Anterior stromal puncture with staining: A modified technique for preoperative reference corneal marking for toric lenses and its retrospective analyses

Toric intraocular lens: A literature review

Toric intraocular lenses (IOLs) are universally recommended in cataract cases with preoperative corneal astigmatism ≥1.5 D. An optimal surgical outcome depends on careful patient selection, complete preoperative evaluation, accurate IOL power calculation, precise marking of the axis, meticulous intraoperative approach, and methodical postoperative care. Understanding the importance of posterior corneal astigmatism, surgically induced astigmatism, and effective lens position in IOL power calculation and newer techniques to measure them directly have resulted in better postoperative refractive outcomes. We present a brief overview of toric IOLs along with the preoperative evaluation, IOL power calculation, different marking methods, intraoperative approach, and postoperative outcomes. Functional and anatomical outcomes, including uncorrected visual acuity, residual refractive astigmatism, and postoperative IOL misalignment, which have been reported for both toric IOLs and multifocal toric IOLs, are reviewed.

Digital versus slit-beam marking for toric intraocular lenses in cataract surgery

Purpose

To compare the visual outcomes of digital and slit-beam manual marking for toric intraocular lenses (IOL) in cataract surgery.

Setting

Single-center, Beijing Tongren Hospital, China.

Design

Retrospective study.

Methods

All patients with cataracts and regular corneal astigmatism greater than 0.75 diopters (D) underwent cataract surgery and astigmatism correction between June 2019 and June 2020. To mark the target axis of the toric IOL and the location of the incision, intraoperative digital marking was used by Callisto eye image-guided system in one group, while preoperative manual slit-beam marking was used in the other group. Uncorrected and best-corrected spectacle visual acuity, refraction, toric IOL axis, total higher order aberrations, coma, spherical aberration, and trefoil were evaluated at 1, 4, and 12 weeks postoperatively.

Results

Seventy-two eyes of 58 patients were included. At 3 months after surgery, the mean residual refractive cylinder was 0.42 ± 0.45D in the digital group and 0.39 ± 0.40D in the manual group (P = 0.844). There were no significant differences between groups in spherical equivalent refraction, uncorrected and best-corrected spectacle visual acuity, or the parameters of vector analysis. All toric IOL alignment errors were within 10° of the intended axis, and among them, about 42% of eyes in the digital group and 61% of eyes in the manual group had a rotation of 0–2° (P = 0.038). Trefoil in the manual group decreased postoperatively compared with the digital group (P = 0.012). Other aberration analyses did not reveal any statistical differences between groups.

Conclusions

Accurate slit-beam manual marking and digital image-guided marking are equally effective for toric IOL alignment.

Comparison of Toric Intraocular Lens Alignment Between Femtosecond Laser-Assisted Capsular Marking and Manual Corneal Marking

PURPOSE

To compare toric intraocular lens (IOL) alignment between femtosecond laser-assisted capsular marking and manual corneal marking.

METHODS

This study prospectively included 72 consecutive eyes (from 72 patients) with cataract and anterior corneal astigmatism of 1.00 diopter (D) or greater that underwent femtosecond laser-assisted cataract surgery with implantation of a toric IOL. These eyes were randomly categorized into two groups based on the IOL alignment method. The femtosecond laser capsular marking group included 36 eyes with capsular markers using the latest femtosecond laser platform. The manual marking group included 36 eyes with manual corneal markers. The preservation of the markers was assessed. Visual acuity and refractive outcomes, as well as deviation from the target axis, were evaluated.

RESULTS

In the femtosecond laser capsular marking group, all capsular markers were retained for at least 3 months. In the manual marking group, 22.2% of the corneal markers disappeared within 1 month and all markers disappeared within 3 months. At 1 month postoperatively, the mean magnitudes of refractive astigmatism were -0.41 ± 0.26 and -0.45 ± 0.31 D (P = .81), and the uncorrected distance visual acuities were 0.07 ± 0.06 and 0.07 ± 0.05 logMAR (P = .56) in the femtosecond laser capsular marking and manual marking groups, respectively. The misalignment of the toric IOL within 1 hour postoperatively was 1.5° ± 1.4° in the femtosecond laser capsular marking group and 4.4° ± 2.1° in the manual marking group (P < .01). The deviation from the target axis of implantation was 1.6° ± 1.3° in the femtosecond laser capsular group and 4.8° ± 2.5° in the manual marking group (P < .01) at 1 month postoperatively.

CONCLUSIONS

IOL misalignment was significantly lower in the femtosecond laser-assisted capsular marking group than in the manual corneal marking group. In addition, the long-term preservation of the capsular marker is helpful in evaluating the rotation of the toric IOL. [J Refract Surg. 2020;36(8):536-542.].

Clinical evaluation of toric intraocular lens implantation based on iTrace wavefront keratometric astigmatism

Background

Currently, there is no standard technique for determining corneal astigmatism. The iTrace wavefront aberrometry of cornea calculated steep power and axis based on the best Zernike mathematical fit from all topo data within 4 mm circle. It was supposed to be more accurate than iTrace simulated keratometry which was calculated based on only 4 points on the circle of 3 mm. This aim of this study was to evaluate visual outcomes and rotational stability after toric intraocular lens (IOL) implantation using the wavefront aberrometry of the cornea with iTrace.

Setting: Single site in China, Shanxi Eye Hospital, Shanxi, China.

Design: Prospective case series.

Methods

The study included 85 eyes of 63 patients undergoing phacoemulsification and toric IOL implantation. The IOL power and cylinders were chosen with the help of the iTrace toric planning program using wavefront keratometric astigmatism. Astigmatic changes were assessed using Alpins vector method over a 3-month follow-up period.

Results

Preoperative mean corneal topographic astigmatism was 1.91 diopters (D) ± 0.69 (standard deviation). Postoperative mean refractive astigmatism decreased significantly to 0.48 D ± 0.34. Surgical induced astigmatism was 1.73 D ± 0.77 and the mean correction index was 0.89 ± 0.22, showing a slight undercorrection. The proportion of astigmatism ≤0.50 D increased from 0 to 71.8% postoperatively.

Conclusions

This is the first study on evaluation of clinical outcomes of toric IOL implantation in corneal astigmatism patients using iTrace wavefront keratometric readings. The findings show that use of iTrace built-in toric calculator is safe and effective for planning toric IOL surgery for wavefront keratometric astigmatism.

Trial registration

Current Controlled Trials ISRCTN94956424, Retrospectively registered (Date of registration: 05 February 2020).

Femtosecond laser-assisted capsulotomy with capsular marks for toric IOL alignment: Comparison of tensile strength with standard femtosecond laser capsulotomy

PURPOSE

To compare the capsulotomy rim strength with capsular marks (CMs) to the rim strength without CMs in porcine eyes, and to demonstrate the practicality of CMs for intraoperative toric intraocular lens (IOL) alignment.

SETTING

LENSAR facility, Orlando, Florida, USA.

DESIGN

Laboratory study.

METHODS

The biomechanical strength of the capsulotomy with CMs was tested under two different load orientations (orthogonal to or in-line with CMs). Thirty-six porcine eyes were randomly assigned to three treatment cohorts: (1) standard capsulotomy with no CMs, (2) capsulotomy with CMs for in-line tensile testing and (3) capsulotomy with CMs for orthogonal tensile testing. Study parameters were capsulotomy break force and maximum extensibility. The ease of using CMs for toric IOL alignment was also evaluated.

RESULTS

There was no significant difference between the mean break force for standard capsulotomy (180.57 mN ± 22 [SD]), capsulotomy with CMs with orthogonal load (178.04 ± 20 mN, P = 1.000), and with in-line load (181.05 ± 15 mN, P = 1.000). Likewise, the mean extensibility at the break point for standard capsulotomy (6.47 ± 0.33 mm) was equivalent to the mean extensibility with CMs with orthogonal load (6.49 ± 0.45 mm, P = 1.000) and with in-line load (6.3 ± 0.47 mm, P = .960). In the implanted eyes, toric IOLs were found to be easily aligned with the CMs.

CONCLUSION

The femtosecond laser capsulotomies with CMs were equivalent in tensile strength and extensibility to standard femtosecond laser capsulotomies and showed high potential for effective alignment of toric IOLs.

Optimizing outcomes with toric intraocular lenses

Toric intraocular lenses (IOLs) are the procedure of choice to correct corneal astigmatism of 1 D or more in cases undergoing cataract surgery. Comprehensive literature search was performed in MEDLINE using “toric intraocular lenses,” “astigmatism,” and “cataract surgery” as keywords. The outcomes after toric IOL implantation are influenced by numerous factors, right from the preoperative case selection and investigations to accurate intraoperative alignment and postoperative care. Enhanced accuracy of keratometry estimation may be achieved by taking multiple measurements and employing at least two separate devices based on different principles. The importance of posterior corneal curvature is increasingly being recognized in various studies, and newer investigative modalities that account for both the anterior and posterior corneal power are becoming the standard of care. An ideal IOL power calculation formula should take into account the surgically induced astigmatism, the posterior corneal curvature as well as the effective lens position. Conventional manual marking has given way to image-guided systems and intraoperative aberrometry, which provide a mark-less IOL alignment and also aid in planning the incisions, capsulorhexis size, and optimal IOL centration. Postoperative toric IOL misalignment is the major factor responsible for suboptimal visual outcomes after toric IOL implantation. Realignment of the toric IOL is needed in 0.65%–3.3% cases, with more than 10° of rotation from the target axis. Newer toric IOLs have enhanced rotational stability and provide precise visual outcomes with minimal higher order aberrations.