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C. J. Shen, IV, N.-W. Kuo, V; The Biometrics, Intraocular Pressure, and Topography in Very High Myopes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1024.
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The aim of this study was to investigate refractive power, axial length, topography, and intraocular pressure between very high myopes and nonmyopes .
170 very high myopic eyes ( cycloplegic spherical equivalent was more than -10.0 diopters) and 20 nonmyopic control participants (cycloplegic spherical equivalent was within ±2.0 diopters ) . Age of them ranged from 20 to 29 years old. They received a complete ophthalmologic examination, which include measurement of manifest and cycloplegic refraction, best corrected visual acuity, intraocular pressure, keratometry, Orbscan topography , and axial length.
The mean spherical equivalent of high myopic group was -11.47 ± 1.38 D and the mean spherical equivalent of nonmyopic control group was +0.14 ± 1.11 D . The mean ocular axial length of high myopic group and control group was 28.08 ± 1.05 mm, 24.08± 0.98 mm, respectively. There was significant difference in spherical equivalent , axial length , mean keratometric power . 3 mm zone-mean keratometric power , and anterior float refractive power between these two groups. ( Mann -Whitney U test p < 0.05). There was no significant difference in intraocular pressure, corneal diameter, corneal thickness, anterior chamber depth, anterior and posterior float refractive power in topography between these two groups. Furthermore , in high myopes, the axial length was found to correlate significantly with cycloplegic refraction , mean keratometric power , and anterior chamber depth, anterior float refractive power in topography (Pearson correlation <0.05) . But axial length has no significant correlation either with intraocular pressure, corneal diameter, nor corneal thickness in topography in very high myopes. There were no significant differences in IOP, and corneal diameter between the two groups ( T-test: p = 0.37 ;0.19 respectively).
People with very high myopia have longer axial length and steeper keratometric values. Longitudinal elongation of the posterior vitreous chamber and the greater corneal curvature contribute to the development of very high myopia. Axial length plays a major role in the ocular biometry and refraction, but is not the only main factor contributed to myopic shift. There was no significant difference in the IOP between the very high myopes and nonmyopes.
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