Amblyopia is the most common cause of monocular visual impairment in children, estimated to
affect as many as 3.6% of the childhood population. The natural history of amblyopia is
relatively unknown although it has been reported that visual acuity may deteriorate further
without treatment.
Although occlusion or patching of the sound eye has been the mainstay for amblyopia therapy,
alternative treatment such as pharmacological or optical penalization may be as effective. In
a randomized, controlled clinical trial of 419 children, 3 years to less than 7 years old
with moderate amblyopia, patching was compared to atropine. Although improvement with
atropine was initially slower, both treatments produced similar improvement after 6 months.
Although both patching and atropine have been proven effective for treating amblyopia,
neither treatment is without adverse side effects. Patching is associated with compliance
difficulties, the need for continuous monitoring, and social stigma. Negative side effects
observed in children treated with atropine include light sensitivity, facial flushing, and
fever. In a randomized clinical trial comparing patching to atropine as a treatment for
amblyopia, a questionnaire to assess the impact of patching and atropine treatment on the
child and family indicated that both treatments were well tolerated overall, however,
patching had lower compliance and higher social stigma than atropine.
Bangerter filters, also known as Bangerter foils, have been used mainly as secondary
amblyopia therapy following patching or atropine to either further improve or maintain the
visual gain. One advantage of Bangerter filters compared to patching is that the lower
density filters are not readily apparent and therefore would be expected to increase patient
compliance due to reduced social stigma. Another advantage of Bangerter filters is that there
is no opportunity for skin irritation from bandage adhesive, a commonly-reported side effect
of patching. In addition, there is a theoretical advantage that Bangerter filters are less
disruptive to binocular function during treatment compared to other modalities such as
patching.
Few data are available comparing Bangerter filters with patching for the treatment of
amblyopia. Bonsall randomized 14 patients, 3 to 10 years old, with previously untreated
strabismic/anisometropic amblyopia to either 6 hours of daily patching or full-time Bangerter
filters. Baseline amblyopic eye acuity was 20/30 to 20/400 for the patching group and 20/30
to 20/200 for the Bangerter group. The Bangerter filter prescribed was the minimum density
foil needed to elicit a switch in fixation from the sound eye to the amblyopic eye. Visual
acuity was measured every 6-8 weeks until the amblyopic eye visual acuity was equal to that
of the sound eye, an improvement that was achieved in 5 of the 14 at the time the study was
stopped. The average time to achieve equal vision between the amblyopic and sound eyes was
about 4.5 months (142 days) for the foil group versus about 9 months (272 days) for the
patching group. Both forms of therapy were equally tolerated. Despite good preliminary data,
a large randomized clinical trial comparing the effectiveness of Bangerter filters to
patching for the treatment of amblyopia has yet to be conducted.
