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D. A. Berntsen, D. O. Mutti, K. Zadnik; Peripheral Image Quality in Myopic Children. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4302.
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The peripheral retina influences eye growth in animal models, and a role for the peripheral retina in myopia progression has been proposed. We describe peripheral retinal image quality under habitual pupil conditions using a single-valued metric in myopic children.
Habitual pupil size was measured under photopic conditions in 85 myopic children with a COAS aberrometer. Aberrations were measured after cycloplegia along the line of sight, 30º nasally, temporally, and superiorly, and 20º inferiorly on the retina. Because the pupil was dilated when measuring aberrations, an analysis circle with diameter equal to the long axis of the habitual peripheral pupil was fit within the oval peripheral wavefront data. Zernike polynomials were fitted through the 6th order and were used to calculate the visual Strehl ratio using the optical transfer function (VSOTF). Prior to calculating VSOTF, reconstructed peripheral wavefronts were masked to eliminate data outside the habitual oval pupil. Because pupil size varied across children, the VSOTF was "un-normalized" relative to the neural-weighted diffraction limited case. The metric was calculated using higher-order aberrations (HOAs) only and with HOAs plus relative peripheral refraction (RPR) (i.e., residual 2nd order aberrations after subtracting central 2nd order terms). A repeated-measure ANOVA with Tukey’s post-hoc t-tests was used to analyze these data.
The mean (± SD) age, spherical equivalent refractive error, and photopic pupil size were 9.8 ± 1.3 years, -1.95 ± 0.78 D, and 5.25 ± 0.80 mm, respectively. Differences in image quality for HOAs and HOAs + RPR depended on the retinal location measured (p < 0.0001). For HOAs only, image quality was highest centrally (114,487 ± 67,861) followed by 20° inferiorly on the retina (80,974 ± 41,295). No difference was found between the 30° nasal (63,415 ± 33,539), temporal (64,057 ± 38,446), and superior locations (64,279 ± 46,779), where image quality was poorest. For HOAs + RPR, image quality was best centrally (114,487 ± 67,861). No difference was found between the inferior (19,815 ± 20,260) and nasal locations (15,616 ± 15,958), both of which were worse than centrally. Image quality was poorest for both the temporal (5,080 ± 4,573) and superior retina (6,555 ± 6,935). Peripheral astigmatism was greater temporally and superiorly than inferiorly and nasally (p < 0.05).
Differences in retinal image quality exist by retinal location with the best image quality centrally and the poorest temporally and superiorly when including relative peripheral refraction. Differences in peripheral image quality are mainly driven by differences in peripheral astigmatism.
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