Crowding in Children's Visual Acuity Tests—Effect of Test Design and Age

Validation of the Waterloo Differential Visual Acuity Test (WatDAT) and Comparison With Existing Pediatric Tests of Visual Acuity

Purpose

The new Waterloo Differential Acuity Test (WatDAT) is designed to allow recognition visual acuity (VA) measurement in children before they can typically undertake matching tests. The study purpose was to validate WatDAT in adults with normal and reduced VA.

Methods

Eighty adults (18 to <40 years of age) participated (32 normal VA, 12 reduced VA, and 36 simulated reduced VA). Monocular VA was measured on two occasions in random order for WatDAT (versions with 3 and 5 distractors for Faces and Patti Pics house among circles), Lea Symbols, Kay Pictures and Patti Pics matching tests, Teller Acuity Cards, Cardiff Acuity Test, and Early Treatment Diabetic Retinopathy Study (ETDRS) letter chart. Pediatric tests were validated against ETDRS using limits of agreement (LoA), sensitivity, and specificity. The LoA for repeatability were also determined.

Results

WatDAT showed minimal bias compared with ETDRS, and LoAs, which were similar to pediatric matching tests (0.241-0.250). Both preferential looking tests showed higher bias and LoAs than ETDRS. Matching tests showed good agreement with ETDRS, except for Kay Pictures and Lea Uncrowded test, which overestimated VA. WatDAT showed high sensitivity (>0.96) and specificity (>0.79), which improved with criterion adjustment and were significantly higher than for the preferential looking tests. LoA for repeatability for WatDAT 3 Faces and WatDAT 5 Faces were comparable with the ETDRS.

Conclusions

WatDAT demonstrates good agreement and repeatability compared with the gold-standard ETDRS letter chart, and performed better than preferential looking tests, the alternative until a child can undertake a matching VA test.

Translational Relevance

Good validity of the Waterloo Differential Acuity Test was demonstrated in adults as a first step to showing its potential for detecting childhood visual disorders.

Retrobulbar Blood Flow Parameters in Patients With Anisometropic Amblyopia

Introduction We aim to compare retrobulbar blood flow parameters between the amblyopic eye and the fellow eye in patients with anisometropic amblyopia. Methods Peak systolic velocity (PSV) and end-diastolic velocity (EDV) of the ophthalmic artery (OA), central retinal artery (CRA), and posterior ciliary artery (PCA) were measured by color Doppler imaging (CDI), and the resistivity index (RI) and pulsatility index (PI) were calculated in 62 patients aged 12-40 years with anisometropic amblyopia. Results The mean PSV values of OA, CRA, and PCA in amblyopic and fellow eyes were 30.38 ± 10.34, 8.45 ± 2.27, and 8.03 ± 2.77, and 33.73 ± 14.46, 8.35 ± 2.05, and 8.81 ± 2.77, respectively. The mean EDV values of OA, CRA, and PCA in amblyopic and fellow eyes were 6.86 ± 2.64, 1.47 ± 1.59, and 1.94 ± 2.03, and 8.57 ± 4.30, 1.80 ± 1.73, and 2.32 ± 1.20, respectively. The mean RI values of OA, CRA, and PCA in amblyopic and fellow eyes were 0.77 ± 0.10, 0.85 ± 0.14, and 0.78 ± 0.15, and 0.75 ± 0.07, 0.79 ± 0.20, and 0.74 ± 0.13, respectively. OA-PSV and OA-EDV values were significantly lower in the amblyopic eye than in the healthy eye (p < 0.05). OA-RI values were significantly higher (p < 0.05) in the amblyopic eye than in the healthy eye. Conclusions Considering the decrease in PSV and EDV and the increase in RI, which are the blood flow parameters of the amblyopic eye, our study may provide guidance to focus on increasing blood flow in the treatment of amblyopia.

Crowding can impact both low and high contrast visual acuity measurements

The adverse impact of adjacent contours on letter visual acuity is known as crowding but there is conflicting evidence that foveal crowding may be reduced or disappears under low contrast conditions. Potential differences in foveal crowding with contrast on clinical measurements of visual acuity, including test–retest repeatability, were assessed. Visual acuity was measured at the fovea on adult participants with normal vision under three different contrast levels (− 90, − 10 and − 5%). Three rows of 5 letters, each row differing in size by 0.05 logarithm of the minimum angle of resolution (logMAR) from largest to smallest were displayed at the center of a monitor. Crowding was varied by varying the separation between horizontally adjacent letters from 100% optotype size to 50%, 20% and 10% optotype size. Inter-row spacing was proportional to optotype size. Observers read the letters on the middle row only. Measurements continued by reducing the size of the letters until 3 or more errors were made and were repeated on two separate days. Visual acuity worsened as both letter contrast decreased and inter-optotype separation reduced (expressed as a percentage of letter width). When expressed in minutes of arc of separation the impact of crowding was the same across all contrasts. Crowding occurs for both high and low contrast charts and should be considered when assessing low contrast visual acuity. Test–retest repeatability showed little or no dependence on either contrast or inter-optotype separation.

The Effect of Test Method on Visual Acuity in School Children Aged 4–5

Purpose:

This study compared two different methods of testing visual acuity (VA) in children aged 4–5 years (The UK’s school vision screening target age). A conventional vision test method was compared to a reversed presentation order of logMAR, where letters are presented in ascending size order up to vision threshold. Threshold VA, test duration and concentration were compared, to assess the most accurate and efficient method of VA testing in this age group, to determine the most clinically and cost-effective method for vision screening.

Methods:

Thirty-four participants completed the study (15 males, 19 females, age range 53–65 months, mean age 59 months’ ±3.7 months). VA was measured in logMAR. Keeler Crowded logMAR screening plates determined the starting line on the vision chart to ensure the initial optotype size was either seen or not seen for the conventional and reversed test methods respectively. Test duration was measured in seconds and a concentration score was given by the examiner.

Results:

The median VA was 0.17 logMAR for each test method. There was no significant difference in the VA outcomes between each test method (p = 0.46). The reversed method was significantly quicker to complete, with a median reduction in test duration of 28 seconds (p = 0.002). There was no difference in concentration levels between the test methods.

Conclusion:

Both test methods gave the same VA threshold, and are therefore comparable. The reversed method was significantly quicker to complete which could benefit school vision screening services and busy clinical contexts.

Analysis of the Reliability and Repeatability of Distance Visual Acuity Measurement with EyeSpy 20/20

Background

Visual acuity is a critical component of visual function assessment for all ages. Standardized vision testing protocols may help prevent testing inconsistencies resulting from variations in test administration and interpretation of different examiners. However, most vision assessments outside of research settings, including in doctor’s offices, rarely employ standardized protocols. Validated protocols such as the Early Treatment for Diabetic Retinopathy Study (ETDRS) are frequently employed by vision researchers to ensure accurate and repeatable visual acuity measurements.

Methods

This study evaluates a desktop-based standardized vision testing algorithm (EyeSpy 20/20) specifically designed for use on mobile electronic platforms. Subjects were tested on a desktop version of the EyeSpy software for both the accuracy and duration of measurement of visual acuity and compared to a e-ETDRS chart in a randomized sequence. Children were recruited for this study and tested between two different visual acuity measurement systems. Bland–Altman analysis and correlation tests were done.

Results

Hundred and ten children were recruited for the study. The EyeSpy 20/20 visual acuity testing algorithm as tested with the desktop version was non-inferior to the gold standard e-ETDRS testing algorithm on a desktop platform, but statistically faster to implement when administered on the same electronic testing platform.

Conclusion

EyeSpy 20/20 is a promising tool for vision screening and visual acuity evaluation in children.

Visual acuity percentile curves in a Spanish paediatric population

PURPOSE

The main objective of this study is to obtain percentile curves of monocular and binocular visual acuity on a decimal scale in a Spanish population aged between 3 and 12 years old.

MATERIALS AND METHOD

Descriptive, observational and transversal study which included children between 3 and 12 years old without any known eye and/or systemic diseases. The selection of the sample was made by means of a convenience sampling method carried out in three schools and a hospital of the Community of Madrid. Far monocular and binocular visual acuity was measured using the Bueno Matilla vision unit on a decimal scale, both for monocular and binocular tests. The test used was the symmetrical letters test included with this unit. A descriptive statistic was performed and the visual acuity percentile values obtained were 5, 10, 25, 50, 75, 90 and 95.

RESULTS

The visual acuity of 1300 children was evaluated and analysed. In all the percentile curves obtained, an increase in age-related visual acuity has been observed, reaching a value close to the unit for the 50th percentile, around five years and three months of age, under monocular conditions and somewhat earlier in binocular conditions.

CONCLUSION

Although the type of sampling performed does not allow a generalization to the entire population, these percentile curves may help the paediatric professional to decide the referral of the relevant child to the eyecare professional, so that certain conditions, like amblyopia or the early stages of school myopia may be early detected.

Actual Visual Acuity Demands in the Classroom

PURPOSE

To address the knowledge gap regarding the actual acuity requirements needed in typical kindergarten through grade 12 classrooms by determining an actual logarithm of the minimum angle of resolution (logMAR) and contrast sensitivity requirements in a sample of classrooms for kindergarten through grade 12 in New York City.

METHODS

Measurements of classroom dimensions with specific attention to viewing distances were made in public and private school classrooms, at various grade levels from kindergarten through grade 12, in New York City. The dimensions of typical text shown to students on classroom smartboards and whiteboards was measured and the mean and range of logMAR values were calculated for various seating locations within the classrooms. Contrast between text and background was estimated by comparing digital images of actual classroom text to Pelli-Robson contrast sensitivity charts.

RESULTS

Fourteen classrooms in five schools were evaluated. Classroom dimensions varied from 8 × 10 feet to 23 × 23 feet. Mean logMAR values of lower case text on smartboards and whiteboards varied from 0.93 ± 0.29 (range: 0.83 to 1.32) in the center of the front row to 0.46 ± 0.21 (range: 0.10 to 0.79) in the center of the back row (P < .001). Contrast was also variable, being highest for black markers on whiteboards (0.00) and lowest on smartboards (0.15 to 0.60). Neither logMAR nor contrast sensitivity values varied significantly by grade level or school (P > .50 for both).

CONCLUSIONS

The data reveal that logMAR demands and contrast vary substantially from classroom to classroom and within a classroom based on room dimensions and seating. Although generally supporting current acuity-based pediatric vision screening referral guidelines, the data also provide insight into the potential impact of reduced visual acuity and seating location on visual performance in the classroom. These findings suggest the need to develop logMAR and contrast standards that optimize visual content in classrooms while accommodating a wider range of visual capabilities. [J Pediatr Ophthalmol Strabismus. 2021;58(1):48-54.].

Effect of Posterior Corneal Vesicles on Corneal Endothelial Cell Density and Anisometropic Amblyopia

PURPOSE

To evaluate the effect of corneal vesicles in patients with posterior corneal vesicles (PCV) on corneal endothelial cell (CEC) density and the acquisition of amblyopia.

METHODS

In this retrospective study of patients with PCV (18 eyes of 14 patients), CEC density was examined by noncontact specular microscopy during each follow-up examination. Best-corrected visual acuity and the objective refractive error were also examined.

RESULTS

Of the 14 total patients, 10 were diagnosed with PCV and 4 were diagnosed with bilateral suspected PCV or posterior polymorphous corneal dystrophy (PPCD), and in all patients, no ocular abnormality other than corneal vesicles was observed. In patients with PCV and patients with bilateral suspected PCV or PPCD, mean CEC density was 1131 ± 338 and 1095 ± 492 cells/mm, respectively. In both PCV group and the bilateral suspected PCV or PPCD-group patients who were followed for 164.2 ± 25.4 months (range: 123-186 months), CEC density tended not to decrease. In patients with PCV, the mean best-corrected visual acuity of the unaffected eyes was significantly higher than that of the affected eyes with corneal vesicles (-0.10 ± 0.06 and 0.05 ± 0.13, respectively, P = 0.012). Four of 9 affected eyes (1 eye was excluded because of retinal atrophy) exhibited amblyopia, and all 4 eyes had astigmatism higher than 2 diopters.

CONCLUSIONS

Although CEC density of patients with PCV in this study was found to be stable over a long-term follow-up period, strict attention should be given to the possibility of amblyopia in eyes with PCV.

Different visual development: norms for visual acuity in children with Down's syndrome

BACKGROUND

Visual acuity is known to be poorer in children with Down's syndrome than in age-matched controls. However, to date, clinicians do not have access to norms for children with Down's syndrome that allow differential discrimination of healthy from anomalous visual development in this population.

METHODS

The Down's Syndrome Vision Research Unit at Cardiff University has been monitoring visual development in a large cohort of children since 1992. Cross-sectional data on binocular visual acuity were retrospectively analysed for 159 children up to 12 years of age in order to establish binocular acuity norms. Longitudinal binocular acuity data were available for nine children who were seen regularly over the 12 years age-range. Monocular acuity was successfully recorded less often in the cohort, but analysis of scores for 69 children allowed assessment of inter-ocular acuity differences and binocular summation.

RESULTS

In comparison with published norms for the various acuity tests used, binocular acuity was consistently poorer in children with Down's syndrome from the age of three years and stabilised at around 0.25 logMAR from the age of four years. Inter-ocular acuity difference and binocular summation were both 0.06 logMAR, which is similar to the reported values in children without Down's syndrome.

CONCLUSIONS

The study provides eye-care practitioners with the expected values for binocular acuity in children with Down's syndrome and demonstrates the visual disadvantage that children with Down's syndrome have when compared with their typically developing peers. The results emphasise the responsibility that practitioners have to notify parents and educators of the relatively poor vision of children with Down's syndrome, and the need for classroom modifications.

Effect of simulated refractive error on adult visual acuity for paediatric tests

PURPOSE

Although vanishing optotype preferential-looking tasks are commonly used to measure visual acuity (VA), the relative sensitivity of these tests to refractive error is not well understood. To address this issue, we determined the effect of spherical and astigmatic simulated refractive errors on adult VA measures obtained using vanishing optotypes, picture optotypes and Sloan letters.

METHODS

VA was determined uniocularly for adults under conditions of spherical (0.0-3.0 DS; n = 23) and astigmatic (0.0-3.0 DC at 90° and 180°; n = 20) defocus using the Cardiff Acuity Test (vanishing optotypes), crowded linear Lea Symbols (picture-optotype recognition task) and the Early Treatment of Diabetic Retinopathy Study (ETDRS) letter chart.

RESULTS

The Cardiff Acuity Test over-estimated VA compared with the Lea Symbols and ETDRS charts in both focused and defocused conditions. The mean difference between the Cardiff Acuity Test and the ETDRS chart was 0.31 logMAR (95% limits of agreement (LOA) 0.10-0.52 logMAR) in focused conditions and 0.64 logMAR (95% LOA 0.25-1.05 logMAR) with 3D of spherical defocus. Defocus degraded VA on all charts, however there was a significant chart-by-defocus interaction whereby the Cardiff Acuity Test was more resistant to the effects of both spherical (P < 0.0001) and cylindrical (P < 0.001) optical defocus than the recognition acuity tasks at all defocus levels.

CONCLUSION

Although the Cardiff Acuity Test provides an easy method for VA measurement in infants and toddlers, there is a considerable overestimation of VA compared with recognition acuity tasks particularly in the presence of defocus. A simple correction factor (of for example three lines overestimate) cannot be applied to Cardiff acuity measures as there is increasing over-estimation of VA with increasing defocus. Infants with significant refractive error may fall within normal visual acuity ranges for the Cardiff Acuity Test.

Do picture-based charts overestimate visual acuity? Comparison of Kay Pictures, Lea Symbols, HOTV and Keeler logMAR charts with Sloan letters in adults and children

Purpose

Children may be tested with a variety of visual acuity (VA) charts during their ophthalmic care and differences between charts can complicate the interpretation of VA measurements. This study compared VA measurements across four pediatric charts with Sloan letters and identified chart design features that contributed to inter-chart differences in VA.

Methods

VA was determined for right eyes of 25 adults and 17 children (4–9 years of age) using Crowded Kay Pictures, Crowded linear Lea Symbols, Crowded Keeler logMAR, Crowded HOTV and Early Treatment of Diabetic Retinopathy Study (ETDRS) charts in focused and defocused (+1.00 DS optical blur) conditions. In a separate group of 25 adults, we compared the VA from individual Kay Picture optotypes with uncrowded Landolt C VA measurements.

Results

Crowded Kay Pictures generated significantly better VA measurements than all other charts in both adults and children (p < 0.001; 0.15 to 0.30 logMAR). No significant differences were found between other charts in adult participants; children achieved significantly poorer VA measurements on the ETDRS chart compared with pediatric acuity tests. All Kay Pictures optotypes produced better VA (p < 0.001), varying from -0.38 ± 0.13 logMAR (apple) to -0.57 ± 0.10 logMAR (duck), than the reference Landolt C task (mean VA -0.19 ± 0.08 logMAR).

Conclusion

Kay Pictures over-estimated VA in all participants. Variability between Kay Pictures optotypes suggests that shape cues aid in optotype determination. Other pediatric charts offer more comparable VA measures and should be used for children likely to progress to letter charts.

Childhood amblyopia: current management and new trends

INTRODUCTION OR BACKGROUND

With a prevalence of 2-5%, amblyopia is the most common vision deficit in children in the UK and the second most common cause of functional low vision in children in low-income countries.

SOURCES OF DATA

Pubmed, Cochrane library and clinical trial registries (clinicaltrials.gov, ISRCTN, UKCRN portfolio database).

AREAS OF AGREEMENT

Screening and treatment at the age of 4-5 years are cost efficient and clinically effective. Optical treatment (glasses) alone can improve visual acuity, with residual amblyopia treated by part-time occlusion or pharmacological blurring of the better-seeing eye. Treatment after the end of the conventional 'critical period' can improve vision, but in strabismic amblyopia carries a low risk of double vision.

AREAS OF CONTROVERSY

It is not clear whether earlier vision screening would be cost efficient and associated with better outcomes. Optimization of treatment by individualized patching regimes or early start of occlusion, and novel binocular treatment approaches may enhance adherence to treatment, provide better outcomes and shorten treatment duration.

GROWING POINTS

Binocular treatments for amblyopia.

AREAS TIMELY FOR DEVELOPING RESEARCH

Impact of amblyopia on education and quality of life; optimal screening timing and tests; optimal administration of conventional treatments; development of child-friendly, effective and safe binocular treatments.

Brief Report: Vision in Children with Autism Spectrum Disorder: What Should Clinicians Expect?

Anomalous visual processing has been described in individuals with autism spectrum disorder (ASD) but relatively few studies have profiled visual acuity (VA) in this population. The present study describes presenting VA in children with ASD (n = 113) compared to typically developing controls (n = 206) and best corrected visual acuity (BCVA) in a sub-group of children with ASD (n = 29). There was no statistically significant difference in presenting VA between groups (z = -1.75, p = 0.08); ASD group median VA (interquartile range, IQR) -0.05 logMAR (IQR: -0.125 to 0.025 logMAR) and typically developing control group -0.075 logMAR (IQR: -0.150 to -0.025 logMAR). Median BCVA was -0.175 logMAR (IQR: -0.200 to -0.125 logMAR) for the ASD sub-group. Clinicians should not anticipate reduced VA when assessing children with ASD.

Preschool children's vision screening in New Zealand: a retrospective evaluation of referral accuracy

OBJECTIVES

To assess the accuracy of preschool vision screening in a large, ethnically diverse, urban population in South Auckland, New Zealand.

DESIGN

Retrospective longitudinal study.

METHODS

B4 School Check vision screening records (n=5572) were compared with hospital eye department data for children referred from screening due to impaired acuity in one or both eyes who attended a referral appointment (n=556). False positive screens were identified by comparing screening data from the eyes that failed screening with hospital data. Estimation of false negative screening rates relied on data from eyes that passed screening. Data were analysed using logistic regression modelling accounting for the high correlation between results for the two eyes of each child.

PRIMARY OUTCOME MEASURE

Positive predictive value of the preschool vision screening programme.

RESULTS

Screening produced high numbers of false positive referrals, resulting in poor positive predictive value (PPV=31%, 95% CI 26% to 38%). High estimated negative predictive value (NPV=92%, 95% CI 88% to 95%) suggested most children with a vision disorder were identified at screening. Relaxing the referral criteria for acuity from worse than 6/9 to worse than 6/12 improved PPV without adversely affecting NPV.

CONCLUSIONS

The B4 School Check generated numerous false positive referrals and consequently had a low PPV. There is scope for reducing costs by altering the visual acuity criterion for referral.

A systematic review on 'Foveal Crowding' in visually impaired children and perceptual learning as a method to reduce Crowding

BACKGROUND

This systematic review gives an overview of foveal crowding (the inability to recognize objects due to surrounding nearby contours in foveal vision) and possible interventions. Foveal crowding can have a major effect on reading rate and deciphering small pieces of information from busy visual scenes. Three specific groups experience more foveal crowding than adults with normal vision (NV): 1) children with NV, 2) visually impaired (VI) children and adults and 3) children with cerebral visual impairment (CVI). The extent and magnitude of foveal crowding as well as interventions aimed at reducing crowding were investigated in this review. The twofold goal of this review is : [A] to compare foveal crowding in children with NV, VI children and adults and CVI children and [B] to compare interventions to reduce crowding.

METHODS

Three electronic databases were used to conduct the literature search: PubMed, PsycINFO (Ovid), and Cochrane. Additional studies were identified by contacting experts. Search terms included visual perception, contour interaction, crowding, crowded, and contour interactions.

RESULTS

Children with normal vision show an extent of contour interaction over an area 1.5-3× as large as that seen in adults NV. The magnitude of contour interaction normally ranges between 1-2 lines on an acuity chart and this magnitude is even larger when stimuli are arranged in a circular configuration. Adults with congenital nystagmus (CN) show interaction areas that are 2× larger than those seen adults with NV. The magnitude of the crowding effect is also 2× as large in individuals with CN as in individuals with NV. Finally, children with CVI experience a magnitude of the crowding effect that is 3× the size of that experienced by adults with NV.

CONCLUSIONS

The methodological heterogeneity, the diversity in paradigms used to measure crowding, made it impossible to conduct a meta-analysis. This is the first systematic review to compare crowding ratios and it shows that charts with 50% interoptotype spacing were most sensitive to capture crowding effects. The groups that showed the largest crowding effects were individuals with CN, VI adults with central scotomas and children with CVI. Perceptual Learning seems to be a promising technique to reduce excessive foveal crowding effects.