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Stephanie X. Shao, Nancy J. Coletta; Perifoveal Retinal Thickness and Acuity in Axial Myopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3601.
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Interferometric acuity decreases with increasing myopia or axial length, and this effect is most likely related to increased cone spacing (Chui et al., IOVS, 2008). Since retinal thinning may be an indicator of increased retinal stretch, and hence decreased acuity, our goal was to determine if perifoveal retinal thinning is associated with an interferometric acuity deficit at the corresponding visual field position.
Refractive errors of 35 subjects ranged from +0.25 D to -9.00 D and axial lengths ranged from 22.5 to 26.7 mm. An Optovue RTVue spectral domain OCT was used to measure perifoveal retinal thickness in the 3-6 mm diameter ring, sub-divided into quadrants. Thickness data was segmented at the inner plexiform layer (IPL) into outer and inner retinal thickness. Interferometric acuity over a 2 deg diameter patch was measured at 7° retinal eccentricity in four meridians.
Acuity at all four perifoveal locations decreased with increasing axial length, significantly in the nasal (p=0.013) and inferior (p=0.013) retina. Retinal thickness decreased with axial length in the perifovea, significantly in the superior (p=0.039) and inferior (p=0.039) quadrants. The superior perifoveal quadrant showed the most inner retinal thinning (p=0.023), but the least outer retinal thinning with axial length, compared to the other quadrants. Acuity was not correlated significantly with full, inner or outer retinal thickness in any perifoveal quadrant, but nasal retinal acuity was significantly lower in subjects with nasal inner retinal thickness below the median (< 105 micron) (p=0.020).
Subjects with long axial lengths exhibit retinal thinning and decreased acuity in the perifovea, but acuity was generally not correlated with retinal thickness. Since the acuity deficit in myopia is consistent with increased cone spacing, the changes in retinal thickness and cone density in axial myopia may have separate underlying factors.
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