Analysis of Asphericity and Corneal Longitudinal Spherical Aberration of 915 Chinese Myopic Adult Eyes

Abstract

Purpose: To analyze the corneal asphericity, longitudinal spherical aberration (LSA), and related factors in Chinese myopic adult eyes.

Methods: This was a retrospective study of myopic adult patients. The corneal asphericity and LSA were measured at 3.0, 4.0, 5.0, 6.0, and 7.0 mm diameter apertures using corneal tomography. Age and refractive power were recorded for correlation analysis.

Results: In total, 531 females and 384 males were included. At the above five diameter settings the corneal asphericity values (Q) of the anterior surface were -0.09±0.21, -0.14±0.16, -0.15±0.13, -0.17±0.11, and -0.20±0.11, and those of the posterior surface were 0.23±0.49, 0.06±0.29, -0.01±0.22, -0.07±0.16, and -0.08±0.15, respectively. The anterior corneal LSA values at these diameters were 0.39±0.19, 0.63±0.27, 0.97±0.36, 0.90±0.30, and 0.83±0.29 D, respectively and the whole corneal values were 0.26±0.20, 0.44±0.27, 0.70±0.36, 0.66±0.30, and 0.59±0.28 D, respectively. Corneal asphericity and peripheral LSA showed no or weak correlation with age or spherical equivalent (all r < 0.2).

Conclusion: Corneal anterior and posterior Q values in myopia patients are negatively correlated with corneal diameter. Corneal anterior and whole corneal LSA increased significantly with diameter up to 5 mm, then decreased slightly with diameter. Corneal asphericity and peripheral LSA showed very weak or no correlation with age or spherical equivalent.

Clinical trial registration number: ChiCTR1800015985.

Keywords: asphericity; longitudinal spherical aberration; myopia; wavefront aberration.

Figure 1

Corneal surface coordinate system. For a point moving along the curve, is its velocity, α the angle of motion, and is its acceleration parallel to the z axis.

Figure 2

Refractive trajectory of light passing through the anterior surface of the cornea. The angle of motion α is also the angle of incidence, θ the angle of reflection; and n1 and n2 are the refractive indices of air and cornea respectively.

Figure 3

Refractive trajectory of light passing through the posterior surface of the cornea. β is the angle of motion; γ the angle of reflection; and n2 and n3 are the refractive indices of the cornea and aqueous humor, respectively.

Figure 4

Distribution of corneal Q value at 3.0, 4.0, 5.0, 6.0, and 7.0 mm aperture diameters, anteriorly and posteriorly, in 915 individuals. The corneal Q values of the anterior surface were: −0.09±0.21, −0.14±0.16, −0.15±0.13, −0.17±0.11, and −0.20±0.11, respectively, and those of posterior surface were 0.23±0.49, 0.06±0.29, −0.01±0.22, −0.07±0.16, and −0.08±0.15, respectively.

Figure 5

Distribution of corneal longitudinal spherical aberration (LSA) values at 3.0, 4.0, 5.0, 6.0, and 7.0 mm aperture diameters, anteriorly and wholly, in 915 individuals. The corneal LSA values of the anterior surface were: 0.39±0.19 D, 0.63±0.27 D, 0.97±0.36 D, 0.90±0.30 D, and 0.83±0.29 D, respectively, and the mean whole corneal LSA values were 0.26±0.20 D, 0.44±0.27 D, 0.70±0.36 D, 0.66±0.30 D, and 0.59±0.28 D respectively.