phase 1 and 2(1, 2) were monumental and important studies, but did
not really address AAPOS guideline screening(3),
but rather just a single pass- pre-K screening assuming no subsequent
K and 1st grade screening.
I think it critical that AAPOS emphasize and encourage a series of age-appropriate
tests rather than one single pre-K catch all screening. If you only had
one opportunity to catch any amblyopia, you would need a SENSITIVE test.
Some amblyopia is manifest (i.e large angle constant strabismus or anterior
cataract) but much is occult. By definition, the occult cases appeared
normal to parents, to pediatricians, school nurses, etc.
The parent, the pediatrician and the overly busy pediatric ophthalmologist
receiving vision screen referrals would much rather have a screen with
high PPV (Positive Predictive Value) than
one with high SENSITIVITY. The liability
of the screen manufacturer or program thinks that it must have high sensitivity,
but that still assumes a single screening. Series of age appropriate SPECIFIC
objective migrating to sensory tests will have high sensitivity.
VIPS, by determining compared sensitivities for a pre-set (90% - 94%)
specificity makes a case for mandated exams instead of single - preK screening.
And for a disease (amblyopia) with just 4% prevalence, the 94% specificity
is still too low.
I briefly comment, in the
BVQ article(4) on Sean's and my experience compared, that our high
PPV photoscreening programs did NOT find large numbers of missed amblyopes
years after screening.
WHAT WE REALLY NEED FROM VIPS(1, 2), COMBINED WITH OTTAR'S(5) STUDIES,
IT TO DETERMINE THE PREVALENCE OF ANISOMETROPIA OVER 1.5 DIOPTERS, HYPEROPIA
OVER 3.5 DIOPTERS, ASTIGMATISM OVER 1.0 OBLIQUE OR 1.5 DIOPTERS, MYOPIA
OVER 3 DIOPTERS, MANIFEST STRABISMUS IN A GROUP OF NON-ENHANCED PRE-K
If we had such populations estimates, then validation studies of existing
and future screening could be done much more cheaply and quickly on real
screening experiences with follow up on mainly referred cases. Robert
W. Arnold, MD July 2006
1. VIPS. Comparison
of preschool vision screening tests as administered by licensed eye care
professionals in the vision in preschoolers study. Ophthalmology. Apr
2. VIPS, Dobson V, Quinn G, et al. Preschool vision screening tests administered
by nurse screeners compared with lay screeners in the Vision in Preschoolers
Study. IOVS. 2005 2005;46:2639-2648.
3. Swanson J. Eye examination in infants, children and young adults by
pediatricians: AAP Policy Statement. Ophthalmology. 2003;110(4):860-865.
4. Arnold RW, Donahue SP.
The yield and challenges of charitable state-wide photoscreening. Binocul
Vis Strabismus Q. 2006;21(2):93-100.
5. Ottar WL, Scott WE, Holgado SI. Photoscreening for amblyogenic factors.
J Pediatr Ophthalmol Strabismus. 1995;32:289-295.
6. Donahue S, Arnold R, Ruben JB. Preschool vision screening: What should
we be detecting and how should we report it? Uniform guidelines for reporting
results from studies of preschool vision screening. J AAPOS. 2003;7(5):314-316.