Clinical and psychosocial determinants influencing treatment effect of occlusion therapy and
rate of recurrence in previously untreated patients with amblyopia between 12 and 40 years of age

Amblyopia, defined as loss of visual function, caused by strabismus,
anisometropia, and/or visual deprivation in the absence of ocular pathology, is
commonly treated by occlusion therapy before age of six, limiting by the end of
the sensitive period. However, recent studies suggest that the plasticity of
the visual system extends into adolescents. In about a third of patients, 1% of
the population, amblyopia persists in adulthood and thereby increasing the risk
of bilateral visual impairment due to loss of vision in the nonamblyopic eye.
This leads to decrease in quality of life and to increase costs to the
healthcare system. The efficacy of occlusion therapy in adult patients, thus,
whether visual improvement after treatment remains or decreases after occlusion
is discontinued, is insufficiently investigated prospectively. Whether
psychological factors or decreasing plasticity limits treatment effect in
amblyopic adults is not clear.

The primary purpose is the efficacy of occlusion therapy initiated in patients
with untreated amblyopia between twelve and forty years of age.

The secondary purposes are rate of recurrence, refractive adaptation, and the
social-economic and ethic status and the psychosocial factors as predictor for
compliance to occlusion therapy.

This study is designed as a prospective interventional study.
The recruitment of patients is expected to start in June 2011 and will last
until March 2012. The follow up controls take place until November 2013.
Each participants is prescribed optical correction (if needed). Participants
are seen at 6 weeks intervals up to 18 weeks (end of period of refractive
adaptation).
After refractive adaptation, each participant will receive part-time occlusion
(3 hours a day) on the sound eye until there is no further improvement (less
than one logMAR line) of visual acuity of the amblyopic eye, for a period of
maximal 18 weeks. Participants are tested within 6 weeks intervals (for a
period of maximal 4 months).
Follow up visits take place three, six and nine months after discontinuation of
treatment.
Participants are asked to fulfil a questionnaire for the evaluation of the
social-economic and ethic status at the day of inclusion, and a questionnaire
about the psychosocial determinants during occlusion therapy is given six weeks
after start of occlusion therapy.

All participants were prescribed three hours per day of part-time occlusion on
the sound eye for a period of maximal 4 months.

Part-time occlusion is the standard therapy for amblyopia treatment. Skin
irritation due to patching or persistent diplopia is unlikely in view of the
small number of hours of daily patching prescribed.