Correlations of Corneal Spherical Aberration with Astigmatism and Axial Length in Cataract Patients

Spherical Aberration of Astigmatic Corneas in a Cataract Population

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.].

Spherical Aberration of Cataractous Eyes and Its Relationship With Age, Ocular Biometry, and Various IOL Platforms

PURPOSE

To determine the median spherical aberration (SA) of the cataractous population, how it relates to biometry, and the theoretical effect of different intraocular lens (IOL) platforms.

METHODS

A retrospective chart review of patients undergoing cataract surgery evaluation with a high quality Pentacam (Oculus Optikgeräte GmbH) were included. Age, gender, Q-value, mean total SA, higher order aberration root mean square wavefront error, and equivalent keratometry were collected from the Holladay report and axial length and anterior chamber depth (ACD) from the IOLMaster 700 (Carl Zeiss Meditec AG).

RESULTS

Data from 1,725 eyes of 999 patients were collected. SA had a median of 0.37 µm (95% confidence interval: 0.36 to 0.38. Age (r = .136, P < .001), Q-factor (r = .743, P < .001), and higher order aberration root mean square wavefront error (r = .307, P < .001) were positively correlated with SA. Average equivalent keratometry (r = -.310, P < .001) was negatively correlated with SA. Axial length (r = -0.037, P = .120) and ACD (r = .004, P = .856) had no association with SA. Up to 1,499 (86.9%) theoretically had SA moved closer to zero with IOLs that had negative SA. Up to 102 (5.9%) had SA theoretically worsened.

CONCLUSIONS

SA is not normally distributed, suggesting that there may be no "average" SA that IOLs should aim to correct. Patients might benefit from tailoring IOL choice to individual SA. Without access to SA data, eyes with steeper average keratometry or younger patients may have less SA, which could influence IOL choice. [J Refract Surg. 2023;39(2):89-94.].

[Optical aberrations of the eyes with various degrees of myopia]

Purpose - to comparatively analyze the wavefront aberrations and biometric parameters of the eyes with various degrees of myopia.

MATERIAL AND METHODS

The study included 134 eyes of 67 patients with mild, moderate and high myopia aged 7-28 (mean age 19.3±1.5 years). The following biometric parameters were examined: anterior chamber depth (ACD), lens thickness (LT), axial length (AL), as well as corneal and total aberrations. The parameters were studied on the Galilei G6 system (Ziemer Ophthalmic Systems AG, Switzerland) and the OPD-Scan III aberrometer (Nidek, Japan). Spherical aberration (SA) was estimated as the sum of Z4+Z8+Z12.

RESULTS

As the refraction increased, the root mean square higher-order aberrations (RMS HOA) also increased significantly: from 0.24±0.02 μm in mild myopia to 0.45±0.03 μm in high myopia, and in eyes with AL of ≥27.0 mm - to 0.57±0.02 μm (p=0.01). An increase in vertical tilt, vertical coma and vertical trefoil were also observed. Total SA was positive and increased in eyes with moderate myopia compared to those with low myopia (from 0.02±0.01 μm to 0.06±0.02 μm, p=0.02), which coincided with changes in the internal optics of the eye: an increase in ACD and a decrease in LT. At the same time, no differences in corneal aberrations were observed among patients with low and moderate myopia. A significant decrease of SA occurred in high myopia (from 0.06 μm in low myopia to 0.015±0.02 μm in high myopia). The average value of SA was 0.005±0.01 μm in eyes with AL of ≥27.0 mm and appeared to be negative in 40% of cases. The average value of corneal SA was negative (-0.002±0.01μm) in eyes with AL of ≥27.0 mm. This group had predominantly patients with congenital myopia.

CONCLUSION

An increase of total positive SA in patients with moderate myopia compared to those with low myopia is associated with changes in the internal optics of the eye (ACD, LT). Significant increase of higher-order aberrations and decrease of SA with the transition to negative values was observed in patients with high axial myopia.

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

Purpose

To 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.

Methods

This 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.

Results

The 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.

Conclusion

This 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.

Eyes of Aniso-Axial Length Individuals Share Generally Similar Corneal Biometrics with Normal Eyes in Cataract Population

AIMS

To determine the characteristics of corneal biometrics in eyes from aniso-axial length cataract patients compared with eyes from non-aniso-axial length individuals.

METHODS

This is a retrospective case series. Cataract patients with preoperative binocular measurements were recruited. A binocular axial difference of ≥1 mm was considered to indicate aniso-axial length. The anterior segmental biometrics were measured using Pentacam HR (Oculus, Wetzlar, Germany) and IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany). Comparisons of biometrics were made among 4 eye conditions: the longer eyes from aniso-axial length patients, the shorter eyes from aniso-axial length patients, the longer eyes from non-aniso-axial length patients, and the shorter eyes from non-aniso-axial length patients. The aniso-axial length eyes were also stratified into 8 subgroups with axial length (AL) increments of 1 mm, and the biometrics of the subgroups were compared.

RESULTS

There was smaller anterior corneal astigmatism in the shorter aniso-axial length group than those in the longer aniso-axial length group (1.01 ± 0.70 D vs 1.12 ± 0.76 D, P=0.031). The longer aniso-axial length eyes had greater anterior corneal steep curvature (44.13 ± 1.69 D vs 43.87 ± 1.69 D, P=0.009) and anterior corneal astigmatism (1.12 ± 0.76 D vs 1.02 ± 0.69 D, P=0.023) compared with longer non-aniso-axial length subjects. Other corneal biometrics were similar between the aniso-axial length eyes and the non-aniso-axial length eyes. In the longer aniso-axial length group, the posterior corneal aberrations of eyes in the ≥5 mm subgroups were greater than those in the <5 mm subgroups (0.879 ± 0.183 μm vs 0.768 ± 0.178 μm for total aberrations, P < 0.001; 0.228 ± 0.086 μm vs 0.196 ± 0.043 μm for high-order aberrations, P=0.036; 0.847 ± 0.173 μm vs 0.741 ± 0.179 μm for low-order aberrations, P=0.001).

CONCLUSION

Eyes of aniso-axial length individuals share generally similar corneal biometrics with normal eyes in cataract population. Anterior corneal astigmatism of the longer eyes from the aniso-axial length cataract patients was higher than that of the longer eyes from the non-aniso-axial length individuals. Total posterior corneal aberrations of the longer aniso-axial length eyes increased when the binocular axial difference was over 5 mm.