Regimens of Intermittent Occlusion Therapy for Amblyopia in Children

This study is designed to answer the question: What if the Intermittent Occlusion (IO-therapy) glasses were prescribed all day (12-hours) in which the total time of treatment only took 4 weeks instead of the current treatment time (4 hours) in which it takes 12 weeks?

Children aged 3- to 8-years with untreated moderate unilateral amblyopia will be enrolled and randomized into 2 groups: 1) Intense 12-hour IO-therapy Group for 4 weeks treatment; or 2) Standard 4-hour IO-therapy glasses Group for 12 weeks treatment.


Eligibility Criteria:
Inclusion Criteria:

The following criteria must be met for the patient to be enrolled in the study:

1. Age 3 to \< 8 years
2. Unilateral amblyopia associated with strabismus (comitant or incomitant), anisometropia, or both

   Criteria for strabismus: At least one of the following criteria must be met:
   * Heterotropia at distance and/or near fixation on examination (with or without spectacles)
   * History of strabismus surgery
   * Documented history of strabismus which is no longer present (which in the judgment of the investigator could have caused amblyopia)

   Criteria for anisometropia: At least one of the following criteria must be met:
   * \>0.50 D difference between eyes in spherical equivalent
   * \>0.50 D difference between eyes in astigmatism in any meridian
3. Amblyopic eye has no myopia (\> -0.25 D spherical equivalent).
4. Visual acuity, measured in each eye without cycloplegia within 7 days prior to enrollment using the ATS single-surround HOTV letter protocol as follows:

   * Visual acuity in the amblyopic eye between 20/40 and 20/80 inclusive
   * Visual acuity in the sound eye 20/32 or better
   * Inter-eye acuity difference ≥ 2 logMAR lines (i.e., amblyopic eye acuity at least 2 lines worse than sound eye acuity)
5. No previous amblyopia treatment within 6 months.
6. Spectacle correction (if applicable) for measurement of enrollment visual acuity must meet the following criteria and be based on a cycloplegic refraction within 6 months:

   * Requirements for spectacle correction:
   * For patients meeting criteria for only strabismus

     * Hypermetropia if corrected must not be undercorrected by more than +1.50 D spherical equivalent, and the reduction in plus sphere must be symmetric in the two eyes. Otherwise, spectacle correction is at investigator discretion.
   * For patients meeting criteria for anisometropia or combined-mechanism

     * Spherical equivalent must be within 0.50 D of fully correcting the anisometropia
     * Hypermetropia must not be undercorrected by more than +1.50 D spherical equivalent, and reduction in plus must be symmetric in the two eyes
     * Cylinder power in both eyes must be within 0.50 D of fully correcting the astigmatism
     * Cylinder axis in the spectacle lenses in both eyes must be within 6 degrees of the axis of the cycloplegic refraction

   Spectacles meeting above criteria must be worn either:
   * for 4 weeks immediately prior to enrollment, or
   * until visual acuity in amblyopic eye is stable (defined as two consecutive visual acuity measurements at least 4 weeks apart with no improvement of one line or more)
   * An acuity measurement done any of the following ways may be considered the first of two consecutive measurements:

     * in current glasses,
     * in trial frames with full correction of hypermetropia with cycloplegia, or
     * in new glasses.
7. Wearing optimal spectacle correction for a minimum of 4 weeks at the time of enrollment.
8. Ocular examination within 6 months prior to enrollment.
9. Gestational age \> 34 weeks and birth weight \> 1500 grams
10. Parent willing to accept randomization
11. Parent willing to be contacted and has access to phone
12. Parent does not anticipate relocation outside area within study period.

Exclusion Criteria:

1. Amblyopic eye has myopia worse than -3.00 D spherical equivalent.
2. Prior intraocular or refractive surgery
3. Ocular pathologies that impact vision
4. Cognitive impairment that prohibits accurate data collection