Higher-order Aberrations Of Cornea Research Articles

Study on the Corneal Higher-Order Aberrations and Correlation in Patients with Different Degrees of Myopia Suitable for Wavefront-Guided FS-LASIK

Background: Individualized corneal refractive surgery requires an understanding of the basis of higher-order aberrations before surgery. To investigate the characteristics and distribution of anterior surface wavefront aberrations in patients suitable for corneal refractive surgery. Methods: A total of 121 myopic patients (121 eyes, 18 - 45 years old) who underwent corneal refractive surgery were recruited from January to May 2016 at Affiliated Hospital, Yanbian University. Patients were randomly selected by the Pentacam anterior segment analysis system with a spherical equivalent (SE) of -0.25 to -10.00 D. The corneal anterior aberrations (total higher-order aberration; spherical aberration; Coma; Trefoil) and Q and K values were detected, and a correlation analysis of the relevant parameters was carried out. Results: The root-mean-square (RMS) of the third to sixth order aberrations of the corneal anterior wavefront aberrations at a 6 mm analysis diameter showed a decreasing trend in patients suitable for the corneal refractive surgery, and the RMS of the third order aberrations accounted for 62.92% of the total HOAs. The coma ratio (coma/total cornea higher-order aberrations) was increased with the increasing diopters, while the spherical aberration ratio (spherical aberration/total cornea higher-order aberrations) was not changed. In addition, the spherical aberration was 0.203 ± 0.082 μm (range: 0.061 to 0.503 μm), and the Q30 was -0.19 ± 0.03 (range: -0.58 to 0.31). There were significant differences in the coma aberrations of preoperative corneal anterior surface (3, 1) between the low, middle and high myopia groups (P = 0.013). The spherical equivalent was positively correlated with the corneal coma of the anterior corneal surfaces (R = -0.241, P = 0.009), and the Q value was positively correlated with the total higher-order aberrations (R = 0.326, P Conclusions: Individual wavefront aberrations on the anterior surfaces of the cornea are comparatively different, and the Zernike coefficients are related to the degree of myopia. Spherical aberrations are the most overriding aberrations of the cornea.

Assessment of Corneal Higher Order Aberrations Before and After Corneal Collagen Cross-Linking in Patients with Keratoconus

Purpose: This study aimed at assessing the shortterm effect of corneal collagen crosslinking on higher order aberrations of cornea in patients with keratoconus using corneal topography. Patients and Methods: The study was a prospective cohort study that was conducted in a private specialized eye hospital on 40 eyes of 28 keratoconus patients. Each patient was fully assessed preoperatively including doing corneal topography using Pentacam® HR. Transepithelial accelerated CXL was done to all patients. Postoperative corneal topography was done at six months and data was retrieved and analyzed. Results: RMS HOA recorded a higher mean value preoperatively, with a high statistically significant difference (p=0.00). All elements of HOAs showed lower postoperative values except for trefoil 30o. The difference was statistically significant in comma 0o, comma 90o, spherical aberrations and fifth order comma 90° (p=0.026, p= 0.003, p=0.005, and p=0.001 respectively). Conclusion: Transepithelial corneal collagen cross-linking improves corneal higher order aberrations. The maximum effect of the procedure is on comma 0o, comma 90o, spherical aberrations and fifth order comma 90° elements.

Characteristics of higher-order aberrations and anterior segment tomography in patients with pathologic myopia.

To investigate prospectively the characteristics in the higher-order aberrations and anterior segment tomography in patients with pathologic myopia. One hundred and twelve consecutive highly myopic patients (mean age 43.4±9.3years, spherical equivalent of refractive error≥8 D and an axial length≥26.5mm) were studied. Thirty-seven emmetropic individuals (mean age 37.0±14.5years, spherical equivalent of refractive error≤±1 D) were analyzed as controls. The ocular and cornea higher-order aberrations were measured using a Hartmann-Shack wavefront sensor (KR-1W; Topcon Corporation, Tokyo, Japan). The crystalline lens rise, the angle-to-angle, and the white-to-white values were measured using anterior segment OCT (SS-1000; Tomey Corporation, Nagoya, Japan). The mean curvature of the anterior corneal surface, the thickness at the thinnest central corneal point, the location of the central corneal point, the corneal volume, the anterior chamber volume, and the anterior chamber depth were measured using the Pentacam HR (Oculus, Inc., Wetzlar, Germany). The ocular total higher-order aberration for 4-mm pupil, the ocular spherical aberrations, and internal spherical aberration for 6-mm pupil were significantly higher in highly myopic eyes than in the emmetropic controls. The crystalline lens rise was significantly smaller in highly myopic eyes than in the emmetropic controls. The anterior chamber depth and the anterior chamber volume were significantly larger in highly myopic eyes than in the emmetropic controls. Highly myopic eyes had higher-order aberrations than emmetropic eyes because of the increasing internal aberrations.

Cohort Study: Corneal Higher-Order Aberrations and Its Related Factors in Chinese People with Emmetropia

Purpose: To evaluate the association among age, gender, central corneal thickness (CCT), anterior chamber depth (ACD) and higher-order aberrations (HOAs) of cornea in Chinese people with emmetropia by Pentacam. Methods: Prospective, a non-randomized population-based study. All subjects came spontaneously for consultation and were subdivided into six age-groups. One thousand two hundred and six candidates (605 male, 601 female) were tested and underwent Anterior segment examination by Pentacam. These parameters were measured: 1) root mean square-HOA (RMS-HOA) from anterior and posterior cornea, 2) RMS of coma, secondary astigmatism and spherical aberration (SA) from anterior and posterior cornea, 3) CCT and ACD. Results: For analysis of variance (ANOVA) between genders, there were statistical differences on: 1) anterior corneal HOAs of x-coma, y-coma and SA (F=5.643, P=0.018; F= 16.971, P=0.000; F=23.443, P=0.000); 2) total corneal HOAs of y-coma and SA (F=12.906, P=0.000; F=111.590, P=0.000). There was significant different between y-second astigmatism of anterior corneal surface and age (r2 =0.023, p<0.000), that of posterior corneal surface and age (r2 =0.021, p=0.001), between RMS-HOAs of anterior corneal surface and age (r2 =0.259, p<0.000), that of posterior corneal surface and age (r2 =0.055, p=0.001), that of total corneal surface and age (r2 =0.359, p<0.000). Conclusion: a) For the ethnic, there was a significant difference on magnitude of corneal HOAs between Chinese people and the other people. b) Pentacam can provide a more precise data of posterior cornea HOAs which seldom reported before.