Purchase this article with an account.
H. C. Howland, K. Angelino; Peripheral Refractions of Myopic Young Adults. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4001.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Recent work of Smith et al (2005,IOVS 46(11)3965) has raised the possibility that human myopic progression is driven by the relative hyperopia of the peripheral retina. We wished to determine if the peripheral retinas of young adult myopes were, in fact, hyperopic relative to the foveal refraction, and we also desired to measure oblique astigmatism in our subjects.
We used a Power Refractor (Multichannel systems, Reutlingen Germany) to refract seven non-cyclopleged subjects (age: 18-19 years, mean equiv sphere = -3.7 D ± 3.3 SD who viewed a tangent screen at 1 meter distance. Eight fixation targets were arranged around a 25 ° circle and another eight around a concentric 15 ° circle with the power refractor in the center. Refractions for central fixation were also obtained. The oblique astigmatism of the eye was estimated by subtracting the mean cylinder from the peripheral refractions at the two eccentricities. Individual cylinder axes at eccentric points were correlated with the expected axes of oblique astigmatism.
The mean difference between peripheral and central refractions for 25 ° eccentricity of the right eyes of 7 subjects was 0.56 D ±0.16 SE (p = 0.006, periphery more hyperopic). The corresponding measure for the 15 ° eccentricity was 0.12 D ±0.23 SE (ns) Good correlations between the predicted axes of oblique astigmatism and the measured axes were obtained (mean correlation coeff = 0.85, mean p = 003). For all eyes the oblique astigmatism at 15 ° was 1.17 D ±0.14 SE and 2.55 D ± 0.14 at 25 °.
From our data it appears possible that the progression of human myopia is driven by a hyperopic peripheral refraction. Our results are consistent with some other studies, but surprisingly, not with one using the same type of instrument (see Seidemann et al. 2002, JOSA 19(12) 2363 for a review) Oblique astigmatism of our population was about the magnitude of that found in the Indiana Chromatic eye (Wang & Thibos, 1997, Opt & Vis Sci 74(7)557), and is well represented (r2 = 0.993) in the range studied by the equation: Interval of Sturm [D] = 0.00422 * a2 , where a is given in degrees.
This PDF is available to Subscribers Only