Analyses of surgically induced astigmatism and axis deviation in microcoaxial phacoemulsification

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.

Comparison of Outcomes after Phacoemulsification with Two Different Corneal Incision Distances Anterior to the Limbus

Purpose

To compare visual performance and visual quality outcomes after phacoemulsification with two different clear corneal incision (CCI) distances anterior to the limbus in senile cataract patients.

Methods

Retrospective case series. Patients who had undergone phacoemulsification were divided into two groups according to the CCI distances anterior to the limbus. The CCI distances in group A range from 1 mm to 1.5 mm, while those in group B range from 0.5 mm to 1 mm. The visual acuity, refraction, surgically induced astigmatism (SIA), corneal aberrations, anterior segment parameters, and subjective vision quality were evaluated.

Results

This study enrolled 54 eyes, with 27 eyes per group. Both groups had significant improvement in postoperative uncorrected visual acuity (UCVA) and corrected distance visual acuity (CDVA) (P < 0.05). There were no statistically significant between-group differences in postoperative UDVA, CDVA, SIA, corneal aberrations, anterior segment parameters, or VF-QOL questionnaire performance (P > 0.05).

Conclusions

The phacoemulsification with CCI distances ranging from 0.5 mm to 1.5 mm is an effective and safe therapy to senile cataract. The CCI distance anterior to the limbus that ranges from 0.5 mm to 1.5 mm is recommended for routine phacoemulsification.

[Effect of different clear corneal incision sites on surgery efficacy and anterior segment parameters in patients undergoing phacoemulsification]

OBJECTIVE

To determine the safe distance range of clear corneal incision (CCI) from the corneal limbus and how different CCI sites affect surgery efficacy and anterior segment parameters in patients undergoing phacoemulsification.

METHODS

This retrospective case-control study was conducted in 44 patients (44 eyes) undergoing phacoemulsification and IOL implantation. The patients were divided into two groups with CCI distances ranging from 1 mm to 1.5 mm (group A, n= 22) and from 0.5 mm to 1.0 mm (group B, n= 22). The visual acuity, surgically induced astigmatism (SIA), corneal aberration, and anterior segment parameters were analyzed.

RESULTS

Compared with the preoperative data, all the patients showed significant improvements in the postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), anterior chamber depth (ACD), and anterior chamber angle (ACA) after the surgery (P &lt; 0.05). No significant differences were found between the two groups in postoperative UCVA, BCVA, SIA, total corneal aberration RMS, lower- and higher-order aberration RMS, spherical aberration (Z₄⁰), horizontal three leaf clover (Z₃³), vertical three leaf clover(Z₃^-3), horizontal coma(Z₃¹), vertical coma(Z₃^-1), ACD, ACA, anterior chamber volume, or central corneal thickness (P&gt;0.05).

CONCLUSIONS

Phacoemulsification is an effective therapy for cataract with a CCI distance range either of 1-1.5 mm or 0.5-1.0 mm. These two CCI distance ranges produce no significant differences in the visual quality following phacoemulsification, indicating that a CCI distance range of 0.5-1.5 mm can be safe for phacoemulsification.

Effect of incision on visual outcomes after implantation of a trifocal diffractive IOL

Background

To evaluate visual acuity, corneal astigmatism and corneal higher-order aberrations (HOAs) after implantation of trifocal diffractive IOLs operated with either a corneal steep-axis incision or 135° incision.

Method

This prospective study enrolled patients randomly assigned to different groups. According to preoperative corneal astigmatism, 101 eyes of 77 patients were assigned into group A₁ (0 ~ 0.50 D) or A₂ (0.51 ~ 1.00 D) with a corneal steep-axis incision or group B₁ (0 ~ 0.50 D) or B₂ (0.51 ~ 1.00 D) with a 135° incision. Visual acuity, corneal astigmatism and corneal higher-order aberrations (HOAs) were followed-up for 3 months.

Results

Corneal astigmatism in group A₂ significantly decreased 3 months after surgery (P < 0.01) and was significantly lower than that in group B₂ 1 day, 2 weeks, 1 month, and 3 months postoperatively (all values of P < 0.01). The following parameters were better in group A₂ than in group B₂: uncorrected intermediate visual acuity (UIVA) at 1 day, 2 weeks, 1 month, and 3 months (P = 0.00, 0.00, 0.01, 0.01, respectively);uncorrected distance visual acuity (UDVA) at 1 day and 2 weeks (P = 0.00, 0.01); and uncorrected near visual acuity (UNVA) at 1 day, 2 weeks, and 1 month postoperatively (P = 0.00, 0.01, 0.02, respectively).

Conclusions

After a corneal steep-axis incision, patients with preoperative corneal astigmatism of 0.51 D to 1.00 D exhibited reduced corneal astigmatism and achieved better UIVA and early postoperative UDVA/UNVA.

Trial registration

Retrospectively Registered Trials ISRCTN10086721, 23/06/2018.

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.

Refractive Results Using a New Optical Biometry Device: Comparison With Ultrasound Biometry Data

The aim of the study was to compare the measurements of optical (AL-Scan; Nidek Co., Ltd.) and ultrasonic (Echo Scan US-800; Nidek Co., Ltd.) biometry devices and to assess refractive results after cataract surgery. Eighty-one cataractous eyes of 81 patients were included in this study. Biometry was performed using the AL-Scan and an ultrasonic biometer (USB). Axial length (AL), keratometry (K) data, and intraocular lens (IOL) power calculations using the SRK/T formula were compared. Bland-Altman analysis was used to assess the extent of agreement between AL-Scan and USB data in terms of AL measurement and IOL power calculation. The K measurements of the AL-Scan were compared to autorefractor data (Canon Autorefractor RK-F1). The AL-Scan assessed the AL as longer (average difference 0.06 ± 0.18 mm; ICC = 0.987; P < 0.001) and the IOL power as greater (average difference 0.19 ± 0.66 D; ICC = 0.964; P < 0.001) than the USB. The AL-Scan also measured average K values (average difference 0.25 ± 0.25 D; ICC = 0.985; P < 0.001) greater than those given by the autorefractor. The postoperative mean absolute error was +0.30 ± 0.04 D (minimum: -0.51 D, maximum +1.04 D). The postoperative mean K value change was 0.36 ± 0.29 D (P < 0.05). The differences between measurements afforded by the AL-Scan and USB may be clinically acceptable. Keratometric changes that develop after cataract operations compromise the attainment of good refractive outcomes.