Development and Validation of a Mobile Visual Acuity Examination App for Universal Use, Including Remote and Rural Regions

2021 ◽  
Author(s):  
Soham V Govande
Keyword(s):  
Visual Acuity ◽  
Low Cost ◽  
Measurement Methods ◽  
T Test ◽  
Refractive Errors ◽  
Altman Analysis ◽  
Rural Regions ◽  
Bland Altman Analysis ◽  
Snellen Chart ◽  
R Project

Background: Visual refractive errors are projected to rise in the coming decades worldwide, especially in remote and rural regions. To combat this, smartphone visual acuity testing apps may allow for the early detection of refractive errors thanks to their low cost and wide availability. Hence, we developed the OcularCheck app as a free mobile vision screening tool for public health use. Objective: We sought to determine whether OcularCheck accurately measures distance visual acuity (DVA) in comparison to a standard Snellen chart (Space Saving Chart SSC-350). Methods and Results: In January 2021, we measured DVA in n=56 eyes using the OcularCheck app and a standard Snellen chart. To minimize bias, we used two separate examiners who were blinded to each other’s measurements. To assess the similarity of measurement methods, we performed a two-tailed, paired t-test and Bland-Altman analysis using the R-Project software. The t-test showed that differences in DVA between testing methods were not significant (P=0.698). Bland-Altman analysis showed that the mean difference between measurement methods was 0.01 LogMAR (95% CI -0.03 to 0.04), and the standard deviation of differences (0.139 LogMAR) was below the test-retest variability of the Snellen chart. The main limitation of the study was that we were not able to measure DVA with non-English optotypes. Conclusion: OcularCheck provides accurate DVA measurements, and it harbors the potential to expand the accessibility of DVA screening to resource-scarce regions.

Development and Validation of a Mobile Visual Acuity Examination App for Universal Use, Including Remote and Rural Region

2021 ◽  
Author(s):  
Soham V Govande
Keyword(s):  
Visual Acuity ◽  
Low Cost ◽  
Measurement Methods ◽  
T Test ◽  
Refractive Errors ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Snellen Chart ◽  
Wide Availability ◽  
R Project

Background: Visual refractive errors are projected to rise in the coming decades worldwide, especially in remote and rural regions. To combat this, smartphone visual acuity testing apps may allow for the early detection of refractive errors thanks to their low cost and wide availability. Hence, we developed the OcularCheck app as a free mobile vision screening tool for public health use. Objective: We sought to determine whether OcularCheck accurately measures distance visual acuity (DVA) in comparison to a standard Snellen chart (Space Saving Chart SSC-350). Methods and Results: In January 2021, we measured DVA in n=56 eyes using the OcularCheck app and a standard Snellen chart. To minimize bias, we used two separate examiners who were blinded to each other’s measurements. To assess the similarity of measurement methods, we performed a two-tailed, paired t-test and Bland-Altman analysis using the R-Project software. The t-test showed that differences in DVA between testing methods were not significant (P=0.698). Bland-Altman analysis showed that the mean difference between measurement methods was 0.01 LogMAR (95% CI -0.03 to 0.04), and the standard deviation of differences (0.139 LogMAR) was below the test-retest variability of the Snellen chart. The main limitation of the study was that we were not able to measure DVA with non-English optotypes. Conclusion: OcularCheck provides accurate DVA measurements, and it harbors the potential to expand the accessibility of DVA screening to resource-scarce regions.

scholarly journals Comparison between optical and digital blur using near visual acuity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David Kordek ◽  
Laura K. Young ◽  
Jan Kremláček
Keyword(s):  
Visual Acuity ◽  
Refractive Error ◽  
Low Cost ◽  
Pairwise Comparison ◽  
Clinical Population ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Laboratory Setup ◽  
Significant Difference ◽  
Near Visual Acuity

AbstractIn a low-cost laboratory setup, we compared visual acuity (VA) for stimuli rendered with Zernike aberrations to an equivalent optical dioptric defocus in emmetropic individuals using a relatively short observing distance of 60 cm. The equivalent spherical refractive error of + 1, + 2 or + 4 D, was applied in the rendering of Landolt Rings. Separately, the refractive error was introduced dioptrically in: (1) unchanged Landolt Rings with an added external lens (+ 1, + 2 or + 4 D) at the subject's eye; (2) same as (1) but with an added accommodation and a vertex distance adjustment. To compare all three approaches, we examined VA in 10 healthy men. Stimuli were observed on a PC CRT screen. For all three levels of refractive error, the pairwise comparison did not show a statistically significant difference between digital blur and accommodation-plus-vertex-distance-adjusted dioptric blur (p < 0.204). The best agreement, determined by Bland–Altman analysis, was measured for + 4 D and was in line with test–retest limits for examination in the clinical population. Our results show that even for a near observing distance, it is possible to use digitally rendered defocus to replicate dioptric blur without a significant change in VA in emmetropic subjects.

scholarly journals Assessment of visual acuity defects among rural adolescent students of tribal Bastar Chhattisgarh (India)

2018 ◽  
Vol 5 (10) ◽  
pp. 4335
Author(s):  
Alakh Ram Verma ◽  
Teeku Sinha ◽  
Gagandeep Singh Bhatia
Keyword(s):  
Visual Acuity ◽  
Low Cost ◽  
Refractive Errors ◽  
Community Based ◽  
Cross Sectional ◽  
Female Ratio ◽  
Adolescent Students ◽  
Eye Screening ◽  
Male To Female ◽  
Rural Adolescent

Background: Defective visual acuity is the most common problem among adolescents which, if remains uncorrected may cause refractive errors and may lead to blindness. Defective visual acuity can be tested early and corrected by spectacles. The objectives of the study were assessment of visual acuity defects among adolescent students.Methods: Present study design is cross sectional community based study. Conducted during July to September 2017 in Higher Secondary School, Pandripani. Predesigned KAP questionnaires were used to collect information and visual acuity was measured by using Snellen’s chart. Students with spectacles were tested for uncorrected and corrected visual acuity. Data was analyzed on MS Excel 2016.Results: Visual acuity defect prevalence rises with age and maximum is seen in age group 19-20 years (85%).Male to female ratio in students with defects was 52:48 Maximum defect is seen in class 12th students (34%).83% students never got their eyes checked out of which 25% had defective visual acuity. Positive attitude toward spectacles preventing normalization of eyes and spectacles leading to dependence and worsening of vision were elicited. Students whose parents have eye related problem have prevalence of 64%.83% of students advised to wear spectacles who don’t have, cost of spectacle is most common cause (80%) and is preceded by not much difference in vision after wearing (20%).Conclusions: The prevalence of visual acuity defect was high in rural adolescent. Eye screening of school going children is recommended and spectacles to be distributed free or at low cost to those students diagnosed with refractive errors.

scholarly journals Advancing Digital Workflows for Refractive Error Measurements

2020 ◽  
Vol 9 (7) ◽  
pp. 2205
Author(s):  
Arne Ohlendorf ◽  
Alexander Leube ◽  
Siegfried Wahl
Keyword(s):  
Refractive Error ◽  
T Test ◽  
Refractive Errors ◽  
Altman Analysis ◽  
Limits Of Agreement ◽  
Clinical Measurement ◽  
Different Types ◽  
Method Of Measurement ◽  
Mean Differences ◽  
The Right

Advancements in clinical measurement of refractive errors should lead to faster and more reliable measurements of such errors. The study investigated different aspects of advancements and the agreement of the spherocylindrical prescriptions obtained with an objective method of measurement (“Aberrometry” (AR)) and two methods of subjective refinements (“Wavefront Refraction” (WR) and “Standard Refraction” (StdR)). One hundred adults aged 20–78 years participated in the course of the study. Bland–Altman analysis of the right eye measurement of the spherocylindrical refractive error (M) identified mean differences (±95% limits of agreement) between the different types of measurements of +0.36 D (±0.76 D) for WR vs. AR (t-test: p < 0.001), +0.35 D (± 0.84 D) for StdR vs. AR (t-test: p < 0.001), and 0.0 D (± 0.65 D) for StdR vs. WR (t-test: p < 0.001). Monocular visual acuity was 0.0 logMAR in 96% of the tested eyes, when refractive errors were corrected with measurements from AR, indicating that only small differences between the different types of prescriptions are present.

Validation of the visual acuity iPad app Eye Chart Pro compared to the standard Early Treatment Diabetic Retinopathy Study chart in a low-vision population

2020 ◽  
pp. 1357633X2096064
Author(s):  
Hassan Hazari ◽  
Rachel Curtis ◽  
Karen Eden ◽  
Wilma M Hopman ◽  
Isabella Irrcher ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Early Treatment ◽  
Low Vision ◽  
Test Methods ◽  
Absolute Difference ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Significant Difference ◽  
Ipad App

Introduction A low-vision assessment (LVA) is central to developing a vision rehabilitation plan. However, access to LVAs is often limited by the quantity and geographic distribution of low-vision providers, as well as patient-centred transportation challenges. A tablet-based LVA tool kit, delivered virtually, has the potential to overcome many of these barriers. The purpose of this research was to validate a key component of the tablet-based tool kit – a commercially available iPad visual acuity (VA) test (Eye Chart Pro) iPad app – in a low-vision population. Methods Participants with low vision ( n = 26) and those who were normally sighted ( n = 25) underwent VA testing with both the iPad VA test application and the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. The VA data were compared using a t-test, linear regression and Bland–Altman analysis. Results There was no significant difference in the mean absolute difference in VA (log of minimum angle of resolution (logMAR)=0.11; p = 0.82). Eye Chart Pro and Standard ETDRS Chart measures were also not significantly different ( p = 0.98). However, there were significant differences between test methods in the low-vision group and the normally sighted group ( p > 0.0001 and p = 0.007, respectively). The Bland–Altman analysis showed a mean bias (difference) of –0.0005 logMAR between methods, and 95% limits of agreement of 0.298 and –0.299 logMAR. Discussion The ETDRS chart function on the Eye Chart Pro application can reliably measure VA across a range, from normally sighted patients to those with low vision.

scholarly journals Comparison of pulmonary vein sizing by transesophageal echocardiogram and by direct angiogram

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
N Bachani ◽  
R Vadivelu ◽  
A Bagchi ◽  
JP Jadwani ◽  
GK Panicker ◽  
...  
Keyword(s):  
Left Atrium ◽  
Pulmonary Vein ◽  
Interatrial Septum ◽  
T Test ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Funding Sources ◽  
Chamber View ◽  
The Right ◽  
Paired T Test

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein (PV) anatomy and sizing is important to know before performing PV isolation. This information is conventionally obtained by angiography or by CT scan. Aim We undertook this study to identify and measure the PVs during TEE studies and validate these against angiography. Method 17 consecutive patients due to undergo PV isolation for paroxysmal atrial fibrillation were analysed. Using TEE, the PVs were visualised (Upper panel) as follows:  i) From the mid-esophageal four chamber view, the chamber probe was turned to the right at 110-130º for the bicaval view, where the RSPV was seen entering the left atrium adjacent to the SVC. ii) At 0º the SVC was imaged in its short axis, and the probe advanced till the interatrial septum was seen. The angle was changed to 30º to visualise the right inferior PV (RIPV). iii) From the two chamber view (70-90º), the probe was turned to the left and withdrawn to display the left superior PV (LSPV) entering the left atrium parallel to the appendage.iv) Keeping the LSPV in focus, the angle was changed to 135º and the probe advanced till the AV groove, where the left inferior PV (LIPV) was visualised. After transseptal puncture, each PV was cannulated. The PV angiograms were performed in several projections to obtain the best PV profile (lower panel). Using electronic callipers, each PV was measured within 1 cm of its entry into the left atrium, after having received all tributaries. Those PVs were considered for analysis which were measured by both TEE and angiography. The paired ‘T’ test was used to compare the PV diameters by TEE and angiography and the Bland Altman analysis was done to see the level of agreement. Results Of a total of 68 PVs, 62 could be adequately visualised by TEE and 50 by angiography. These 50 PVs were measured using both methods. The diameters of the PVs measured by TEE and angiography were not statistically different by the paired t test; LSPV14 ± 1.8 mm v/s 14.4 ± 2.1 mm; RSPV 13 ± 1.8 mm v/s 14.6 ± 3.5 mm; LIPV 11.9 ± 2.1 vs 13.2 ± 2.8 mm and RIPV 10.5 ± 2.7 vs 12.1 ± 2.9 mm. Bland Altman analysis showed most PV sizes estimated by TEE and angiography lay within limits of agreement. Conclusions A majority of PVs can be visualised by TEE using a defined protocol. TEE is a good technique to visualise and assess the size of PVs, avoiding the need for contrast medium and radiation. Abstract Figure. TEE and angiographic images of PVs

scholarly journals Comparison of Rumen Fluid pH by Continuous Telemetry System and Bench pH Meter in Sheep with Different Ranges of Ruminal pH

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Leonardo F. Reis ◽  
Antonio H. H. Minervino ◽  
Carolina A. S. C. Araújo ◽  
Rejane S. Sousa ◽  
Francisco L. C. Oliveira ◽  
...  
Keyword(s):  
Lactic Acidosis ◽  
Continuous Measurement ◽  
Rumen Fluid ◽  
Measurement Methods ◽  
Telemetry System ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Ruminal Ph ◽  
Rumen Ph ◽  
Paired Analysis

We aimed to compare the measurements of sheep ruminal pH using a continuous telemetry system or a bench pH meter using sheep with different degrees of ruminal pH. Ruminal lactic acidosis was induced in nine adult crossbred Santa Ines sheep by the administration of 15 g of sucrose per kg/BW. Samples of rumen fluid were collected at the baseline, before the induction of acidosis (T0) and at six, 12, 18, 24, 48, and 72 hours after the induction for pH measurement using a bench pH meter. During this 72-hour period, all animals had electrodes for the continuous measurement of pH. The results were compared using the Bland-Altman analysis of agreement, Pearson coefficients of correlation and determination, and paired analysis of variance with Student’st-test. The measurement methods presented a strong correlation (r=0.94,P<0.05) but the rumen pH that was measured continuously using a telemetry system resulted in lower values than the bench pH meter (overall mean of 5.38 and 5.48, resp.,P=0.0001). The telemetry system was able to detect smaller changes in rumen fluid pH and was more accurate in diagnosing both subacute ruminal lactic acidosis and acute ruminal lactic acidosis in sheep.

Measurement of the normal feline pituitary gland in brachycephalic and mesocephalic cats

2017 ◽  
Vol 20 (6) ◽  
pp. 578-586 ◽  
Author(s):  
Thomas Christian Häußler ◽  
Kerstin Heike von Pückler ◽  
Cetina Thiel ◽  
Sylke Enderlein ◽  
Klaus Failing ◽  
...  
Keyword(s):  
Body Weight ◽  
Pituitary Gland ◽  
Significant Influence ◽  
Surgical Intervention ◽  
T Test ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Weight Range ◽  
The Mean ◽  
Fast Field

Objectives The purpose of this study was to determine differences in normal feline pituitary dimensions in brachycephalic and mesocephalic cats as a basis for establishing cryohypophysectomy in cats. Methods Measurements were performed on sagittal T2-weighted and transverse post-gadolinium T1-weighted or T1 3D fast field echo-weighted MRI images. A total of 32 brachycephalic and 27 mesocephalic cats were examined. Inter-observer reproducibility was assessed by t-test and Bland–Altman analysis. Results The cats were 0.6–15.9 years of age with a body weight range of 1.84–6.60 kg. For brachycephalic cats, the mean pituitary gland sagittal height was 2.15 ± 0.15 mm, pituitary gland transverse height was 2.42 ± 0.21 mm, pituitary gland transverse width was 4.44 ± 0.27 mm and pituitary gland sagittal length was 3.14 ± 0.30 mm. In mesocephalic cats, the pituitary gland dimensions were 2.94 ± 0.16 mm, 3.09 ± 0.26 mm, 4.73 ± 0.31 mm and 4.88 ± 0.30 mm for pituitary gland sagittal height, transverse height, transverse width and sagittal length, respectively. There was a highly significant correlation between brachycephalic and mesocephalic cats and pituitary gland height and length ( P <0.0001), respectively. Sex also had an effect on pituitary gland measurements. Neutering status had no significant effect on hypophyseal measurements. Age had a significant influence on pituitary gland height, width and length in the brachycephalic population. Inter-observer reproducibility was good to excellent. Conclusions and relevance The different pituitary measurements in brachycephalic and mesocephalic cats has to be considered if surgery comes into question. There are ranges in pituitary gland sizes, even among the mesocephalic cat population. Thus, exact measuring of the pituitary gland is crucial before any surgical intervention.

Reply: Bland-Altman analysis for pupillometer comparison

2010 ◽  
Vol 36 (10) ◽  
pp. 1803-1804
Author(s):  
Magdalena Scheffel ◽  
Christoph Kuehne ◽  
Thomas Kohnen
Keyword(s):  
Altman Analysis ◽  
Bland Altman Analysis

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

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