The goals of this study are:
- To determine whether the visual acuity improvement obtained with part-time (6 hours)
patching is equivalent to the visual acuity improvement obtained with full-time
patching (all or all but one waking hour) for severe amblyopia.
- To develop more precise estimates than currently available for the visual acuity
improvement that occurs during treatment of amblyopia with patching.
- To identify factors that may be associated with successful treatment of amblyopia with
Amblyopia is the most common cause of monocular visual impairment in both children and young
and middle-aged adults. Patching has been the mainstay of amblyopia therapy. It is generally
held that the response to treatment is best when it is instituted at an early age,
particularly by age two or three, and is poor when attempted after eight years of age.
For severe amblyopia, it is generally accepted that occlusion with patching is the standard
of care. Other modalities of treatment, such as atropine penalization and optical
penalization, are widely considered insufficient as initial treatments for severe amblyopia.
However, controversy exists with regard to how many hours per day of patching should be
prescribed. Advocates of full-time patching purport that such a regimen is needed to restore
visual acuity more rapidly and more effectively. Advocates of part-time patching believe it
to be better tolerated by the child and family, therefore producing less stress on the
parent-child relationship and producing better results through better compliance. Part-time
patching may also promote the development of binocularity in patients who have
"straight-eyes", reduce the chance of a straight-eyed patient developing manifest strabismus
or losing stereopsis, and reduce the incidence of reverse- or occlusion-amblyopia.
The study is a randomized trial comparing daily patching regimes for children with severe
amblyopia. It will consist of about 160 children. Patients in the severe (20/100 to 20/400)
group will patch part-time (6 hours) or full-time (all or all but one waking hour) of each
day for the 4 month study period. There are at least two follow up visits during the 4-month
period. Visual acuity is the major study outcome. It is assessed at the 4-month exam.
- Patients must be less than 7 years of age with the original cause of amblyopia as
strabismus or anisometropia (a refractive error difference of more than one diopter
between the two eyes.)
- Visual acuity in the amblyopic eye must be between 20/100 and 20/400.
- Visual acuity in the sound eye of 20/40 or better.
- There must be at least 3 lines of acuity difference between the two eyes.
- Patching treatment (other than spectacles) within six months prior to enrollment and
other amblyopia treatment of any type used within one month prior to enrollment.