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Stephanie Shao, Nancy Coletta; Comparison of foveal and perifoveal acuity in myopia. Invest. Ophthalmol. Vis. Sci. 2013;54(15):576.
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© ARVO (1962-2015); The Authors (2016-present)
Visual acuity and cone density both decrease at parallel rates with increasing myopia (Coletta and Watson, Vis. Res., 2006; Chui et al., IOVS, 2008). Young adult eyes with refractions less than 3D are reported to have relatively lower perifoveal cone density when the foveal cone density is high, implying that foveal specialization involves greater migration of perifoveal cones to the foveal area (Elsner et al., ARVO 2012). We compared perifoveal and foveal acuity in a group of young adult subjects with the aim of determining whether higher foveal acuity was associated with relatively lower perifoveal acuity and if this relationship was affected by the degree of myopia.
The subjects (n=33) had a mean age of 24.4 years +/- 1.8 s.d. Refractive errors ranged from +0.25 D to -8.88 D with a mean of -3.04 D and axial lengths, measured with a Zeiss IOL Master, ranged from 22.5 to 26.7 mm with a mean of 24.3 mm. Acuity was measured with 543nm laser interference fringes displayed in a 2 deg patch at the fovea and at 7° eccentricity in the temporal, nasal, superior and inferior retinal meridians. Acuity was expressed in cycles per mm on the retina, adjusted by the axial lengths.
Foveal and perifoveal acuity both decreased with increasing myopia, significantly at the fovea (p=0.0004). The perifoveal to foveal acuity ratio was on average 0.40 on the horizontal meridian and 0.28 on the vertical meridian. Perifoveal acuity in each retinal meridian increased with foveal acuity when all subjects were included. On the nasal retinal meridian, however, there was a negative correlation between perifoveal acuity and foveal acuity that was evident only for refractions in the range of -1.00 to -6.00 D.
A comparison of perifoveal and foveal acuity in young adults over a range of refractive errors indicates that acuity in the fovea and perifovea are generally positively correlated. However, in subjects with low to moderate myopia, perifoveal acuity on the nasal meridian decreased with increasing foveal acuity, implying that myopia may affect the relative cone density distribution on the nasal side of the fovea.
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