Effects of steep meridian incision on corneal astigmatism in phacoemulsification cataract surgery

The Influence of Corneal Thickness on Surgically Induced Corneal Astigmatism Derived from Total Keratometry Measured by Anterior Segment Swept-Source OCT

INTRODUCTION

The purpose of the study was to explore the possible correlations between the anterior segment parameters derived from anterior segment swept-source optical coherence tomography (AS-SS-OCT) with the surgically induced corneal astigmatism (CSIA) calculated from total keratometry (TK) measured by AS-SS-OCT.

METHODS

Seventy-one eyes of 67 patients with age-related cataract who underwent phacoemulsification combined with intraocular lens implantation with 2.2-mm incision were included. The CSIA values were calculated from anterior keratometry (CSIAKant) and TK (CSIATK) measured by AS-SS-OCT, respectively. Hotelling's T2 test was used to evaluate the difference. The correlation of CSIA with various parameters derived from AS-SS-OCT was tested with the Spearman correlation coefficient.

RESULTS

The centroid of CSIAKant and of CSIATK were 0.31 ± 0.55 D @ 54° and 0.41 ± 0.59 D @ 51°, with no significant difference (F = 1.283, p = 0.281, Hotelling's T2). The mean absolute CSIAKant and CSIATK were 0.58 ± 0.24 D and 0.65 ± 0.28 D. Spearman test showed that the magnitude of CSIAKant was negatively correlated with preoperative peripheral corneal thickness (PCT, p = 0.045) and the magnitude of anterior keratometry (p = 0.044). The magnitude of CSIATK was negatively correlated with preoperative central corneal thickness (CCT, p = 0.003) and preoperative PCT (p = 0.015).

CONCLUSIONS

The increased thickness of the peripheral cornea is correlated with the decrease in the magnitude of the CSIA. The correlation we identified between the corneal thickness and the CSIA indicated that certain preoperative parameters should be considered for the prediction of CSIA for a more precise refractive outcome.

Long Term Evaluation of Surgically Induced Astigmatism and Corneal Higher-Order Aberrations After 2.2 Mm Clear Corneal Incisions in Femtosecond Laser-Assisted Cataract Surgery: Temporal versus Superior Approach

Purpose

To assess long term changes of the surgically induced astigmatism (SIA) and corneal higher-order aberrations (HOAs) after 2.2 mm clear corneal incisions (CCIs) in femtosecond laser-assisted cataract surgery and compare them between 2 types of CCIs: temporal and superior approach.

Patients and Methods

Patients received the temporal CCIs (Group A) or the superior CCIs (Group B). Outcome measures included visual acuity, manifest refraction, corneal astigmatism, SIA, flattening effect, and corneal HOAs. Correlation between postoperative corneal HOA and SIA at each follow-up were analysed.

Results

This study assessed data from 106 eyes, of which 64 in Group A and 42 in Group B. The two groups had similar postoperative visual acuity of distance, intermediate and near (all P > 0.05). SIA and corneal HOAs were significantly lower in Group A than Group B in the early postoperative period, while there was no significant difference in the late postoperative period. At 6 months after surgery, the arithmetic mean of SIA over corneal 4mm zone was 0.33 ± 0.19D for temporal incision, and 0.37 ± 0.25D for superior incision. For Group A, the correlations of HOAs and SIA persisted from 1 week to 6 months after surgery. For Group B, the changes in corneal HOAs were significantly related to the SIA at 1 week and 1 month postoperatively.

Conclusion

This study suggested the consistency of increasing and recovering process of corneal HOAs and SIA after surgery. Compared to the superior incisions, temporal incisions might induce quicker corneal recovery and less change in SIA and corneal HOAs.

Clear corneal incision, an important step in modern cataract surgery: a review

A clear corneal incision (CCI) is the most commonly used entrance site in modern phacoemulsification cataract surgery. Despite some initial concerns about increased endophthalmitis rates through a self-sealing CCI, recent literature suggests that the risk of infection with proper wound construction and all other necessary precautions is minimal. The technique of creating a clear corneal incision has, with recent developments in corneal imaging, undergone critical appraisal leading to a better understanding of incision architecture. Many surgeons operate through smaller incisions, and they have a wide choice of surgical instruments to create their corneal incisions. The aim of this review is to discuss the history and the current status of clear corneal incision creation, the design and materials of surgical blades, and the current trends in manufacturing and sustainability. Although disposable instruments have some advantages and are very popular, recycling, if possible, and avoiding unnecessary plastic waste are important considerations. In any case, the step of CCI is a small one for the surgeon, but a big one for the eye. That is why it has to be done with the utmost precision and in-depth knowledge is important.

Prediction of corneal power vectors after cataract surgery with toric lens implantation-A vector analysis

BACKGROUND

Intraocular lenses are typically calculated based on a pseudophakic eye model, and for toric lenses (tIOL) a good estimate of corneal astigmatism after cataract surgery is required in addition to the equivalent corneal power. The purpose of this study was to investigate the differences between the preoperative IOLMaster (IOLM) and the preoperative and postoperative Casia2 (CASIA) tomographic measurements of corneal power in a cataractous population with tIOL implantation, and to predict total power (TP) from the IOLM and CASIA keratometric measurements.

METHODS

The analysis was based on a dataset of 88 eyes of 88 patients from 1 clinical centre before and after tIOL implantation. All IOLM and CASIA keratometric and total corneal power measurements were converted to power vector components, and the differences between preoperative IOLM or CASIA and postoperative CASIA measurements were assessed. Feedforward neural network and multivariate linear regression prediction algorithms were implemented to predict the postoperative total corneal power (as a reference for tIOL calculation) from the preoperative IOLM and CASIA keratometric measurements.

RESULTS

On average, the preoperative IOLM keratometric / total corneal power under- / overestimates the postoperative CASIA keratometric / real corneal power by 0.12 dpt / 0.21 dpt. The prediction of postoperative CASIA real power from preoperative IOLM or CASIA keratometry shows that postoperative total corneal power is systematically (0.18 dpt / 0.27 dpt) shifted towards astigmatism against the rule, which is not reflected by keratometry. The correlation of postoperative CASIA real power to the corresponding preoperative CASIA values is better than those as compared to the preoperative IOLM keratometry. However, there is a large variation from preoperative IOLM or CASIA keratometry to the postoperative CASIA real power of up to 1.1 dpt (95% confidence interval).

CONCLUSION

One of the challenges of tIOL calculation is the prediction of postoperative total corneal power from preoperative keratometry. Keratometric power restricted to a front surface measurement does not fully reflect the situation of corneal back surface astigmatism, which typically adds some extra against the rule astigmatism.

Effect of two different preoperative calculation schemes on visual outcomes of patients after toric intraocular lens implantation

PURPOSE

To compare the postoperative visual outcomes of two different preoperative corneal incision schemes in TECNIS toric intraocular lens (IOL) implantation.

METHODS

In this randomized controlled study, patients with preoperative corneal astigmatism greater than 1.0 diopter (D) were included. These patients were grouped according to the different preoperative schemes: steep-axis group and minimum-residual refractive astigmatism group. The outcome measurements were the residual refractive astigmatism, visual acuity, changes of corneal astigmatism, and high-order aberration at 1 month postoperatively.

RESULTS

This study consisted of 90 eyes (45 eyes steep-axis group, 45 eyes minimum-residual refractive astigmatism group). 1 month after surgery, the refractive astigmatism was statistically lower in the minimum-residual refractive astigmatism group compared with the steep-axis group (0.58 ± 0.40D vs 0.38 ± 0.37D, P = 0.021). The minimum-residual refractive astigmatism group had a smaller difference vector (0.56 ± 0.38D vs 0.36 ± 0.35D; P = 0.047) and a smaller prediction error (0.60 ± 0.44D vs 0.37 ± 0.35D; P = 0.004). In the steep-axis group, corneal astigmatism significantly decreased compared with preoperative value (1.65 ± 0.57D vs 1.17 ± 0.64D; P < 0.001). In the minimum-residual refractive astigmatism group, the changes of corneal astigmatism before and after surgery were not significant. Moreover, total aberration and second astigmatism in ocular aberration were lower in the minimum-residual refractive astigmatism group compared with the steep-axis group (1.86 ± 1.09 vs 1.37 ± 0.95; P = 0.035 and 0.47 ± 0.28 vs 0.31 ± 0.19; P = 0.015, respectively).

CONCLUSION

Minimum-residual refractive astigmatism incision had better astigmatism correction and more accurate prediction. The corneal astigmatism was stable 1 month after surgery. It might lead to better visual quality in the early postoperative stage. Trial registration number for prospectively registered trials: clinicaltrials.gov NCT04006912, 07/02/2019.

The Impact of Posterior Corneal Astigmatism on Surgically Induced Astigmatism in Cataract Surgery

PURPOSE

This study aimed to evaluate the changes in posterior corneal astigmatism after cataract surgery and provide a theoretical basis to accurately evaluate the total corneal astigmatism (TA) to be corrected before toric intraocular lens (IOL) implantation.

PATIENTS AND METHODS

Sixty-two patients (89 eyes) who underwent phacoemulsification combined with toric IOL implantation (AcrySof IQ Toric SN6AT2-T9) at Shanxi Eye Hospital between January 2017 and September 2018 were enrolled. Surgically induced astigmatism of the posterior cornea (SIAPA) was analysed using vector analysis during pentacam examination.

RESULTS

The vector variances of keratometric astigmatism (KA), TA, and posterior corneal astigmatism (PA) preoperatively and postoperatively in the "with-the-rule (WTR) astigmatism" group and "overall patient" group were statistically significant (P < 0.05). A statistically significant difference was observed between surgically induced KA (SIAKA) and surgically induced astigmatism of the total cornea (SIATA) for all patients, including those with WTR astigmatism. For all patients, SIAKA was less than SIATA by 0.05 ± 0.21 D, and for patients with WTR astigmatism, SIAKA was less than SIATA by 0.09 ± 0.22 D. For patients in the "against-the-rule (ATR) astigmatism" group, there were no statistically significant differences between SIAKA and SIATA, although SIAKA was greater than SIATA by 0.03 ± 0.18 D. When PA ≤0.4 D or KA ≤2.0 D, SIAPA can be ignored. However, when PA >0.4 D or KA >2.0 D, ignoring SIAPA caused by cataract surgery incision will cause SIAKA in patients with WTR astigmatism to underestimate SIATA, while SIAKA in patients with ATR astigmatism will cause an overestimation of SIATA.

CONCLUSION

SIA on the posterior corneal astigmatism may have a significant role on more precise planning of toric IOL implantation, especially in cases with higher preoperative anterior or posterior corneal astigmatism.

Surgically induced astigmatism after cataract surgery - a vector analysis

Background: Surgically induced astigmatism (SIA) has been widely discussed in the literature as the change in corneal astigmatism resulting from corneal incision. The purpose of this study was to investigate the change in corneal refractive power preoperative to postoperative using a vector analysis of keratometry, total keratometry, and corneal back surface data from a modern optical biometerMethods: The analysis was based on a dataset of 122 eyes of 122 patients with preoperative and 1 month postoperative measurements performed with the IOLMaster 700 biometer from 1 clinical centre and a standardised surgical technique involving a corneal 2.5 mm 45°-incision made from the superior direction. Keratometry, total keratometry and corneal back surface data were processed in 3 vector components (spherical equivalent power SEQ and astigmatism considered in 0°/90° (C_0°) and in 45°/135° (C_45°) meridian), and the changes in corneal power vectors were analysed, comparing preoperative to postoperative values.Results: The mean corneal power of total keratometry reduced slightly after cataract surgery (-0.05 dpt), resulting mostly from a decrease in back surface power (-0.04 dpt). The astigmatism vector component C_0° of total keratometry reduced by -0.28 dpt, mostly due to a decrease at the corneal front surface (-0.26 dpt). With the corneal incision at 12 o'clock position this flattening in the 90° meridian refers to a SIA of around ¼ dpt. The change in C_0° and the C_45° astigmatic vector components for both keratometry and total keratometry show a large variation ranging between 0.24 and 0.33 dpt (standard deviations), indicating a poor predictability of the change in astigmatism due to cataract surgery.Conclusion: Cataract surgery locally flattens the cornea in the incision meridian. This flattening shows a large individual variation and therefore a poor predictability. Our study indicates that SIA in modern cataract surgery with standardised corneal incision is in a range of 1/4 dpt.

Comparison of surgically induced astigmatism between anterior and total cornea in 2.2 mm steep meridian incision cataract surgery

Background

This study aimed to compare surgically induced astigmatism (SIA) on the anterior and total cornea during cataract surgery through a 2.2 mm steep meridian incision.

Methods

The study included 69 left eyes of 69 patients who had undergone cataract surgery. The 69 eyes were classified into three subgroups according to the preoperative steep meridian. Following phacoemulsification, an intraocular lens was inserted into the bag. The keratometric measurements were taken 12 months postoperatively, on the anterior cornea (automated keratometer and anterior keratometry [K] from a rotating Scheimpflug camera) and total cornea (equivalent K reading [EKR] 3.0 mm, EKR 4.5 mm, total corneal refractive power (TCRP) 2.0 mm ring, TCRP 3.0 mm zone, TCRP 4.0 mm zone). The SIA was analyzed for each parameter.

Results

On the double-angle polar plot, the summated vector mean values of SIA determined by the automated keratometer and Scheimpflug anterior K were 0.28 diopter (axis: 177°) and 0.37 diopter (axis: 175°) in with-the-rule (WTR) astigmatism; 0.03 diopter (axis: 156°) and 0.18 diopter (axis: 177°) in oblique astigmatism; 0.15 diopter (axis: 96°) and 0.17 diopter (axis: 73°) in against-the-rule (ATR) astigmatism. The mean SIAs on the total cornea ranged from 0.31 to 0.42 diopter in WTR astigmatism; from 0.16 to 0.27 diopter in oblique astigmatism; from 0.04 to 0.11 diopter in ATR astigmatism. Mean magnitude SIA ranged from 0.41 to 0.46 diopter on anterior corneal surface and 0.50 to 0.62 diopter on total cornea. J₀ and J₄₅ of the posterior cornea showed no significant changes after cataract surgery, and the changes in J₀ and J₄₅ did not show any statistical differences between the anterior and total cornea (all p > 0.05).

Conclusions

There were no differences in the summed vector mean values of SIA between the anterior cornea and the total cornea.

Surgically induced astigmatism and coupling effect-mediated keratometric changes after conventional phacoemulsification cataract surgery

Background

The aim of the present study was to describe surgically induced astigmatism (SIA) and the coupling effect after conventional phacoemulsification cataract surgery (CPS) in relation to the incisional axis.

Material and methods

A total of 42 patients were included in the retrospective case series study. Corneal topography was obtained for patients with significant cataract before and 6 weeks after CPS with a main clear corneal incision size of 2.4 mm. Patients were grouped according to the relationship of the incisional axis to the position of the steep axis into a steep incisional group and a flat incisional group.

Results

In total, 46 eyes were included in the study. While the steep incisional group showed an SIA of −0.15 D (± 0.35), the flat incisional group had a significantly higher SIA of 0.20 D (± 0.51) (p = 0.03). The coupling ratio (CR) in the steep incisional group was −0.38 (± 1.41) and in the flat incisional group it was 0.16 (± 0.97). Correspondingly, a coupling constant (CC) of −0.25 was found for group 1 and a CC of 0.0 for group 2.

Conclusion

Our results suggest that the location of the main incision should be decided with consideration of the corneal astigmatism in order to minimize the SIA. The CR helps to understand the effect of induced astigmatism and the change in spherical equivalent.

Evaluation of the Cataract Surgery 2018 Survey in Terms of Achieving Refractive Cataract Surgery Targets

Objectives

The aim of this study was to show at what rate the technological equipment used in cataract surgery by Turkish ophthalmologists and their knowledge are reflected in practice and how up to date they are.

Materials and Methods

A questionnaire conducted using SurveyMonkey was used to evaluate the answers to 17 questions from 823 members of the Turkish Ophthalmological Association. Results were evaluated in subgroups according to the participants' age, occupational status, institutions, and whether they conducted relevant academic activities, and the data were compared as inadequate, standard, and contemporary approaches according to the determined criteria.

Results

Optical biometry devices were used at rates of 77.7% and 67.3% for intraocular lens (IOL) power calculations and keratometric measurements in preparation for cataract surgery, respectively. For IOL power calculation, third-generation formulas, especially the SRK-T, were used most commonly (46.2%), followed by second-generation formulas (21.9%), and fourth/fifth-generation formulas and multiple evaluations for different axial lengths (31.9%). The most common incision size was 2.8 mm (51.6%), while the percentage of 2.2 mm and shorter incisions considered to be neutral in terms of surgically induced astigmatism was 18.8%. When selecting incision location, approaches to reduce corneal astigmatism were reported by 28.9%, neutral approaches by 26.2%, and insensitive approaches by 44.9%. Additionally, 55.6% of participants never implanted toric IOLs and 50.7% did not use presbyopia-correcting IOLs. The proportion of surgeons who have experience with femtosecond laser-assisted cataract surgery was 10.3% and the rate of intracameral antibiotic injection at the end of the operation was 89.4%.

Conclusion

It was seen that Turkish cataract surgeons were able to use high technology for surgical preparation and surgery at high rates, but this was not reflected in practice at same rate in terms of achieving contemporary standards of refractive cataract surgery.

The differences of corneal astigmatism in different populations and its quantitative analysis

Objective

To analyze the differences of corneal astigmatism in different age groups.

Methods

The clinical data of the patients from the outpatient Department of Ophthalmology of the Tengzhou Central People's Hospital from April 2014 to June 2014 was screened and statistically analyzed. The corneal curvature was measured by three different instruments: Keratometer, IOL Master and Sirius corneal topography. The changes of the corneal astigmatism in different groups were evalutaed in the study.

Results

Corneal astigmatism of different groups showed no statistical difference and the average corneal astigmatism of 70˜79 age group were higher than younger groups. As the age grew, the with-the-rule astigmatism gradually reduced from 85.8% ( A Group) to 31.0% (F Group). The against-the-rule astigmatism increased from 6.7% ( A Group ) to 45.0% (F Group).

Conclusion

The proportion of the with-the-rule astigmatism gradually reduced with the growth of age. The proportion of the against-the-rule astigmatism increased significantly. The oblique astigmatism had no obvious change before the age of 40. The proportion of oblique astigmatism increased obviously at the 40˜49 group and tended to be stable. After the age of 60, the proportion of different types of astigmatism tended to be stable.

Site of clear corneal incision in cataract surgery and its effects on surgically induced astigmatism

Clear corneal incision (CCI) is a commonly used surgical approach in cataract surgery. In this prospective study, we evaluated the effect of CCI site on surgically induced astigmatism (SIA) and other postoperative astigmatic changes. CCIs were constructed based on the steep meridian of the total corneal refractive power in the 4.0-mm-zone (TCRP_4.0), and patients were divided into four groups: temporal, superotemporal, superonasal, and superior according to the site of the incision. TCRP_4.0 analysis demonstrated a statistically significant reduction of astigmatism with superior incisions (P < 0.001), and the combined mean polar values for SIA changed significantly in the temporal (Hotelling T² = 1.977), superotemporal (Hotelling T² = 0.544), superonsal (Hotelling T² = 1.066), and superior incision groups (Hotelling T² = 1.134) (all P < 0.001). The posterior axis alignment should be considered in cataract surgery with CCI, and the SIA is affected by axis rotation, and incision orientation.

Effective Lens Position According to Incision Width in Cataract Surgery Using Phacoemultification and Posterior Chamber Lens Implantation

PURPOSE

To compare effective lens position (ELP) after phacoemulsification between micro-incision (2.25 mm) and small-incision (2.75 mm) groups.

METHODS

Sixty-seven eyes with age-related cataracts were randomly divided into two groups based on the width of the corneal incision (micro-incision [n = 33] and small-incision groups [n = 34]). Participants underwent clear corneal incision phacoemulsification combined with intraocular lens implantation. Uncorrected visual acuity, refractive error, corneal astigmatism, and ELP were measured preoperatively and at 2 months postoperatively. ELP was calculated using the Sheimpflug method.

RESULTS

Postoperative mean visual acuity and refractive error did not differ between the groups (logMAR 0.02 vs. logMAR 0.04, P = 0.108; -0.30 diopter [D] vs. + 0.07 D, P = 0.339). The postoperative surgically-induced corneal astigmatism was higher in the small-incision group than it was in the micro-incision group, although the difference did not reach statistical significance (+ 0.01 D vs. -0.36 D, P = 0.063). The mean difference between the pre and postoperative ELP values was significantly higher in the small-incision group than that in the micro-incision group (-0.04 mm vs. -0.51 mm, P = 0.024).

CONCLUSIONS

Although there was no significant difference in postoperative refractive error and corneal astigmatism between the micro- and small-incision phacoemulsification groups, the mean error between pre and postoperative ELP was higher in eyes that underwent phacoemulsification with larger corneal incisions than it was in those that underwent smaller incisions.

Improving the Toric Intraocular Lens Calculation by Considering Posterior Corneal Astigmatism and Surgically-induced Corneal Astigmatism

PURPOSE

To investigate the effect of surgically induced corneal astigmatism (SICA) and total corneal astigmatism (TCA) estimation on the anterior corneal astigmatism (ACA)-based toric intraocular lens (IOL) calculation.

METHODS

Data from preoperative and postoperative corneal astigmatism, postoperative visual acuities, and refractive outcomes were collected. The incision was superior in with the rule anterior corneal astigmatism (WTRA) eyes and temporal in against the rule anterior corneal astigmatism eyes. The following five methods of calculating the toric IOL were compared: (1) ACA only and estimated SICA; (2) ACA with a fixed posterior corneal astigmatism (PCA) and estimated SICA; (3) ACA with a fixed PCA value and actual SICA; (4) and (5) TCA derived from the regression equations of ACA and actual SICA. The residual astigmatism was simulated. The Alpins method was used to analyze the astigmatism.

RESULTS

Sixty eyes from 46 patients were enrolled. Thirty eyes had WTRA and the other thirty had against the rule anterior corneal astigmatism. The vector and arithmetic means of the difference vector decreased when the information regarding the actual SICA and PCA was added to the calculation (from 0.59 diopters [D] @ 87.5° to 0.15 D @ 48.5°, and from 0.95 ± 0.53 to 0.71 ± 0.63 D, respectively; p < 0.001). The mean difference vector across the whole sample was lowest using model 5. The correction index was significantly closest to 1.0 in the WTRA group.

CONCLUSIONS

Researchers may improve the accuracy of post-implantation predictions by calculating toric IOL using exact SICA and TCA, with consideration of the PCA derived from the regression equation of ACA.

Investigation of a real-time location system of corneal astigmatic axis

Background

To construct a real-time computerized location system (RCLS) to analyze and display the axis of corneal astigmatism and to compare its accuracy with the Scheimpflug method.

Methods

Fifty-seven eyes of 39 volunteers with corneal astigmatism more than 1.00 diopter (D) were recruited. The RCLS was composed of a circular light-emitting diode (LED) light source, surgical microscope, surgical video system, computer and self-programming image analysis software. Scheimpflug imaging measurements (Pentacam HR, Oculus, Wetzlar, Germany) were performed on all subjects to determine the axis and power of corneal astigmatism. Thereafter, the axis of corneal astigmatism was analyzed in real-time and displayed by the RCLS on supine position, and videos were recorded. The MB-Ruler 4.0 software was used to measure the astigmatic axis. The accuracy of the RCLS was compared with the Scheimpflug method.

Results

The RCLS was able to display the axis of corneal astigmatism in real-time. The axial deviation of corneal astigmatism between the two methods was 0.63 ± 3.78° when astigmatism was 1.00 to 2.00 D and decreased to 0.06 ± 1.38° when astigmatism was greater than 2.00 D. A linear correlation of astigmatic axis was noted between the two methods: Axis_RCLS = 1.01 × Axis_Scheimpflug − 1.02 (R² = 0.998, P < 0.001). The Bland-Altman analysis revealed that the RCLS agreed sufficiently well with the Scheimpflug method.

Conclusions

The RCLS can accurately analyze and display the axis for corneal astigmatism greater than 1.00 D in real-time. The RCLS simplifies marking procedures and may have potential clinical application to improve the postoperative visual outcomes in surgical correction of corneal astigmatism.

Penetrating and Intrastromal Corneal Arcuate Incisions in Rabbit and Human Cadaver Eyes: Manual Diamond Blade and Femtosecond Laser-Created Incisions

OBJECTIVES

To compare morphologic differences between freehand diamond or femtosecond laser-assisted penetrating and intrastromal arcuate incisions.

METHODS

Freehand diamond blade, corneal arcuate incisions (180° apart, 60° arc lengths) and 150 kHz femtosecond laser (80% scheimpflug pachymetry depth corneal thickness) arcuate incisions were performed in rabbits. Intrastromal arcuate incisions (100 μm above Descemet's membrane, 100 μm below epithelium) were performed in rabbit corneas (energy 1.2 μJ, spot line separation 3 × 3 μm, 90° side cut angle). Eyes were examined by slit lamp and light microscopy up to 47 days post-procedure. Freehand diamond blade penetrating incisions, and femtosecond laser penetrating and intrastromal arcuate incisions (energy 1.8 μJ, spot line separation 2 × 2 μm) were performed in cadaver eyes. Optical coherence tomography was performed immediately after surgery and the corneas were fixed for light scanning and transmission electron microscopy.

RESULTS

The rabbit model showed anterior stromal inflammation with epithelial hyperplasia in penetrating blade and laser penetrating wounds. The laser intrastromal and penetrating incisions showed localized constriction of the stromal layers of the cornea near the wound. In cadaver eyes, penetrating wound morphology was similar between blade and laser whereas intrastromal wounds did not affect the cornea above or below incisions.

CONCLUSION

Penetrating femtosecond laser arcuate incisions have more predictable and controlled outcomes shown by less post-operative scarring than incisions performed with a diamond blade. Intrastromal incisions do not affect uncut corneal layers as demonstrated by histopathology. The femtosecond laser has significant advantages in its ability to make intrastromal incisions which are not achievable by traditional freehand or mechanical diamond blades.

Polar Value Analysis of Corneal Astigmatism in Intrastromal Corneal Ring Segment Implantation

Purpose. To evaluate surgically induced astigmatism (SIA) and the average corneal power change in symmetric intrastromal corneal ring segment (ICRS) implantation. Methods. The study included 34 eyes of 34 keratoconus patients who underwent symmetric Intacs SK ICRS implantation. The corneal pocket incision meridian was the preoperative steep meridian. Corneal power data were obtained before and 3 months after Intacs SK ICRS implantation using scanning-slit topography. Polar value analysis was used to evaluate the SIA. Hotelling's trace test was used to compare intraindividual changes. Results. Three months postoperatively, the combined mean polar value for SIA changed significantly (Hotelling's T² = 0.375; P = 0.006). The SIA was 1.54 D at 99° and the average corneal power decreased significantly by 3.8 D. Conclusion. Intacs SK ICRS placement decreased the average corneal power and corneal astigmatism compared to the preoperative corneal power and astigmatism when the corneal pocket incision was made at the preoperative steep meridian.

MANAGEMENT OF VITREAL LOSS FROM POSTERIOR CAPSULAR RUPTURE DURING CATARACT OPERATION: Posterior Versus Anterior Vitrectomy

PURPOSE

To compare the efficacy between 23-gauge sutureless pars planar vitrectomy (PPV) and anterior vitrectomy in the management of vitreous loss associated with posterior capsular rupture during cataract surgery.

METHODS

Medical records of 139 eyes which sustained posterior capsular rupture and vitreal prolapse to anterior chamber during cataract surgery were retrospectively reviewed. Thirty-two eyes which underwent 23-gauge sutureless PPV (group PPV) and 107 eyes which underwent anterior vitrectomy (group AntV) were compared in postoperative visual and anatomical outcomes, operation time, and complications.

RESULTS

No significant differences were found between the groups in final best-corrected visual acuity of 20/40 or better (AntV vs. PPV = 80.4 vs. 90.6%, P = 0.139). However, the visual recovery rates (20/40 or better) 1 day, 1 week, 1 month postoperatively were significantly higher in group PPV (AntV vs PPV = 22.4 vs. 44%, 32.2 vs 58.6, 51.9 vs. 78.1%). Postoperative intraocular pressure-related complications requiring medication were less evident in group PPV (AntV vs. PPV = 52.3 vs. 6.3%, P < 0.001). Twelve cases (11.2%) of group AntV and 0 cases of group PPV underwent secondary operation during follow-up. Although no postoperative complications occurred in group PPV, complications such as endophthalmitis, retinal detachment, cystoid macular edema, intraocular lens instability were observed in the AntV group (none vs. 14%, P = 0.022).

CONCLUSION

Twenty-three-gauge sutureless PPV is a safe and reliable solution for managing vitreous loss during cataract surgery. Therefore, it is expected to be considered primarily in institutes with vitreoretinal surgeons.

The location of incision in cataract surgery and its impact on induced astigmatism

PURPOSE OF REVIEW

The purpose of the present study is a systematic review of previous studies on choosing the best incision site for the correction of astigmatism in cataract surgery and assessing the amount of surgically induced astigmatism (SIA) with each approach.

RECENT FINDINGS

Regardless of astigmatism axis, studies show that using an on-axis incision is associated with favorable results for 0.5-1.0 diopter (D) of astigmatism. In cases with more than 1.0 D astigmatism, paired on-axis incisions can be appreciably efficient in astigmatism correction and cause at least 1.5 D SIA. Considering the amount of SIA, a temporal incision is the best approach when the patient has minimal amounts of corneal astigmatism preoperatively. At higher levels of astigmatism, if no other astigmatism correction method is used simultaneously, the temporal incision is used less frequently; however, since it is associated with the least SIA, it is still the choice site when another correction method is used.

SUMMARY

The temporal incisions in cataract surgery are associated with little SIA and are appropriate choices for mild preoperative astigmatism. At higher levels of preoperative astigmatism, superior incisions are associated with better results when combined methods are not applied.

Influence of Patient Age at Surgery on Long-Term Corneal Astigmatic Change Subsequent to Cataract Surgery

PURPOSE

To examine whether long-term corneal astigmatic change with age after cataract surgery depends on patient age at the time of surgery, and to evaluate whether this change is different from that in eyes that did not undergo surgery.

DESIGN

Retrospective cohort study.

METHODS

A total of 437 eyes that underwent phacoemulsification with a 4.1-mm horizontal corneoscleral incision more than 11 years ago and 600 control eyes without surgery were divided into 4 age groups: (1) 60 years or younger, (2) 61-65 years, (3) 66-70 years, and (4) 71 years or older. The corneal astigmatic change between baseline and 5 years after baseline, between 5 and 10 years, and between baseline and 10 years, as calculated using the polar (x-y) coordinate analysis, were compared among the age groups and between eyes with and without surgery.

RESULTS

Corneal astigmatic change, expressed as x- and y-coordinates, showed an against-the-rule change of 0.2-0.4 diopter during the 10 years in all age groups of the surgery and nonsurgery groups. Using multivariate analysis of variance, the mean x- and y-coordinates did not differ significantly among the age groups in either the surgery or nonsurgery groups (P ≥ .4112). Furthermore, the mean x- and y-coordinates did not differ significantly between the surgery and nonsurgery groups in any age group (P ≥ .1359).

CONCLUSION

Long-term corneal astigmatic change with age after cataract surgery does not differ significantly depending on patient age at the time of surgery, and is comparable to that of eyes without surgery.

Cataract surgery audit at an Australian urban teaching hospital

BACKGROUND

To provide local data on visual acuity and surgical outcomes for cataract surgery performed in an Australian teaching hospital.

DESIGN

Continuous audit over 7 years in a public teaching hospital.

PARTICIPANTS

A total of 3740 eyes had cataract surgery performed at The Queen Elizabeth Hospital, South Australia, from May 2006 to September 2013.

METHODS

Visual acuity and complication rates were recorded for cataract surgery cases operated on between May 2006 and September 2013 on a digital database with data entry contemporaneous with final follow-up.

MAIN OUTCOME MEASURES

Visual acuity and surgical complications.

RESULTS

Of the patients, 91.4% achieved postoperative best-measured vision better than preoperative best-measured vision. The rate of posterior capsular tear was 2.59%, endophthalmitis was 0.11% and the overall complication rate was 11.7%.

CONCLUSIONS

This audit is the first to document modern cataract surgery, overwhelmingly dominated by phacoemulsification in an Australian population and can be used to benchmark cataract surgery outcome in an urban Australian population.

Effect of steep meridian clear corneal incisions in phacoemulsification

PURPOSE

To evaluate the torque and flattening effect of steep meridian clear corneal incisions on cornea in phacoemulsification when posterior cornea surface measurements were considered.

METHODS

Thirty-six eyes underwent cataract surgery with steep meridian clear corneal incisions. Before surgery and at 1 month and 3 months after surgery, corneal topography was measured with a rotating Scheimpflug camera. Both preoperative and postoperative corneal astigmatism were calculated in 2 ways: total corneal astigmatism and keratometric astigmatism. Polar analysis was used to evaluate the flattening and torque effect of steep meridian incisions on corneal astigmatism.

RESULTS

Total corneal astigmatism changed significantly after 3 months (p = 0.005) and univariate analysis revealed a significant change 0.25D ± 0.36 D in astigmatic polar value AKP(+45) of total corneal astigmatism (p = 0.047). A decrease in AKP(+0) was observed in both keratometric and total astigmatism at 1 and 3 months, although the decreases were not statistically significant (p = 0.394, p = 0.442, p = 0.602, p = 0.503, respectively).

CONCLUSIONS

Steep meridian incision performed on the preoperative steeper meridian of keratometric astigmatism may cause a significant torsional effect on total corneal astigmatism as well as reducing the astigmatism along the meridian.

Evaluation of femtosecond laser-assisted and manual clear corneal incisions and their effect on surgically induced astigmatism and higher-order aberrations

PURPOSE

To evaluate femtosecond laser-assisted and manual clear corneal incisions and their effect on surgically induced astigmatism (SIA) and corneal higher-order aberrations (HOAs).

METHODS

In a prospective randomized study, conventional phacoemulsification with a 2.8-mm clear corneal incision using a disposable keratome was performed in 20 eyes of 20 patients (manual group), and femtosecond laser-assisted cataract surgery with a 2.8-mm biplanar clear corneal tunnel created by a femtosecond laser (LenSx; Alcon Laboratories, Inc., Aliso Viejo, CA) was performed in 20 eyes of 20 patients (femtosecond laser group). Corneal topography readings and corneal wavefront aberrations (diameter: 9.0 mm) were obtained using a Scheimpflug camera (Pentacam HR; Oculus Optikgerate, Wetzlar, Germany) preoperatively and 3 months postoperatively.

RESULTS

There was no significant difference in SIA between the groups (femtosecond laser group: 0.47 ± 0.13 vs manual group: 0.41 ± 0.14; P = .218), but the axis deviation of the SIA axis from the previously planned axis was significantly smaller in the femtosecond laser group compared to the manual group (4.47°± 2.59° vs 7.38°± 4.72°, respectively; P = .048). Corneal HOAs increased significantly in both groups (femtosecond laser group: 0.13 ± 0.09 to 0.18 ± 0.12, P = .025; manual group: 0.13 ± 0.05 to 0.15 ± 0.05, P = .002), but preoperative and postoperative values did not differ significantly between them (P = .472 and .078, respectively). Lower-order and total corneal aberration values remained stable in both groups (P > .05).

CONCLUSIONS

There was no difference in SIA and induced HOAs between manual and femtosecond laser-created clear corneal incisions.

Analysis of surgically induced astigmatism on the posterior surface of the cornea

PURPOSE

To measure surgically induced astigmatism (SIA) on the posterior surface of the cornea using Scheimpflug-based keratometry on eyes with with-the-rule astigmatism.

METHODS

Repeated Scheimpflug-based keratometry was obtained preoperatively and a mean of 8.65 weeks postoperatively following superior clear corneal incisions. Differences in the keratometric values and SIA were determined on the anterior and posterior surfaces separately and the data were analyzed.

RESULTS

The study included 88 eyes of 88 patients (age range: 46.4 to 87.5 years), with the steepest total corneal meridian between 75° and 105°. Preoperatively, the magnitude of the anterior and posterior corneal astigmatism was 0.74 ± 0.44 and 0.29 ± 0.14 diopters (D), respectively, which was greater than 0.5 D in 10 eyes (11.36%). The difference between preoperative and postoperative keratometric data on the posterior surface was significant, as was the difference between the preoperative and postoperative posterior astigmatism. The mean magnitude of posterior corneal SIA was 0.32 ± 0.29 D, which was 0.5 D or greater in 22 eyes (25.00%). A statistically significant correlation was observed between the diopter of the preoperatively measured posterior corneal astigmatism and the postoperative SIA on the posterior surface (r = 0.34, P = .001). The correlation was not significant between SIA on the anterior and posterior surfaces (r = 0.10, P = .36).

CONCLUSIONS

SIA on the posterior surface of the cornea may have a significant role, especially in cases of toric intraocular lens implantation. Posterior corneal astigmatism and SIA may have a significant clinical impact on more precise planning of cataract surgeries.

Preliminary Investigation of Corneal Wavefront Aberration following Femtosecond Laser Clear Corneal Incision for Cataract Surgery

Purpose

To investigate the early changes of the anterior corneal wavefront aberration (WA) following femtosecond laser clear corneal incision (FS-CCI) for cataract surgery.

Methods

Twenty consecutive patients (20 eyes) with cataract underwent phacoemulsification and were divided into 2 groups: the study group received a 2.75-mm FS-CCI using an iFS Intralase; the control group received a 2.75-mm manual CCI using disposable knives. High-order corneal WA was analyzed over 3.5- and 6.0-mm pupils and corneal astigmatism was evaluated using vector analysis pre-operatively, 1 week postoperatively, and 1 month postoperatively.

Results

At 1 month postoperatively, the mean surgically induced astigmatism (D) of the anterior cornea was 1.22 ± 0.60 at 144° and 1.04 D ± 0.64 at 90° in the study and control groups (p<0.05), respectively. Over 3.5-mm pupil, there were no changes of corneal high-order aberrations (p>0.05) following FS-CCI. Trefoil increased significantly (p<0.01) following manual CCI at 1 week postoperatively. Over 6.0-mm pupil, FS-CCI did not induce any statistically significant change in corneal WA during follow-up. One week after manual CCI, total root mean square–high order aberrations (p<0.01), spherical aberration (p<0.05), and trefoil (p<0.001) were statistically significantly higher than pre-operatively.

Conclusions

The CCI method was shown to influence changes in corneal WA during the first month postoperatively. The different changes of corneal high-order WA between the study and control groups may depend on the different CCI geometry. These preliminary data are valuable to improve understanding of FS-CCI design.

Analyses of surgically induced astigmatism and axis deviation in microcoaxial phacoemulsification

To evaluate surgically induced astigmatism (SIA) and axis deviation after coaxial microincision superotemporal clear corneal phacoemulsification incision in eyes with differently located steep axis. This prospective, comparative study included four groups of 45 eyes with age-related cataracts; each group underwent 2.2-mm superotemporal clear corneal incision (CCI) cataract surgery. The four groups of patients were divided by location of the steep axis. Groups were matched according to symmetry of the steep axis for both right and left eyes as follows--0°-45° of steep axis for right eyes, and 136°-180° for left eyes (group 1); 46°-90° for right eyes and 91°-135° for left eyes (group 2); 91°-135° for right eyes and 46°-90° for left eyes (group 3); and 136°-180° for right eyes and 0°-45° for left eyes (group 4). Outcome measures included changes in mean total astigmatism, SIA, and axis deviation. Astigmatism was measured by manual keratometry readings before surgery and week 1, week 4, week 8, and week 12 postoperatively. SIA was calculated by the vector analysis (Holladay-Cravy-Koch method). The magnitude of mean total astigmatism was lowest in group 3 and highest in group 1 at week 12. SIA was 0.39 diopters (D), 0.22 D, 0.17 D, and 0.28 D in group 1, group 2, group 3, and group 4, respectively. The change in astigmatic axis deviation was highest in group 3 (23.6 ± 16.6) (P < 0.05). Axis deviation and SIA were stable after week 4. Planning of CCI on or near the steep axis can help decrease corneal astigmatism.

Smaller Incision Size Leads to Higher Predictability in Microcoaxial Cataract Surgery

Purpose.

The aim of the study was to compare the clinical outcomes of a 1.8 mm, 2.2 mm, and 2.75 mm microcoaxial cataract surgery system.

Methods.

In this retrospective study, 129 eyes of 129 patients were included. Patients underwent phacoemulsification using a Stellaris system or an Infiniti system. The incision size was 1.8 mm, 2.2 mm, or 2.75 mm, respectively. Subjects were examined before surgery and 4 weeks after. The surgically induced astigmatism (SIA) was examined.

Results.

The SIA in the 1.8 mm group was statistically lower compared to the 2.2 mm group (p=0.046) and the 2.75 mm group (p=0.017). There was no significant difference between the 2.2 mm group and the 2.75 mm group.

Conclusions.

With the use of appropriate support systems, 1.8 mm incisions appear to result in less SIA than 2.2 mm and 2.75 mm incisions. Advantages may arise from this, especially in the implantation of aspheric, toric, or multifocal lenses.