Woog Kelly, Legras Richard
Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Paris-Saclay, Université Paris-Saclay, Orsay, France.
Ophthalmic Physiol Opt. 2019 Mar;39(2):94-103. doi: 10.1111/opo.12604. Epub 2019 Jan 29.
We measured in vivo cone photoreceptors up to 24° of eccentricity along the horizontal meridian of healthy human retina. We also investigated the impact on cone densities of axial eye length elongation occurring with myopia.
Using a flood illumination device coupled with an adaptive optics system, rtx1™, ( www.imagine-eyes.com), 55 right healthy retinas were imaged along the horizontal (i.e. nasal and temporal) meridian over a 48° field (i.e. from 3° to 24° each 3°). Then, cones were manually detected within 80 × 80 pixel regions of interest. Cone density and packing geometry (i.e. number of neighbours) were calculated (AOdetect software™). Subjects were divided into three groups: a group of 36 emmetropic (i.e. refractive error from -0.25D to +0.50D) subjects; a group of 10 low myopic subjects (i.e. refractive error from -0.50D to -2.50D); and a group of nine high myopic subjects (i.e. >-2.50D).
Cone density decreased with eccentricity in both semi-meridians. The decrease in cone photoreceptors occurred mainly in the first 9°. The difference of cone density between the nasal and temporal semi-meridian increased with eccentricity from 0.6% at 3° to 26% at 24°. Average cone density of emmetropes (850 cones deg or 11 087 cones mm ), low myopes (830 cones deg or 9731 cones mm ), and high myopes (912 cones deg or 9744 cones mm ), suggested that the retinas of the high myopic subjects were more stretched than the low myopic subjects retinas and even more stretched than that of the emmetropes. The axial eyeball elongation (square of the ratio of the axial eye length of 9%) seems to explain the cone density (11%) difference between emmetropes and low myopes. However, while the eyeball elongation between low and high myopes is still important (i.e. 11%), cone density difference between both populations was negligible (i.e. 3%). The ratio of cone density varied from -17% to 22% as a function of eccentricity involving that the retinal stretching is not uniform along the horizontal meridian.
The difference of cone density (i.e. cone mm ) between groups supports the hypothesis that the retina is stretched with the eyeball elongation. However, this elongation does not seem to be uniform along the horizontal meridian favouring the hypothesis of a local elongation of the retina.
我们测量了健康人视网膜水平子午线上偏心度达24°的活体视锥光感受器。我们还研究了近视导致的眼轴长度延长对视锥细胞密度的影响。
在两个半子午线上，视锥细胞密度均随偏心度降低。视锥光感受器的减少主要发生在最初的9°。鼻侧和颞侧半子午线之间视锥细胞密度的差异随偏心度增加，从3°时的0.6%增加到24°时的26%。正视眼（850个视锥细胞/度或11087个视锥细胞/平方毫米）、低度近视者（830个视锥细胞/度或9731个视锥细胞/平方毫米）和高度近视者（912个视锥细胞/度或9744个视锥细胞/平方毫米）的平均视锥细胞密度表明，高度近视受试者的视网膜比低度近视受试者的视网膜拉伸程度更大，甚至比正视眼的视网膜拉伸程度更大。眼轴伸长（眼轴长度比例的平方为9%）似乎可以解释正视眼和低度近视者之间视锥细胞密度（11%）的差异。然而，虽然低度和高度近视者之间的眼轴伸长仍然很显著（即11%），但这两组人群之间的视锥细胞密度差异可以忽略不计（即3%）。视锥细胞密度的比例随偏心度在-17%到22%之间变化，这表明视网膜在水平子午线上的拉伸并不均匀。
各组之间视锥细胞密度（即视锥细胞/平方毫米）的差异支持了视网膜随眼轴伸长而拉伸的假说。然而，这种伸长在水平子午线上似乎并不均匀，这支持了视网膜局部伸长的假说。
