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The Clinical Profile of Moderate Amblyopia in Children Younger Than 7 Years
The Pediatric Eye Disease Investigator Group
Arch Ophthalmol. 2002;120:281-287.
ABSTRACT
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Objective To describe the demographic and clinical characteristics of a cohort
of children with moderate amblyopia participating in the Amblyopia Treatment
Study 1, a randomized trial comparing atropine and patching.
Methods The children enrolled were younger than 7 years and had strabismic,
anisometropic, or combined strabismic and anisometropic amblyopia. Visual
acuity, measured with a standardized testing protocol using single-surround
HOTV optotypes, was 20/40 to 20/100 in the amblyopic eye, with an intereye
acuity difference of 3 or more logMAR lines. There were 419 children enrolled,
409 of whom met these criteria and were included in the analyses.
Results The mean age of the 409 children was 5.3 years. The cause of the amblyopia
was strabismus in 38%, anisometropia in 37%, and both strabismus and anisometropia
in 24%. The mean visual acuity of the amblyopic eyes (approximately 20/60)
was similar among the strabismic, anisometropic, and combined groups (P = .24), but visual acuity of the sound eyes was worse
in the strabismic group compared with the anisometropic group (P<.001). For the patients randomized into the patching group, 43%
were initially treated for 6 hours per day, whereas 17% underwent full-time
patching. Patients with poorer visual acuity in the amblyopic eye were prescribed
more hours of patching than patients with better acuity (P = .003).
Conclusions In the Amblyopia Treatment Study 1, there were nearly equal proportions
of patients with strabismic and anisometropic amblyopia. A similar level of
visual impairment was found irrespective of the cause of amblyopia. There
was considerable variation in treatment practices with regard to the number
of hours of initial patching prescribed.
INTRODUCTION
AMBLYOPIA IS the most common cause of visual impairment in children.
The prevalence of amblyopia in children has been estimated at between 1% and
4%.1-4
Most cases are associated with eye misalignment, usually esotropia in infancy
or early childhood.5-6 Less frequently,
anisometropia (difference in refractive error between the two eyes) or a combination
of strabismus and anisometropia are causally associated with amblyopia.
The Amblyopia Treatment Study 1 (ATS1) is a randomized, controlled,
single-masked multicenter clinical trial designed to compare the visual acuity
improvement achieved using patching therapy with adhesive patches with pharmacological
penalization using topical atropine sulfate 1% drops. Children younger than
7 years with moderate amblyopia were enrolled at both community-based and
university-based practices throughout North America by the Pediatric Eye Disease
Investigator Group. In this article, we describe the demographic and clinical
characteristics of the cohort of patients enrolled into the ATS1.
PATIENTS AND METHODS
The study was supported through a cooperative agreement with the National
Eye Institute of the National Institutes of Health (Bethesda, Md) and conducted
at 47 clinical sites in North America. Institutional review boards approved
the protocol and informed consent forms. The parent or guardian of each study
patient gave written informed consent. An independent data and safety monitoring
committee provided study oversight.
PATIENT SELECTION
Eligibility and exclusion criteria for enrollment are listed in Table 1. Eligibility testing included the
measurement of visual acuity in both eyes using the ATS visual acuity testing
protocol (see "Measurement of Visual Acuity"), a cycloplegic refraction, an
ocular examination, and a sensorimotor evaluation. Procedures were performed
according to the investigator's usual routine except for the visual acuity
testing protocol. Visual acuity testing was performed within the 7 days prior
to randomization, whereas the remainder of the examination was completed within
2 months prior to randomization.
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Table 1. Eligibility and Exclusion Criteria
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STUDY DEFINITIONS OF AMBLYOPIA
For each patient, amblyopia was classified as either strabismic, refractive/anisometropic,
or combined-mechanism to indicate the presumptive cause of amblyopia. Strabismic amblyopia was defined as amblyopia (1) in the
presence of either a heterotropia at distance and/or near fixation or a history
of strabismus surgery (or botulinum toxin injection), and (2) in the absence
of refractive error meeting the criteria for combined-mechanism amblyopia. Refractive/anisometropic amblyopia (subsequently referred
to as anisometropic amblyopia) was defined as amblyopia
in the presence of anisometropia that was 0.50 diopter (D) or more in spherical
equivalent or a 1.50 D or greater difference in astigmatism in any meridian
that persisted after at least 4 weeks of spectacle correction, with no measurable
heterotropia at distance or near fixation. Combined-mechanism
amblyopia was defined as amblyopia in the presence of (1) either a
heterotropia at distance and/or near fixation or a history of strabismus surgery
(or botulinum toxin injection), and (2) anisometropia that was 1.00 D or more
in spherical equivalent or a 1.50 D or greater difference in astigmatism in
any meridian that persisted after at least 4 weeks of spectacle correction.
The refractive error criteria for these classifications were set arbitrarily
based on the consensus opinion of the investigator group. These criteria must
be viewed in the context of a patient diagnosed as having amblyopia who has
at least a 3-line decrease in visual acuity in the amblyopic eye compared
with the sound eye. Some of the patients classified as having anisometropic
amblyopia may have had a small deviation of 8 D or less that was not detected
during the examination. Different refractive criteria were used in the definitions
of anisometropic amblyopia and combined-mechanism amblyopia, such that a patient
with 0.50 or 0.75 D of spherical anisometropia and strabismus would be classified
as strabismic rather than combined-mechanism. Small differences in refractive
error between eyes are common, and in such cases the strabismus is likely
the primary amblyogenic factor.
CORRECTION OF REFRACTIVE ERROR
For patients with strabismic amblyopia, refractive error was corrected
according to the investigator's usual routine. Patients with anisometropic
or combined-mechanism amblyopia were required to wear their current spectacle
correction for at least 4 weeks when there was anisometropia of 1.00 D or
more in spherical equivalent or a 1.50 D or greater meridional difference
subject to the following guidelines: (1) full correction of anisometropia;
(2) hyperopia of more than 3 D corrected by either prescribing the maximum-tolerated
hyperopic correction or reducing the cycloplegic refraction by up to +1.50
D; and (3) correction of astigmatism in either eye of 1.50 D or greater (full
correction of astigmatism preferred). If a patient was already wearing glasses,
a new prescription was not necessary as long as (1) both the spherical equivalent
and cylinder were within 0.50 D of fully correcting the anisometropia, and
(2) the cylinder axis in both eyes was within 10° of the axis in the spectacles
when the cylinder power was 1.00 D or greater (if cylinder power was <1.00
D, a spectacle change was at the investigator's discretion).
MEASUREMENT OF VISUAL ACUITY
Visual acuity was measured in both eyes using the ATS visual acuity
testing protocol7 administered by a study-certified
vision tester. The testing protocol consists of the presentation of single-surround
HOTV optotypes on the Baylor Video Acuity Tester (Medtronic Xomed Solan Ophthalmics,
Jacksonville, Fla) in 4 steps: a screening phase, followed by a first-threshold
determination (phase 1), reinforcement phase, and second-threshold determination
(phase 2). In the screening phase, starting from 20/100, a single letter at
each logMAR size is shown until one is missed. In phase 1, letters are shown
starting 2 logMAR levels above the missed level in the screening phase to
determine the smallest level at which 3 of 3 or 3 of 4 letters are correctly
identified. In the reinforcement phase, to get the child with drifting attention
back on track, 3 larger letters are shown starting 2 levels above the lowest
correct level in phase 1. In phase 2, the child is retested at the last level
missed in phase 1; if 3 of 3 or 3 of 4 are correctly identified, the test
continues at the next-smallest level until a level is failed. The visual acuity
score is the lowest level at which 3 of 3 or 3 of 4 presentations are correctly
identified in phase 1 or phase 2.
DATA ANALYSIS
Ten patients enrolled in the study did not meet the eligibility criteria
and were not included in the analyses (5 patients did not have a definable
cause for amblyopia, 1 had a visual acuity in the amblyopic eye of 20/30,
1 had an acuity in the amblyopic eye of 20/125, and 3 had an interocular difference
of only 2 logMAR lines).
Differences in baseline characteristics among subgroups based on cause
of amblyopia and age at enrollment were assessed, as indicated, with  2 tests as well as analysis of variance and analysis of covariance (with t tests used for subsequent 2-subgroup comparisons). The
association between prior treatment for amblyopia and amblyopic eye visual
acuity was assessed using a t test. The associations
between the number of hours of daily patching prescribed at enrollment and
visual acuity in the amblyopic eye, age at enrollment, practice type (community
vs institution), and physician type (ophthalmologist vs optometrist) were
evaluated with Kruskal-Wallis tests. Statistical analyses were performed using
SAS statistical software (PC version 8.01; SAS Institute Inc, Cary, NC).
RESULTS
Between April 1999 and April 2001, 419 patients were enrolled at 47
sites (10 patients were ineligible and were not included in the analyses,
as indicated in the "Methods" section). There were 188 patients enrolled at
16 community-based ophthalmology practices, 183 patients at 24 departments
of ophthalmology, and 48 patients at 7 schools or colleges of optometry.
The mean ± SD age of the 409 patients was 5.3 ± 1.1 years,
ranging from 2.6 to 6.9 years. Forty-six percent were girls. The racial distribution
was 83% white, 6% African American, 6% Hispanic, 2% Asian, and 3% mixed or
other. Of these patients, 73% had received no prior treatment for amblyopia,
24% had been previously treated with patching, 2% had been previously treated
with atropine, and 1% had previously received some other form of amblyopia
therapy.
The cause of amblyopia was strabismus in 38% of patients, anisometropia
in 37%, and both strabismus and anisometropia (combined-mechanism) in 24%.
The visual acuity in the amblyopic eye was 20/40 in 11%, 20/50 in 21%, 20/60
in 22%, 20/80 in 23%, and 20/100 in 23% (mean, 0.53 logMAR units [approximately
20/60]). The interocular acuity difference ranged from 3 to 8 lines with a
mean of 4.4 lines. There was no difference in mean visual acuity of the amblyopic
eyes of patients who had received prior amblyopia therapy compared with those
who had received no prior therapy (mean ± SD, 0.53 ± 0.13 logMAR
units for both; P = .68).
The baseline characteristics of the cohort according to cause of amblyopia
are summarized in Table 2. The
patients with strabismic amblyopia were slightly younger at enrollment (mean
age, 5.1 years) than the patients with anisometropic or combined-mechanism
amblyopia (mean age, 5.4 years and 5.2 years, respectively; P = .04). Mean visual acuity in the amblyopic eye was similar for all
3 causes of amblyopia (P = .24), but acuity in the
sound eye was worse with strabismic amblyopia and best with pure anisometropic
amblyopia even after adjusting for age, refractive error in the sound eye,
and prior treatment of amblyopia (P<.001). This
resulted in a smaller interocular acuity difference with strabismic amblyopia
than with the other 2 causes (P<.001). Refractive
error data for the 3 causes differed, consistent with the definitions for
each cause. The magnitude of the anisometropia was greater when the amblyopia
was due to anisometropia alone than when due to anisometropia combined with
strabismus (P = .02). Among the patients with anisometropia,
visual acuity in the amblyopic eye was worse when anisometropia was 3.00 D
or more than when it was less than 3.00 D (mean visual acuity, 0.57 logMAR
units [approximately 20/80] and 0.48 logMAR units [approximately 20/60], respectively; P<.001).
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Table 2. Baseline Characteristics According to Cause of Amblyopia*
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The baseline characteristics according to age at enrollment are listed
in Table 3. Mean visual acuity
in both the amblyopic and sound eyes was worse in the younger children (P = .005 and P<.001, respectively),
but the intereye acuity difference did not vary with age (P = .59). The mean refractive errors of the amblyopic and sound eyes,
as well as the anisometropia, varied little with age.
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Table 3. Baseline Characteristics According to Age at Enrollment*
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For patients randomized into the patching group, the initial number
of daily patching hours was at the discretion of the investigator, with a
minimum of 6 hours. Six or 8 hours per day were prescribed for 73% of the
212 patients, whereas 10 or more hours were prescribed for 27%. Although the
number of hours prescribed had no consistent relationship to age (P = .50), it was related to the amblyopic eye acuity (P = .003). Among the 19 patients with an amblyopic eye acuity of 20/40,
all were prescribed 6 or 8 hours per day of patching, whereas among the 49
patients with 20/100 amblyopic eye acuity, only 53% were prescribed 6 or 8
hours of patching per day. In contrast, full-time patching was prescribed
for no patients with 20/40 amblyopic eye acuity and for 22% of patients with
20/100 acuity (Table 4). There
was no difference in the number of patching hours prescribed by university-based
investigators compared with community-based investigators (P = .36). However, on average the optometrist investigators prescribed
fewer hours of patching than the ophthalmologist investigators (P = .01); only 4% of patients enrolled by an optometrist were initially
prescribed 10 or more hours of patching per day, compared with 31% of patients
enrolled by an ophthalmologist.
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Table 4. Number of Hours of Daily Patching Prescribed at Enrollment
for Patients in the Patching Group According to Baseline Visual Acuity in
the Amblyopic Eye*
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COMMENT
The ATS 1 was conducted using a simple protocol to compare the effectiveness
of patching and topical atropine 1% solution as treatments for moderate amblyopia
in children younger than 7 years. The study group investigators included pediatric
ophthalmologists and optometrists from both university and community-based
practices. The study was designed to approximate clinical practice as much
as possible, with the exceptions being the use of randomization to determine
the treatment prescribed for each patient and the use of a standardized single-surround
HOTV optotype visual acuity testing protocol, which we developed specifically
for this study.7
The clinical profile of the cohort must be viewed in the context of
the eligibility and exclusion criteria for the study (Table 1). The eligibility criteria for enrollment were broad, with
the intention to include most children with amblyopia younger than 7 years
who were developmentally able to perform single-surround HOTV optotype visual
acuity testing. This effectively set a lower age limit of about 3 years, although
7 children between the ages of 2.5 and 3 years successfully completed visual
acuity testing and were enrolled. To avoid including prior treatment failures
in the study, children who had received more than 2 months of amblyopia treatment
in the prior 2 years were not enrolled. The visual acuity limit for the amblyopic
eye was set at 20/100 because atropine is not thought to be an effective treatment
for worse acuities.8-9 Eligibility
required a 3-line difference in visual acuity between eyes (1) to assure that
a true reduction in acuity was present (a reliability study using our acuity
testing protocol found that a 3-line interocular difference was required for
reasonable certainty that amblyopia was present7),
and (2) to have a sufficient depth of amblyopia to assess improvement with
treatment.
Our cohort's mean age of 5.3 years and the equal sex distribution are
consistent with several previous reports describing populations with amblyopia.5-6,10-11 Our
cohort was 83% white, with small percentages of African American, Hispanic,
and Asian patients. This racial distribution likely reflects the nature of
the investigators' clinical practices. Because our study is not population
based, our data should not be used to suggest any demographic variation in
the prevalence of amblyopia between ethnic or racial groups.
Our cohort had approximately equal proportions of patients with amblyopia
due to strabismus and anisometropia, with about a quarter of the patients
having elements of both. The mean ages at enrollment for these groups of children
were 5.1, 5.4, and 5.2 years, respectively. These data differ somewhat from
those in the population-based study by Woodruff et al6
of 961 children with amblyopia in the United Kingdom. The authors found the
cause to be strabismus in 57%, anisometropia in 17%, and a combination of
the two in 27% of patients. The mean ages of children with strabismic, anisometropic,
and combination amblyopia were 3.3, 5.6, and 4.4 years, respectively. Our
data also differ from those of Shaw et al,5
who reported that in 1531 children with amblyopia in the United Kingdom, strabismus
was the cause in 45%, anisometropia in 17%, a combination of the two in 35%,
and deprivation due to cataract or corneal scarring in 3%. In the study by
Shaw and colleagues, the median ages of children with strabismic, anisometropic,
and combination amblyopia were 3.6, 6.3, and 4.7 years, respectively.
The 2 studies from the United Kingdom differ from ours in 4 important
ways. First, extensive prior treatment was an exclusion in our study. This
criterion would reduce the proportion of patients diagnosed (and presumably
treated) at younger ages entering the ATS1. These younger patients would more
often have strabismus, as seen in the 2 studies from the United Kingdom.5-6 The second difference was our requirement
for the children to complete a single-surround HOTV optotype visual acuity
testing protocol. This reduced the proportion of patients with strabismus
in our cohort by excluding most children with amblyopia younger than 3 years.
The third difference was our exclusion of deep amblyopia, also more frequently
associated with strabismus.12-13
Finally, the studies from the United Kingdom defined anisometropia as at least
1 D, compared with the 0.5-D minimum used in the ATS1. However, this creates
only a small difference between studies; our cohort included just 18 patients
with anisometropia of less than 1 D, and 12 of the 18 had a difference in
astigmatism between eyes of +1.50 D or more.
We found that the visual acuity of the amblyopic eyes was similar whether
the amblyopia was caused by strabismus, anisometropia, or both conditions.
Rodier et al14 also found no difference in
initial acuity among their patients with these 3 types of amblyopia. Although
previous studies have suggested that strabismic and combined-mechanism amblyopia
represent a more severe physiological deficit, due to active cortical suppression,
than purely anisometropic amblyopia,2, 15-16
the restriction of our cohort to children with an amblyopic eye acuity of
20/100 or better limits our ability to address this issue.
As expected, visual acuity in the sound eye was slightly better with
older age. This phenomenon may reflect the child's increasing sophistication
with testing and optotypes at older ages.17
For this reason, the interocular difference in acuity should be a useful measure
to account for this age effect on acuity testing. However, for assessing change
in visual acuity with treatment during a several-month period (in which the
age effect is expected to be minimal), the change in interocular acuity difference
may be less useful than the change in amblyopic eye acuity alone; the former
is affected by the testing variability in both eyes, whereas the latter is
affected by the variability in only one eye.7, 18
We were surprised by the variation in visual acuity of the sound eye
according to cause of amblyopia, which persisted even after statistically
adjusting for age, refractive error in the sound eye, and prior treatment
for amblyopia. We do not have a simple explanation for why sound eye acuity
would be best in patients with anisometropia, worst in patients with strabismus,
and intermediate in patients with both anisometropia and strabismus. Levi
and Klein19 previously reported a similar finding
for Vernier acuity. They noted that the sound eyes of patients with strabismus
had poorer visual acuity than those of patients with anisometropia. The authors
suggested that strabismus may produce cortical deficits in the sound eye due
to abnormal binocular interactions.
Patching therapy has been the mainstay of amblyopia treatment in North
America despite the lack of meaningful data demonstrating its superiority
compared with other modalities.20-21
In planning this study, when we surveyed the Pediatric Eye Disease Investigator
Group about their treatment practices for moderate amblyopia, we found that
very few prescribed atropine as a primary treatment modality; when patching
was prescribed, the intensity of treatment varied widely, from a few hours
a day to all waking hours. Our study data support the survey results. The
small number of study patients who had been previously treated with atropine
compared with the number previously treated with patching is suggestive of
the investigators' limited use of atropine as a treatment for amblyopia prior
to this study. The number of patching hours prescribed at enrollment for the
patching group varied from the allowable minimum of 6 hours per day, prescribed
for 43%, to full-time patching, prescribed for 17%. The number of patching
hours was related to the severity of the amblyopia but not to the age of the
patient or to whether the investigator was institutionally or community based.
The optometrist investigators tended to prescribe fewer hours of initial patching
than the ophthalmologist investigators.
In summary, we describe the clinical profile of a large cohort of children
younger than 7 years with moderate strabismic and anisometropic amblyopia.
There was a nearly equal distribution of cause between strabismus and anisometropia
(38%), with about 25% of patients having characteristics of both conditions.
Although visual acuity in the amblyopic eye did not differ according to cause
of amblyopia, acuity in the sound eye was worse with strabismic amblyopia
than with anisometropic amblyopia. There was considerable variation in treatment
practices with regard to the number of hours of initial patching prescribed
by the investigators. However, we did find that the number of patching hours
was positively related to the depth of the amblyopia and was greater for ophthalmologists
than for optometrists. The data reported in this article define the clinical
profile of the patients enrolled in the ATS1. These data will be useful for
interpreting the results of the randomized trial comparing patching with atropine
as treatments for moderate amblyopia.
AUTHOR INFORMATION
Submitted for publication November 20, 2001; final revision received
December 28, 2001; accepted January 7, 2002.
Supported by a cooperative agreement (EY11751) from the National Eye
Institute, Bethesda, Md.
| The Pediatric Eye Disease Investigator Group
Writing Committee
Michael X. Repka, MD; Roy W. Beck, MD, PhD; Raymond T. Kraker, MSPH;
Stephen R. Cole, PhD; Jonathan M. Holmes, BM, BCh; Eileen E. Birch, PhD; D.
Robbins Tien, MD; William F. Astle, MD; Susan A. Cotter, OD.
A complete list of the participating sites and investigators and the
study committee members appears in this article: http://archopht.ama-assn.org/issues/v120n3/rfull/ecs10241.html.
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Corresponding author: Roy W. Beck, MD, PhD, Jaeb Center for Health
Research, 3010 E 138th Ave, Suite 9, Tampa, FL 33613 (e-mail: rbeck{at}jaeb.org).
Reprints: PEDIG Data Coordinating Center, Jaeb Center for Health
Research.
From the Jaeb Center for Health Research, Tampa, Fla.
REFERENCES
| |
1. Flom MC, Neumaier RW. Prevalence of amblyopia. Public Health Rep. 1966;81:329-341.
ISI
| PUBMED
2. Simons K. Preschool vision screening: rationale, methodology and
outcome. Surv Ophthalmol. 1996;41:3-30.
FULL TEXT
|
ISI
| PUBMED
3. Lennerstrand G, Jakobsson P, Kvarnstrom G. Screening for ocular dysfunction in children: approaching a common
program. Acta Ophthalmol Scand Suppl. 1995;214(suppl):26-38.
4. Leske MC, Hawkins B. Screening: relationship to diagnosis and therapy. In: Duane TD, Jaeger EA, eds. Clinical Ophthalmology. Vol. 5. Philadelphia, Pa: Harper & Row; 1994:10-15.
5. Shaw DE, Fielder AR, Minshull C, Rosenthal AR. Amblyopia: factors influencing age of presentation. Lancet. 1988;2:207-209.
FULL TEXT
| PUBMED
6. Woodruff G, Hiscox F, Thompson JR, Smith LK. Factors affecting the outcome of children treated for amblyopia. Eye. 1994;8:627-631.
7. Holmes JM, Beck RW, Repka MX, et al. The Amblyopia Treatment Study visual acuity testing protocol. Arch Ophthalmol. 2001;119:1345-1353.
FREE FULL TEXT
8. Repka MX, Ray JM. The efficacy of optical and pharmacological penalization. Ophthalmology. 1993;100:769-775.
ISI
| PUBMED
9. Simons K, Stein L, Sener EC, Vitale S, Guyton DL. Full-time atropine, intermittent atropine, and optical penalization
and binocular outcome in treatment of strabismic amblyopia. Ophthalmology. 1997;104:2143-2155.
ISI
| PUBMED
10. Köhler L, Stigmar G. Vision screening of four-year-old children. Acta Paediatr Scand. 1973;62:17-27.
ISI
| PUBMED
11. Altebo K, Mitchell P, Cumming R, et al. Prevalence and causes of amblyopia in an adult population. Ophthalmology. 1998;105:154-159.
FULL TEXT
|
ISI
| PUBMED
12. Levi DM, Klein SA, Wang H. Amblyopic and peripheral vernier acuity: a test-pedestal approach. Vision Res. 1994;34:3265-3292.
FULL TEXT
|
ISI
| PUBMED
13. Birch EE, Swanson WH. Hyperacuity deficits in anisometropic and strabismic amblyopes with
known ages of onset. Vision Res. 2000;40:1035-1040.
FULL TEXT
|
ISI
| PUBMED
14. Rodier DW, Mayer DL, Fulton AB. Assessment of young amblyopes: array vs single picture acuities. Ophthalmology. 1985;92:1197-1202.
ISI
| PUBMED
15. Flynn JT, Woodruff G, Thompson JR, et al. The therapy of amblyopia: an analysis comparing the results of amblyopia
therapy utilizing two pooled data sets. Trans Am Ophthalmol Soc. 1999;97:373-390.
PUBMED
16. Flynn JT, Schiffman J, Feuer W, Corona A. The therapy of amblyopia: an analysis of the results of amblyopia therapy
utilizing the pooled data of published studies. Trans Am Ophthalmol Soc. 1998;96:431-453.
PUBMED
17. Fern KD, Manny RE. Visual acuity of the preschool child: a review. Am J Optom Physiol Opt. 1986;63:319-345.
ISI
| PUBMED
18. Moke PS, Turpin AH, Beck RW, et al. Development of a computerized method of visual acuity testing: adaptation
of the amblyopia treatment study visual acuity testing protocol. Am J Ophthalmol. 2001;132:903-909.
FULL TEXT
|
ISI
| PUBMED
19. Levi DM, Klein SA. Vernier acuity, crowding and amblyopia. Vision Res. 1985;25:979-991.
FULL TEXT
|
ISI
| PUBMED
20. von Noorden GK. Binocular Vision and Ocular Motility: Theory and
Management of Strabismus. St Louis, Mo: Mosby–Year Book Inc; 1996.
21. American Academy of Ophthalmology. Amblyopia: Preferred Practice Pattern. San Francisco, Calif: American Academy of Ophthalmology; 1997.
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The Pediatric Eye Disease Investigator Group*
Arch Ophthalmol 2003;121:603-611.
ABSTRACT
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A randomised controlled trial of written information
Lempert
Br J Ophthalmol 2003;87
:517-518.
FULL TEXT
Amblyopia therapy
Fleck
Br J Ophthalmol 2003;87:255-256.
FULL TEXT
A randomised controlled trial of written information
Lempert
Br J Ophthalmol 2003;87:124-124.
FULL TEXT
A Randomized Trial of Atropine vs Patching for Treatment of Moderate Amblyopia in Children
The Pediatric Eye Disease Investigator Group
Arch Ophthalmol 2002;120:268-278.
ABSTRACT
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