Glasses for growth: how farsightedness and astigmatism in infants are linked to strabismus and amblyopia - and what early correction gives

The journal Strabismus published a review that examines a simple but fundamental issue in pediatric ophthalmology: should we add refractive error screening to mass screening of visual acuity in preschoolers? And does prescribing glasses “from infancy” really help prevent amblyopia (“lazy eye”) and accommodative esotropia (focus-dependent convergent strabismus)? The authors collected longitudinal studies where children were assessed at 6-24 months and followed up to 3-9 years. The conclusions are stark: high hyperopia and significant astigmatism in infancy greatly increase the risk of amblyopia and accommodative esotropia, while the effect of “early glasses” on these outcomes is present, but moderate.

Background of the study

In many countries, children undergo mass vision screening: usually only visual acuity is checked. But amblyopia often develops on the basis of “hidden” refractive errors - hyperopia (farsightedness), astigmatism and, less frequently, anisometropia - long before the child “fails” the chart. Therefore, it is logical to ask: if high refractive errors are detected earlier and correction is prescribed, is it possible to reduce the risk of amblyopia and strabismus?

The authors of the review specifically selected longitudinal studies: start in infancy (6-24 months), mandatory cycloplegic skiascopy at least once, and final assessment in preschool years (3-9 years). This design allows not only to compare "slices", but to track what precedes what.

The results boil down to several patterns. First, high hyperopia at 8-12 months is a powerful predictor: the chances of getting amblyopia by preschool age increased tens of times; similarly - for accommodative esotropia. Second, early astigmatism is also significantly associated with future amblyopia (and with esotropia - weaker). Third, anisometropia without concomitant "high" hyperopia looked like a weak factor.

And finally, the main practical point is early optical correction. According to the aggregate data, it reduced the risk of amblyopia in "refractive-high-risk" children, but the effect on the risk of accommodative esotropia was less stable: in some studies, the effect was noticeable, in others, minimal. This sets the tone for realism: glasses are an important tool for preventing amblyopia, but not an absolute "shield" from strabismus.

Why is this important?

In early childhood practice, the "winning year" often decides the outcome. If high hyperopia and astigmatism in infants are real markers of increased risk, then adding refractive screening to visual acuity testing can intercept "quiet" cases while neuroplasticity is still on our side. And knowing the moderate benefit of "early glasses" does not diminish their role - it simply helps to build honest expectations, an observation route, and to include additional measures (pleioptics, occlusion, etc.) in time.

Purpose of the study

To assess how hyperopia, astigmatism and anisometropia at 6-24 months are associated with the risk of amblyopia and accommodative esotropia at 3-9 years, and to determine whether early prescription of spectacle prescriptions reduces the likelihood of these outcomes in real-world longitudinal studies.

Materials and methods

The authors conducted a thematic search with the keywords “refractive errors”, “amblyopia/strabismus”, “children”, selected longitudinal studies with entry at 6-24 months, mandatory cycloplegic retinoscopy and final assessment at 3-9 years; cross-sectional studies were excluded. As a result, 1 RCT, 2 controlled studies and 13 cohort studies were included in the analysis; 5458 publications were initially found.

What exactly was included and what was measured:

• Exposures: hyperopia (usually thresholds ≥+3.5 D; also ranges >+2.66 to ≥+4 D), astigmatism (≥1.0-1.5 D), anisometropia (≥0.75 D, often in combination with hyperopia).
• Results: diagnosed amblyopia and/or accommodative esotropia by preschool age; the effect of early correction (glasses) on the risks of these outcomes.

Results and interpretation

The associations were strong and consistent across independent centers. For hyperopia ≥+3.5 D at 8-12 months, the odds of developing amblyopia by preschool age were 17-142 times higher (3 studies), and accommodative esotropia - 16-23 times (2 studies). At hyperopia thresholds >+2.66-≥+4 D (0-12 months) with growth by 3 years, the odds of esotropia increased 5-195 times (3 studies). For astigmatism ≥1.5 D at 12 months, the risk of amblyopia increased ≈9 times (1 study), and for ≥1.0 D at 12 months with growth by 3 years - 10-141 times (2 studies). Anisometropia ≥0.75 D alone (even in combination with hyperopia) showed a weak association with future esotropia (OR ≈1.31). Early prescription of glasses at 6-24 months was associated with a reduced risk of amblyopia (OR 0.10-0.79, 3 studies), but for esotropia the effect varied (OR 0.79-2, 5 studies), which the authors interpret as a moderate effect of early correction on strabismus.

Discussion

The signal is clear: high hyperopia and pronounced astigmatism in infancy are "red flags" for amblyopia, and hyperopia is especially critical for esotropia. The moderate and not always stable effect of early glasses on esotropia is understandable mechanistically: glasses relieve accommodation and reduce convergence, but do not eliminate all causes of sensorimotor imbalance; some children will still require occlusion therapy, orthotopy, or surgery. An important practical caveat is that most of the included studies are observational, with different refractive thresholds and approaches to prescribing glasses: this explains the range of estimates and requires careful interpretation at the level of population programs. However, the magnitude of effects in high hyperopia/astigmatism and the consistency between centres (Kettering, Cambridge, Gothenburg, Columbus) make the case for early refractive screening very compelling.

Practical significance

The findings of the review can be translated into the field at the level of children's offices and screening programs.

What makes sense to do in the clinic and public health:

• Add refraction to screening: if possible - cycloplegic autorefractometry/skiascopy in children 6-24 months from risk groups (family history of strabismus/amblyopia, prematurity, neurological factors), as well as in case of “suspicious” pupillary reflexes/photo-screening.
• Prescribe glasses in a targeted manner: for hyperopia ≥+3.5 D and/or astigmatism ≥1-1.5 D, consider early optical correction as a way to reduce the risk of amblyopia, with an honest explanation to parents that for esotropia the effects are variable and the child may need additional therapy.

Restrictions

This is a review with a predominance of observational longitudinal studies; RCTs are few. Refractive cutoff values and correction protocols varied, as did age windows, introducing heterogeneity and preventing the derivation of a “uniform” prescribing nomogram. A number of studies primarily examined photoscreener accuracy, refractive error prevalence, or program effectiveness rather than causality; therefore, the authors deliberately included only 1 RCT, 2 controls, and 13 cohorts. Finally, the resulting “odds” are associations, not proven causality for each family.

Conclusions

High hyperopia and significant astigmatism in the first and second years of life are strong markers of future amblyopia and accommodative esotropia. Early prescription of glasses significantly reduces the risk of amblyopia, but has a moderate effect on the risk of esotropia. From a practical point of view, this is an argument in favor of early refractive screening in addition to visual acuity testing and targeted correction in children at risk - with the readiness to timely include additional treatment methods.

Source: Steltman JS, Loudon SE, Simonsz HJ Evidence for hypermetropia, astigmatism, and anisometropia associated with, and early glasses preventing, the development of amblyopia and accommodative esotropia. Strabismus. Online ahead of print: September 2, 2025 DOI: 10.1080/09273972.2025.2551059.