Trial of Overminus Spectacle Therapy for Intermittent Exotropia

The main objectives of this randomized trial comparing overminus lens treatment to non-overminus (spectacles without overminus or spectacles with plano lenses) are to determine:

* The long-term on-treatment effect of overminus treatment on distance intermittent exotropia (IXT) control score.
* The off-treatment effect of overminus treatment on distance IXT control score (following weaning and 3 months off treatment).

The main objectives of this randomized trial comparing overminus lens treatment to non-overminus (spectacles without overminus or spectacles with plano lenses) are to determine:

* The long-term on-treatment effect of overminus treatment on distance IXT control score.
* The off-treatment effect of overminus treatment on distance IXT control score (following weaning and 3 months off treatment).

The recently completed IXT3 pilot study (NCT02223650) addressed the question of whether overminus lens therapy has an initial short-term therapeutic effect for IXT while wearing overminus spectacles. There have been no rigorous studies that address the following important questions related to overminus lens therapy:

* Does overminus lens therapy have a long-term therapeutic effect for IXT while wearing overminus spectacles (over many months or years)?
* Does overminus lens therapy have a long-term therapeutic effect for IXT when overminus spectacles are discontinued?

In November 2019, a protocol amendment discontinued overminus lens treatment and extended the study for an additional 18 months after the 18-month randomized trial has ended. The objective of the extension study is to compare long-term refractive error between subjects originally treated with either overminus spectacles or non-overminus spectacles as part of the 18-month randomized trial; treatment is at investigator discretion.

Eligibility Criteria:
Inclusion Criteria:

* Age 3 years to \< 11 years
* Intermittent exotropia (manifest deviation) meeting all of the following criteria:
* At distance: intermittent exotropia or constant exotropia

  o Mean distance control score of 2 points or more (mean of 3 assessments over the exam)
* At near: intermittent exotropia, exophoria, or orthophoria

  o 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)
* Distance visual acuity (any optotype method) in each eye of 0.4 logMAR (20/50) or better if age 3 years and 0.3 logMAR (20/40) or better if 4 years or older.
* Interocular difference of distance visual acuity ≤0.2 logMAR (2 lines on a logMAR chart)
* Refractive error between -6.00 diopters (D) standard error (SE) and +1.00D SE (inclusive) in the most myopic / least hyperopic eye based on a cycloplegic refraction performed within the past 2 months or at the end of the enrollment exam.
* If refractive error (based on cycloplegic refraction performed within past 2 months or at the end of the enrollment exam) meets any of the following criteria, then pre-study spectacles are required and must have been worn for at least 1 week prior to enrollment:
* SE anisometropia ≥1.00D
* Astigmatism ≥1.50D in either eye
* SE myopia ≥-1.00D in either eye

Pre-study refractive correction, if worn, must meet the following criteria relative to the cycloplegic refraction performed within past 2 months or at the end of the enrollment exam:

* SE anisometropia must be corrected within \<1.00D of the SE anisometropic difference
* Astigmatism must be corrected within \<1.00D of full magnitude; axis must be within 10 degrees.
* The SE of the spectacles must not meet the definition of substantial overminus (see exclusion criteria below)
* Gestational age ≥ 32 weeks
* Birth weight \> 1500 grams
* Parent understands the protocol and is willing to accept randomization to overminus spectacles or non-overminus spectacles
* 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 18 months is not anticipated

Exclusion Criteria:

* Treatment for IXT or amblyopia (other than refractive correction) within the past 4 weeks, including vision therapy, patching, atropine, or other penalization.
* Current contact lens wear
* Substantial deliberate overminus treatment within the past 6 months, defined as spectacles overminused by more than 1.00D SE than the cycloplegic refractive error (within 2 months or at the end of the enrollment exam)
* Prior strabismus, intraocular, or refractive surgery (including BOTOX injection)
* Abnormality of the cornea, lens, or central retina
* Down syndrome or cerebral palsy
* 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.
* Any disease known to affect accommodation, vergence, and ocular motility such as multiple sclerosis, Graves orbitopathy, dysautonomia, myasthenia gravis, or current use of atropine for amblyopia
* Anti-seizure medications \[e.g., carbamazepine (Tegretol, Carbatrol, Epitol, or Equetro), diazepam (Valium or Diastat), clobazam (Frisium or Onfri), clonazepam (Klonopin), lorazepam (Ativan), ethosuximide (Zarontin), felbamate (Felbatol), lacosamide (VIMPAT), gabapentin (Neurontin), oxcarbazepine (Oxtellar XR or Trileptal), phenobarbital, phenytoin (Dilantin or Phenytek), pregabalin (Lyrica), tiagabine (Gabitril), topiramate (Topamax), valproate (Depakote), or zonisamide (Zonegran), vigabatrin (Sabril)\]