Convergence Exercises and Prism Therapy for Exophoria/Exotropia with Loss of Smooth Pursuit
For a patient with exophoria/exotropia and loss of smooth pursuit, convergence orthoptic exercises are often helpful, with office-based training being more effective than home-based exercises, and prism reading glasses can be used as an adjunctive or alternative nonsurgical treatment option. 1
Treatment Approach
Convergence Orthoptic Exercises
Office-based training is superior to home-based exercises for improving positive fusional vergence, particularly in younger adults (19-30 years), though both modalities show similar effects on near point of convergence and symptom relief 1. The key distinction is that office-based training allows better control of compliance and participation 1.
Important caveat: Results of convergence training are less consistent in adults than in children 1. This means you should set realistic expectations with adult patients and consider earlier escalation to other treatment modalities if exercises fail.
Specific Exercise Modalities
Recent evidence supports several approaches:
Smartphone-based fusion exercises combined with modified glasses prescription (overcorrection of myopia by -0.5D or undercorrection of hyperopia by +0.5D) can improve near point of convergence by approximately 2.89 cm, positive fusion vergence by 10.2 prism diopters, and reduce near phoria by 3.13 prism diopters 2
Localization exercises with hypercorrection prisms (30 prism diopters base-in) where patients touch surrounding objects while looking through each eye separately can provide persistent results 3
Post-surgical physiotherapy exercises (if applicable) delivered in 24 sessions over 3 months significantly improve both near and far exotropia control 4
Prism Therapy
Prism reading glasses are a viable nonsurgical treatment option that can be used alone or in combination with convergence exercises 1.
Prism Prescription Strategy
The evidence shows mixed results depending on the clinical scenario:
For convergence insufficiency with exophoria/exotropia: Prism reading glasses are recommended as part of nonsurgical management 1
For intermittent exotropia in children: Base-in relieving prism equal to 40% of the larger deviation (distance or near) was not more effective than refractive correction alone in a 2023 randomized trial 5. This suggests caution in using relieving prisms for this specific population.
For decompensated exophoria: Mini-prisms (horizontal or oblique depending on associated conditions) show promising results and complement orthoptic reeducation well 6
For long-term fusion disruption: A combination of prism therapy and orthoptic treatment over many months to years can restore fusion, though vertical fusion is less responsive and most often requires permanent prismatic correction 7
Critical Pitfall
Prism adaptation is challenging to define and measure in patients with exotropia 5. Patients who fully adapt to prisms during in-office testing may not benefit from prism spectacles, so perform a 30-minute prism adaptation test before prescribing.
Treatment Algorithm
First-line: Office-based convergence orthoptic exercises (preferred over home-based) 1
- Consider smartphone-based fusion exercises with modified glasses prescription 2
- Duration: Several months with close monitoring
Adjunctive or alternative: Prism reading glasses 1
- Perform prism adaptation testing first
- Start with temporary membrane prisms if needed
- Horizontal prisms respond better than vertical 7
If symptoms are mild and occasional: Monitor/observe without active treatment 1
If nonsurgical treatment fails: Consider strabismus surgery, particularly when manifest distance deviation is present and symptoms are consistent 1
Special Consideration: Loss of Smooth Pursuit
The loss of smooth pursuit suggests possible central nervous system involvement (Parkinson's disease, concussion) 1. Obtain detailed history of CNS disorders or trauma, as convergence insufficiency secondary to concussion may improve over time 1.
Provider Requirements
Management requires an ophthalmologist familiar with this diagnosis, with treatment benefiting from assistance of an orthoptist or optometrist 1.