The Use of the RETeval Portable Electroretinography Device for Low-Cost Screening: A Mini-Review.

Electroretinography (ERG) provides crucial insights into retinal function and the integrity of the visual pathways. However, ERG assessments classically require a complicated technical background with costly equipment. In addition, the placement of corneal or conjunctival electrodes is not always tolerated by the patients, which restricts the measurement for pediatric evaluations. In this short review, we give an overview of the use of the RETeval portable ERG device (LKC Technologies, Inc., Gaithersburg, MD, USA), a modern portable ERG device that can facilitate screening for diseases involving the retina and the optic nerve. We also review its potential to provide ocular biomarkers in systemic pathologies, such as Alzheimer's disease and central nervous system alterations, within the framework of oculomics.

Technical Report: A New Device Attached to a Smartphone for Objective Vision Screening.

SIGNIFICANCE: A new device attached to a smartphone was created for objective vision screening of young children including infants and newborns. The device is compact, lightweight, portable, cost-effective, and easy to operate. Therefore, it is suitable for screening large numbers of children in clinical settings, schools, and communities. PURPOSE: This article introduces a new device attached to a smartphone for objective vision screening. It can detect and categorize significant refractive errors, anisometropia, strabismus, cloudy ocular media, and ptosis that may cause amblyopia. METHODS: The new device applies the same principles as conventional streak retinoscopy but examines both eyes simultaneously and records the results electronically. The device comprises optical elements that produce a precise streak light beam and move it across a child's both eyes. The smartphone's video camera catches and records the motion of retinal reflex inside the child's pupils. By observing the direction of motion of the retinal reflex relative to the light beam motion, as well as its speed, width, and brightness, the examiner is able to assess the individual and comparative refractive status, ocular alignment, and other conditions. RESULTS: Vision screening with this device does not require any subjective response from children. The examination can be performed and analyzed by nonprofessionals after a short learning period of time. Because the examination results are electronically recorded by the smartphone, they can be stored in the child's files and sent out for professional consultations. CONCLUSIONS: The new device will provide the same functions as conventional streak retinoscopy but examines a child's both eyes simultaneously, so that, in addition to categorizing refractive errors and assessing clarity of refractive media of the eyes, it can also detect anisometropia, strabismus, and anisocoria. In addition to showing the examination results on the smartphone's screen, the device can also store the results electronically.

Detection of Amblyogenic Refractive Error Using the Spot Vision Screener in Children.

SIGNIFICANCE: Vision screenings are conducted to detect significant refractive errors, amblyopia, and ocular diseases. Vision screening devices are desired to have high testability, sensitivity, and specificity. Spot has demonstrated high testability, but previous reports suggest that the Spot has low sensitivity for detecting amblyogenic hyperopia and moderate sensitivity for amblyogenic astigmatism. PURPOSE: This study assessed the concurrent validity of detecting amblyogenic refractive errors by the Spot (v.1.1.50; Welch Allyn Inc., Skaneateles Falls, NY) compared with cycloplegic retinoscopy. METHODS: A total of 475 subjects (24 to 96 months) were screened by Spot and then received a masked comprehensive examination. Sensitivity and specificity, Bland-Altman plot, receiver operating characteristic area under the curve, and paired t test were evaluated by comparing the results of the Spot (v1.1.50) using the manufacturer referral criteria with the results of the comprehensive examination using the 2013 American Association for Pediatric Ophthalmology and Strabismus criteria. RESULTS: The Spot (v.1.1.50) referred 107 subjects (22.53%) for the following: 18.73% (89/475) astigmatism, 4.63% (22/475) myopia, 0.42% (2/475) hyperopia, and 2.11% (10/475) anisometropia. The sensitivity and specificity of the Spot vision screener for detecting amblyogenic risk factors were 86.08% (95% confidence interval [CI], 76.45 to 92.84%) and 90.15% (95% CI, 86.78 to 92.90%). Areas under the curve were 0.906 (95% CI, 0.836 to 0.976) for hyperopia, 0.887 (95% CI, 0.803 to 0.972) for spherical equivalent, and 0.914 (95% CI, 0.866 to 0.962) for astigmatism. A modified hyperopia criteria cutoff of greater than +1.06 D improved the sensitivity from 25 to 80% with 90% specificity. The current cutoff criterion, greater than -1.75 D, for astigmatism seemed optimal. CONCLUSIONS: This study shows that the Spot vision screener accurately detects low spherical refractive errors and astigmatism. Lowering the hyperopia cutoff criteria from the current Spot screener referral criteria improves the sensitivity with desired (high) specificity.

Performance of the Lea symbols chart for screening Nigerian children aged 3 to 5 years.

BACKGROUND: Vision screening in children of preschool age (age 3-5 years) gives the opportunity for timely detection of amblyopia. The tools that would be used for screening must have high rates of testability in these young children, and must have high enough sensitivity and specificity to be reliable and cost effective. AIMS: To assess the performance of the Lea symbols chart as a screening tool in children aged 3 to 5 years attending primary schools in Kwara State, Nigeria. METHODS: Visual acuity (VA) of 464 children selected from 12 schools by a multistage sampling procedure was checked using the Lea symbols chart by trained Lea screeners. Children meeting the referral criteria and untestable children had a comprehensive eye examination. Testability rates, sensitivity, specificity, positive, and negative predictive values were analyzed based on age and gender, with corresponding significance values generated. RESULTS: Testability rates among 5 year olds were as high as 99.1%, decreasing significantly to 95.5% in 4 year olds and 85.7% in 3 year olds (p value < 0.001). Visual acuity performance improved with age (p value 0.002) but was unrelated to gender. The Lea symbols chart had an overall specificity of 77.4% (63.2% among 3 year olds and 83.5% among 5 year olds). At VA thresholds of 6/12 for 5 year olds and 6/15 for 3-4 year olds, the screening tool became 87.7% specific among 3 year olds and 94.3% specific among 5 year olds (overall 92.5%). CONCLUSION: The Lea symbols chart was found to be a useful screening tool in this environment, especially among 5 year olds. The reduced specificity among 3-4 year olds may prompt further research into the appropriate VA thresholds for 3-4 year olds to reduce the burden of unnecessary comprehensive eye evaluations resulting from too many false positive results.

Visual Acuity Assessment and Vision Screening Using a Novel Smartphone Application.

OBJECTIVES: To evaluate a smartphone-based application's (Peek Acuity) ability to assess visual acuity and screen for ocular conditions in children, we compared visual acuity assessment between Peek Acuity and the pediatric ophthalmology examination and evaluated Peek Acuity's ability to identify children with referable ocular conditions. STUDY DESIGN: We prospectively recruited 111 children age 3-17 years, presenting to a pediatric ophthalmology clinic, who could follow instructions. Monocular visual acuity assessments by Peek Acuity and standard clinical methods were performed in randomized order. We compared visual acuity assessments between methods using intraclass correlation coefficient (ICC) and evaluated Peek Acuity's ability to identify children with referable ocular conditions. RESULTS: ICC comparing visual acuity assessed between methods was 0.88 (95% CI 0.83-0.92) for first and 0.85 (95% CI 0.78-0.89) for second eyes examined. ICC among 3 to 5-year-olds (preschool-age children) was 0.88 (95% CI 0.77-0.94) for first and 0.45 (95% CI 0.13-0.68) for second eyes examined. Peek Acuity had a sensitivity of 83%-86% for decreased vision and 69%-83% for referable ocular disease. Sensitivity was highest among 3 to 5-year-olds with decreased vision, 93%-100%. CONCLUSIONS: Overall, Peek Acuity visual acuity assessment correlated well with visual acuity assessed by standard clinical methods, though preschool-age children appeared more susceptible to examination fatigue. Peek Acuity performed adequately as a screening tool and had the greatest sensitivity among those with decreased vision and preschool-age children. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03212222.

Objective vision screening using PlusoptiX for children aged 3-11 years in rural Turkey.

BACKGROUND: This population based cross sectional study was conducted to detect amblyopia risk factors and myopia in a rural district of Northwestern Turkey by using PlusoptiX S12R (Photoscreener PlusoptiX Inc., Nuremberg, Germany). METHODS: Children from 38 rural schools in Caycuma district of Zonguldak Turkey underwent vision screening in their school using PlusoptiX S12 photoscreener. Data were analyzed using the factory default level 5 referral criteria targeting 80% sensitivity and 95% specificity. Referral, unable readings, and positive predictive value (PPV) were reported. RESULTS: Data from 2846 children were analyzed. Mean age was 7.9 years (±0.8) (range 36 months to 11 years). Three hundred ten (11%) were referred of whom 32% were read as 'unable'. 150 children (48% of the referred) received a gold standard examination. Positive predictive value of PlusoptiX was 69%. PPV was 83% when unable readings were excluded. 93 children with amblyopia risk factors were identified. Only 26% (n = 25) had received glasses priorly. 49 children had amblyopia of whom 33 were newly diagnosed. CONCLUSIONS: PlusoptiX showed a reasonable level of positive predictive value in community setting and the device could be a useful tool for vision screening in preschoolers and schoolers. We found most of the amblyogenic refractive errors were underdiagnosed in rural school children leading to a call for action on vision screening.

Diagnostic test accuracy of diabetic retinopathy screening by physician graders using a hand-held non-mydriatic retinal camera at a tertiary level medical clinic.

BACKGROUND: The evidence on diagnostic test accuracy (DTA) of diabetic retinopathy (DR) screening utilising photographic studies by non-ophthalmologist personnel in low and middle-income country (LMIC) settings is scarce. We aimed to assess DTA of DR screening using a nonmydriatic hand-held digital camera by trained general physicians in a non-ophthalmic setting. METHODS: This study is a validation of a screening intervention. We selected 700 people with diabetes (PwDM) > 18 years of age, not previously screened or treated for DR, presenting at a tertiary medical clinic in Sri Lanka. Two-field retinal imaging was used to capture fundus images before and after pupil dilatation, using a hand-held non-mydriatic (Visuscout 100®-Germany) digital retinal camera. The images were captured and graded by two trained, masked independent physician graders. The DTA of different levels of DR was assessed comparing physician's grading with a retinologist's clinical examination by mydriatic bio-microscopy, according to a locally adopted guideline. RESULTS: Seven hundred eligible PwDM were screened by physician graders. The mean age of participants was 60.8 years (SD ±10.08) and mean duration of DM was 9.9 years (SD ±8.09). Ungradable image proportion in non-mydriatic imaging was 43.4% (either eye-31.3%, both eyes 12.1%). This decreased to 12.8% (either eye-11.6%, both eyes-1.2%) following pupil dilatation. In comparison to detection of any level of DR, a referable level DR (moderate non-proliferative DR and levels above) showed a higher level of DTA. The sensitivity of the defined referable DR was 88.7% (95% CI 81.7-93.8%) for grader 1 (positive predictive value [PPV] 59.1%) and 92.5% (95% CI 86.4-96.5%) for grader 2 (PPV 68%), using mydriatic imaging, after including ungradable images as screen positives. The specificity was 94.9% (95% CI 93.6-96.0%) for grader 1 (negative predictive value [NPV] 99%) and 96.4% (95% CI 95.3-97.3%) for grader 2 (NPV 99.4%). CONCLUSIONS: The Physicians grading of images from a digital hand-held non-mydriatic camera at a medical clinic, with dilatation of pupil of those who have ungradable images, provides a valid modality to identify referable level of DR. This could be a feasible alternative modality to the existing opportunistic screening to improve the access and coverage. TRIAL REGISTRATION: Current Controlled Trials ISRCTN47559703 . Date of Registration 18th March 2019, Retrospectively registered.

Calibration of the PlusOptix PowerRef 3 with change in viewing distance, adult age and refractive error.

PURPOSE: The PowerRef 3 is frequently used in studying the near triad of accommodation, vergence and pupil responses in normal and clinical populations. Within a range, the defocus measurement of the PowerRef 3 is linearly related to the eye's defocus. While the default factory-calibrated slope of this relation (calibration factor) is 1, it has been shown that the slope can vary across individuals. Here, we addressed the impact of changes in viewing distance, age and defocus of the eye on the calibration factor. METHODS: We manipulated viewing distance (40 cm, 1 m and 6 m) and recruited participants with a range of accommodative capabilities: participants in their 20s, 40s and over 60 years old. To test whether any effect was larger than the range of measurement reliability of the instrument, we collected data for each condition four times: two in the same session, another on the same day, and one on a different day. RESULTS: The results demonstrated that viewing distance did not affect the calibration factor over the linear range, regardless of age or uncorrected refractive error. The largest proportion of the variance was explained by between-subject differences. CONCLUSIONS: Calibration data for the PowerRef 3 were not sensitive to changes in viewing distance. Nevertheless, our results re-emphasise the relevance of calibration for studies of individual participants.

Diagnostic test accuracy of Spot and Plusoptix photoscreeners in detecting amblyogenic risk factors in children: a systemic review and meta-analysis.

PURPOSE: Amblyopia is a permanent visual impairment developed in early childhood. Recently, instrument-based photoscreeners have been widely used for vision screening to detect amblyopia risk factors, which is key for the prevention and treatment of amblyopia. This meta-analysis aims to evaluate the diagnostic test accuracy of Spot and Plusoptix photoscreeners in detecting risk factors for amblyopia in children. METHODS: An electronic literature search was performed in October 2018 using the MEDLINE, Embase, and Web of Science databases. Twenty-one publications with a total of 5022 subjects were included. Subjects given a comprehensive examination were considered to have amblyopia or amblyogenic risk factors based on the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) referral criteria guidelines. RESULTS: The overall sensitivity for Spot and Plusoptix was 87.7% and 89.4%, respectively (p = 0.38); the specificity was 78.0% and 89.9%, respectively (p = 0.90). For subjects under 7 years old (preschool children), the overall sensitivity for Spot and Plusoptix was 91.7% and 90.2%, respectively (p = 0.81); the specificity was 82.6% and 93.0%, respectively (p = 0.46). CONCLUSION: Both Spot and Plusoptix photoscreeners demonstrated good sensitivity and specificity in detecting amblyopia risk factors in children, especially at preschool ages. There was no significant difference in diagnostic test accuracy between them.

Comparison of the PlusOptix S09 and Spot Vision photorefractor to cycloretinoscopy.

PURPOSE: The purpose of this study was to compare refraction measurements for children with the PlusOptix S09 and Spot Vision with cycloplegic retinoscopy. METHODS: One hundred thirty-six eyes of 68 children (26 boys and 42 girls) were evaluated prospectively. The subjects were separated into two groups. Group 1 comprised the subjects age between 5 and 9 years. Group 2 comprised the subjects age between 10 and 18 years. Photorefraction with PlusOptix S09, photorefraction with Spot Vision and cycloplegic retinoscopy were performed in each patient. Spherical equivalents, spherical power, cylindrical power and axis values were compared between three methods. RESULTS: The mean age of the patients was 7.12 ± 1.5 years in group 1 and 12.24 ± 1.8 years in group 2. Spherical equivalent and spherical power measured with PlusOptix S09 were statistically smaller than measured with cycloplegic retinoscopy for group 1 (p = 0.001, p = 0.001) and for group 2 (p = 0.000, p = 0.000). The mean cylindrical power measured with PlusOptix S09 was not statistically different compared to cycloplegic retinoscopy for both groups (p = 0.314, p = 0.05). Spherical equivalents measured with Spot Vision were statistically smaller than measured with cycloplegic retinoscopy for both groups (p = 0.000, p = 0.012). Spherical power measured with Spot Vision was statistically smaller than measured with cycloplegic retinoscopy for group 1 (p = 0.000), but the difference was not statistically significant for group 2 (p = 0.084). The mean cylindrical power measured with Spot Vision was statistically higher than cycloplegic retinoscopy for both groups (p = 0.000, p = 0.012). CONCLUSIONS: PlusOptix S09 and Spot Vision devices give acceptable results for screening, but prescription of spectacles should not be made according to PlusOptix S09 or Spot Vision devices alone.

Early diagnosis of amblyopia.

Amblyopia can be improved or eliminated more easily when treated early in life. Because amblyopia in older children is generally less responsive to treatment (Holmes et al., 2011), there is a premium on the early identification of amblyopia and its risk factors and the subsequent treatment thereof. Clinical preference is to institute treatment in children before 7 years of age when an optimal visual outcome is typically easier to obtain.

Testability Study of the Titmus V3 Test in Pre-school Children.

SIGNIFICANCE: Vision screening can identify people who have vision problems requiring a comprehensive examination. When children are screened, the most prevalent serious problem is amblyopia secondary to uncorrected ametropia. Screening also identifies strabismus, which can lead to loss of binocularity. Early diagnosis permits treatment with restoration of balanced vision and binocularity. PURPOSE: The study evaluated the testability of the Titmus V3 Vision Screener as a method to screen vision and strabismus in pre-school children. METHODS: Pre-school children between 36 and 66 months of age underwent vision screening in six Michigan counties. The State of Michigan screening consists of the LEA Symbols test for visual acuity and the stereo butterfly for near-strabismus testing. The proposed Titmus V3 screening tests were the LEA Symbols slide for vision and near-strabismus test slide. Primary and secondary objectives of this study were to evaluate the percentage of pre-school children who completed the Titmus V3 screening tests for vision and near strabismus and factors associated with an inability to complete the tests, contrasting the pass/fail results between the state and Titmus V3 results. RESULTS: Two-hundred sixty-three children were tested. The percentages of children unable to score on the Titmus V3 instrument versus the state's LEA Symbols test were 16.0% and 5.3%, respectively. The percentage of children unable to score on the Titmus V3 near-strabismus test slide was 6.9 versus 3.4% on the State of Michigan stereo butterfly test. Younger age at testing was the most important factor associated with the inability to complete testing. CONCLUSIONS: Because of testability limitations and higher failure rates relative to the State of Michigan testing methods, the Titmus V3 screening device is not a feasible alternative to the standard methods used by the State of Michigan for vision and near-strabismus screening among the pre-school subjects we tested.

Comparative Study of the Usefulness of the Binocular Spot Vision Screener Autorefractor in the Detection of Childhood Visual Disorders.

BACKGROUND: The Spot Vision Screener (SVS) is designed to detect significant ametropia, anisometropia, and strabismus in non-dilated eyes. This study evaluates the efficacy of the SVS in paediatric visual screening. PATIENTS AND METHODS: All children screened during the paediatric visual screening day in Lausanne in 2016 were evaluated with the SVS, conventional monocular autorefractors, and clinical orthoptic examination. Recommendations for a further eye examination of the SVS were compared with those issued from traditional clinical screenings (monocular refraction and orthoptic examination). RESULTS: One hundred and sixty-eight consecutive children were included. The median age was 3.9 years. The SVS median spherical equivalent (SE) was + 0.25 D OU and it detected seven cases of (4.2%) anisometropia (SE difference ≥ 1 D). The conventional monocular autorefractor median SE was - 0.13 D OU and 20 cases of anisometropia (11.9%) were detected. Refraction could not be measured in 1.2% of patients with SVS versus 17.2% with monocular refractors. The SVS screened two manifest strabismus cases against five manifest and > 100 latent strabismus with orthoptic examination. As expected, the SVS was unable to assess reactions to monocular occlusion, visual acuity, and stereovision as well as to detect ocular motility disorders without strabismus in the primary position, and missed two cases of abnormal Brückner reflexes. Overall, the SVS identified 66 suspect patients (39.3%) against 102 (60.7%) after complete clinical examination. CONCLUSIONS: The SVS can be a useful objective screening tool for non-ophthalmologists. However, because it fails to detect ocular motility troubles, organic visual acuity loss, or to assess the visual potential, it should only be used in association with a clinical examination, even in routine screening procedures.

Instrument-based pediatric vision screening.

PURPOSE OF REVIEW: The purpose is to review currently available instruments for vision screening in young children. RECENT FINDINGS: Instrumentation continues to evolve. Although the current generation of photoscreeners and autorefractors strive to identify amblyopia risk factors, newer technology aims to directly identify amblyopia in young children. Acceptance of instrument-based vision screening for this population has led to increased reimbursement for the procedure in primary care practices. SUMMARY: Instrument-based vision screening in the young child is an accepted method of screening for amblyopia. Innovations in instrumentation will continue to improve its implementation.

New pediatric vision screener, part II: electronics, software, signal processing and validation.

BACKGROUND: We have developed an improved pediatric vision screener (PVS) that can reliably detect central fixation, eye alignment and focus. The instrument identifies risk factors for amblyopia, namely eye misalignment and defocus. METHODS: The device uses the birefringence of the human fovea (the most sensitive part of the retina). The optics have been reported in more detail previously. The present article focuses on the electronics and the analysis algorithms used. The objective of this study was to optimize the analog design, data acquisition, noise suppression techniques, the classification algorithms and the decision making thresholds, as well as to validate the performance of the research instrument on an initial group of young test subjects-18 patients with known vision abnormalities (eight male and 10 female), ages 4-25 (only one above 18) and 19 controls with proven lack of vision issues. Four statistical methods were used to derive decision making thresholds that would best separate patients with abnormalities from controls. Sensitivity and specificity were calculated for each method, and the most suitable one was selected. RESULTS: Both the central fixation and the focus detection criteria worked robustly and allowed reliable separation between normal test subjects and symptomatic subjects. The sensitivity of the instrument was 100 % for both central fixation and focus detection. The specificity was 100 % for central fixation and 89.5 % for focus detection. The overall sensitivity was 100 % and the overall specificity was 94.7 %. CONCLUSIONS: Despite the relatively small initial sample size, we believe that the PVS instrument design, the analysis methods employed, and the device as a whole, will prove valuable for mass screening of children.

SMARTPHONE-BASED DILATED FUNDUS PHOTOGRAPHY AND NEAR VISUAL ACUITY TESTING AS INEXPENSIVE SCREENING TOOLS TO DETECT REFERRAL WARRANTED DIABETIC EYE DISEASE.

PURPOSE: To compare clinical assessment of diabetic eye disease by standard dilated examination with data gathered using a smartphone-based store-and-forward teleophthalmology platform. METHODS: 100 eyes of 50 adult patients with diabetes from a health care safety-net ophthalmology clinic. All patients underwent comprehensive ophthalmic examination. Concurrently, a smartphone was used to estimate near visual acuity and capture anterior and dilated posterior segment photographs, which underwent masked, standardized review. Quantitative comparison of clinic and smartphone-based data using descriptive, kappa, Bland-Altman, and receiver operating characteristic analyses was performed. RESULTS: Smartphone visual acuity was successfully measured in all eyes. Anterior and posterior segment photography was of sufficient quality to grade in 96 and 98 eyes, respectively. There was good correlation between clinical Snellen and smartphone visual acuity measurements (rho = 0.91). Smartphone-acquired fundus photographs demonstrated 91% sensitivity and 99% specificity to detect moderate nonproliferative and worse diabetic retinopathy, with good agreement between clinic and photograph grades (kappa = 0.91 ± 0.1, P < 0.001; AUROC = 0.97, 95% confidence interval, 0.93-1). CONCLUSION: The authors report a smartphone-based telemedicine system that demonstrated sensitivity and specificity to detect referral-warranted diabetic eye disease as a proof-of-concept. Additional studies are warranted to evaluate this approach to expanding screening for diabetic retinopathy.

Assessment of near visual acuity in 0-13 year olds with normal and low vision: a systematic review.

BACKGROUND: The inclusion for rehabilitation of visually impaired children is partly based on the measurement of near vision, but guidelines for near visual acuity assessment are currently lacking. The twofold purpose of this systematic review was to: (i) provide an overview of the impact of the chart design on near visual acuity measured, and (ii) determine the method of choice for near vision assessments in children of different developmental ages. METHODS: A literature search was conducted by using the following electronic databases: PubMed, Cochrane Library, and EMBASE. The last search was run on March 26th 2016. Additional studies were identified by contacting experts and searching for relevant articles in reference lists of included studies. Search terms were: vision test(s), vision assessment(s), visual acuity, chart(s) and near. RESULTS: For children aged 0-3 years the golden standard is still the preferential looking procedure. Norms are available for this procedure for 6-36 month old children. For 4-7 year olds, we recommend using the LEA symbols, because these symbols have been properly validated and can be used in preliterate children. Responses can be verbal or by matching the target symbol. In children aged 8-13 years, the recommended method is the ETDRS letter chart, because letter acuity is more predictive for functional vision and reading than symbol acuity. In 8-13 year olds, letter acuity is 0.1-0.2 logMAR poorer than symbol acuity. CONCLUSIONS: Chart design, viewing distance, and threshold choice have a serious impact on near visual acuity measurements. Near visual acuity measured with symbols is lower than near visual acuity measured with gratings, and near visual acuity measured with letters is lower than near visual acuity measured with symbols. Viewing distance, chart used, and letter spacing should be adapted to the child's development and reported in order to allow comparisons between measurements.

Evaluation of the SVOne: A Handheld, Smartphone-Based Autorefractor.

PURPOSE: The SVOne is a portable Hartmann-Shack wavefront aberrometer that can be attached to a smartphone to determine the refractive error of the eye objectively. The aim of the present study was to compare the findings of the SVOne with retinoscopy, subjective refraction, and two commercially available autorefractors (Topcon KR-1W and Righton Retinomax-3). METHODS: Refractive error was assessed both with and without cycloplegia in 50 visually normal, young adults using the five techniques described above. Further, to assess repeatability of the instruments, the entire procedure was repeated in a subgroup of 10 subjects. All data were analyzed in terms of power vectors (M, J0, and J45). RESULTS: No significant difference was observed between the mean values of M (spherical equivalent) for the different techniques. However, a significantly higher mean value of precyclopegic J0 was recorded for the SVOne, which also had the highest limits of agreement for both the J0 and J45 astigmatic components. Retinoscopy and subjective refraction showed the best repeatability (in terms of M values) for precycloplegic and postcycloplegic measurements, respectively. High and significant linear correlations were observed between the subjective findings and the other four techniques. CONCLUSIONS: The results indicate that the SVOne handheld aberrometer provides measurements of refractive error in normal, young individuals that are not significantly different from other subjective and objective procedures. This instrument is valuable for vision screenings, as well as examinations taking place outside the clinical office. It may also serve as an adjunct in the standard optometric examination.

Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in adults: an update.

PURPOSE: The Shin-Nippon SRW-5000 is an open view autorefractor that superseded the Canon R-1 autorefractor in the mid-1990 s and has been used widely in optometry and vision science laboratories. It has been used to measure refractive error, accommodation responses both statically and dynamically, off-axis refractive error, and adapted to measure pupil size. This paper presents an overview of the original 2001 clinical evaluation of the SRW-5000 in adults (Mallen et al., Ophthal Physiol Opt 2001; 21: 101) and provides an update on the use and modification of the instrument since the original publication. RECENT FINDINGS: The SRW-5000 instrument, and the family of devices which followed, have shown excellent validity, repeatability, and utility in clinical and research settings. The instruments have also shown great potential for increased research functionality following a number of modifications. SUMMARY: The SRW-5000 and its derivatives have been, and continue to be, of significant importance in our drive to understand myopia progression, myopia control techniques, and oculomotor function in human vision.

How representative is the 'Representative Value' of refraction provided by the Shin-Nippon NVision-K 5001 autorefractor?

PURPOSE: The aim of the study was to evaluate the level of agreement between the 'Representative Value' (RV) of refraction obtained from the Shin-Nippon NVision-K 5001 instrument with values calculated from individual measurement readings using standard algebraic methods. METHODS: Cycloplegic autorefraction readings for 101 myopic children aged 8-13 years (10.9 ± 1.42 years) were obtained using the Shin-Nippon NVision-K 5001. Ten autorefractor measurements were taken for each eye. The spherical equivalent (SE), sphere (Sph) and cylindrical component (Cyl) power of each eye were calculated, firstly, by averaging the 10 repeated measurements (Mean SE, Mean Sph and Mean Cyl), and secondly, by the vector representation method (Vector SE, Vector Sph and Vector Cyl). These calculated values were then compared with those of RV (RV SE, RV Sph and RV Cyl) provided by the proprietary software of the NVision-K 5001 using one-way analysis of variance (anova). The agreement between the methods was also assessed. RESULTS: The SE of the subjects ranged from -5.37 to -0.62 D (mean ± SD, = -2.89 ± 1.01 D). The Mean SE was in exact agreement with the Vector SE. There were no significant differences between the RV readings and those calculated using non-vectorial or vectorial methods for any of the refractive powers (SE, p = 0.99; Sph, p = 0.93; Cyl, p = 0.24). The (mean ± SD) differences were: RV SE vs Mean SE (and also RV SE vs Vector SE) -0.01 ± 0.06 D; RV Sph vs Mean Sph, -0.01 ± 0.05 D; RV Sph vs Vector Sph, -0.04 ± 0.06 D; RV Cyl vs Mean Cyl, 0.01 ± 0.07 D; RV Cyl vs Vector Cyl, 0.06 ± 0.09 D. Ninety-eight percent of RV reading differed from their non-vectorial or vectorial counterparts by less than 0.25 D. CONCLUSION: The RV values showed good agreement to the results calculated using conventional methods. Although the formula used to calculate RV by the NVision-K 5001 autorefractor is proprietary, our results provide validation for the use of RV measurements in clinical practice and vision science research.