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Andreas Hartwig, David A. Atchison, Hema Radhakrishnan; Higher Order Aberrations In Anisometropia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2708. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Myopia incidence is increasing around the world. Myopisation is considered to be caused by a variety of factors. One consideration is whether higher order aberrations (HOA) influence myopisation. Anisometropia is a special case, where both eyes are exposed to same conditions, but emmetropisation differs between both eyes. More knowledge of optics in anisometropic eyes might give further insight into the development of refractive error. To analyse the possible influence of HOA on refractive error development, we compared HOA between anisometropes and isometropes.
We analysed HOA up to the 4th order for both eyes of 17 anisometropes (mean age: 41±18 years) and 17 isometropes (mean age: 28±12 years). HOA were measured with the Shack-Hartman i.Profiler (Carl Zeiss, Germany) and were recalculated for a 4mm pupil. Mean spherical equivalent (MSE) was based on the subjective refraction. Anisometropia was defined as ≥1D interocular difference in MSE and ranged between 1.0D and 8.8D. Interocular differences in HOA were compared with the interocular difference in MSE using Pearson correlations. HOA in the two eyes of anisometropes were also analysed using paired t-tests.
Significant correlations were found between the interocular difference in MSE and the interocular difference of the following HOA: vertical coma (p=0.01), horizontal coma (p=0.03), oblique tetrafoil (p=0.05), spherical aberration (p=0.05) and tetrafoil (p=0.02). Correlations for oblique trefoil, trefoil, oblique 2nd astigmatism and 2nd astigmatism were not significant (p>0.05). Slopes of significant correlations for vertical coma (-0.4µm/D), horizontal coma (0.4µm/D), oblique tetrafoil (-0.3µm/D), spherical aberration (0.3µm/D) and tetrafoil (0.4µm/D) indicate an increase in the difference of these aberrations with increasing anisometropia. Comparing interocular HOA of anisometropes using t-tests showed significant differences for horizontal coma (p=0.01), oblique tetrafoil (p=0.02), oblique 2nd astigmatism (p=0.04) and spherical aberration (p=0.03).
With increasing anisometropia, the difference in HOA between eyes increases. However, it remains unclear, if HOA are a cause or the consequence of refractive error development.
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