[Correlation between axial length and corneal curvature and spherical aberration]

Objective: To discuss the correlation between axial length and corneal curvature and corneal spherical aberration in a group of cataract patients with axial length greater than 24 mm. Methods: Retrospective case series. This study comprised 117 (234 eyes) age-related cataract patients. There were 51 men (43.59%) and 66 women (56.41%) with mean age of (69.0±8.7) years (range from 52.0 to 85.0 years). The average axial length was 27.6±1.8 (range from 24.2 to 31.9 mm). We devided them into four groups according to the axial length. A-scan was used to measure the axial length and Pentacam was used to get the corneal curvature and corneal spherical aberration of both anterior and posterior surface. kolmogorov-smirnov test was used to check the normal distribution. ANOVA test was used to compare eachcorneal parameter among different groups. Pearson correlation analysis was used to obtain the correlation of corneal parameters in groups. Results: There were correlations between the axial length and the anterior and posterior corneal curvature (r=-0.213, r=0.174, respectively, P<0.05). No correlation was found between the axial length and anterior or posterior corneal spherical aberration (r=-0.114, 0.055, respectively, P>0.05). Mean values of corneal anterior surface curvature were (45.26±1.60) D (group 1), (44.17±1.45) D (group 2), (44.40±1.99)D (group 3), and (44.53±1.69) D (group 4) respectively. Mean values of corneal posterior surface curvature were(-6.57±0.26)D (group 1), (-6.40±0.24)D (group 2), (-6.41±0.38)D (group 3), and (-6.43±0.26)D (group 4) respectively. There were significant difference of corneal anterior and posterior surface curvature among 4 groups (P=0.004, P=0.001). There was significant difference of corneal curvature of anterior surface in group 1 compared to group 2 and group 3(P<0.01, P=0.01). There was significant difference of curvature of posterior surface in group 1 compared to group 2 and group 3, respectively (P<0.01). Mean values of anterior surface corneal spherical aberration were (2.09±0.53) μm (group 1), (1.90±0.44) μm (group 2), (2.00±0.74) μm (group 3), and (1.78±0.52) μm (group 4) respectively. Mean values of posterior surface corneal spherical aberration were (2.69±1.15) μm (group 1), (2.46±1.16) μm (group 2), (2.92±2.51) μm (group 3), and (2.69±1.13) μm (group 4) respectively. No correlation was found in anterior and posterior surface corneal spherical aberration(P>0.05) among different groups. Conclusions: The eye with a longer axial length have a flatter cornea. Cornea fails to compensate for axial length elongation when the axial length is longer than 28mm. The corneal spherical aberration varies among individuals, which suggests us to do the customized measurement before cataract surgery to make a decision on choosing the aspherical intraocular lens. (Chin J Ophthalmol, 2017, 53: 255-259).