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Screening for Amblyogenic Factors Using a Volunteer Lay Network
and the MTI PhotoScreener™ |
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Initial Results from 15,000 Preschool Children in a Statewide
Effort |
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Sean P. Donahue, MD, PhD, Tammy M. Johnson, MPH, Thomas C.
Leonard-Martin, PhD, MPH |
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Purpose: To describe the results from a statewide preschool
vision screening program using the MTI PhotoScreener™ (Medical
Technology and Innovations, Inc., Cedar Falls, IA). |
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Design: Cross-sectional study. |
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Participants: A total of 15,059 children aged 6 to 47 months
enrolled in childcare and preschool settings throughout the
state of Tennessee. |
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Methods: Volunteers from local Lions Clubs took photoscreening
photographs of children in a statewide effort. Photographs were
interpreted at the Vanderbilt Ophthalmic Photography Reading
Center using predetermined criteria. Children who failed the
screening were referred to community ophthalmologists or
optometrists who performed a comprehensive evaluation and
forwarded the results to the authors. |
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Main Outcome Measures: Referral rate, unreadable rate, and
predictive value positive (PVP). |
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Results: During the 2 years of the screening program, 15,059
children were screened in 850 screenings. The screening referred
1013 children (6.7%), and 704 photographs (4.7%) were
unreadable. Children who failed the screening had a significant
abnormality (strabismus, anisometropia, high hypermetropia, high
astigmatism, or high myopia) in 320 of the 531 cases where
adequate follow-up results were reported. The PVP ranged from
84% when a diagnosis of strabismus was suggested by the
photoscreen reading to 41% for astigmatism. Despite intense
attention to follow-up, many children who failed the screening
never received a formal eye examination. |
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Conclusions: The MTI PhotoScreener™ can be used by volunteers to
screen preschool children and can have a high PVP in organized
settings, provided that meticulous attention is paid to
photograph interpretation and quality control. The PVP of the
MTI PhotoScreener™ depends on the diagnosis suggested when the
photograph is read. Significant obstacles exist in obtaining
care for those who fail screening. |
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Click here to view the full study. (PDF) |
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Photoscreening for Amblyogenic Factors |
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Wanda L. Ottar, OC(C),Comt:William E.Scott, MD; and Sandra I.
Holgado, MD |
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ABSTRACT |
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Background: The Medical Technology, Inc. PhotoScreener™ is a new
eccentric photo screener that is being marketed as a device for
the detection of amblyogenic factors in preverbal children. The
purpose of this study was to evaluate the accuracy of the
PhotoScreener™ in the target population of young, healthy
children. |
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Methods: One thousand and three healthy children between the age
of 6 months and 59 months were photoscreened with the
PhotoScreener™ . Nine hundred and forty nine children were
included in the study and their results were compared with a
complete ophthalmologic examination with cycloplegia. |
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Results: The sensitivity of the PhotoScreener™ was determined to
be 81.8% with a specificity of 90.6%. The overall agreement rate
was 88.8%. The positive and negative predictive values were
68.9% and 95.2%, respectively. All cases of strabismus and media
opacities were detected. |
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Conclusion: The PhotoScreener™ is an accurate and reliable
device designed to detect amblyogenic factors in young children.
The camera offers promise as a useful mass-screening tool. |
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| INTRODUCTION |
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Amblyopia is a common childhood disorder affecting 3% to 5% of
the population. 1,2 The need for early detection of amblyopia
and amblyogenic factors is widely recognized. 3,4 However, most
current vision screening methodologies are not effective in
screening preverbal children.5 |
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Interest has increased in photoscreening as a method for
detecting amblyogenic factors in young children. The methodology
is simple: a flash photograph of the subject's eyes is taken.
The light reflected from the retina is analyzed to detect
refractive errors, strabismus, and/or media opacities. Two types
of photo screeners based on the relationship between the flash
source and the optical axis of the camera have been described.
6-11The on-axis system has a coaxial camera and flash source.
The off-axis system has a flash source slightly off the optical
axis of the camera. Several studies comparing the two systems
have found that the off-axis system provides more information
with fewer photographs and is better suited for non-cycloplegic
refractive screening.6,12,14 |
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An off-axis instant film photo screener, The Medical Technology,
Inc. PhotoScreener™, was commercially manufactured after several
studies were conducted with the prototype, EyeCor camera.1, 5-17
The purpose of this study was to measure the sensitivity,
specificity and accuracy of the PhotoScreener™ in detecting
strabismus, media opacities, and refractive errors in a large
population of healthy children between the ages of 6 months and
59 months. |
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MATERIAL AND CONSTRUCTION |
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Camera |
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The PhotoScreener™ was designed and tested to have the same
sensitivity on model eye testing as its prototype, the Eyecor
camera. The specifications of the Eyecor camera have been
previously described.15-17 Some additional modifications were
made, including automatic rotation of the flash and a sliding
film that places both the horizontal and vertical photographs on
the same instant photograph. A 9-D lens with a back focal
distance of 5 inches results in a 1:1 magnification. Each
photograph was examined for the presence of strabismus, media
opacities, and refractive errors. The diagnosis was determined
from examination of the photographs as discussed below (see
procedure). |
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A pupil-crescent measurement tool supplied with the camera was
used to measure the pupil and crescent sizes in all photographs.
The measurement tool is designed with 3 mm through 9 mm offset
openings and complete hole openings. Each template is marked
with one-mm lines. A small millimeter ruler also is located
along the side (Fig 1). |
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Figure 1: Pupil-crescent measurement tool. |
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Subjects |
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One thousand and three "healthy" children between the ages of 6
months and 59 months were examined. Approximately two thirds of
the children were photoscreened during routine screening at
Public Health and Women, Infants and Children's (WIC) clinics in
Iowa and Illinois. The remaining one third were screened in the
private offices of pediatricians in Iowa and Texas. Children
with history of an eye problem or who had previously examined by
an ophthalmic professional were excluded. Children with known
systemic disease also were excluded. The gender distribution was
51% male and 49% female. Of the patients, 81.3% were Caucasian,
7.8% African American, 5.8% Hispanic, and 2.9% Asian. |
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