Background

***A Randomized Trial Comparing Part-time to\
Minimal-time Patching for Moderate Amblyopia***

The term \"amblyopia\" derives from the Greek word for \"dullness of
vision.\" It is estimated that amblyopia affects two or three of every
100 children in the United States.

The disorder is caused by conditions that affect normal visual
development. These conditions can include an imbalance in the
positioning of the eyes, such as strabismus, in which the eyes are
crossed inward (esotropia) or turned outward (exotropia). Amblyopia can
also result from a major difference in refractive error between the two
eyes, such as nearsightedness, farsightedness, or astigmatism. Less
common causes of amblyopia are cornea and lens diseases and injury to
the eye of a young child. The results reported in this study do not
include amblyopia from these less common causes.

Despite the common occurrence of amblyopia, there has been little
quality data on its natural history. For decades, patching the
unaffected eye had been the standard treatment for amblyopia (In March
2002, researchers reported the effectiveness of drug therapy with a
cycloplegic eye drop \[atropine\] that dilates the pupil and blurs the
image seen by the unaffected eye). However, opinions varied widely on
the number of hours of patching per day that should be prescribed. No
prior study had provided conclusive evidence of the optimal number of
prescribed patching hours. This information would be crucial, since
reported rates of compliance for patching varied widely, from 49 to 87
percent. Compliance with the prescribed dosage of patching hours is an
important factor in determining the level of success of amblyopia
treatment.

**A Randomized Trial Comparing Part-time to Minimal-time Patching**

To address the clinical issue of the optimal number of patching hours
for moderate amblyopia, researchers conducted a clinical trial called *A
Randomized Trial Comparing Part-time to Minimal-time Patching for
Moderate Amblyopia*. Its purpose was to compare two hours versus six
hours of daily patching for children with moderate amblyopia (20/40 to
20/80) and less than seven years of age. The study was funded by the
National Eye Institute and conducted by the Pediatric Eye Disease
Investigator Group (PEDIG), a network of eye care professionals at
universities and community offices in North America. The PEDIG
professionals have a goal of determining the best treatment for various
eye problems in children.

Between May 2001 and May 2002, 189 patients entered the trial, with 95
randomly assigned to the two-hour patching group and 94 assigned to the
six-hour patching group. The number of patients enrolled per site at the
35 sites ranged from one to 21 (median three). The average age of the
patients was 5.2 years; 44 percent were female, and 85 percent were
white. To avoid including in the study those patients whose prior
treatment was unsuccessful, enrollment was restricted to children who
had not been previously treated for amblyopia; or had not received
patching treatment within six months of enrollment and had not received
other amblyopia treatment of any type (other than eyeglasses) within one
month of enrollment.

Parents in both groups were advised that the daily hours of patching
should be continuous when possible. In addition to patching, parents
were instructed to have the child spend at least one of the hours of
patching time each day doing \"near\" visual activities, such as
reading, writing homework assignments, making crafts, coloring, tracing,
cutting out objects, connecting dots, doing hidden pictures and word
finds, playing computerized video games, or other activities requiring
eye-hand coordination. Instructions of one hour of near activities were
identical in both the two-hour and six-hour patching groups.

After four months, 97 percent of patients in the two-hour group and 95
percent in the six-hour group completed the primary outcome exam.
Patients in both groups showed substantial improvement in the eye with
amblyopia, averaging 2.40 lines from baseline in each group. At four
months, 79 percent of patients in the two-hour group and 76 percent of
patients in the six-hour group had improved by two or more lines on the
eye chart.

Vision in the *unaffected* eye decreased by either one or two lines on
the standard eye chart in about 21 percent of patients in the two-hour
group, and about 24 percent of patients in the six-hour group. However,
this is normal for patients with amblyopia, and vision in the unaffected
eye is expected to return to normal when treatment is completed.

Researchers note that the amount of vision improvement after four months
in the eye with amblyopia should not be considered to be the maximum
amount of improvement that can occur with patching. Instead, four months
represented the maximum length of time they believed the treatments
could be maintained in the study before either increasing the prescribed
number of hours of patching or switching to an alternate treatment for
amblyopia might be necessary.

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