Bifocal Spectacles vs. Single Vision Spectacles for Esotropia Greater at Near

Inclusion Criteria: * Age 3 to \<9 years * Esodeviation meeting all the following criteria is present in refractive correction (if required or worn) * Constant or intermittent esotropia ≥10∆ measurable by SPCT at near * Distance esotropia (constant, intermittent), esophoria, or orthophoria, with near esodeviation ≥10∆ larger than distance deviation by PACT * If constant ET at distance, then must be ≤6∆ by SPCT * If intermittent ET or esophoric at distance, can be any magnitude at distance (as long as near esodeviation is ≥10∆ larger than distance deviation by PACT) * Cycloplegic refraction within past 3 months (but not on day of exam) * Wearing spectacles for at least 4 weeks if refractive error is 0.75 D SE or more * Spectacles (if worn) must meet the following criteria: * SE refractive error must be corrected within ±0.625 D * Sphere power must be corrected within ±0.50 D * Anisometropia must be corrected within ±0.50 D SE * Cylinder power must be corrected within ±0.50 D * Cylinder axis must be within ±10 degrees if cylinder power is ≤1.00 D and within ±5 degrees if cylinder power is \>1.00 D. * Best-corrected VA meeting the following criteria: * Better-seeing eye VA is age-normal (see section 2.2) * IOD in VA within 0.2 logMAR (although previous amblyopia is allowed) * Worse-seeing eye VA of 20/63 or better * Investigator and parent willing to forgo treatment of ET other than assigned randomized treatment for 36 months unless failure criteria are met. * Investigator willing to prescribe BFL-spectacles only (in both treatment groups) for 2 months after meeting failure criteria (if failed prior to 36 months); otherwise, between 36 and 38 months Exclusion Criteria: * Previous BFL wear (SVL spectacle wear of any duration is allowed) * Current or planned contact lens wear over the next 3 years * Myopic refractive error of more than -6.00 D SE * Previous strabismus surgery (including Botox injection), intraocular surgery (e.g., laser, anti-VEGF injection, or cataract), extraocular surgery (e.g., scleral buckle), or refractive surgery * Previous treatment for ET using miotics, VT, or prism within prior 3 months * Amblyopia treatment other than refractive correction within prior 3 months * Vertical deviation ≥3Δ at distance or near by PACT * Oculomotor findings consistent with infantile ET (e.g., latent nystagmus, manifest nystagmus, DVD) * AV pattern: ≥10∆ difference between upgaze and downgaze by PACT at distance * Paretic or restrictive strabismus * Constant exotropia at near when tested through the +3.00 D add (intermittent XT and exophoria are allowed) * Diplopia "more than 2 times per day" over the last week prior to enrollment by parental report. The frequency of diplopia, if any, must be "2 times or less per day" to be eligible. * Significant developmental delay that would interfere with child's ability to complete testing * Neurological conditions that could affect ocular motility (e.g., cerebral palsy, Down syndrome) * Immediate family member (child or sibling) of any site personnel directly affiliated with the study