Is vision training still needed after strabismus surgery?
What do surgery and vision training each address?
One way to think about it: surgery deals with the "hardware", while vision training deals with the "software".
Strabismus surgery improves how the eyes are aligned by adjusting the position or tension of the extraocular muscles. But "both eyes pointing in the same direction" and "the brain knowing how to use the images from both eyes at the same time" are two different things. Binocular vision is a function of the brain—the brain needs to fuse the images from the left and right eyes into a single image with depth. If a child has had strabismus for a long time, the brain may already be used to suppressing the signal from one eye to avoid double vision; once the eyes are aligned after surgery, this habit of suppression does not necessarily disappear on its own.
The role of vision training is, after the eye alignment has improved, to rebuild fusion, reduce suppression, and develop stereopsis through systematic exercises.
Which children may need a post-operative vision assessment?
- Still complaining of double vision after surgery, or tiring especially easily during near work
- Still tilting the head or squinting one eye when looking at things, or only feeling comfortable with one eye closed
- Longer duration of strabismus before surgery, or a diagnosis of amblyopia before surgery
- After surgery for intermittent strabismus, the eye "drifts back out" again when tired or unwell
- Weak performance on stereopsis tests (such as hidden-figure or stereo images)
Can vision training replace surgery?
The honest answer: in most cases no, because the two address different problems. Large-angle constant strabismus usually needs surgery to correct the eye alignment; vision training cannot "straighten" an eye that is noticeably turned. The area with stronger evidence supporting vision training is convergence insufficiency—a large randomised controlled trial (CITT) showed that in-office vision training combined with home exercises has a clear therapeutic effect on convergence insufficiency in children¹. As for binocular vision rehabilitation after strabismus surgery, the goal of training is to consolidate the surgical outcome and build fusion; the two are complementary rather than substitutes.
When should assessment begin?
A detailed binocular vision assessment is generally carried out once the ophthalmologist has confirmed that the eye alignment is stable and the wound has healed after surgery (usually several weeks to several months post-operatively, depending on the doctor's advice). The assessment includes measurement of eye alignment, suppression testing, fusion ranges, stereopsis, and accommodation. The ophthalmologist and optometrist then decide together whether training is needed, the goals of training, and a rough timeline.
Signs for parents to watch for
- The child often closes one eye or tilts the head when doing homework or reading
- Complains that words "move around", skips lines or misses words, or reads especially slowly
- Misjudges distance when going down stairs or catching a ball, falls easily, or is afraid of heights
- Reports double vision, or that "one eye drifts off" when tired
If any of the above appears, it is worth arranging a comprehensive binocular vision assessment.
Registered Optometrist (Part I) in Hong Kong, BSc (Hons) in Optometry from The Hong Kong Polytechnic University, and doctoral researcher in visual neuroscience. Seven years of clinical and research experience, having co-managed strabismus and post-operative cases together with ophthalmologists at a multi-specialty eye clinic. Full professional profile →
- Convergence Insufficiency Treatment Trial (CITT) Study Group (2008). Randomized Clinical Trial of Treatments for Symptomatic Convergence Insufficiency in Children. Archives of Ophthalmology, 126(10), 1336–1349.
- Wong, S.-C., Leung, T.-W., Thompson, B., & Cheong, A. M. Y. (2024). Continuous Theta Burst Stimulation on V5/MT+ Induces Hemifield-Specific Modulation of Motion Sensitivity. IOVS, 65(7), 2453.