A Prospective Observational Study of Adult Strabismus

Eligibility Criteria for Convergence Insufficiency (CI) Group:

The following inclusion criteria must be met for the subject to be enrolled into the study:

• Adults ≥18 years of age (adult onset of CI not required)
• No strabismus surgery within the past 10 years
• CI Symptom Survey score ≥21 points
• Near exodeviation of ≥4∆ and at least 4∆ larger than at distance by PACT
• Distance exodeviation ≤15∆ by PACT
• Vertical deviation ≤2∆ at distance and near by PACT
• No constant exotropia at distance or near
• Reduced positive fusional vergence (PFV) at near (<20∆ or fails Sheard's criterion that the PFV measures less than twice the magnitude of the near phoria)
• Near point of convergence (NPC) of ≥6 cm break
• Visual acuity 20/50 or better in both eyes by ETDRS or Snellen
• No paralytic strabismus (e.g., 3rd, 4th, or 6th cranial nerve palsies, skew deviation, Duane syndrome)
• No restrictive strabismus (e.g., blowout fracture, thyroid eye disease, post scleral buckle, Brown syndrome)
• No monocular diplopia
• No paretic strabismus, thyroid eye disease, myasthenia gravis, chronic progressive external ophthalmoplegia, or eye movement abnormalities associated with known neurological disease. Patients with Parkinson's disease can be enrolled if non-paretic deviation.
• No inferior or superior oblique overaction defined as 2+ or greater
• Ability to fuse with prism in space (see section 2.4.1)
• Ability to understand and complete a survey
• Investigator is initiating treatment with prism, orthoptic exercises, botulinum toxin injection or surgery
• If initiating treatment with botulinum toxin or surgery, planned injection or surgery to be within 60 days of enrollment
• Single treatment modality is planned (e.g., no combined prism and orthoptic exercises)
• Treatment to be initiated has not been used within the past one year

Eligibility Criteria for Divergence Insufficiency (DI) Group:

The following inclusion criteria must be met for the subject to be enrolled into the study:

• Adults ≥18 years of age
• Adult-onset DI (at ≥18 years of age)
• No prior strabismus surgery
• Symptoms of diplopia at distance with a frequency of sometimes or worse in primary position (in current glasses if wearing glasses)
• Distance esodeviation of 2∆ to 30∆ and at least 50% larger than at near by PACT
• No more than 5∆ difference between right and left gaze by PACT
• No more than 10∆ difference between the primary position at distance and either upgaze or downgaze ≤10∆ by PACT
• Any coexisting vertical deviation must be less than distance esodeviation and ≤10∆ by PACT
• Visual acuity 20/50 or better in both eyes by ETDRS or Snellen
• No paralytic strabismus (e.g., 3rd, 4th, or 6th cranial nerve palsies, skew deviation, Duane syndrome)
• No restrictive strabismus (e.g., blowout fracture, thyroid eye disease, post scleral buckle, Brown syndrome)
• No monocular diplopia
• No paretic strabismus, thyroid eye disease, myasthenia gravis, chronic progressive external ophthalmoplegia, or eye movement abnormalities associated with known neurological disease. Patients with Parkinson's disease can be enrolled if non-paretic deviation
• No inferior or superior oblique overaction defined as 2+ or greater
• Ability to fuse with prism in space (see section 2.4.2)
• Ability to understand and complete a survey
• Investigator is initiating treatment with prism, orthoptic exercises, botulinum toxin injection or surgery
• If initiating treatment with botulinum toxin or surgery, planned injection or surgery to be within 60 days of enrollment
• Single treatment modality planned (e.g., no combined prism and orthoptic exercises)
• Treatment to be initiated has not been used within the past one year

Eligibility Criteria for Small-angle Hypertropia (HT) Group:

The following inclusion criteria must be met for the subject to be enrolled into the study:

• Adults ≥18 years of age
• Adult-onset HT (at ≥18 years of age)
• No prior strabismus surgery
• Symptoms of diplopia at dista