Mean Corneal Spherical Aberration Research Articles

Spherical Aberration of Astigmatic Corneas in a Cataract Population.

To study the distribution of spherical aberration (SA) in astigmatic corneas in a cataract population and the relationship between magnitude of corneal astigmatism and fourth-order corneal SA. Data routinely collected using a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH) were retrospectively analyzed. Patients with a minimum age of 60 years were included. Total corneal SA (from anterior and posterior corneal surface) was obtained for a 6-mm cor-neal area aligned with the pupil center. Exclusion criteria were insufficient measurement quality, total deviation index (Belin/Ambrósio Deviation) greater than 1.60, and corneal thickness at the thinnest point of less than 490 μm. One eye per patient was chosen randomly. Eyes were divided into low (≤ 1.00 diopters [D]), moderate (> 1.00 to ≤ 2.00 D), and high (> 2.00 D) astigmatism groups according to the Scheimpflug measurements. A total of 528 eyes were included in this analysis. Low astigmatism was found in 129 patients, moderate astigmatism in 265 patients, and high astigmatism in 134 patients. Mean astigmatism was 0.68 ± 0.24, 1.45 ± 0.28, and 2.91 ± 0.95 D in the low, moderate, and high astigmatism groups, respectively. Mean corneal SA in patients with moderate and high astigmatism was higher than in the low astigmatism group. The difference reached the significance level for the comparison of low and high astigmatism groups (P = .023). The fourth-order SA increased gradually with the magnitude of astigmatism with a slope of 0.015. SA was significantly larger in the cataract population with high corneal astigmatism. The increase of positive sign SA with the magnitude of astigmatism suggests that patients with moderate to high astigmatism may benefit more from intraocular lenses with negative sign SA correction. [J Refract Surg. 2023;39(8):532-538.].

Normative Values of Corneal Spherical Aberration, Pupil Size, and Other Key Refractive and Topographic Parameters in a Large Cohort of Egyptian Cataract Surgery Candidates.

PurposeTo determine the spherical aberration, pupil size, and other key refractive and topographic parameters in a large cohort of Egyptian cataract surgery candidates, and to investigate any existent relations between the spherical aberration and other possibly related parameters.MethodsThis is a cross-sectional, descriptive study that was conducted at Ain Shams University Hospitals, Cairo, Egypt. The study was performed on the right eyes of 1658 cataract surgery candidates. The mean corneal spherical aberration [Z4] and the pupil diameter, both photopic [P. Pupil] and mesopic [M. Pupil], were measured by the Oculus Keratograph 3, while the white-to-white corneal diameter [WTW], average keratometric readings [average K], axial length measurements [AL] and Anterior Chamber Depth [ACD] were all obtained from the IOL Master 500.ResultsThe mean age was 65 ± 11.3 years. The mean value of the Z4 was +0.26 ± 0.12 μm [95% Confidence Interval “CI” (0.2570–0.2681)]. The mean values of the measured parameters were: P. Pupil 2.43 ± 0.87 mm [95% CI (2.3867–2.4700)], M. Pupil 4.61 ± 0.91 mm [95% CI (4.5683–4.6557)], WTW 11.72 ± 0.44 mm [95% CI (11.6969–11.7394)], average K 43.89 ± 1.89 D [95% CI (43.7938–43.9701)], AL 24.23 ± 2.21 mm [95% CI (24.1118–24.3166)], and ACD 3.16 ± 0.43 mm [95% CI (3.1414–3.1827)]. Weak statistically significant correlations were found between the Z4 and each of age (r = 0.049, p = 0.044), average K (r = 0.191, p < 0.001), and ACD (r = 0.122, p < 0.001). Multivariate analysis showed weaker relations between Z4 and both average K (beta coefficient= 0.091) and ACD (beta coefficient= 0.130), with an r2 = 0.024.ConclusionThis is the first normative data report of corneal spherical aberration [Z4], pupil size, and related refractive and topographic parameters in an old Egyptian population. The detected correlations have a weak clinical relevance and negate the existence of significant relations between the Z4 and the studied refractive and topographic parameters.

Pupillodynamics and corneal spherical aberrations in a set of Indian cataract patients and its implications for aberrometric customisation of intraocular lenses.

Purpose:Assessment of pupil diameter in various light conditions and the corresponding corneal spherical aberrations in a cohort of Indian eyes with bilateral senile cataracts and the possible use of this data in aberrometric customization of intraocular lenses (IOLs).Methods:In this prospective observational study done at a tertiary eye care centre in India, the selected patients were subjected to measurement of their pupil diameters in scotopic, mesopic, and photopic conditions as well as the corresponding corneal spherical aberrations, using the Sirius Topographer (Costruzione Strumenti Oftalmici, Florence, Italy). Shapiro–Wilk test, Independent t-test, ANOVA with Bonferroni correction on post-hoc testing were used for statistical analysis.Results:104 eyes of 52 patients were enrolled for the study. The mean age was 53 ± 11.88 years. The mean scotopic, mesopic, and photopic pupil sizes were 4.37 mm (4.11–4.63 mm), 3.92 mm (3.71 mm–4.15 mm), and 3.37 mm (3.18–3.67 mm), respectively. There was a statistically significant difference (P = <0.001) in the mean corneal spherical aberration measured at the 6 mm zone (0.23 ± 0.02 microns) and at the 4 mm zone (0.06 ± 0.01 microns).Conclusion:The mean corneal spherical aberration corresponding to the average mesopic pupil size of our patient population was substantially lower than that of the scotopic pupil size and also less than the amount corrected by most of the negative aspheric IOLs. This perhaps indicates the need for customising IOLs based on the spherical aberrations of cornea at the zone corresponding to the mesopic pupil diameter for optimal residual total postoperative spherical aberrations.

Distribution of corneal spherical aberration in a Tanzanian population

PurposeTo investigate the distribution of corneal spherical aberration (SA) in Tanzanian people of African descent, and to examine the correlation between corneal SA and ocular parameters.DesignCross-sectional population-based study.MethodsResidents aged 40 years and older in three villages in the Mkuranga district in Tanzania were enlisted as study participants. Corneal higher-order aberrations (HOAs) for the right eye were measured with a wavefront analyzer (KR-1W, Topcon) and calculated for the central 6.0-mm zone. Corneal curvature radius (CR), corneal astigmatism, and axial length (AL) were also measured and their correlation with corneal SA was assessed.ResultsThe right eyes of 657 participants (336 male, 321 female) were analyzed. The mean age of the subjects was 57.2 ± 10.3 years (mean ± SD). The mean corneal SA (Zernike spherical aberration coefficient C40) was 0.188 ± 0.095 μm (-0.242 to 0.613). The SAs in about three-quarters of all subjects were between 0.10 and 0.30 μm. The root mean squares of total corneal HOAs and the third- and fourth-order aberrations were 0.629 ± 0.250 μm, 0.539 ± 0.236 μm, and 0.269 ± 0.110 μm, respectively. Corneal SA showed weak significant correlations with CR (Spearman’s rank correlation coefficient, r = -0.177, p < 0.001), corneal astigmatism (r = -0.142, p < 0.001), AL (r = -0.168, p < 0.001), and age (r = -0.085, p < 0.05).ConclusionsThis finding may be beneficial for selecting aspheric intraocular lens in this population.

Corneal Analysis before Cataract Surgery; Significance as the Clue for Unexplained Visual Complaint After Surgery

PurposeWe analyzed the corneal optics before cataract surgery to evaluate whether the corneal abnormalities are correlated with the unexplained visual complaints after successful surgery.MethodsSeventy‐eight eyes of forty‐seven patients who had undergone uncomplicated cataract surgery were enrolled in this retrospective study. The eyes were divided into group I which had visual complaint despite good visual acuity and group II without complaints after surgery. All included eyes had preoperative corneal data such as slit lamp bio‐microscopy, automatic keratometer, corneal topography (Orbscan II, Bausch &amp; Lomb, Germany), and aberrometer (KR‐1W®, Topcon, Japan). We investigated whether there are any correlations between the corneal abnormalities and unexplained visual complaint by comparing the corneal parameters of two groups.ResultsThe mean patient age was 67.9 years old. The mean preoperative topographic astigmatism in 78 eyes was 0.98 diopter (D); 19.23% of eyes had irregular astigmatism. Mean corneal spherical aberration measured by KR‐1W was 0.31 ± 11.01 µm and corneal total higher order aberration (HOA) was 0.24 ± 0.17 µm. Total corneal HOA was correlated with irregularity index from topography. (P &lt; 0.01, r = 0.548) No differences were shown between two groups in preoperative astigmatism. However, comparing the corneal parameters, irregularity index of 3 mm, 5 mm zone and corneal total HOA of group I were statistically significantly higher than those of group II respectively. (p &lt; 0.05, respectively).ConclusionsUnsatisfactory results associated with visual quality after cataract surgery might be originated from cornea irregularity and HOA. Evaluation of preoperative corneal optics is necessary to predict visual quality after surgery.

Corneal spherical aberration in Saudi population

PurposeTo find out the mean corneal spherical aberration and its changes with age in Saudi population. SettingAlHokama Eye Specialist Center, Riyadh, Saudi Arabia. MethodsThree hundred (300) eyes of 185 Saudi subjects (97 men and 88 women), whose age ranged from 15 to 85years old, with matched refractive errors, were divided into three groups according to their age, 100 for each. All the subjects were included in measuring the spherical aberration (SA) using pentacam HR (OCULUS, Germany) at the 6-mm optical zone. ResultsThe mean corneal spherical aberration (CSA) of the fourth order (Z40) of the whole groups was 0.252±0.1154μm. Patients from 15 to 35years old have root mean square (RMS) of CSA of 0.2068±0.07151μm, 0.2370±0.08023μm was the RMS of CSA of the patients from 35 to 50years old, while those from 50 to 85years old have a CSA-RMS of 0.31511±0.1503μm (P<0.0001). A positive correlation was found between the spherical aberration (Z40) and the progress of age (r=0.3429, P<0.0001). The high order aberration (HOA) presented 28.1% of the total corneal aberrations. While the fourth order corneal spherical aberration constituted 57% of the HOA and 16% of the total aberration. The pupil diameter shows a negative correlation with the increase in age (P=0.0012). ConclusionOur results showed a CSA (Z40) that is varied among the population, comparable to other studies, and significantly correlates to the progress of age.

Changes in Spherical Aberration after Various Corneal Surface Ablation Techniques

PurposeThe corneal change induced by refractive procedures influence both the postoperative refractive status and the ocular spherical aberration (SA). We evaluated changes in corneal SA after three types of surface ablation: phototherapeutic keratectomy (PTK), myopic photorefractive keratectomy (PRK), and myopic wavefront-guided laser epithelial keratomileusis (LASEK).MethodsTwenty-six eyes (25 patients) were subjected to PTK 26 eyes (14 patients) to PRK, and 34 eyes (17 patients) to wavefront-guided LASEK. Corneal SA was measured with the iTrace in all patients both preoperatively and 6 months postoperatively.ResultsSix months after surgery, mean corneal SA was -0.173 ± 0.171 µm in the PTK group, 0.672 ± 0.200 µm in the PRK group, and 0.143 ± 0.136 µm in the wavefront-guided LASEK group. The mean difference between the preoperative and postoperative corneal SA (ΔSA) was -0.475 µm in the PTK group, 0.402 µm in the PRK group, and -0.143 µm in the wavefront-guided LASEK group.ConclusionsSurgically induced changes in corneal SA vary with procedure. The prediction of the pattern of SA change induced by various surface ablation procedures may be helpful for developing future surgical procedures.

Corneal asphericity and spherical aberration after refractive surgery

To evaluate changes in corneal asphericity (Q) and spherical aberrations after refractive surgery using Scheimpflug imaging. University of California, San Diego, Shiley Eye Center, La Jolla, California, USA. Cohort study. After wavefront-guided laser in situ keratomileusis, patients within ± 0.50 diopter of plano and with an uncorrected distance visual acuity of at least 20/20 were evaluated. The Q values and corneal spherical aberration Zernike values were obtained using Scheimpflug imaging preoperatively and 1 to 3 months postoperatively. The study enrolled 177 myopic eyes and 32 hyperopic eyes. The mean Q value was -0.28 ± 0.11 (SD) and -0.22 ± 0.15, respectively, preoperatively and +0.35 ± 0.44 and -0.64 ± 0.31, respectively, postoperatively. The asphericity change was highly correlated with preoperative spherical equivalent (r(2) = 0.81; P ≤ .001). The mean corneal spherical aberration was +0.21 ± 0.08 μm in myopic eyes and +0.36 ± 0.11 μm in hyperopic eyes preoperatively and +0.36 ± 0.17 μm and 0.00 ± 0.29 μm, respectively, postoperatively. The corneal spherical aberration changes were correlated with the amount of preoperative refractive error (r(2) = 0.34; P < .001). There was a tendency for Q values and spherical aberrations to become more positive after myopic ablation and more negative after hyperopic ablation. Myopic and hyperopic corrections induced changes in the Q value and spherical aberrations in opposite directions (ie, positive and negative, respectively). The changes depended on the magnitude of the refractive correction. No author has a financial or proprietary interest in any material or method mentioned.

Corneal Spherical Aberration of Eyes with Cataract in a Japanese Population

To investigate the distribution of corneal spherical aberration in Japanese eyes with cataract for implantation of aspheric intraocular lenses (IOLs). Corneal spherical aberration (Zernike coefficient Z04) in the central 6-mm zone was measured with a wavefront analyzer (KR9000PW, Topcon) in 257 eyes of 168 Japanese patients with cataract. Axial length was also measured for each eye. Mean corneal spherical aberration was 0.203+/-0.100 microm (range: -0.103 to 0.497 microm). A significant negative correlation was found between axial length and corneal spherical aberration (r =/-0.135, P=.036). Corneal spherical aberration varied among cataract patients and correlated with axial length. Japanese patients showed a relatively smaller corneal spherical aberration than previous studies of Caucasians. Preoperative measurement of wavefront aberrations is thus important in using aspheric IOLs.

Decentration and tilt of a single-piece aspheric intraocular lens compared with the lens position in young phakic eyes

To compare the tilt and decentration of a single-piece aspheric intraocular lens (IOL) and the position of the natural crystalline lens in young individuals. Department of Ophthalmology, Knappschafts Hospital, Sulzbach, Germany. This prospective noncomparative single-center study included volunteers younger than 40 years with no ocular abnormalities (crystalline lens group) and patients older than age 62 who had uneventful cataract surgery and Tecnis ZCB00 IOL implantation (IOL group). All eyes were examined with the OPD-Scan II; spherical aberration, vertical coma Z(3,-1), and horizontal coma Z(3,1) were analyzed with a 5.0 mm pupil. Lens tilt and decentration were studied with a new Purkinje meter. The crystalline lens group and IOL group comprised 20 subjects (40 eyes) each. Both groups showed compensation for corneal spherical aberration and neutralization of horizontal corneal coma. All lenses were tilted upward (mean 2.2 degrees, crystalline lens; 2.5 degrees, IOL) and to the temporal side (mean 3.1 degrees, crystalline lens; 2.6 degrees, IOL). The crystalline lenses were decentered downward (mean 0.16 mm) and to the temporal side (mean 0.07 mm). The IOL was displaced to the nasal side of the pupil (mean 0.06 mm) with almost no vertical mean decentration (0.02 mm upward). The aspheric IOL and young crystalline lens compensated for mean corneal spherical aberration, resulting in low total spherical aberration. The position of the IOLs showed minimal decentration and tilt and was mirror symmetrical, comparable to the position of the crystalline lens in young individuals. The slight malpositioning partially compensated for corneal horizontal coma.

Corneal Wavefront-Guided Retreatments for Significant Night Vision Symptoms after Myopic Laser Refractive Surgery

To evaluate the results of corneal wavefront (WF)-guided enhancements in patients with night vision symptoms and significantly high positive spherical aberration (SA) after myopic laser refractive surgery. Noncomparative, interventional case series. Twenty-eight eyes of 20 patients with significant night vision symptoms and positive corneal SA (Z(4)(0)) higher than 0.5 microm after myopic laser refractive surgery were included in the study at Vissum-Instituto Oftalmologico de Alicante, Spain. Enhancement surgery was planned to remove residual refractive error and corneal SA (Z(4)(0)) in all cases. All patients underwent corneal WF-guided excimer laser retreatments using the ESIRIS/SCHWIND excimer laser system (Schwind Eye Tech Solutions, Kleinostham, Germany). The main outcome measures were visual symptoms, change in corneal SA (Z(4)(0)), and corneal asphericity (Q-value). Subjective reports of night vision symptoms were improved in all patients. Mean corneal SA (Z(4)(0)) decreased from 0.75 +/- 0.19 microm before surgery to 0.43 +/- 0.42 microm after surgery (P < .001). Mean asphericity in the 4.5-mm zone significantly decreased from 1.02 +/- 1.07 before surgery to 0.52 +/- 0.88 after surgery (P = .008), and the mean asphericity in 8 mm did not change significantly (P = .362). The mean spherical equivalent significantly shifted to hyperopia from -0.22 +/- 1.14 diopters (D) before surgery to 0.33 +/- 0.54 D after surgery (P = .025). Cornea wavefront-guided retreatment was effective in improving subjective night vision symptoms, reducing corneal SA, and decreasing asphericity in eyes that underwent myopic laser refractive surgery.