A Pilot Clinical Trial of Overminus Spectacle Therapy for Intermittent Exotropia

The objective of this short-term, pilot randomized trial comparing 2.50 diopters (D) overminus lens treatment vs. non-overminus (spectacles without overminus or no spectacles) in children with intermittent exotropia (IXT) 3 to \<7 years of age is to determine whether to proceed to a full-scale, longer-term randomized trial.

The objective of this short-term, pilot randomized trial comparing 2.50D overminus lens treatment vs. non-overminus (spectacles without overminus or no spectacles) is to determine whether to proceed to a full-scale, longer-term randomized trial. This decision will be based primarily on assessing the initial (8-week) response to overminus by comparing treatment groups on the following outcomes:

* Mean distance IXT control score (each patient's score is the mean of 3 control scores) (primary outcome)
* The proportion of subjects with treatment response, defined as 1 or more points improvement in mean of 3 distance IXT control scores (secondary outcome)
* Adverse effects, near visual acuity outcomes, and spectacle wear compliance

Eligibility Criteria:
The following criteria must be met for the child to be enrolled in the study:

* Age 3 years to \< 7 years
* Intermittent exotropia (manifest deviation) meeting all of the following criteria:

  * Intermittent exotropia or constant exotropia at distance

    * Mean distance control score of 2 points or more (mean of 3 assessments over the exam)
  * Intermittent exotropia, exophoria, or orthophoria at near

    * Subject cannot have a score of 5 points on all 3 near assessments of control
  * Exodeviation at least 15∆ at distance measured by PACT
  * Near deviation does not exceed distance deviation by more than 10∆ by PACT (convergence insufficiency type IXT excluded)
* No previous non-surgical treatment for IXT (other than refractive correction), including vision therapy for IXT, within the past 6 months.
* No previous substantial overminus treatment, defined as wearing spectacles that are overminused by 1.00D SE or more (treatment with lenses overminused by less than 1.00D SE is allowed at any time prior to enrollment).
* No vision therapy, patching, atropine, or other penalization for amblyopia during the last 2 weeks
* No prior strabismus, intraocular, or refractive surgery (including BOTOX injection)
* Cycloplegic refraction within 7 months, but NOT on the day of enrollment
* Spherical equivalent (SE) in both eyes between -6.00D and +1.00D inclusive
* Distance visual acuity 0.3 logMAR (20/40) or better (by ATS-HOTV) in both eyes
* No interocular difference of distance visual acuity more than 0.2 logMAR (2 lines)
* Child must be wearing refractive correction (pre-study spectacles) for at least 1 week if refractive error (based on cycloplegic refraction performed within 7 months) meets any of the following:

  * SE anisometropia ≥1.00 D
  * Astigmatism ≥1.00 D in either eye
  * SE myopia ≥-0.50 D in either eye
* Refractive correction must meet the following criteria relative to the cycloplegic refraction:

  * SE anisometropia must be within \<1.0D of the SE anisometropic difference
  * Astigmatism must be within \<1.00D of full magnitude; axis must be within 10 degrees if ≤1.00D, and within 5 degrees if \>1.00D.
  * The SE of the spectacles must be within \<1.00D of the full cycloplegic refraction SE.

    * A correction that yields at least 1.00 D more minus SE than the cycloplegic refraction SE is considered previous substantial overminus lens treatment and the patient is not eligible.
* No current contact lens wear
* No abnormality of the cornea, lens, or central retina
* Gestational age ≥ 32 weeks
* Birth weight \> 1500 grams
* No Down syndrome or cerebral palsy
* No severe developmental delay which would interfere with treatment or evaluation (in the opinion of the investigator). Subjects with mild speech delays or reading and/or learning disabilities are not excluded.
* No disease known to affect accommodation, vergence, and ocular motility such as multiple sclerosis, Graves orbitopathy, myasthenia gravis, diabetes mellitus, or Parkinson disease
* No current use of any ocular or systemic medication known to affect accommodation or vergence, such as anti-anxiety agents (e.g., Librium or Valium), anti-arrhythmic agents (e.g., Cifenline, Cibenzoline), anti-cholinergics (e.g., motion sickness patch (scopolamine)), bladder spasmolytic drugs (e.g., Propiverine), hydroxychloroquine, chloroquine, phenothiazines (e.g., Compazine, Mellaril, Thorazine), tricyclic antidepressants (e.g., Elavil, Nortriptyline, Tofranil)
* Parent understands the protocol and is willing to accept randomization to overminus spectacles or non-overminus status
* Parent has home phone (or access to phone) and is willing to be contacted by Jaeb Center staff and Investigator's site staff
* Relocation outside of area of an active PEDIG site within next 8 weeks is not anticipated