalized linear model and allows easy reparameterization of the parameters of the PFs, for example, to constrain parameter values across conditions or to code for experimental effects (e.g., main effects and interactions in a factorial design). Simulations indicate that fitting PFs for multiple conditions and observers simultaneously using the hierarchical structure effectively eliminates bias and improves precision in parameter estimates relative to fitting PFs individually in each condition. The method is further validated by analyzing human psychophysical data obtained in an experiment investigating the effect of attention on correspondence matching in an ambiguous long-range motion display. The method converges successfully, even for experiments that use a low number of trials per subject, without the need for fine-tuning by the user and while using the default essentially uninformative priors. The latter may make the method more acceptable to those critical of applying informative priors. The method is implemented in the freely downloadable Palamedes Toolbox, which also includes routines that graphically display the fitted psychometric functions alongside the data, and derive and display posterior distributions of parameters, summary statistics, and diagnostic measures. Overall, these features make hierarchical Bayesian modeling of PFs easily available to researchers who wish to use Bayesian statistics but lack the expertise to implement these methods themselves.

The Random Step Method for Measuring the Point of Subjective Equality.

Points of Subjective Equality (PSE) are commonly measured using staircase or constant stimuli methods. However, the staircase method is highly dependent on the step size, and the constant stimuli method is time-consuming. Thus, we wanted to develop an efficient and quick method to estimate both the PSE and the slope of the psychometric function. We developed a random-step algorithm in which a one-up-one-down rule is followed but with a random step size in a pre-defined range of test levels. Each stimulus would be chosen depending on the previous response of the subject. If the subject responded "up", any random level in the lower range would be picked for the next trial. And if the subject responded "down", any random level in the upper range would be picked for the next trial. This procedure would result in a bell-shaped distribution of the test levels around the estimated PSE, while a substantial amount of trials would still be dispersed at both bounds of the range. We then compared this method with traditional constant stimuli procedure on a task based on the Pulfrich phenomenon while the PSEs of participants could be varied using different neutral density filters. Our random-step method provided robust estimates of both the PSE and the slope under various noise levels with small trial counts, and we observed a significant correlation between the PSEs obtained with the two methods. The random-step method is an efficient way to measure the full psychometric function when testing time is critical, such as in clinical settings.

BPACE: A Bayesian, Patient-Centered Procedure for Matrix Speech Tests in Noise.

Matrix sentence tests in noise can be challenging to the listener and time-consuming. A trade-off should be found between testing time, listener's comfort and the precision of the results. Here, a novel test procedure based on an updated maximum likelihood method was developed and implemented in a German matrix sentence test. It determines the parameters of the psychometric function (threshold, slope, and lapse-rate) without constantly challenging the listener at the intelligibility threshold. A so-called "credible interval" was used as a mid-run estimate of reliability and can be used as a termination criterion for the test. The procedure was evaluated and compared to a STAIRCASE procedure in a study with 20 cochlear implant patients and 20 normal hearing participants. The proposed procedure offers comparable accuracy and reliability to the reference method, but with a lower listening effort, as rated by the listeners (-1.8 points on a 10-point scale). Test duration can be reduced by 1.3 min on average when a credible interval of 2 dB is used as the termination criterion instead of testing 30 sentences. Particularly, normal hearing listeners and well performing, cochlear implant users can benefit from shorter test duration. Although the novel procedure was developed for a German test, it can easily be applied to tests in any other language.

Diminished Auditory Cortex Dynamic Range and its Clinical Correlates in First Episode Psychosis.

BACKGROUND AND HYPOTHESIS: There is growing appreciation for the contribution of sensory disruptions to disease morbidity in psychosis. The present study examined auditory cortex (AC) dynamic range: the scaling of neurophysiological responses to stimulus intensity, among individuals with a schizophrenia spectrum illness (FESz) and its relationship to clinical outcomes at disease onset. STUDY DESIGN: Magnetoencephalography (MEG) was recorded from 35 FESz and 40 healthy controls (HC) during binaural presentation of tones at three intensities (75 dB, 80 dB, and 85 dB). MRIs were obtained to enhance cortical localization of MEG sensor-level activity. All participants completed the MATRICS cognitive battery (MCCB) and Global Functioning: Role and Social scales (GFR/GFS). Patients were administered the Positive and Negative Syndrome Scale (PANSS). STUDY RESULTS: FESz exhibited reduced AC response relative to HC. Enhancement of AC activity to tones of increasing intensity was blunted in FESz relative to HC. Reduced dynamic range (85-75 dB AC response) was associated with lower GFS (r = .58) and GFR (r = .45) scores, worse MCCB performance (r = .45), and increased PANSS Negative symptom subscale scores (r = -.55) among FESz, relationships not observed with AC responses to individual tones. CONCLUSION: Beyond an impaired AC response to pure tones, FESz exhibit reduced dynamic range relative to HC. This impairment was correlated with markers of disease morbidity including poorer community functioning as well as cognitive and negative symptoms. The relationship with impaired social functioning may reflect the role of AC dynamic range in decoding the emotional content of language and highlights its importance to future therapeutic sensory remediation protocols.

Spatial summation of cold and warm detection: Evidence for increased precision when brisk stimuli are delivered over larger area.

Cold and warm stimuli delivered over a larger skin area tend to be more easily detected/elicit stronger sensations, a phenomenon referred to as spatial summation. The aim of the present study was to clarify how stimulation area affects thermal detection processes by evaluating whether increasing the stimulation area simply reduces the detection threshold or also reduces the uncertainty of the detection process. Psychometric functions were fitted to the detection performance of 16 healthy subjects. Stimuli (duration: 200 ms; rate of change: 300 °C/s) were delivered to the volar forearm using a Peltier-effect contact thermode and three different stimulation surfaces (23 mm2, 69 mm2, and 116 mm). Stimulation intensities were selected trial-by-trial by the psi marginal method to optimize estimation of slope and threshold parameters of the psychometric function. The raw data (100 stimulus-response pairs per subject per surface and per modality) was used to fit group-level hierarchical models of cold and warm detection, allowing to assess the effect of stimulation surface and account for inter-individual variability. Increasing stimulation area led to a compression of the psychometric function towards baseline skin temperature (reduced threshold and steeper slope), suggesting that spatial summation reflects a change in the precision of the neural representation of the stimulus which in turn influences the ability of the nervous system to distinguish true stimuli from sensory noise. Regardless of area, with the stimulation settings used in this study, cold detection appeared easier than warm detection, possibly because of structural and functional differences between cold- and warm-sensitive afferents.

Impact of induced pseudomyopia and refractive fluctuations of accommodative spasm on visual acuity.

CLINICAL RELEVANCE: High-contrast visual acuity is disproportionately poor in patients with accommodative spasm subtype of near reflex (SNR-A), relative to uncorrected refractive errors of equivalent magnitude. This exaggerated loss of performance in SNR-A may be explained by the combination of pseudomyopia and its fluctuations, vis-à-vis, each factor considered separately. BACKGROUND: To determine how combinations of pseudomyopic refraction and its temporal variations in SNR-A impact high-contrast visual acuity by inducing these patterns in healthy cyclopleged adults, relative to their baseline acuity. METHODS: Refractive profiles of 15 patients with SNR-A were obtained from a previous study, averaged, and induced before the right eye of 14 cyclopleged adults (mean ±1 SD age: 22.7 ± 2.6 yrs) by feeding the profile into a coaxially placed, motorised, Badal optometer. LogMAR acuity was measured using the method of constant stimuli: (1) before cycloplegia, (2) after cycloplegia and post-cycloplegia with (3) combination of pseudomyopia and its temporal fluctuations, (4) only pseudomyopia, (5) only temporal fluctuations in refraction about emmetropia, (6) condition 5 with double the amplitude of induced fluctuations and (7) condition 5 with half the amplitude of induced fluctuations. RESULTS: The induced refractive fluctuations ranged from -0.80 to -1.75D, around a mean pseudomyopia of -1.20D. Visual acuity deterioration was maximum for the combination of pseudomyopia and temporal fluctuations condition (0.51 ± 0.07logMAR), followed by only pseudomyopia (0.27 ± 0.05logMAR) and only refractive fluctuations conditions (0.17 ± 0.04logMAR), all relative to baseline post-cycloplegia (0.13 ± 0.04logMAR) (p < 0.001). Visual acuity loss increased with doubling of refractive fluctuations (0.20 ± 0.04logMAR), relative to native fluctuations or halving the amplitude (0.15 ± 0.03logMAR) (p < 0.01). Task precision, as adjudged from the slope of psychometric function, followed a similar pattern of loss as visual acuity. CONCLUSION: Combination of induced pseudomyopia and temporal fluctuations in refraction produces an additive loss of visual acuity and task precision, relative to baseline and each factor considered separately.

The effect of initial performance on motion perception improvements is modulated by training method.

Repeated practice of a perceptual task, termed "perceptual learning," can improve visual performance. Previously, the training thresholds were determined in two ways. One is that the stimulus corresponding to a certain level in individually set psychometric functions was selected as the training threshold. The other is that the certain stimulus was selected as the training threshold without consideration of individual differences. However, little is known about how the two training methods modulate perceptual learning. This study aimed to evaluate the effect of initial performance on patterns of motion perceptual learning under two methods-individually set or group averaged-for setting the training threshold. Thirty-six observers were randomly divided into individual and group thresholds. Psychometric functions, with the percentage correct as a function of coherence, were measured using the coherent motion direction identification task. For the individual threshold, each observer was trained at individualized coherence level, targeting 60% correct for each observer's psychometric function. For the group threshold, each observer was trained at one coherence level, targeting 60% correct in the group-averaged psychometric function. The threshold was reduced after training with the method of constant stimulus in both groups, indicating improvements following perceptual learning. Furthermore, observers with a poorer initial performance exhibited greater learning gains independent of the training method. Importantly, the correlation between the initial performance and learning gains was larger in the individual threshold than in the group threshold, suggesting the influence of the initial performance on the learning amount depends on the training method.

Sucrose detection and discrimination estimated by the analysis of psychometric functions with linear and non-linear models.

Sucrose detection and discrimination thresholds were determined by conducting two alternative forced-choice tests with aqueous solutions. The standard models probit and logit, and non-linear were fitted to the empirical psychometric functions. 0, 7 and 15 g/L sucrose solutions were used as standard stimuli in the detection and discrimination experiments (two levels) respectively. Comparison stimuli consisted of aqueous sucrose solutions with concentrations from 0.5 to 25 g/L. Observed absolute threshold was around 2.96 g/L and the difference limen for 7 and 15 g/L standard stimuli was around 2.98 g/L and 5.29 g/L, respectively. Calculated Weber fractions for 7 and 15 g/L standard stimuli were 0.42 and 0.35, respectively. Judges' performance in the discrimination experiment was similar to that observed in the detection experiment. Goodness of fit for probit and logit models was similar. The non-linear model showed a lower average error and demonstrated an excellent predictive ability.

Assessing Proprioception in an Older Population: Reliability of a Protocol Based on Active Movement Extent Discrimination.

Proprioceptive ability - the sense of where body parts are located in space - is one of many factors thought to affect falls risk among the elderly. Active movement extent discrimination is an approach to measuring proprioception that is administered in an ecologically valid testing environment to better reflect the exercise of proprioceptive skills in daily life. The Active Movement Extent Discrimination Apparatus (AMEDA) was developed to objectively measure this proprioceptive discrimination. However, the current absolute identification testing protocol is cognitively demanding, and it yields results that are insufficiently reliable to assess performance at the individual level. The objectives of this pilot study were to test the reliability and feasibility of a proposed new AMEDA testing protocol and to explore how performance related to cognitive ability and any perceived dysfunction in the foot or ankle. We tested 42 participants (aged 19 - 94 years) three times on the ankle AMEDA using a newly developed protocol that asked participants to report whether a given angle of ankle inversion was shallower or deeper than the immediately preceding inversion. Participants also completed the Stroop test, as a measure of cognitive ability, and two validated questionnaires for identifying foot or ankle dysfunction (the Cumberland Ankle Instability Tool and the Foot and Ankle Ability Measure). The proportion of correct responses for the AMEDA test showed the expected sigmoid shape of the psychometric function as signal strength increased. The intraclass correlation coefficient measured over the three tests was 0.65 (95% confidence interval: 0.49 - 0.78), suggesting moderate reliability. We found a positive and statistically significant correlation between AMEDA performance and Stroop results but no relationship between the AMEDA score and questionnaire-measured foot or ankle dysfunction. This study confirmed that the alternative testing protocol was simple to administer and easily understood by participants.

Reduced direction discrimination sensitivity in visual motion adaptation, and the role of perceptual learning.

We investigated visual direction discrimination under the influence of motion aftereffect (MAE). Participants in each experiment first adapted to a horizontally drifting grating before deciding whether a drifting test grating moved to the left or right. A psychometric function was obtained as a function of the velocity of the test. Interestingly, in addition to the horizontal shift of the psychometric function that typified the MAE, the slope of the psychometric function became shallower after adaptation, indicating decreased discrimination sensitivity. However, this decrease was only observed in psychophysically experienced participants. Motivated, but psychophysically inexperienced participants only showed this effect after weeks of perceptual learning. This shallowing effect transferred to the untrained adaptation direction (e.g., from leftward adaptation to rightward), although perceptual learning of improved discrimination could not transfer. When the test duration was lengthened to reduce task difficulty, less training was needed to produce the same effect. These results indicate that, post-adaptation and when steady measurements could be obtained, left-right motion direction discrimination sensitivity was reduced.

Decline of Orientation and Direction Sensitivity in the Aging Population.

While the aging population is growing, our knowledge regarding age-related deterioration of visual perception remains limited. In the present study, we investigated the effects of aging on orientation and direction sensitivity in a healthy population using a weighted up-down adaptive method to improve the efficiency and reliability of the task. A total of 57 healthy participants aged 22-72 years were included and divided into old and young groups. Raw experimental data were processed using a psychometric method to determine the differences between the two groups. In the orientation task, the threshold of the discrimination angle and bias (i.e., the difference between the perceived midpoint from the logistic function and the reference point) was increased, while the lapsing rate (i.e., 1-the maximum logistic function) did not significantly change in the old group compared with the young group. In the motion direction task, the threshold, bias, and lapsing rate were significantly increased in the old group compared with the young group. These results suggest that the decreased ability of old participants in discrimination of stimulus orientation and motion direction could be related to the impaired function of visual cortex.

Comparing and modeling absolute auditory thresholds in an alternative-forced-choice and a yes-no procedure.

Detecting sounds in quiet is arguably the simplest task performed by an auditory system, but the underlying mechanisms are still a matter of debate. Threshold stimulus levels depend not only on the physical properties of the sounds to be detected but also on the experimental procedure used to measure them. Here, thresholds of human subjects were measured for sounds consisting of different numbers of bursts using both an alternative-forced-choice and a yes-no procedure in the same experimental sessions. Thresholds measured with the yes-no procedure were typically higher than thresholds measured with the alternative-forced choice procedure. The difference between the two thresholds decreased as stimulus duration increased. It also varied between subjects and varied with the probability of false alarms in the yes-no procedure. It is shown that a previously proposed model of detection (Heil et al., Hear Res 2017) can account for these findings better than other models. It can also account for the shapes of the psychometric functions. The model is consistent with basic concepts of signal detection theory but is based on a decision variable that follows Poisson statistics. It also differs from other models of detection with respect to the transformation of the stimulus into the decision variable. The findings in this study further support the model.

ADOpy: a python package for adaptive design optimization.

Experimental design is fundamental to research, but formal methods to identify good designs are lacking. Advances in Bayesian statistics and machine learning offer algorithm-based ways to identify good experimental designs. Adaptive design optimization (ADO; Cavagnaro, Myung, Pitt, & Kujala, 2010; Myung, Cavagnaro, & Pitt, 2013) is one such method. It works by maximizing the informativeness and efficiency of data collection, thereby improving inference. ADO is a general-purpose method for conducting adaptive experiments on the fly and can lead to rapid accumulation of information about the phenomenon of interest with the fewest number of trials. The nontrivial technical skills required to use ADO have been a barrier to its wider adoption. To increase its accessibility to experimentalists at large, we introduce an open-source Python package, ADOpy, that implements ADO for optimizing experimental design. The package, available on GitHub, is written using high-level modular-based commands such that users do not have to understand the computational details of the ADO algorithm. In this paper, we first provide a tutorial introduction to ADOpy and ADO itself, and then illustrate its use in three walk-through examples: psychometric function estimation, delay discounting, and risky choice. Simulation data are also provided to demonstrate how ADO designs compare with other designs (random, staircase).

Chicken colour discrimination depends on background colour.

How well can a bird discriminate between two red berries on a green background? The absolute threshold of colour discrimination is set by photoreceptor noise, but animals do not perform at this threshold; their performance can depend on additional factors. In humans and zebra finches, discrimination thresholds for colour stimuli depend on background colour, and thus the adaptive state of the visual system. We have tested how well chickens can discriminate shades of orange or green presented on orange or green backgrounds. Chickens discriminated slightly smaller colour differences between two stimuli presented on a similarly coloured background, compared with a background of very different colour. The slope of the psychometric function was steeper when stimulus and background colours were similar but shallower when they differed markedly, indicating that background colour affects the certainty with which the animals discriminate the colours. The effect we find for chickens is smaller than that shown for zebra finches. We modelled the response to stimuli using Bayesian and maximum likelihood estimation and implemented the psychometric function to estimate the effect size. We found that the result is independent of the psychophysical method used to evaluate the effect of experimental conditions on choice performance.

Order effects in two-alternative forced-choice tasks invalidate adaptive threshold estimates.

Adaptive psychophysical methods are widely used for the quick estimation of percentage points (thresholds) on psychometric functions for two-alternative forced-choice (2AFC) tasks. The use of adaptive methods is supported by numerous simulation studies documenting their performance, which have shown that thresholds can be reasonably estimated with them when their founding assumptions hold. One of these assumptions is that the psychometric function is invariant, but empirical evidence is mounting that human performance in 2AFC tasks needs to be described by two different psychometric functions, one that holds when the test stimulus is presented first in the 2AFC trial and a different one that holds when the test is presented second. The same holds when presentations are instead simultaneous at two spatial locations rather than sequential. We re-evaluated the performance of adaptive methods in the presence of these order effects via simulation studies and an empirical study with human observers. The simulation study showed that thresholds are severely overestimated by adaptive methods in these conditions, and the empirical study corroborated these findings. These results question the validity of threshold estimates obtained with adaptive methods that incorrectly assume the psychometric function to be invariant with presentation order. Alternative ways in which thresholds can be accurately estimated in the presence of order effects are discussed.

Modelling the effects of ongoing alpha activity on visual perception: The oscillation-based probability of response.

Substantial evidence has shown that ongoing neural activity significantly contributes to how the brain responds to upcoming stimuli. In visual perception, a considerable portion of trial-to-trial variability can be accounted for by prestimulus magneto/electroencephalographic (M/EEG) alpha oscillations, which play an inhibitory function by means of cross-frequency interactions with gamma-band oscillations. Despite the fundamental theories on the role of oscillations in perception and cognition, the current literature lacks a clear theorization of the neural mechanisms underlying the effects of prestimulus activity, including electrophysiological phenomena at different scales (e.g., local field potentials and macro-scale M/EEG). Here, we present a model called the oscillation-based probability of response (OPR), which directly assesses the link between meso-scale neural mechanisms, macro-scale M/EEG, and behavioural outcome. The OPR includes distinct meso-scale mechanisms through which alpha oscillations modulate M/EEG gamma activity, namely, by decreasing a) the amplitude and/or b) neural synchronization of gamma oscillations. Crucially, the OPR makes specific predictions on the effects of these mechanisms on visual perception, as assessed through the psychometric function. SIGNIFICANCE STATEMENT: The oscillation-based probability of response (OPR) is grounded on a psychophysical approach focusing on the psychometric function estimation and may be highly informative in the study of ongoing brain activity, because it provides a tool for distinguishing different neural mechanisms of alpha-driven modulation of sensory processing.

The Do's and Don'ts of Psychophysical Methods for Interpretability of Psychometric Functions and Their Descriptors.

Many areas of research require measuring psychometric functions or their descriptors (thresholds, slopes, etc.). Data for this purpose are collected with psychophysical methods of various types and justification for the interpretation of results arises from a model of performance grounded in signal detection theory. Decades of research have shown that psychophysical data display features that are incompatible with such framework, questioning the validity of interpretations obtained under it and revealing that psychophysical performance is more complex than this framework entertains. This paper describes the assumptions and formulation of the conventional framework for the two major classes of psychophysical methods (single- and dual-presentation methods) and presents various lines of empirical evidence that the framework is inconsistent with. An alternative framework is then described and shown to account for all the characteristics that the conventional framework regards as anomalies. This alternative process model explicitly separates the sensory, decisional, and response components of performance and represents them via parameters whose estimation characterizes the corresponding processes. Retrospective and prospective evidence of the validity of the alternative framework is also presented. A formal analysis also reveals that some psychophysical methods and response formats are unsuitable for separation of the three components of observed performance. Recommendations are thus given regarding practices that should be avoided and those that should be followed to ensure interpretability of the psychometric function, or descriptors (detection threshold, difference limen, point of subjective equality, etc.) obtained with shortcut methods that do not require estimation of psychometric functions.

Objective Estimation of Sensory Thresholds Based on Neurophysiological Parameters.

Reliable determination of sensory thresholds is the holy grail of signal detection theory. However, there exists no assumption-independent gold standard for the estimation of thresholds based on neurophysiological parameters, although a reliable estimation method is crucial for both scientific investigations and clinical diagnosis. Whenever it is impossible to communicate with the subjects, as in studies with animals or neonates, thresholds have to be derived from neural recordings or by indirect behavioral tests. Whenever the threshold is estimated based on such measures, the standard approach until now is the subjective setting-either by eye or by statistical means-of the threshold to the value where at least a "clear" signal is detectable. These measures are highly subjective, strongly depend on the noise, and fluctuate due to the low signal-to-noise ratio near the threshold. Here we show a novel method to reliably estimate physiological thresholds based on neurophysiological parameters. Using surrogate data we demonstrate that fitting the responses to different stimulus intensities with a hard sigmoid function, in combination with subsampling, provides a robust threshold value as well as an accurate uncertainty estimate. This method has no systematic dependence on the noise and does not even require samples in the full dynamic range of the sensory system. We prove that this method is universally applicable to all types of sensory systems, ranging from somatosensory stimulus processing in the cortex to auditory processing in the brain stem.

Application of Correlation-Based Scoring Scheme for Visual Acuity Measurements in the Clinical Practice.

PURPOSE: Visual acuity tests are generally performed by showing eye charts to the subjects and registering their correct/incorrect identifications for the presented optotypes. We recently developed a correlation-based scoring method that significantly reduces the statistical error associated with relative letter legibility. In this paper, our purpose was to demonstrate the advantages and clinical utility of our scoring scheme compared to standard methods. METHODS: We developed a new computer-controlled measurement setup aligned with the ophthalmological standard. With this system, we presented the application of our correlation-based scoring in conventional clinical environment for 25 subjects and estimated the systematic error of the obtained acuity values. A separate experiment was performed by 14 additional subjects to reveal the test-retest variability of the new scoring method. RESULTS: The average systematic error relative to standard probability-based scoring is 0.01 logMAR over the examined subject group. Application of the correlation-based scheme when used in clinical environment with five letters per size decreases the repeatability error by ∼20% and increases diagnosis time by ∼10%. CONCLUSIONS: The new scoring scheme is directly applicable in clinical practice providing unbiased results with improved repeatability compared to standard visual acuity measurements. It reduces test-retest variability by the same amount as if the number of letters was doubled in traditional tests. TRANSLATIONAL RELEVANCE: Our new method is a promising alternative to conventional acuity tests in cases when high-precision measurements are required, for example evaluating implanted intraocular lenses, testing subjects with retinal diseases or cataract, and refractive surgery candidates.