She's Been Wearing Minus Lenses Since She Was Two. She's Nearsighted.

August 28, 2026
​​​​​​​Dr. Eric Chow

Have  you been given "overminus glasses" for your child's intermittent exotropia?  Let's dig deeper into what the research says on the efficacy of that treatment and what the side effects are.  

MIAMI — A six-year-old girl comes in with her mother, who has been watching one of her daughter's eyes drift outward since she was an infant.

The story is a long one. At four months old, a local Miami pediatric ophthalmologist examined her and diagnosed pseudostrabismus — the very common situation where a baby's wide nasal bridge and epicanthal folds create the appearance of an eye turn that isn't actually there. That was a reasonable call. Most infants who look like they have a turn don't.

But by age two, the turn was real, and it had a name: intermittent exotropia. Two separate pediatric ophthalmologists confirmed it. The management plan was the standard conservative one — alternate patching, and overminus glasses. She's six years old now, she has been wearing minus lenses ever since. She is in them today, at −1.50 in both eyes.  

Her mother notices that without the glasses, she says, the eye turn looks the same. With them, she thinks it helped a little, but she isn't sure.

Then there's what the child herself reports. Her eyes water when she looks at something for a long time. She sometimes sees double. Things at near occasionally go blurry. Her eyes are itchy and, sitting in the chair, they visibly bother her.

"When a six-year-old volunteers that her eyes water and go blurry and sometimes double, that's not a child being difficult," says Dr. Eric Chow of Miami Vision Therapy. "That's a child describing a visual system under stress. The question is where the stress is coming from."

The main point: Overminus lenses are a legitimate, widely used, evidence-supported treatment for intermittent exotropia. They also carry a documented refractive cost, and they do not work for every child. When a child is wearing them without benefit — and especially when the child is nearsighted (myopic) — it is worth asking what other options there are. For many families, nobody has mentioned that vision therapy is an option at all. 

What overminus lenses actually do

The logic behind overminus is elegant. The eyes' focusing system and their inward-turning system are wired together: when you focus, your eyes converge. That linkage is called accommodative convergence.

So if a child's eyes drift outward, you can borrow convergence from the focusing system. Put a minus lens in front of the eye, and the child must accommodate to keep the world clear. That extra accommodation drags extra convergence along with it, pulling the drifting eye back in.

It works. In a network meta-analysis of 11 randomized trials covering 1,411 patients, published in BMC Ophthalmology in late 2024, overminus lenses ranked first among the four common non-surgical treatments for improving control of intermittent exotropia. This is not a fringe approach, and the ophthalmologists who prescribed it for this child were practicing within the evidence.

But borrowing has a price, and recent research in the field has now measured it fairly precisely.

What the research says it costs

The definitive study is a trial run by the Pediatric Eye Disease Investigator Group and published in JAMA Ophthalmology in March 2021. It enrolled 386 children aged 3 to 10 with intermittent exotropia and randomized them to overminus spectacles — −2.50 D for twelve months, then tapered — or to non-overminus spectacles.

At twelve months, the overminus group had meaningfully better distance control: a mean score of 1.8 versus 2.8.

Two other findings complicate that success.

1. First, the advantage did not survive the taper. By eighteen months, control scores were 2.4 in the overminus group and 2.7 in the non-overminus group — a difference that had largely evaporated.
2. Second, and more consequentially, the overminus group became more nearsighted. Mean myopic shift at twelve months was −0.42 D, against −0.04 D in the comparison group. Children who shifted by more than a full diopter: 17% on overminus, versus 1% without it. The finding was significant enough that the trial's overminus arm was stopped early, in November 2019.

A three-year extension published in JAMA Ophthalmology in March 2024 followed 205 of these children further and clarified the shape of the problem. The extra myopia did not keep compounding — between months 12 and 36 both groups progressed at nearly identical rates, −0.34 D and −0.36 D. But it also didn't go away. The net effect of one year of overminus, measured at three years, was about 0.33 D of additional myopia and roughly double the risk of a shift of 1.00 D or more. The authors' own recommendation is that this risk be discussed before treatment begins, "particularly for those already myopic."

That last phrase deserves to be pushed further than the paper pushes it.

"'Already myopic' is the obvious flag, and I'm glad they named it," Dr. Chow says. "But parental myopia is one of the strongest predictors we have of which children will become nearsighted and how fast they'll progress. If one or both parents are in glasses for distance, that absolutely belongs in the conversation before a child goes into overminus — even if the child's own refraction reads plano or plus today. You are deciding whether to add years of accommodative load to a visual system that already has a running start toward myopia. A family history question takes ten seconds to ask."

"I want to be careful here, because this is not a story about anyone doing something wrong," Dr. Chow says. "Overminus is in the guidelines. It has randomized evidence behind it. But the same randomized evidence tells us it buys control that fades when you take the lenses away, and that it costs the child some diopters on the way. Parents deserve to hear both halves of that sentence."

Back to the six-year-old

Here is where this particular case becomes unusual. Her uncorrected vision was 20/20 in each eye. Retinoscopy showed she is a +1.00 hyperope — farsighted.  She has been wearing −1.50 in both eyes.

Relative to her actual refractive state, those lenses ask her to hold roughly two and a half diopters of accommodation just to see the distance clearly, and to stack her near demand on top of that, all day, at school. Watery eyes on sustained viewing, intermittent double vision, and blur at near are precisely the symptoms that sustained accommodative demand produces.

And the measurement that mattered most: her exodeviation was 20 prism diopters at distance and 8 at near — identical with her glasses on and with them off.

"That's the finding that stops you," Dr. Chow says. "The entire justification for the lens is that it changes the angle. Hers doesn't move. So she's paying the full price of overminus and collecting none of the benefit — and her mother has been telling everyone for years that she wasn't sure it was helping. She was right."

The distance-greater-than-near pattern also matters. It points toward the divergence excess type of intermittent exotropia, which behaves differently and responds differently than the basic type, and which is worth identifying specifically rather than treating exotropia as one undifferentiated thing.

What nobody had told this family, across four years and three examinations, is that vision therapy exists as a treatment option for intermittent exotropia.

What the evidence actually shows about vision therapy for exotropia

For a long time, the honest answer about vision therapy for intermittent exotropia was that the clinical experience was encouraging and the randomized evidence was thin. That changed recently.

In 2019, Ma and colleagues published a pilot study in Optometry and Vision Science showing that twelve weeks of office-based vergence and accommodative therapy with home reinforcement produced statistically and clinically significant improvement in distance control and in the size of the near deviation.

A separate case series in the Journal of Optometry followed 40 patients through office-based vergence/accommodative therapy in a private practice setting and found distance and near control scores each improved by about 1.1 points — in patients who had already had strabismus surgery as well as those who hadn't.

Then, in Ophthalmic and Physiological Optics in 2024, the same group published the study the field had been waiting for: a single-masked randomized clinical trial of office-based vergence and anti-suppression therapy against observation alone, in 40 children and teenagers aged 6 to under 18 with untreated intermittent exotropia. Participants received sixteen weekly sessions with home reinforcement.

The therapy group finished with significantly better distance control — an adjusted mean difference of −0.9 points (p = 0.008). And the proportion of participants who improved by at least a full point was 75% in the therapy group against 25% in the observation group.

The authors' conclusion is worth quoting in full force: this provides the first randomized trial data demonstrating the effectiveness of office-based therapy for improving control of intermittent exotropia, and eye care practitioners should consider it a viable non-surgical treatment option.

Key takeaways:

• Overminus lenses treat intermittent exotropia by forcing accommodation, which drags convergence along with it. They are evidence-supported and they do improve control for many children.
• Randomized trial data show the control benefit fades once the lenses are tapered, and that one year of overminus is associated with roughly 0.33 D of extra myopia at three years and about double the risk of a shift of 1.00 D or more.
• The trial authors flag children who are already myopic as needing that conversation. Parental myopia deserves the same weight — if one or both parents are nearsighted, the child's risk of progression is meaningfully higher, and that should be stated before overminus is prescribed.
• The benefit is not universal. If a child's measured angle is the same with and without the lenses, the lens is imposing a cost without delivering the thing it was prescribed to do.
• A farsighted child in overminus lenses is carrying a substantial sustained accommodative load, which can produce watery eyes, intermittent double vision, and blur at near.
• Office-based vergence and anti-suppression therapy now has randomized trial support in intermittent exotropia, with 75% of treated participants improving by at least a full control point versus 25% under observation.
• Vision therapy belongs on the list of options presented to families. Too often it is never mentioned.

What we'd want any parent in this situation to ask

If your child has intermittent exotropia and is wearing overminus glasses, these are fair and specific questions to bring to your next appointment:

• What is my child's actual refractive error, without the overminus factored in?
• What is the measured angle of deviation with the glasses on, and with them off?
• Has the myopic shift risk from the PEDIG trial been discussed with us?
• Are either of us nearsighted — and has our family history been factored into this decision?
• Is this the divergence excess type or the basic type, and does that change the plan?
• Has vision therapy been considered as a treatment option, and if not, why not?

Where this leaves that six-year-old

She is farsighted, she has been in minus lenses for four years, her angle has never budged because of them, and her eyes hurt.

"Her mother did everything right," Dr. Chow says. "She noticed early, she sought care, she followed the plan, and she kept asking whether it was working. The system just never handed her the whole menu."

If your child has an eye that drifts, has been in glasses for years without a clear change, or is telling you their eyes water and the words go double — a functional vision evaluation will measure what the eyes are actually doing, with and without correction, and tell you plainly whether the current plan is earning its keep.

Miami Vision Therapy provides comprehensive functional vision evaluations and office-based vision therapy for children with intermittent exotropia and other binocular vision disorders. To schedule an evaluation with Dr. Eric Chow, call (786) 558-7295 or visit miamivt.com/request-an-appointment.

References

1. Chen A, Erzurum A, Chandler D, et al. Overminus Lens Therapy for Children 3 to 10 Years of Age With Intermittent Exotropia: A Randomized Clinical Trial. JAMA Ophthalmol. 2021 Mar. PMID 33662112.
2. Writing Committee for the Pediatric Eye Disease Investigator Group. Refractive Error Change and Overminus Lens Therapy for Childhood Intermittent Exotropia. JAMA Ophthalmol. 2024 Mar 21. PMID 38536764.
3. Song D, Ma Y, Ji H, Zhou Q, Cheng H. Non-surgical therapy for intermittent exotropia: a systematic review and network analysis. BMC Ophthalmol. 2024 Dec 19;24(1):527. PMID 39696091.
4. Ma MM, Kang Y, Scheiman M, et al. Office-based vergence and anti-suppression therapy for the treatment of small-to-moderate angle intermittent exotropia: A randomised clinical trial. Ophthalmic Physiol Opt. 2024 Mar;44(2):356-377. PMID 38146812.
5. Ma MM, Kang Y, Scheiman M, Chen X. Office-based Vergence and Accommodative Therapy for the Treatment of Intermittent Exotropia: A Pilot Study. Optom Vis Sci. 2019 Dec;96(12):925-933. PMID 31834152.
6. Vision therapy for intermittent exotropia: A case series. J Optom. 2020. PMID 32800454.
7. Long-Term Outcomes of Intermittent Exotropia: A Real-World Longitudinal Cohort Study of 415 Patients. Medicina. 2026;62(3):481.
8. Ma MM, Scheiman M. Divergence excess and basic exotropia types of intermittent exotropia: a major review. Part 2. Strabismus. 2024 Sep;32(3):159-194. PMID 38944823.