Purchase this article with an account.
Ji C. He, Maggie X. Dong; The Relationship of Corneal Asymmetry and Pupil Center Shift with Peripheral Astigmatism Asymmetry. Invest. Ophthalmol. Vis. Sci. 2012;53(14):150.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Recent myopia study has shown an increasing interest in periphery refraction because peripheral hyperopia might be a risk factor for myopia development. While asymmetry of peripheral astigmatism over the temporal and nasal retina has been exhibited in previous studies, possible contribution for the astigmatism asymmetry from the factors at the anterior segment, however, is not well understood. The purpose of this study is to investigate the relationship of the asymmetry of peripheral astigmatism with the corneal asymmetry and pupil center shift.
Refractions at primary gaze, 5°, 10°, 15°, 20°, and 25° eccentricity on the horizontal meridian in both nasal and temporal fields were measured for 21 young subjects aged 18-30 yrs old by using an open field autorefractor (WAM-5500). Peripheral astigmatism J0 and J45 were derived from the refractive measurements. A corneal topography system (Medmont E300U) was employed to measure anterior corneal heights, from which 35 Zernike terms were calculated with MatLab Program and the x-axis coma term was used to estimate corneal asymmetry.
On average, main axis astigmatism J0 for this group of subjects was asymmetrical to visual axis with more astigmatism in the temporal retinal side than in the nasal retinal side (e.g. -0.95±0.29D vs. -0.35±0.25D at 25°). The difference in mane astigmatism between temporal and nasal retina at the 25° was significant (t=7.30, p<0.0001). The mean x-axis coma of the anterior cornea and the mean x-axis pupil center shift relative to the corneal vertex were 0.18±0.39micron and -0.19±0.11mm respectively. When the difference in peripheral J0 between the 25° temporal and nasal fields was correlated to the corneal coma and pupil shift, significant correlation coefficients were found for both corneal coma (Pearson correlation R= 0.61, p<0.001) and pupil center shift (R=0.69, p<0.0001).
The results suggest that anterior structure of the eye plays important role in determining peripheral astigmatism asymmetry, and both corneal shape asymmetry and pupil center shift have significant contribution for the asymmetrical property in peripheral astigmatism.
This PDF is available to Subscribers Only