Scotopic and Photopic Conventional Visual Acuity and Hyperacuity - Binocular Summation.

Purpose: The purpose of this study was to determine and compare binocular summation (BiS) of conventional visual acuity (cVA) versus hyperacuity (hVA) for photopic and scotopic luminance conditions as a potential biomarker to assess the outcome of interventions on binocular function. Methods: Sixteen young adults (age range [years] = 21-31; 8 women; cVA logMAR < 0.0) participated in this study. The Freiburg Visual Acuity Test (FrACT) was used for VA testing and retested on another day. Both cVA and hVA were determined for dark grey optotypes on light grey background. Participants underwent 40 minutes of dark adaptation prior to scotopic VA testing. Binocular and monocular VA testing was performed. The eye with better VA over the 2 days of testing was selected, the BiS was quantified (binocular VA - better monocular VA) and repeated measures ANOVAs were performed. Results: Binocular VA exceeded monocular VA for all luminance conditions, VA-types, and sessions. We report BiS estimates for photopic and scotopic cVA and hVA, (logMAR BiS ± SEM [decimal BiS]): photopic = -0.01 ± 0.01 [1.03] and -0.06 ± 0.03 [1.15]; and scotopic = -0.05 ± 0.01 [1.12] and -0.11 ± 0.04 [1.28], respectively). Improvement for binocular vision estimates ranged from 0.01 to 0.11 logMAR. A repeated-measures ANOVA (RM ANOVA) did not reveal significant effects of LUMINANCE or VA TYPE on BiS, albeit a trend for strongest BiS for scotopic hVA (15% vs. 28%, photopic versus scotopic, respectively) and weakest for photopic cVA (3% vs. 12%, photopic versus scotopic conditions, respectively). Conclusions: Our results indicate that BiS of VA is relevant to scotopic and photopic hVA and cVA. It appears therefore a plausible candidate biomarker to assess the outcome of retinal therapies restoring rod or cone function on binocular vision. Translational Relevance: Binocular summation of visual acuity might serve as a clinical biomarker to monitor therapy outcome on binocular rod and cone-mediated vision.

Evaluation of contrast sensitivity in visually impaired individuals using K-CS test. A novel smartphone-based contrast sensitivity test-Design and validation.

BACKGROUND: To describe the development and investigate the accuracy of a novel smartphone-based Contrast Sensitivity (CS) application, the K-CS test. METHODS: A total of 67 visually impaired and 50 normal participants were examined monocularly using the novel digital K-CS test and the Pelli-Robson (PR) chart. The K-CS test examines letter contrast sensitivity in logarithmic units, using eight levels of contrast from logCS = ~0,1 to logCS = ~2,1 at two spatial frequencies of 1.5 and 3 cycles per degree (cpd). The K-CS test was compared to the gold standard, PR test and intra-session test repeatability was also examined. RESULTS: The K-CS test in normally sighted was found to agree well with the PR, providing comparable mean scores in logCS (±SD) (K-CS = 1.908 ± 0.06 versus PR = 1.93 ± 0.05) at 1.5 cpd and mean (± SD) logCS at 3 cpd (K-CS = 1.83 ± 0.13 versus PR = 1.86 ± 0.07). The mean best corrected visual acuity of visually impaired participants was 0.67 LogMAR (SD = 0.21) and the K-CS was also found to agree well with the Pelli-Robson in this group, with an equivalent mean (±SD) logCS at 1.5 cpd: (K-CS = 1.19 ± 0.27, PR = 1.15 ± 0.31), 3 cpd: K-CS = 1.01 ± 0.33, PR = 0.94 ± 0.34. Regarding the intra-session test repeatability, both the K-CS test and the PR test showed good repeatability in terms of the 95% limits of agreement (LoA): K-CS = ±0.112 at 1.5 cpd and ±0.133 at 3 cpd, PR = ±0.143 at 1.5 cpd and ±0.183 in 3 cpd in visually impaired individuals. CONCLUSION: The K-CS test provides a quick assessment of the CS both in normally sighted and visually impaired individuals. The K-CS could serve as an alternative tool to assess contrast sensitivity function using a smartphone and provides results that agree well with the commonly used PR test.

Clinical report: Virtual reality enables comparable contrast sensitivity measurements to in-office testing (pilot study).

SIGNIFICANCE: Vision health disparities largely stem from inaccessibility to vision specialists. To improve patient access to vision tests and to expedite clinical workflows, it is important to assess the viability of virtual reality (VR) as a modality for evaluating contrast sensitivity. PURPOSE: This study aimed to assess the validity of a VR version of the Pelli-Robson contrast sensitivity test by comparing its results with those of the corresponding in-office test. METHODS: Twenty-eight participants (mean ± standard deviation age, 37.3 ± 20.5 years) with corrected vision were recruited for testing on a voluntary basis with randomized administration of the in-office test followed by the VR analog or vice versa. Nineteen participants took each test twice to assess test-retest consistency in each modality. Virtual reality tests were conducted on a commercial Pico Neo Eye 2 VR headset, which has a 4K screen resolution. The environment for both tests was controlled by the participant for location and lighting. RESULTS: Similar sensitivity scores were obtained between testing modalities in both the right (n = 28 participants; Wilcoxon match-paired signed rank [SR], p=0.7) and left eyes (n = 28 participants; Wilcoxon match-paired SR, p=0.7). In addition, similar test-retest scores were found for VR (n = 19 participants; Wilcoxon match-paired SR, p=1.0) or in-office (n = 19 participants; Wilcoxon match-paired SR, p=1.0) tests. Virtual reality Pelli-Robson results correlated well with in-office test results in variably diseased participants (n = 14 eyes from 7 participants, R2 = 0.93, p<0.0001). CONCLUSIONS: In this pilot trial, we demonstrated that VR Pelli-Robson measurements of corrected vision align with those of in-office modalities, suggesting that this may be a reliable method of implementing this test in a more interactive and accessible manner.

Reliability of self-measurement of visual acuity in AMD patients with two electronic devices based on the ETDRS chart: A randomized study.

INTRODUCTION: Age-related macular degeneration (AMD) requires continuous visual acuity (VA) monitoring, increasing the burden on the health care system. Self-measurement VA tests are available on various devices. However, none of them have been based on an internationally validated benchmark chart, such as that of the Early Treatment Diabetic Retinopathy Study (ETDRS). The goal of this study was to assess the reliability of two digitized ETDRS charts adapted to two electronic devices for self-measurement of VA. MATERIAL AND METHODS: A prospective, single-center, 1:1 randomized, two-arm, parallel group trial was conducted. The main objective was to compare VA variation as conventionally measured on a 4-m ETDRS chart versus self-measured with digitized ETDRS charts in patients treated for AMD. At each visit, conventional measurement and patient self-measurement, either on a computer at 80-cm (arm 1) or on a tablet at 40-cm (arm 2), were performed. RESULTS: Eighty patients were included (25 men, 55 women, mean age 81.3±7.4 years). No significant differences were observed between VA variation, conventionally measured and self-measured on a computer (arm 1; P=0.914) or tablet (arm 2; P=0.913). CONCLUSION: These results confirm the reliability of these two methods for self-measurement of VA, and will lead to the development of a wider "telemedicine" project extended to self-measurement of VA in various pathologies.

Effect of different screen brightness and devices on online visual acuity test.

PURPOSE: This study aimed to study the difference in test results of online visual acuity (VA) test under different devices and screen brightness conditions and to compare online VA test with Early Treatment Diabetic Retinopathy Study (ETDRS). METHODS: Healthy volunteers with the best corrected VA of 0.0 LogMAR or higher were recruited. VAs under ETDRS were tested first, and then online VA test (the Stanford Acuity Test, StAT) visual acuities using iPad Air2 and Microsoft Surface pro4 under 50% and 100% screen brightness were performed. The VA results and the testing times were compared between different devices and screen brightness conditions. RESULTS: A total of 101 eyes were included in this study. The VA results measured by the StAT were better than those of ETDRS. The VA results measured at 100% screen brightness were better than those of 50% brightness (mean difference, 0.013 logMAR at most, less than 1 letter); the VA results measured by iPad Air2 were better than those of Surface pro4 (mean difference, -0.009 logMAR at most, less than 1 letter). Significantly less time was spent on VA testing under StAT than that under ETDRS. CONCLUSION: The impact of screen brightness and the device on the VA results generated by online VA tests was clinically insignificant. In addition, online VA tests are found to be reliable and more time efficient than ETDRS.

Ametropia detection using a novel, compact wavefront autorefractor.

INTRODUCTION: Despite the well-known reproducibility issues of subjective refraction, most studies evaluating autorefractors compared differences between the device and subjective refraction. This work evaluated the performance of a novel handheld Hartmann-Shack-based autorefractor using an alternative protocol, which considered the inherent variability of subjective refraction. METHODS: Participants underwent an initial measurement with a desktop autorefractor, two subjective refractions (SR1 and SR2) and a final measurement with the QuickSee Free (QSFree) portable autorefractor. Autorefractor performance was evaluated by comparing the differences between the QSFree and each of the subjective refractions with the difference between the subjective refractions (SR1 vs. SR2) using Bland-Altman analysis and percentage of agreement. RESULTS: A total of 75 subjects (53 ± 14 years) were enrolled in the study. The average difference in the absolute spherical equivalent (M) between the QSFree and the SR1 and SR2 was ±0.24 and ±0.02 D, respectively, that is, very similar or smaller than the SR1 versus SR2 difference (±0.26 D). Average differences in astigmatic components were found to be negligible. The results demonstrate that differences between QSFree and both subjective refractions in J0 and J45 were within ±0.50 D for at least 96% of the measurements. The limits of agreement (LOAs) of the differences between QSFree and SR1, as well as QSFree and SR2, were higher than those observed between SR1 and SR2 for M, J0 and J45 . CONCLUSIONS: A protocol was designed and validated for the evaluation of a refractive device to account for the variability of subjective refraction. This protocol was used to evaluate a novel portable autorefractor and observed a smaller difference between the device and subjective refractions than the difference between the two subjective refraction measurements in terms of mean bias error, although the standard deviation was higher.

OKN-Fast: Objective visual acuity threshold measurement using the optokinetic response.

Visual acuity (VA) is the gold-standard measure for the assessment of visual function, but it is challenging to obtain in non-verbal adults and young children. We present OKN-Fast, an objective, automated method for estimation of VA using a reflexive eye movement called optokinetic nystagmus (OKN) that does not require a verbal response from the patient (VA-OKN). We tested the method in a cohort of healthy adults (n=12) with good vision, who were also blurred using a lens. On average OKN-Fast reduced the number of trials needed to determine threshold by half, as compared to a gold standard trial-by-trial assessment. The VAs determined by OKN and ETDRS were similar when blurred (no statistically significant difference). However, a significant bias of logMAR 0.2 was observed for the good vision condition. VA-OKN was highly repeatable with limits of agreement (LOA) similar to those found for ETDRS charts when blurred. However, this VA-OKN was only moderately correlated with VA measured using a ETDRS chart (r2 = 0.55). These results suggest that further optimization is warranted.Clinical Relevance- This work provides an automated approach for the estimation of visual acuity in non-verbal populations such as young children or non-verbal adults.

Comparison of stereopsis thresholds measured with conventional methods and a new eye tracking method.

PURPOSE: Stereopsis is the ability to perceive depth using the slightly different views from two eyes. This study aims to conduct innovative stereopsis tests using the objective data outputted by eye tracking technology. METHODS: A laptop and an eye tracker were used to establish the test system. Anaglyphic glasses were employed to execute the stereopsis assessment. The test symbol employed was devised to emulate the quantitative measurement component of the Random Dot 3 Stereo Acuity Test. Sub-pixel technology was used to increase the disparity accuracy of test pages. The tested disparities were: 160″, 100″, 63″, 50″, 40″, 32″, 25″, 20″, 16″, and 12.5″. The test was conducted at a distance of 0.65m. Conventional and eye tracking stereopsis assessments were conducted on 120 subjects. Wilcoxon signed-rank test was used to test the difference, while the Bland-Altman method was used to test the consistency between the two methods. RESULTS: The Wilcoxon signed-rank test showed no significant difference between conventional and eye tracking thresholds of stereopsis (Z = -1.497, P = 0.134). There was a high level of agreement between the two methods using Bland- Altman statistical analysis (The 95 per cent limits of agreement were -0.40 to 0.47 log arcsec). CONCLUSIONS: Stereoacuity can be evaluated utilizing an innovative stereopsis measurement system grounded in eye tracking technology.

Test retest variability in stereoacuity measurements.

Background: A clinician's choice of stereotest is influenced by the robustness of the measurement, in terms of sensitivity, specificity and test-retest variability. In relation to the latter aspect, there are limited data on the test-retest variability of these new tests and how they compare to the more commonly used stereotests. Therefore, the aim of the study was to determine the test-retest variability of four different measures of stereoacuity (TNO, Frisby, Lang Stereopad and Asteroid (Accurate STEReotest On a mobIle Device)) and to compare the stereoacuity measurements between the tests in an adult population. Methods: Stereoacuity was measured twice using TNO, Frisby, Lang Stereopad and Asteroid. Inclusion criteria included adult participants (18 years and older), no known ophthalmic condition and VA (Visual Acuity) equal to or better than 0.3 logMAR (Logarithm of the Minimum Angle of Resolution) with interocular difference of less than 0.2 logMAR. Bland-Altman analysis was used to assess agreement within and between stereotests. Differences in stereo thresholds were compared using signed Wilcoxon tests. Results: Fifty-four adults (male: 23 and female: 31) with VA equal to or better than 0.3 logMAR in either eye and interocular difference less than 0.2 logMAR were assessed (mean age: 38 years, SD: 12.7, range: 18-72). The test-retest variability of all the clinical stereotests, with the exception of the Lang Stereopad (p = .03, Wilcoxon signed-rank test), was clinically insignificant as the mean bias was equal or less than 0.06 log seconds of arc (equivalent to 1.15 seconds of arc). While the Asteroid test had the smallest variation between repeated measures (mean bias: -0.01 log seconds of arc), the Frisby and Lang Stereopad tests had the narrowest and widest limits of agreement respectively. When comparing results between tests, the biggest mean bias was between Frisby and Lang Stereopad (-0.62 log seconds of arc), and 64.8% and 31.5% of differences were in the medium (21-100" of arc) and larger (>100" of arc) ranges respectively. Conclusion: The TNO and Frisby tests have good reliability but measure stereoacuity over a narrower range compared to the Asteroid which shows less variation on repeated testing but has a larger testing range. The data reported here show varying degrees of agreement in a cohort of visually normal participants, and further investigation is required to determine if there is further variability when stereoacuity is reduced.

[A prospective cohort study on visual development in infants and young children].

Objective: This study aimed to analyze the trends and characteristics of early visual development in infants and young children. Methods: A prospective cohort study was conducted, including full-term infants born between 2008 and 2013 at the Maternal and Child Health Hospital in Sanhe City, Hebei Province, China. Visual acuity was assessed at three time points 42 days after birth, 9 months of age, and 18 months of age, using the Teller Acuity Card Ⅱ (TAC Ⅱ) grating visual acuity test. At 3 years of age, visual acuity was assessed using the Lea Symbols chart and converted to grating visual acuity. Visual acuity of both eyes was measured at 42 days, 9 months, and 18 months. For children at 9 and 18 months, monocular visual acuity was also assessed, while at 3 years of age, monocular visual acuity was measured. Visual acuity measurements at different time points and changes in visual acuity within each period were recorded. The visual development of the participants was analyzed and compared with previous literature results. Results: A total of 1 496 children were included in the study, including 773 males (51.67%) and 723 females (48.33%). The binocular visual acuity at 42 days, 9 months, and 18 months was 0.9 (0.6, 1.1), 6.4 (6.4, 9.6), and 9.6 (9.6, 9.6) cycles per degree (cpd), respectively, with statistically significant differences (P<0.001). Visual acuity increased by a factor of 3.21±0.70 between 42 days and 9 months, and by a factor of 0.23±0.48 between 9 and 18 months. At 9 months of age, the monocular visual acuity in the right and left eyes was 6.4 (4.8, 6.4) cpd, which remained the same at 18 months, and the median visual acuity at 3 years of age for both eyes was 18.75 cpd, with a Snellen visual acuity of 20/32 (20/40, 20/32). The differences in binocular visual acuity at each time point were not statistically significant (all P>0.05). At 9 months of age, 68.7%(633/921) of children had visual acuity of ≥6.5 cpd, which increased to 92.7%(342/369) at 18 months. Monocular visual acuity increased by a factor of 0.26±0.46 between 9 and 18 months, and by a factor of 1.36±0.52 between 18 months and 3 years. At 9 months of age, 72.01% (921 out of 1 279) of children who completed binocular visual acuity testing also underwent monocular visual acuity testing, while this proportion decreased to 35.83% (369 out of 1 030) at 18 months. Visual acuity improved with increasing age (P<0.001). The visual acuity of children at each age group in this study was higher than that reported in the literature for children in Guangzhou (P<0.001). Conclusions: The visual acuity of healthy infants and young children below 3 years of age improves with age. Visual development progresses rapidly before 9 months of age, slows down afterward, and then resumes rapid growth at 18 months of age.

Discrimination of paediatric acuity test optotypes by 6-year-old children.

PURPOSE: To compare the discrimination performance of 6-year-old children for optotypes from six paediatric visual acuity tests and to fit Luce's Biased Choice Model to the data to estimate the relative similarities and bias for each optotype. METHODS: Full data sets were collected from 20 typically developing 6-year-olds who had passed a vision screening. They were presented with single optotypes labelled 6/12 at a distance of 9 m and were asked to identify the optotype using a matching task containing all optotypes from the relevant test. The data were combined to form a confusion matrix for each test and a biased choice model was fitted to the data. RESULTS: Median correct performance varied from 40% to 100% across optotypes, with the HOTV test having the highest values. Estimates of the similarity of each pair of optotypes indicated equal values for all pairs in the Landolt C, HOTV, Lea numbers and Tumbling E tests. The values differed for the picture tests, that is Lea Symbols and Allen figures. The estimates of bias for each individual optotype also indicated different values with the picture tests. CONCLUSIONS: Previous studies of the threshold acuity of young children and adults have indicated differences in acuity estimates across paediatric tests. A recognition acuity task typically requires resolving the difference information between optotypes. The performance of the 6-year-olds here reveals variance in similarity and bias values for picture tests, particularly for the Allen figures when compared with the Lea Symbols. Ideally, this analysis should be performed when designing new tests, and these results motivate progression from the use of current picture tests to well calibrated letter or number tests at the earliest possible age.

[Visual acuity charts in the Russian Empire, the USSR and modern Russia]. / Tablitsy dlya opredeleniya ostroty zreniya v Rossiiskoi imperii, SSSR i sovremennoi Rossii.

Visual acuity is the quantitative parameter of the visual system characterizing its functional spatial resolution. Special test charts are commonly used for visual acuity assessment. The development of foreign tests for visual acuity is comprehensively covered in the literature, while the history of improving visual acuity charts in modern Russia, the USSR, and in the territory of the Russian Empire is only considered fragmentarily. In particular, there are almost no mentions of D.A. Sivtsev's work on proper letter-signs selection, and of A.A. Kryukov's tests. The purpose of this article is to review the history of developing visual acuity assessment methods in the Russian Empire, the USSR and modern Russia. One of the first sets of tests for visual acuity assessment available in the Russian Empire was developed by A.A. Kryukov; it was republished several times, but some criticism of the test can be encountered in the literature of that period. Subsequently, a task of developing a more accurate method was presented, which was implemented in the form of several editions of the visual acuity charts by D.A. Sivtsev and S.S. Golovin. The authors put a lot of effort into selecting the letters for the most reliable results of visual acuity assessment, excluded some unsuccessful characters (Cyrillic letters 'Ж' and 'Ю') and changed the size levels of the chart (the lines corresponding to the visual acuity levels of 1.25 and 1.5 were substituted by 1.5 and 2.0). Around the same period, A. Holina's chart appeared in print, but due to its poor structure the chart did not gain popularity, although it had a number of advantages. The review also considers some modern tests: the RORBA chart (named after the authors Rosenbaum, Ovechkin, Roslyakov, Bershanskiy, Aizenshtat), the vanishing optotypes by S.A. Koskin et al., the three-bar optotypes by the Institute for Information Transmission Problems (IITP), and the "Quartet" optotypes. Despite a large number of options, the search for the best method of measuring visual acuity for various medical and scientific tasks continues.

Children's visual acuity tests without professional supervision: a prospective repeated measures study.

BACKGROUND: Home visual acuity tests could ease pressure on ophthalmic services by facilitating remote review of patients. Home tests may have further utility in giving service users frequent updates of vision outcomes during therapy, identifying vision problems in an asymptomatic population, and engaging stakeholders in therapy. METHODS: Children attending outpatient clinics had visual acuity measured 3 times at the same appointment: Once by a registered orthoptist per clinical protocols, once by an orthoptist using a tablet-based visual acuity test (iSight Test Pro, Kay Pictures), and once by an unsupervised parent/carer using the tablet-based test. RESULTS: In total, 42 children were recruited to the study. The mean age was 5.6 years (range 3.3 to 9.3 years). Median and interquartile ranges (IQR) for clinical standard, orthoptic-led and parent/carer-led iSight Test Pro visual acuity measurements were 0.155 (0.18 IQR), 0.180 (0.26 IQR), and 0.300 (0.33 IQR) logMAR respectively. The iSight Test Pro in the hands of parents/carers was significantly different from the standard of care measurements (P = 0.008). In the hands of orthoptists. There was no significant difference between orthoptists using the iSight Test Pro and standard of care (P = 0.289), nor between orthoptist iSight Test Pro and parents/carer iSight Test Pro measurements (P = 0.108). CONCLUSION: This technique of unsupervised visual acuity measures for children is not comparable to clinical measures and is unlikely to be valuable to clinical decision making. Future work should focus on improving the accuracy of the test through better training, equipment/software or supervision/support.

Dioptric differences between clinically determined and metric-optimised refractions for adults with Down syndrome.

PURPOSE: Refractions based on the optimisation of single-value wavefront-derived metrics may help determine appropriate corrections for individuals with Down syndrome where clinical techniques fall short. This study compared dioptric differences between refractions obtained using standard clinical techniques and two metric-optimised methods: visual Strehl ratio (VSX) and pupil fraction tessellated (PFSt), and investigated characteristics that may contribute to the differences between refraction types. METHODS: Thirty adults with Down syndrome (age = 29 ± 10 years) participated. Three refractive corrections (VSX, PFSt and clinical) were determined and converted to vector notation (M, J0 , J45 ) to calculate the dioptric difference between pairings of each type using a mixed model repeated measures approach. Linear correlations and multivariable regression were performed to examine the relationship between dioptric differences and the following participant characteristics: higher order root mean square (RMS) for a 4 mm pupil diameter, spherical equivalent refractive error and Vineland Adaptive Behavior Scales (a measure of developmental ability). RESULTS: The least squares mean estimates (standard error) of the dioptric differences for each pairing were as follows: VSX versus PFSt = 0.51 D (0.11); VSX versus clinical = 1.19 D (0.11) and PFSt versus clinical = 1.04 D (0.11). There was a statistically significant difference in the dioptric differences between the clinical refraction and each of the metric-optimised refractions (p < 0.001). Increased dioptric differences in refraction were correlated with increased higher order RMS (R = 0.64, p < 0.001 [VSX vs. clinical] and R = 0.47, p < 0.001 [PFSt vs. clinical]) as well as increased myopic spherical equivalent refractive error (R = 0.37, p = 0.004 [VSX vs. clinical] and R = 0.51, p < 0.001 [PFSt vs. clinical]). CONCLUSIONS: The observed differences in refraction demonstrate that a significant portion of the refractive uncertainty is related to increased higher order aberrations and myopic refractive error. Methodology surrounding clinical techniques and metric-optimisation based on wavefront aberrometry may explain the difference in refractive endpoints.

An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System.

Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants is difficult because of deficiencies in their communication ability. This paper presents a novel automated method to assess visual acuity in children (5-36 months old). This method, the automated acuity card procedure (AACP), uses a webcam for eye tracking and recognizes children's watching behaviors automatically. A two-choice preferential-looking test is performed when the tested child watches the visual stimuli shown on a high-resolution digital display screen. When the tested child watches the stimuli, their facial pictures are recorded by the webcam. These pictures are used by the set computer program to analyze their watching behavior. With this procedure, the child's eye movement responses to different stimuli are measured, and their visual acuity is assessed without communication. By comparing the results with grating acuity obtained by Teller Acuity Cards (TACs), AACP performance is deemed comparable to that of TACs.

Clinical validation of a novel smartphone application for measuring best corrected visual acuity.

PURPOSE: Personal mobile devices such as smartphones are proving their usefulness in ever more applications in tele-eyecare. An inconvenience and potential source of error in these past approaches stemmed from the requirement for the subjects to situate their devices at a distance. The present study aims to clinically validate best corrected visual acuity (BCVA) measures carried out by a novel smartphone application "vision.app" (VisionApp Solutions S.L.) using comparative statistics against clinical measurements. MATERIALS AND METHODS: BCVA was measured in both eyes of 40 subjects using vision.app which displayed a black Landolt-C optotype with crowding on a white background, and utilized a 4 forced-choice procedure for the subjects to find (by means of swiping in either of four directions) the smallest optotype size they could resolve. Results were compared to BCVA measurements taken using a standard Snellen chart placed at 20 feet (6 m). RESULTS: The t-test revealed no significant differences between the app- and clinically-measured VA (p = 0.478 (OD) and 0.608 (OS)), with a mean difference between clinical and app measurements of less than one line of the eye chart (-0.009 logMAR (OD) and -0.005 logMAR (OS)). A limit of agreement for a 95% confidence interval of ± 0.08 logMAR for OD and OS was found. CONCLUSIONS: The results show the potential use of a smartphone to measure BCVA at a handheld distance. The newly validated study results can hold major future advancements in tele-eyecare and provide eye care professionals with a reliable and accessible method to measure BCVA.

Agreement between Lea Symbols and Patti Pics visual acuity in children and adults.

BACKGROUND: Patti Pics (PP) and Lea Symbols (LS) are commonly used by eye care practitioners worldwide. Although the relationship between the two tests is fairly well understood, the availability of different chart designs (single optotypes, multiple optotypes, multiple optotypes with crowding box) merits futher understanding. The purpose of this study is to explore the agreement between the acuity measures obtained with Patti Pics and Lea Symbols in children and adults and compare their performance with the Sloan Letter (SL) chart in adults. METHODS: Monocular visual acuity was obtained from ninety-three 3 to 5-year-old children using Patti Pics and Lea Symbols. Acuities were also obtained from 113 adults using the same tests under identical conditions. Acuity results obtained with the pediatric tests were compared with the gold-standard Sloan Letter chart in adults. The Bland-Altman method was implemented to compare the level of agreement between tests. RESULTS: Patti Pics yielded worse visual acuity than the Lea Symbols by approximately half a logMAR line in both children (mean difference: -0.07 ± 0.07 logMAR, p <0.01) and adults (Mean difference: -0.05 ± 0.06 logMAR, p <0.01). The 95% limits of agreement between Lea Symbol acuity and Patti pics acuity in children was ± 0.14 logMAR. Mean difference between the Sloan Letter chart and Lea Symbols acuity was not statistically significant (p = 0.08) in adults but the difference was statistically significant between PP and SL (p<0.001). The 95% limits of agreement between LS and SL and between PP and SL was ± 0.19 logMAR and ± 0.22 logMAR, respectively. CONCLUSION: Patti Pics consistently underestimated visual acuity as compared to Lea Symbols both in children and adults although the differences were not clinically significant. The LS and PP did not yield clinically significant differences in acuities when compared with Sloan letters in adults.

PandAcuity in paediatrics: a novel clinical measure of visual function based on the panda illusion.

BACKGROUND/AIMS: To evaluate the PandAcuity test for visual function testing in a paediatric cohort and to examine its agreement with conventional visual acuity (VA) testing. METHODS: PandAcuity scores were determined in 152 children (77 males) aged between 3 and 15 years after VA testing (LEATM-test, E-chart, Landolt-C-rings or numbers). The PandAcuity test consisted of illusions made up from silhouettes of animals 'hidden' within zig-zag-patterns of decreasing spatial frequencies. Correlation analyses between PandAcuity score and VA were performed. RESULTS: 150 children completed the test in at least one eye, 148 in both eyes. The PandAcuity test demonstrated good test-retest reliability (intraclass correlation coefficient=0.89) between two runs. VA and PandAcuity score showed a medium to large correlation (Spearman's ρ=0.52, p<0.0001). 93% of the children's visual impairment was classified in the same range by both test types. Receiver operating characteristic analysis of predicted visual impairment showed an excellent agreement with the classification based on VA testing (AUC=0.84). CONCLUSION: The PandAcuity test is rapid, simple and well accepted, rendering it a suitable supplement for the clinical assessment of VA in children. Because of its counterintuitive application (a higher number of correctly identified images means worse VA), it can be used to cross-validate conventional acuity tests to assure children's compliance.