Wavefront Aberrations in the Peripheral Retina Are Different in the Eyes of Myopic and Emmetropic Young Adults

Abstract

Purpose: : To measure wavefront aberrations in the central and peripheral retina and compare the amounts and patterns in myopic and emmetropic subjects.

Methods: : The Complete Ophthalmic Analysis System (COAS) was used to measure wavefront aberrations in the eyes of 36 young adult subjects (27 females, 9 males; mean age = 23.6 yrs). 18 were emmetropic (mean Rx = -0.10 D +/- 0.31) and 18 were myopic (mean Rx = -3.32 D +/- 1.86). Mean cylinder was -0.15D. The COAS was aligned to the subject's right eye which saw a red light surrounded by concentric circles. A mirror was aligned to the left eye so that they saw a target 33 cm away with small black letters on a white background. Aberrations were measured centrally, at 10 and 30 deg nasally and 10, 20, and 30 deg temporally. Three measurements were taken at each position. Means of the three measurements were compared by position and refractive group, using repeated measures ANOVA and t-tests for total RMS, higher order (HO) RMS, and 7 Zernike aberration terms (Z₂^-2 ,Z₂² ,Z₃^-3 ,Z₃^-1 ,Z₃¹ ,Z₃³ ,Z₄⁰ ).

Results: : For total RMS aberrations, there was a significant interaction between position and refractive status (p<0.001). Aberrations were greater in the far periphery than centrally and more aberrations were found in the temporal than nasal retina. More aberrations were found in emmetropes than myopes at temporal 20 (p=0.0005) and 30 deg (p=0.0001). Higher order aberrations differed significantly across the 6 positions (p< 0.0001), with more peripheral aberrations, but there were no refractive group differences (p = 0.31) and no interaction between position and refractive group (p = 0.72). Similar to total RMS, main axis astigmatism (Z₂²) was greater in the far periphery than centrally, and more astigmatism was found temporally than nasally. Z₂² was significantly greater in emmetropes than myopes at temporal 20 deg (p< 0.0001) and temporal 30 deg (p< 0.0001). Oblique astigmatism (Z₂^-2) was positive nasally and negative temporally, and was significantly greater in emmetropes than myopes at nasal 30 deg (p=0.005). Horizontal coma (Z₃¹) was positive nasally and negative temporally, but only for emmetropes (in myopes it was positive by a small amount at all positions). For the other higher order terms there were no consistent differences between positions or between emmetropes and myopes.

Conclusions: : Emmetropes were found to have higher total RMS aberrations than myopes in the peripheral retina, mainly due to more astigmatism. The astigmatism results are consistent with Hoogerheide et. al.(1971). Peripheral aberrations are now being measured after a period of near work to see if the pattern changes in either refractive group.

Keywords: myopia • aberrations • astigmatism