Effect of Ocular Alignment on Emmetropization in Children <10 Years With Amblyopia

doi:10.1016/j.ajo.2012.02.035

American Journal of Ophthalmology

Volume 154, Issue 2, August 2012, Pages 297-302.e1

https://doi.org/10.1016/j.ajo.2012.02.035 Get rights and content

Purpose

To determine whether change in refractive error is associated with ocular alignment in 105 children 3 to <7 years of age who previously participated in a randomized trial comparing atropine and patching for moderate amblyopia.

Design

Prospective cohort study.

Methods

One hundred five children 3 to <7 years of age previously participated in a randomized trial comparing atropine with patching for moderate amblyopia. Cycloplegic refraction was measured at baseline and 10 years of age. Ocular alignment at baseline was categorized as orthotropic, microtropic (1–8 Δ horizontal tropia), or heterotropic (>8 Δ horizontal tropia). Multivariate regression models evaluated whether change in spherical equivalent refractive error was associated with alignment category, after adjusting for age, baseline spherical equivalent refractive error, and type of amblyopia treatment.

Results

Between enrollment and the age 10–year examination, there was a decrease in spherical equivalent refractive error from hyperopia to less hyperopia (amblyopic eye: −0.65 diopter, 95% CI −0.85, −0.46; fellow eye: −0.39 diopter, 95% CI −0.58, −0.20). A greater decrease in amblyopic eye refractive error was associated with better ocular alignment category (P = .004), with the greatest decrease occurring in orthotropic patients. There was no relationship between ocular alignment category and change in fellow-eye refractive error.

Conclusions

Among children treated for anisometropic, strabismic, or combined mechanism amblyopia, there is a decrease in amblyopic eye spherical equivalent refractive error to less hyperopia after controlling for baseline refractive error. This negative shift toward emmetropia is associated with ocular alignment, which supports the suggestion that better motor and sensory fusion promote emmetropization.

Section snippets

Methods

The study protocol has been detailed elsewhere,4, 5 is available on the PEDIG website (www.pedig.net), and is summarized at www.clinicaltrials.gov under the identifier NCT00000170. A brief summary of the protocol follows.

Primary eligibility criteria for the multicenter randomized trial included age less than 7 years, visual acuity in the amblyopic eye of 20/40 to 20/100, visual acuity in the fellow eye of 20/40 or better, interocular acuity difference of 3 or more logarithm of minimal angle of

Demographics of Cohort

The median age of the 105 subjects at randomization was 5.2 years (range 2.6 to 7.0 years). At enrollment, median amblyopic eye visual acuity was 20/63 (range 20/40 to 20/125)⁴; median fellow eye visual acuity was 20/25 (range 20/16 to 20/40); median amblyopic eye spherical equivalent refractive error was +4.50 D (range 0.00 to +8.75 D); and median fellow eye spherical equivalent refractive error was +2.50 D (range 0.00 to +8.00 D). Of the 58 subjects with a tropia at enrollment, 51 (88%) had

Discussion

We evaluated change in amblyopic eye refractive error in 105 (104 hyperopic, 1 emmetropic) children who were treated with the appropriate refractive correction followed by occlusion or atropine for strabismic, anisometropic, or combined-mechanism amblyopia at age 3 to <7 years and followed to age 10 years. We found a negative shift in amblyopic eye spherical equivalent refractive error. The shift was small, so that the majority of subjects remained hyperopic in each eye at age 10 years. A

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Observations on the relationship between anisometropia, amblyopia and strabismus
2017, Vision Research
Citation Excerpt :
In this scenario, because the degree of relative peripheral myopia generally increases with eccentricity (at least along the horizontal meridian) (Millodot, 1981; Millodot & Lamont, 1974), it would be expected that these stop signals would be greater in individuals with larger degrees of esotropia. In agreement with this idea, larger emmetropizing responses have been observed in the amblyopic deviating eyes of individuals with smaller ocular misalignments (Kulp et al., 2012). During nearwork, depending on the size of the object of regard and the angle of deviation, the fovea of the deviating eye could also receive images that are myopically defocused.
We investigated the potential causal relationships between anisometropia, amblyopia and strabismus, specifically to determine whether either amblyopia or strabismus interfered with emmetropization. We analyzed data from non-human primates that were relevant to the co-existence of anisometropia, amblyopia and strabismus in children. We relied on interocular comparisons of spatial vision and refractive development in animals reared with 1) monocular form deprivation; 2) anisometropia optically imposed by either contact lenses or spectacle lenses; 3) organic amblyopia produced by laser ablation of the fovea; and 4) strabismus that was either optically imposed with prisms or produced by either surgical or pharmacological manipulation of the extraocular muscles. Hyperopic anisometropia imposed early in life produced amblyopia in a dose-dependent manner. However, when potential methodological confounds were taken into account, there was no support for the hypothesis that the presence of amblyopia interferes with emmetropization or promotes hyperopia or that the degree of image degradation determines the direction of eye growth. To the contrary, there was strong evidence that amblyopic eyes were able to detect the presence of a refractive error and alter ocular growth to eliminate the ametropia. On the other hand, early onset strabismus, both optically and surgically imposed, disrupted the emmetropization process producing anisometropia. In surgical strabismus, the deviating eyes were typically more hyperopic than their fellow fixating eyes. The results show that early hyperopic anisometropia is a significant risk factor for amblyopia. Early esotropia can trigger the onset of both anisometropia and amblyopia. However, amblyopia, in isolation, does not pose a significant risk for the development of hyperopia or anisometropia.
The relationship between anisometropia and amblyopia
2013, Progress in Retinal and Eye Research
Citation Excerpt :
After a further 18 months of standard clinical care the full set of patients still had on average a two line difference in acuity between the eyes (Repka et al., 2005), so while their amblyopia did respond to manipulation of visual experience (average improvement was 3–4 lines), the difference in acuity between the eyes was not routinely fully eliminated, and when 169 of these patients were tested at 10 years of age the results had been maintained in that the average amblyopic eye visual acuity was 20/32 with only 46% of amblyopic eyes having an acuity of 20/25 or better (Repka et al., 2008). Interestingly this group has recently noted that the amblyopic eye of non-strabismic patients is likely to undergo a small amount of emmetropization over this period up to 10 years of age (Kulp et al., 2012). Other studies have addressed the question of treatment compliance with patching by incorporating a device designed to monitor occlusion compliance (Fielder et al., 1995).
This review aims to disentangle cause and effect in the relationship between anisometropia and amblyopia. Specifically, we examine the literature for evidence to support different possible developmental sequences that could ultimately lead to the presentation of both conditions. The prevalence of anisometropia is around 20% for an inter-ocular difference of 0.5D or greater in spherical equivalent refraction, falling to 2–3%, for an inter-ocular difference of 3D or above. Anisometropia prevalence is relatively high in the weeks following birth, in the teenage years coinciding with the onset of myopia and, most notably, in older adults starting after the onset of presbyopia. It has about one-third the prevalence of bilateral refractive errors of the same magnitude. Importantly, the prevalence of anisometropia is higher in highly ametropic groups, suggesting that emmetropization failures underlying ametropia and anisometropia may be similar.
Amblyopia is present in 1–3% of humans and around one-half to two-thirds of amblyopes have anisometropia either alone or in combination with strabismus. The frequent co-existence of amblyopia and anisometropia at a child's first clinical examination promotes the belief that the anisometropia has caused the amblyopia, as has been demonstrated in animal models of the condition. In reviewing the human and monkey literature however it is clear that there are additional paths beyond this classic hypothesis to the co-occurrence of anisometropia and amblyopia. For example, after the emergence of amblyopia secondary to either deprivation or strabismus, anisometropia often follows. In cases of anisometropia with no apparent deprivation or strabismus, questions remain about the failure of the emmetropization mechanism that routinely eliminates infantile anisometropia. Also, the chronology of amblyopia development is poorly documented in cases of ‘pure’ anisometropic amblyopia. Although indirect, the therapeutic impact of refractive correction on anisometropic amblyopia provides strong support for the hypothesis that the anisometropia caused the amblyopia. Direct evidence for the aetiology of anisometropic amblyopia will require longitudinal tracking of at-risk infants, which poses numerous methodological and ethical challenges. However, if we are to prevent this condition, we must understand the factors that cause it to develop.
Can Amblyopia of Any Severity be Treated Successfully Irrespective of a Patient’s Age?
2023, Research Square
Insights Regarding Optometric Findings of CHARGE Syndrome in a Pediatric Low Vision Clinic
2023, Optometry and Vision Science
Assessment of Retinal Nerve Fiber Layer and Ganglion Cell Complex Thickness in Myopic versus Emmetropic Children attending Ophthalmology Outpatient Clinic in Suez Canal University Hospital
2022, Suez Canal University Medical Journal

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Original articleEffect of Ocular Alignment on Emmetropization in Children <10 Years With Amblyopia

Purpose

Design

Methods

Results

Conclusions

Section snippets

Methods

Demographics of Cohort

Discussion

J AAPOS

J AAPOS

Am J Ophthalmol

Am J Ophthalmol

J AAPOS

Vision Res

A randomized trial of atropine vs patching for treatment of moderate amblyopia: follow-up at age 10 years

Arch Ophthalmol

Developmental visual system anomalies and the limits of emmetropization

Ophthalmic Physiol Opt

A randomized trial of atropine vs patching for treatment of moderate amblyopia in children

Arch Ophthalmol

Original article
Effect of Ocular Alignment on Emmetropization in Children <10 Years With Amblyopia