Visual acuity tests using chart, line, and single optotype in healthy and amblyopic children

doi:10.1016/S1091-8531(99)70077-7

Journal of American Association for Pediatric Ophthalmology and Strabismus

Volume 3, Issue 2, April 1999, Pages 94-97

https://doi.org/10.1016/S1091-8531(99)70077-7 Get rights and content

Abstract

Purpose: The purpose of this study was to evaluate the difference between full chart, single line, and single optotypes visual acuity (VA) test results in healthy and amblyopic children. Methods: Thirty-five children with amblyopia (20 with strabismus and 15 with anisometropia) and 40 ophthalmologically normal age-matched children were examined. The mean age of the patients in the study and control groups did not differ significantly (P = .9). A commercial projector that projected tumbling-E randomly placed optotypes was used. The VA of the amblyopic eye of the patients in the study group and the right eye of the patients in the control group was examined first using a full chart of optotypes, then using a single line of optotypes, and finally with individual symbols. The procedure was repeated with the other eye. Results: LogMAR VA improved when the full chart was substituted with a single line, and improved by a similar increment further with single optotypes, in both the study and control groups. VA improved significantly more in eyes with amblyopia than in control subjects. Results were not influenced by age. Conclusion: VA testing using a single line gives better, sometimes misleading results, than tests with a full chart because it reduces but does not eliminate the crowding effect. When using a device that can employ more than 1 mode, the exact test mode should be specified and maintained throughout the follow-up. (J AAPOS 1999;3:94-7)

Section snippets

Patients and methods

Two groups of children were studied, 35 children with amblyopia (5 to 12 years of age; mean, 7.33 ± 1.8 years) and 40 age-matched (5 to 12 years of age; mean, 7.91 ± 1.9 years) healthy control subjects with normal vision.

The 35 children with amblyopia treated in our Pediatric Ophthalmology clinic underwent slit lamp biomicroscopy, dilated fundus examination, cycloplegic refraction, and ocular alignment examination. Inclusion criteria included a difference in best-corrected VA test results

Results

The mean age was statistically similar in the study and control groups (P = .9) and in the strabismic and anisometropic subgroups (P = .143). Because right and left eye VA did not differ significantly when tested using single optotype, line, or chart in the control group (P = .261, .457, and .826 respectively), we used the mean VA of the right and left eyes of each subject for further statistical analysis.

The average VA in all test modes is presented in Figure 1 and in Table 1.

. VA results using

Discussion

The fact that many patients with amblyopia and even children and adults with normal vision achieve better VA results when tested with single optotype than with line or chart VA tests is well documented. 2, 3, 4, 5 Single optotypes yield greater testability, which is particularly important in easily distracted young children. On the other hand, a “crowded” chart may be necessary for the detection and follow-up of amblyopia.⁷

The various methods used for testing VA in children and adults have

References (15)

J Stuart et al.
A study of separation difficulty: its relationship to visual acuity in normal and amblyopic eyes
Am J Ophthalmol
(1962)
DW Rodier et al.
Assessment of young amblyopes: array vs single pictures acuities
Ophthalmology
(1985)
FL Ferris et al.
New visual acuity charts for clinical research
Am J Ophthalmol
(1982)
HM Burian et al.
Binocular vision and ocular motility
MC Flom et al.
Contour interaction and visual resolution
Science
(1963)
ME. Woodruff
Observation on the visual acuity of children during the first five years of life
Am J Optom
(1972)
HM Burian et al.
Binocular vision and ocular motility

There are more references available in the full text version of this article.

Cited by (27)

Crowding and visual acuity measured in adults using paediatric test letters, pictures and symbols
2016, Vision Research
Citation Excerpt :
Visual acuity for a target optotype measured with surrounding features is worse than that measured when isolated (Flom, Weymouth, & Kahneman, 1963; Formankiewicz & Waugh, 2013; Jacobs, 1979; Leat, Li, & Epp, 1999). This negative spatial interaction effect on target resolvability is generally referred to as “crowding” and may be greater in amblyopes than in individuals with normal vision (Hess, Dakin, Tewfik, & Brown, 2001; Levi, Hariharan, & Klein, 2002; Mayer & Gross, 1990; Morad, Werker, & Nemet, 1999; but see Flom, Weymouth, & Kahneman, 1963; Stuart & Burian, 1962). Contour interaction was proposed to be a sub-component of crowding (along with attention and eye movements) by Flom et al. (1963) and refers to the detrimental effects of bars (or contours) that surround the target.
Crowding refers to the degradation of visual acuity for target optotypes with, versus without, surrounding features. Crowding is important clinically, however the effect of target-flanker spacing on acuity for symbols and pictures, compared to letters, has not been investigated. Five adults with corrected-to-normal vision had visual acuity measured for modified single target versions of Kay Pictures, Lea Symbols, HOTV and Cambridge Crowding Cards, tests. Single optotypes were presented in isolation and with surrounding features placed 0–5 stroke-widths away. Visual acuity measured with Kay Picture optotypes is 0.13–0.19 logMAR better than for other test optotypes and varies significantly across picture. The magnitude of crowding is strongest when the surrounding features abut, or are placed 1 stroke-width away from the target optotype. The slope of the psychometric function is steeper in the region just beyond maximum crowding. Crowding is strongest and the psychometric function steepest, with the Cambridge Crowding Cards arrangement, than when any single optotype is surrounded by a box. Estimates of crowding extent are less variable across test when expressed in units of stroke-width, than optotype-width. Crowding for single target presentations of letters, symbols and pictures used in paediatric visual acuity tests can be maximised and made more sensitive to change in visual acuity, by careful selection of optotype, by surrounding the target with similar flankers, and by using a closer target-flanker separation than half an optotype-width.
The Handy Eye Check: A mobile medical application to test visual acuity in children
2014, Journal of AAPOS
To compare visual acuity results obtained with the Handy Eye Chart to results obtained using the Handy Eye Check, a mobile medical application that electronically presents isolated Handy Eye Chart optotypes according the Amblyopia Treatment Study (ATS) protocol.
Consecutive patients 6-18 years of age presenting for eye examinations between May 30, 2012, and June 26, 2012, were invited to participate. Monocular visual acuity testing was performed on the subject's poorer-seeing eye using both the Handy Eye Check and the Handy Eye Chart under the same conditions. Visual acuity was first tested using the mobile application, then using the chart, followed by repeated application testing. Patients were excluded if they were unable to undergo the required visual acuity testing or if visual acuity in the worse-seeing eye was less than 20/200 (for validity testing, but not reliability testing).
There was a strong linear correlation (r = 0.92) and a mean difference in acuity of −0.005 logMAR, or less than one letter (95% CI, −0.03 to 0.02), between the two tests. The 95% limits of agreement were ± 2 lines. Test–retest reliability was high, with 81% of retest scores within 0.1 logMAR (5 letters) and 100% within 0.2 logMAR (10 letters), an intraclass correlation coefficient of 0.93, and a standard error of measurement of 0.08.
The Handy Eye Check mobile application compares similarly to the Handy Eye Chart as a valid and reliable test of visual acuity in children age 6-18 years.
Normative pediatric visual acuity using single surrounded HOTV optotypes on the Electronic Visual Acuity Tester following the Amblyopia Treatment Study protocol
2008, Journal of AAPOS
Citation Excerpt :
Although there is some variability in visual acuity, the data of the present study appear to be in agreement with those from other studies. Note, however, that the visual acuity scores of participants from the three studies that report the best acuities used lenient optotype detection criteria,15 testing protocols that allowed numerous optotype identification mistakes16 or potential learning effects.17 It is also of particular interest to compare the visual acuity data reported here to those of the fellow eye of children with amblyopia who were assessed recently using the ATS protocol.18
To provide normative pediatric visual acuity data using HOTV optotypes presented on the Electronic Visual Acuity Tester following the Amblyopia Treatment Study (ATS) protocol.
Monocular testing was conducted on 384 healthy full-term children ranging from 3 to 10 years of age (mean, 5.4 years; SD, 1.8 years). A total of 373 children completed monocular testing of each eye. In addition, 23 adults (mean, 28.7 years; SD, 4.9 years) were tested for comparison. Both monocular visual acuity and interocular acuity differences were recorded.
Mean visual acuity improved by slightly more than one line (0.12 logMAR) from 3 years of age to adulthood, increasing from 0.08 logMAR to −0.04 logMAR (F_6,400 = 26.3, p < 2.0 × 10⁻²⁶). At all ages, mean interocular acuity difference was less than one line on a standard acuity chart (overall mean difference = 0.04 logMAR; SD, 0.06 logMAR).
These results represent the first normative data reported for HOTV optotypes using the ATS protocol on the Electronic Visual Acuity Tester. These data may play an important role in clinical practice, screening, and clinical research.
The Sonksen logMAR test of visual acuity: II. Age norms from 2 years 9 months to 8 years
2008, Journal of AAPOS
Citation Excerpt :
The strengths of the study are a test design1,27 that adheres to international guidelines for standardized logMAR tests,5-9 test administration according to a developmentally strong1,4,17,27 standardized test protocol,8,5 and age norms that are derived from a large and representative normative population sample13 using statistically strong methodology.18,26 Provision of age norms together with test design in close accord with the adult standard complies with recommendations for improving comparability of measurement from childhood into adulthood.3,28,29 The limitations of the study are that the centiles of visual acuity for crowded singles viewed binocularly are based on only one presentation at each level and that there were no serial measurements within the dataset with which to identify the extent to which children track centiles.
To establish age norms and interocular differences in visual acuity between 2 years 9 months and 8 years for the Sonksen logMAR Test.
Cross-sectional population-based study. Binocular measures of linear visual acuity were achieved in 2,940 children and monocular measures were achieved in 2,820 right eyes and 2,821 left eyes, respectively. Measures for both right and left eyes were achieved by 2,807. Asymmetric logistic models were used to construct smoothly changing age-related centile curves showing how visual acuity changes with age in a normative population sample.
All curves demonstrated an increase in visual acuity with age that was steepest between 2 years 9 months and 5 years 3 months. Equivalent centiles for linear visual acuity were better when viewed binocularly than monocularly; the difference was least between the 95th centiles (best levels) and greatest between the 5th centiles (worst levels). There were no clinically significant differences between group measures of visual acuity from right and left eyes—average within child difference 0.0095 logMAR units, 95% CI, 0.0059-0.013. Interocular differences did not vary significantly with age (p = 0.73). The 90th and 95th centiles for interocular difference were 0.125 and 0.175 log units, respectively.
This study demonstrates how visual acuity varied with age for the Sonksen logMAR Test and presents the findings in the clinically useful format of centile charts.
Effect of myopia on visual acuity measured with laser interference fringes
2006, Vision Research
The aim was to determine how visual acuity is affected by myopia when optical factors of the eye are controlled. Grating acuity was measured with interference fringes to avoid the effects of aberrations, and ocular biometry was used to compensate for differences in retinal image size among subjects. Distance spectacle refractions ranged from +2.25 to −14.75 D. The retinal magnification factor (RMF) in mm/deg was computed for each eye from the distance refraction, central corneal power and ultrasound biometry. A forced-choice orientation discrimination method was used to measure acuity for high-contrast 543 nm laser interference fringes in three retinal locations: the fovea, and at 4 deg and 10 deg eccentricity in the temporal retina. Acuity, expressed in c/deg and adjusted for spectacle magnification, was not significantly correlated with refraction at any of the three retinal locations. When acuity was converted to retinal spatial frequency units (c/mm) via the RMF, acuity decreased with increasing myopia at all three retinal locations (significantly at the fovea and at 10 deg eccentricity). Retinal acuity values in highly myopic subjects (>6 D) are consistent with retinal sampling distances that are larger than published values of human cone or ganglion cell spacing. The results imply that a highly myopic eye has retinal neurons that are more widely spaced than normal, but the increased axial length enlarges the retinal image enough to compensate for the retinal stretching. The data are consistent with a retinal stretching model that primarily affects the posterior pole.
Amblyopia characterization, treatment, and prophylaxis
2005, Survey of Ophthalmology
Citation Excerpt :
Another approach to achieving high testability and chart-equivalent “crowding” has been to use only a single chart line, with surround contours, as in the Glasgow Visual Acuity Test.95,354,472 Addition of the surround contour is significant because there is evidence that a non-surrounded single line produces indicated visual acuity half-way between the level of full chart visual acuity and single-optotype visual acuity.370 Although the Glasgow test has been shown more sensitive in detecting amblyopes than single optotype testing,354,472 it has not yet been validated for amblyopes against chart visual acuity and has for the most part in extant studies only been tested on samples of older (i.e., mean age of 5 years) preschoolers,95,354,472 many of whom could be tested on conventional visual acuity charts, leaving the test's utility with younger children unclear.
Amblyopia has a 1.6–3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5′-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63–83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2–3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

View all citing articles on Scopus

^☆: Reprint requests: Yair Morad MD, Tlalim 3, Rosh-Ha'ayin, 48630, Israel.

View full text

Major ArticlesVisual acuity tests using chart, line, and single optotype in healthy and amblyopic children☆

Abstract

Section snippets

Patients and methods

Results

Discussion

Am J Ophthalmol

Ophthalmology

Am J Ophthalmol

Binocular vision and ocular motility

Contour interaction and visual resolution

Science

Observation on the visual acuity of children during the first five years of life

Am J Optom

Binocular vision and ocular motility

Major Articles
Visual acuity tests using chart, line, and single optotype in healthy and amblyopic children☆