Postoperative intraocular lens rotation: a randomized comparison of plate and loop haptic implants

Dynamic Changes of Capsular-Intraocular Lens Adhesion in Plate-Haptic Hydrophilic and Loop-Haptic Hydrophobic Eyes

INTRODUCTION

The aim of this work is to investigate the dynamic changes of capsular-intraocular lens (IOL) adhesion in plate-haptic hydrophilic and loop-haptic hydrophobic eyes.

METHODS

Cataract eyes that met the inclusion criteria were randomly assigned to receive implantation of a plate-haptic hydrophilic or loop-haptic IOL. The anterior capsular adhesion, posterior capsular adhesion, and the configurations of the capsular bend were evaluated using swept-source optical coherence tomography at 1 day, 1 week, 1 month, and 3 months postoperatively.

RESULTS

In total, 66 eyes of 66 patients were eligible for the analysis: 33 in the plate-haptic group and 33 in the loop-haptic group. The contact between the anterior capsule and IOL in the plate-haptic group was earlier than that in the loop-haptic group upon comparing the measurements taken at 1 day and 1 week (p = 0.001, p = 0.003, respectively). The complete attachment of the posterior capsule and IOL in the plate-haptic group was significantly greater at 1 week, 1 month, and 3 months (p = 0.001, p = 0.000, p = 0.001, respectively). The capsular bend index of the plate-haptic group was significantly greater than that of the loop-haptic group at each time points except at 1 day (p = 0.007, p = 0.049, p = 0.005, respectively). Furthermore, a new type of capsular bend, "cocked adhesion," was observed in the plate-haptic eyes.

CONCLUSIONS

The plate-haptic IOL demonstrated excellent capsular adhesion compared to the loop-haptic IOL, which was probably attributed to haptic compressibility. A special cocked configuration of the capsular bend in plate-haptic IOL was observed for the first time. Further studies are warranted to confirm the effect of the new type of capsular bend.

Comparison of clinical outcome after implantation of two toric intraocular lenses with different haptic type: a prospective randomized controlled trial

OBJECTIVE

To study the effect of astigmatism correction, rotational stability, and related factors of two different haptic type toric intraocular lenses.

METHODS

A prospective, randomized, controlled trial. Cataract patients with preoperative corneal astigmatism of > 1 D were randomly implanted with C-loop haptic toric IOL (AcrySof-toric IOL) (group A) or plate-haptic toric IOL (AT TORBI 709 M IOL) (group B). The residual astigmatism, intraocular lens rotation, and visual quality were determined and compared between the two groups at 3 months after surgery.

RESULTS

Seventy-nine eyes were included in this study, including 40 eyes in the group A and 39 eyes in the group B. No significant difference in preoperative visual acuity, intraocular pressure, and ophthalmic biological parameters was found between the two groups. There was no significant difference in residual astigmatism between the two groups at 3 months after surgery (P > 0.05). The rotation degree in the group A was 3.85 ± 2.92°, the rotation degree in the group B was 2.33 ± 2.31°, and a significant difference in intraocular lens rotation was identified between the two groups (P < 0.05). Upon exploring the rotation-related factors of the two different haptic type toric intraocular lenses, the rotation after implanting C-loop haptic toric IOL was positively correlated with axial length (Pearson r = 0.522, P = 0.01) and corneal white-to-white distance (Pearson correlation analysis r = 0.356, P = 0.024).

CONCLUSIONS

The two different haptic type toric intraocular lenses effectively corrected regular corneal astigmatism and provided a good rotational stability after surgery. But the stability of plate-haptic toric IOL was better than that of C-loop haptic toric IOL. The rotational stability of C-loop haptic toric IOL was often related to axial length and corneal white-to-white distance.

Rotational stability and capsular bag performance of a hydrophobic acrylic open-loop single-piece intraocular lens

PURPOSE

To evaluate the rotational stability and capsular bag performance of a blue light-absorbing hydrophobic acrylic open-loop single-piece intraocular lens (IOL) with a blast-finished anchor wing haptic design during the first 6 postoperative months.

METHODS

In this prospective clinical study, patients with age-related cataract and potential postoperative corrected distance visual acuity (CDVA) of 0.2 logMAR or better were included. The patients received a non-toric hydrophobic acrylic single-piece IOL with an axis mark (YST0.00; Nidek Co. Ltd, Japan). Surgeries were video-taped. Retroillumination images were acquired 1 h, 1 week and 6 months postoperatively. Rotational stability was assessed by precise image overlay. At 6 months, Purkinje meter measurements were performed to evaluate tilt and decentration.

RESULTS

In total, 100 eyes of 77 patients were included in the analysis. Mean absolute rotation was 2.1 ± 1.7° (median 1.7, range: 0-7.9) at 6 months (1 h - 6 months postoperatively). IOL rotation was ≤3° and ≤6° in 74 (74%) and 98 (98%) eyes, respectively. Mean absolute IOL rotation from the end of surgery to 6 months was 2.5 ± 2.2° (median 2.3, range: 0-15.6; n = 78). Mean tilt (pupillary axis) and decentration were 4.1 ± 1.9° (median 4.0, range: 0.5-8.2) and 0.35 ± 0.17 mm (median 0.32, range: 0.06-0.91) respectively (n = 84). Postoperatively, 98 (98%) eyes achieved a CDVA of 0.2 logMAR or better, 95 (95%) of ≤0.1 and 81 (81%) of ≤0.0.

CONCLUSIONS

This hydrophobic acrylic single-piece IOL showed an excellent rotational stability and capsular bag position with low tilt and decentration values.

Insights into the rotational stability of toric intraocular lens implantation: diagnostic approaches, influencing factors and intervention strategies

Toric intraocular lenses (IOLs) have been developed to enhance visual acuity impaired by cataracts and correct corneal astigmatism. However, residual astigmatism caused by postoperative rotation of the toric IOL is an important factor affecting visual quality after implantation. To decrease the rotation of the toric IOL, significant advancements have been made in understanding the characteristics of toric IOL rotation, the factors influencing its postoperative rotation, as well as the development of various measurement techniques and interventions to address this issue. It has been established that factors such as the patient's preoperative refractive status, biological parameters, surgical techniques, postoperative care, and long-term management significantly impact the rotational stability of the toric IOL. Clinicians should adopt a personalized approach that considers these factors to minimize the risk of toric IOL rotation and ensure optimal outcomes for each patient. This article reviews the influence of various factors on toric IOL rotational stability. It discusses new challenges that may be encountered to reduce and intervene with rotation after toric IOL implantation in the foreseeable future.

Determination of the toric axis by using internal astigmatism axis in non-dilated eyes

PURPOSE

To determine the toric intraocular lens (IOL) axis by using internal astigmatism axis obtained from Optical Path Difference (OPD) Scan III (Nidek Co.) in non-dilate eyes.

METHODS

The eyes of patients who underwent toric IOL implantation for astigmatic correction were investigated. Patients who have ocular surface disorder, keratoconus, posterior capsule opacification were excluded. The IOL axis measured in non-dilated eyes in mesopic conditions by OPD scan III device and the IOL axis measured by using classical slit lamp biomicroscopy method in dilated eyes were detected at postoperative 1st and 6th months. Results were compared with correlation and linear regression analysis.

RESULTS

Totally, 26 eyes of 18 patients were included. The difference between biomicroscopic IOL axis and OPD internal astigmatism axis was 4.96 ± 4.41 degrees at the 1st month and 3.62 ± 3.5 degrees at the 6th month. There was a significant and high correlation between biomicroscopic IOL axis and OPD internal astigmatism axis at both 1st month (r = 0.992 p < 0.001) and 6th month (r = 0.995 p < 0.001). According to regression analysis, the results of two measurement methods were significantly compatible with each other at 1st month (R Sq = 0.984 p < 0.001) and 6th month (R Sq = 0.990 p < 0.001) and there was a close to ideal linear (R Sq = 1) relationship between two methods.

CONCLUSIONS

In eyes with toric IOL implantation, the IOL axis and IOL rotation according to target IOL axis can be detected easily and effectively in a short time by OPD scan internal astigmatism axis without the need to dilate the pupil.

Preferred cataract surgery practices in Malaysia: a survey based study

BACKGROUND

To describe the preferred cataract surgery practices among Malaysian ophthalmologists and medical officers in comparison with the recommended practices.

METHODS

An online questionnaire was sent out in April 2021, to Malaysian Ophthalmologists and medical officers who perform cataract surgeries. The questions were focused on the preferred cataract surgery practices of the participants. All data obtained were collected, tabulated and analysed.

RESULTS

A total of 173 participants responded to the online questionnaire. 55% of the participants were within 31-40 years of age. 56.1% preferred peristaltic pump over venturi system. 91.3% of participants practised povidone iodine instillation to the conjunctival sac. With regards to the main wound incision, more than half of the surgeons (50.3%) preferred fixed superior incision and 72.3% of them preferred 2.75 mm microkeratome blade. Most of the participants (63%) were inclined towards C-Loop clear intraocular lens (IOL) with a single-handed push preloaded system. 78.6% of the surgeons routinely use carbachol in their cataract surgery.

CONCLUSIONS

This survey provides some insight into the current practices among Malaysian ophthalmologists. Most of the practices are in line with international guidelines for preventing postoperative endophthalmitis. This article could help trainees and ophthalmologists benchmark and observe the common cataract surgery practices among their seniors and peers in Malaysia.

Influence of design parameters and capsulorhexis on intraocular lens stabilities: A 3D finite element analysis

BACKGROUND

Current treatment of cataract widely used in clinics is by removal of the opacified content from the lens capsule which is followed by insertion of an artificial intraocular lens (IOL). The IOL needs to remain stabilized in the capsular bag for the eye to achieve desired optical quality. The present study aims to investigate how different design parameters of the IOL can influence the axial and rotational stabilities of IOLs using Finite Element Analysis.

METHODS

Eight designs of IOL with variations in types of optics surface, types of haptics and haptic angulation were constructed using parameters obtained from an online IOL databank (IOLs.eu). Each IOL was subjected to compressional simulations both by two clamps and by a collapsed natural lens capsule with an anterior rhexis. Comparisons were made between the two scenarios on axial displacement, rotation, and distribution of stresses.

RESULTS

The clamps compression method set out by ISO does not always produce the same outcome as the in-the-bag analysis. The open-loop IOLs show better axial stability while the closed-loop IOLs show better rotational stability when compressed by two clamps. Simulations of IOL in the capsular bag only demonstrate better rotational stability for closed-loop designs.

CONCLUSIONS

The rotational stability of an IOL is largely dependent on its haptic design whilst the axial stability is affected by the appearance of the rhexis to the anterior capsule which has a major influence on designs with a haptic angulation.

Optimal Timing of Repositioning Surgery for a Plate-Haptic Toric Intraocular Lens: A Multicenter Retrospective Study

PURPOSE

To evaluate risk factors for significant rotation and determine optimal timing for repositioning surgery following a plate-haptic toric intraocular lens (IOL) implantation.

METHODS

This retrospective study enrolled patients who underwent the plate-haptic toric IOL implantation at seven hospitals in Shanghai. IOL rotation and residual astigmatism were compared before and after repositioning surgery. Risk factors for significant IOL rotation after cataract surgery were identified by stepwise multiple linear regression analysis. Spearman's and linear regression analyses were performed to identify factors associated with IOL rotation after repositioning. The receiver operator characteristic (ROC) curve was used to analyze the optimal timing for repositioning surgery.

RESULTS

Among 2,745 eyes implanted with the toric IOL, 46 eyes (1.68%) of 45 patients underwent repositioning surgery. Axial length and lens thickness were significantly associated with IOL rotation before repositioning. After repositioning surgery, IOL rotation and residual astigmatism were significantly reduced (all P < .001). IOL rotation after repositioning was negatively associated with the timing of repositioning surgery (all P < .001). The ROC curve showed that the optimal cut-off for the timing of repositioning surgery was 15 days or greater.

CONCLUSIONS

The prevalence of repositioning surgery after the plate-haptic toric IOL implantation was 1.68%, and the optimal timing for repositioning surgery was recommended to be 2 to 3 weeks after cataract surgery. [J Refract Surg. 2023;39(2):120-126.].

Effect of capsular bend on the rotational stability of toric intraocular lens

PURPOSE

To assess the effect of capsular bend and axial length on the rotational stability of toric IOL.

METHODS

The prospective study included patients with preexisting astigmatism that were implanted with Acrysof IQ Toric IOL. According to the pre‑operative axial length, all patients were divided into 2 groups: high myopia (AL ≥ 26 mm) group, and emmetropia or low to moderate myopia group (AL <26 mm). High-speed Swept-source Optical Coherence Tomography (SS-OCT) radial scanning was performed after pupil dilation to obtain the toric IOL axial orientation and capsular bending index (CBI) at 1-day, 1-week, 1-month and 3-month intervals postoperatively. The correlation between the rotation of toric intraocular lens and the axial length or CBI was subsequently analyzed.

RESULTS

68 eyes of 57 patients were included in the research. The rotation of toric IOL within the high myopia group was greater than the control group (P = 0.001, 1month postoperative). Capsular contact with the IOL was delayed in highly myopic eyes, although the results were not statistically significant (P = 0.094, 1-month postoperatively). There was a positive correlation between the degree of rotation and axial length at the interval found between 1-week and 1-month after the operation (r = 0.333, P = 0.005). There was a significant negative correlation between the IOL rotational speed and CBI (P < 0.001). The regression equation was Y = -0.441*X + 1.712 (R2 = 0.323, P < 0.001).

CONCLUSION

There was a significant negative correlation between the IOL rotation speed and the CBI, while the influence of the axial length and capsular bending mainly occurred between one week and one month after the operation.

Efficacy of a One-Piece Aberration Neutral Hydrophobic Acrylic Toric Intraocular Lens

PURPOSE

To assess the refractive outcomes, intraocular centration and rotational stability of the enVista toric intraocular lens (IOL).

PATIENTS AND METHODS

This study was a prospective, multi-centre, double-masked, partially randomized and partially controlled clinical trial. A total of 191 participants were implanted with toric IOL (1.25, 2.00, or 2.75D) or non-toric IOL (control). The lowest range of corneal astigmatic eyes were randomized to 1.25D toric or control. Higher astigmatic powers were allocated to the treatment arm. Subjects were assessed immediately postoperatively, 1-2 (V1), 7-14 (V2), 30-60 (V3) and 120-180 (V4) days postoperatively. Unaided (UDVA) and distance corrected visual acuity (CDVA), manifest refraction and corneal curvature were assessed. Vector analysis was used to calculate surgically induced refractive correction (SIRC), correction ratio (CR), error magnitude (EM) and error vector (EV). Slit-lamp photography was used to measure centration and rotational stability.

RESULTS

UDVA was better in the low toric IOL group in comparison with the control group at V4 (p<0.001). There was an undercorrection in the control group, whereas the average CR for all toric subjects was 1.00 ± 0.32: V2, 0.98 ± 0.34: V3 and 0.98 ± 0.35: V4. The absolute IOL rotational stability in comparison to the position of the IOL at V1 was 1.35° ± 0.97°: V2, 1.35° ± 1.07°: V3 and 1.38° ± 1.25°: V4. Decentration was generally inferior (V1: 0.04 ± 0.22mm, V2: 0.05± 0.20mm, V3: 0.08 ± 0.22mm, V4: 0.04 ± 0.21mm) and nasal (V1: 0.19 ± 0.23mm, V2: 0.20 ± 0.20mm, V3: 0.20 ± 0.21mm, V4: 0.17 ± 0.22mm).

CONCLUSION

Participants with low levels of corneal astigmatism achieved superior vision and refractive outcomes in the low toric group over the control. Moderate and high levels of astigmatism achieved excellent refractive outcomes. The toric IOL demonstrated high levels of both rotational and centrational stability.

Deviation from the planned axis of three toric intraocular lenses

In this study, we retrospectively evaluated the deviation from the planned axis of 3 Toric intraocular lenses (TIOL). Included in the study 190 eyes, operated by two surgeons using two different manual marking techniques. The patients were implanted with either AcrySof IQ Toric SN6AT (Alcon) (n = 90), POD FT (PhysIOL) (n = 50), or TECNIS Symfony Toric (J&J) (n = 50). At least 1 month postoperatively, the IOL was photographed, and the axis was measured using a designed software. The difference between the planned and actual axis was defined as axis deviation. The effect of IOL type, astigmatism direction, and marking techniques on the average degree and direction of the IOL deviation were evaluated and compared. There was no significant difference in the average deviation between the IOLs (TECNIS Symfony: 4.03° ± 4.34, POD FT: 3.52° ± 3.38, and SN6AT: 4.24° ± 4.10), and its direction (55.8%, 39.0%, and 56.6% clockwise (CW) deviation, respectively). With the rule, astigmatism had significantly more CW deviation compared with against the rule and oblique astigmatism (64.3%, 43.8%, and 41.7%, respectively, P = 0.027), but the average deviation was similar. The marking techniques did not influence the degree or direction of the deviation.

Predicting the biomechanical stability of IOLs inside the postcataract capsular bag with a finite element model

BACKGROUND AND OBJECTIVES

Although cataract surgery is a safe operation in developed countries, there is still room for improvement in terms of patient satisfaction. One of the key issues is assessing the biomechanical stability of the IOL within the capsular bag to avoid refractive errors that lead to a second surgery. For that purpose, a numerical model was developed to predict IOL position inside the capsular bag in the short- and long-term.

METHODS

A finite element model containing the implanted IOL, the postcataract capsular bag, the zonules, and a portion of the ciliary body was designed. The C-loop hydrophobic LUCIA IOL was used to validate the numerical model and two more worldwide IOL designs were tested: the double C-loop hydrophobic POD FT IOL and the plate hydrophilic AT LISA IOL. To analyze the biomechanical stability in the long-term, the effect of the fusion footprint, which occurs days following cataract surgery, was simulated. Moreover, several scenarios were analyzed: the size and location of the capsulorexhis, the capsular bag diameter, the initial geometry of the capsular bag, and the material properties of the bag.

RESULTS

The biomechanical stability of the LUCIA IOL was simulated and successfully compared with the in vitro results. The plate AT LISA design deformed the capsular bag diameter up to 11.0 mm against 10.5 mm for the other designs. This design presented higher axial displacement and lower rotation, 0.19 mm and 0.2^∘, than the C-loop design, 0.09 mm and 0.9^∘.

CONCLUSIONS

All optomechanical biomarkers were optimal, assuring good optical performance of the three IOLs under investigation. Our findings showed that the capsulorexhis size influences the stiffness of the capsular bag; however, the shape in the anterior and posterior curvature surfaces of the bag barely affect. The results also suggested that the IOL is prone to mechanical perturbations with the fusion footprint, but they were not high enough to produce a significant refractive error. The proposed model could be a breakthrough in the selection of haptic design according to patient criteria.

Impact of Material and Lens Design on Repositioning Surgery of Toric Intraocular Lenses: A Single-Arm Meta-Analysis

Aim

To analyze the pooled incidence rate in repositioning surgery by considering different materials and designs.

Methods

All published studies investigating the repositioning surgery of toric intraocular lenses (IOLs) before September 1, 2020, were searched and evaluated. The R3.5.2 software was used to extract the data, and a single arm meta-analysis was performed.

Results

19 cases from 18 published studies articles were included in the meta-analysis. The pooled incidence rate in repositioning surgery was 2% (I² = 53%, P_{heterogeneity}<0.01). Plate and silicone IOLs had significantly higher incidence rates (6% for each) than loop (2%) and hydrophobic acrylate (2%). Incidence rates of Acrysof, Staar, TECNIS, PhysIOL SA, T-flex 623T, and Microsil 6116TU groups were 1% (95% CI [1%–2%]), 6% (95% CI [4%–9%]), 3% (95% CI [2%–4%]), 1.40% (1/71), 3.03% (1/33), and 4.76% (1/21), respectively.

Conclusions

The pooled incidence rate of repositioning surgery in IOLs was 2%. Materials and designs would be risk factors for the rotational stability of the toric IOLs. Pooled incidence rates of the hydrophobic acrylate and loop group were lower than those of the silicone and plate group. Product identity is the main driver of heterogeneity.

Rotational stability of Toric intraocular lenses

BACKGROUND

A prospective study to evaluate the rotational stability of toric intraocular lenses (IOLs).

METHODS

A prospective study of 30 eyes in 29 patients. All patients with regular astigmatism of range 0.75-4 D were included in the study. Exclusion criteria included irregular corneal astigmatism, post-refractive surgery and corneal dystrophies. All patients underwent uncomplicated phacoemulsification cataract surgery by the same surgeon. Three eyes with corneal astigmatism of 0.75-1.5 D were implanted with the AcrySof SA60T3 IOL, eight eyes with astigmatism between 1.5 and 2.0 D received the SA60T4 IOL and eight eyes with astigmatism between 2.0 and 2.50 D received the SA60T5 and rest with astigmatism of 2.5 D and higher received SA60T6 and above models. Main outcome measure was the post-operative position of the lens, assessed at day 1, 1 week, 1 month and 6 months, using toric marker and the slit lamp.

RESULTS

There was no significant rotation of IOL observed during a follow-up period of 6 months. Overall, the post-operative rotation was within 5° in 95% of cases. There was no trend for either clockwise or anti-clockwise rotation. However, IOL rotation happens mostly within the first month of surgery, and if it is significant, it requires early repositioning.

CONCLUSION

Toric IOLs are very effective and consistent in correcting astigmatism during the cataract surgery. Once placed to its position, toric IOLs demonstrate rotational stability in the capsular bag.

Toric intraocular lenses: Expanding indications and preoperative and surgical considerations to improve outcomes

Since the introduction of the first toric intraocular lens (IOLs) in the early 1990s, these lenses have become the preferred choice for surgeons across the globe to correct corneal astigmatism during cataract surgery. These lenses allow patients to enjoy distortion-free distance vision with excellent outcomes. They also have their own set of challenges. Inappropriate keratometry measurement, underestimating the posterior corneal astigmatism, intraoperative IOL misalignment, postoperative rotation of these lenses, and IOL decentration after YAG-laser capsulotomy may result in residual cylindrical errors and poor uncorrected visual acuity resulting in patient dissatisfaction. This review provides a broad overview of a few important considerations, which include appropriate patient selection, precise biometry, understanding the design and science behind these lenses, knowledge of intraoperative surgical technique with emphasis on how to achieve proper alignment manually and with image-recognition devices, and successful management of postoperative complications.

Associations between anterior segment parameters and rotational stability of a plate-haptic toric intraocular lens

PURPOSE

To evaluate the associations between anterior segment parameters and the rotational stability of a plate-haptic toric intraocular lens (IOL).

SETTING

Eye and Ear, Nose, Throat Hospital of Fudan University.

DESIGN

Retrospective case series.

METHODS

Patients who underwent uneventful phacoemulsification and plate-haptic toric IOL (AT TORBI 709M IOL) implantation were included. Preoperative axial length (AL) and anterior segment parameters, including the white-to-white (WTW) distance, anterior chamber depth (ACD), lens thickness (LT), and anterior segment length (ASL; the sum of ACD and LT) were recorded. IOL rotation, residual astigmatism (RAS), and visual acuity were evaluated 1 month postoperatively. The associations between the anterior segment parameters and IOL rotation were evaluated.

RESULTS

A total of 102 eyes of 102 patients were included. The mean AL was 26.43 ± 2.65 mm (range 21.71-34.60 mm). The mean IOL rotation was 4.59 ± 3.18 degrees, and RAS was 0.62 ± 0.39 D postoperatively. No correlation was detected between AL, ACD, or LT and the rotation of the plate-haptic toric IOL (all P > .05). However, its rotation correlated positively with the WTW distance (r = 0.250, P = .011) and ASL (r = 0.214, P = .030). Backward stepwise multiple linear regression revealed that the WTW distance (β = 2.142, P = .014) and ASL (β = 2.060, P = .037) were independent predictors of plate-haptic toric IOL rotation.

CONCLUSIONS

Plate-haptic toric IOLs rotate more in eyes with larger WTW distances and longer ASLs; therefore, toric IOL implantation should be performed with caution in eyes with these characteristics.

Transitional conic toric intraocular lens evaluation after femtosecond laser-assisted cataract surgery using intraoperative aberrometry

PURPOSE

To assess refractive and visual outcomes following phacoemulsification with femtosecond laser-assisted cataract surgery (FLACS) using intraoperative aberrometry and implantation of a toric intraocular lens (IOL) in eyes with different degrees of astigmatism.

METHODS

One hundred two eyes of 70 patients who underwent implantation of the transitional toric 565 Precizon IOL (Ophtec BV) were enrolled. FLACS, capsular tension ring insertion, and intraoperative aberrometry were performed. Main outcome measures were refractive error, uncorrected- and corrected distance snellen decimal visual acuity values (UDVA and CDVA, respectively), and IOL rotation. Specifically, a vector analysis was carried out with J0 and J45 evaluation. Eyes were evaluated 1-year after surgery.

RESULTS

Overall, 94.12% (96 eyes) and 100% (102 eyes) of the eyes showed a spherical equivalent (SE) within ± 0.50D and ± 1.00D, respectively. The mean SE and refractive cylinder were - 0.06 ± 0.29D and - 0.23 ± 0.37D, respectively. Vector analysis revealed that 100% of the eyes were within ± 0.50D for the J0 and J45 cylindrical components. The mean toric axis rotation was 1.10 ± 1.71° (from 0° to 5°), 77% (79 eyes), and 100% (102 eyes) of the eyes showed UDVA and CDVA of 20/25, respectively. The postoperative mean values of monocular UDVA and CDVA were 0.88 ± 0.17 and 0.96 ± 0.07 (about 20/20), respectively. No patient required IOL realignment during the postoperative follow-up.

CONCLUSIONS

The present study suggests that the use of the Precizon IOL after FLACS, using intraoperative aberrometry in patients with different amounts of astigmatism, provides good visual acuity, accurate refractive outcomes, and excellent rotational stability.

Rotational stability of toric intraocular lenses with a newly modified capsular tension ring

PURPOSE

To determine whether a newly modified capsular tension ring (CTR) is effective at preventing toric intraocular lens (TIOL) rotation and misalignment.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Ten human cadaver eyes were used to test the ease or difficulty of TIOL rotation in the capsular bag under 3 experimental conditions: a TIOL alone, a TIOL with a standard CTR, or a TIOL with a newly modified CTR with indentations in a sinusoidal pattern. Scores for the ease of IOL rotation were compared by using the nonparametric Friedman analysis of variance test. In addition, both anterior and posterior Miyake-Apple views were filmed to observe the rotational stability of TIOLs in the capsular bag under the 3 test conditions.

RESULTS

In the ten eyes of five patients, the rotational stability improved with a standard CTR, but further improvement was statistically observed (P < .05) with the newly modified CTR under all test conditions. This was true for both IOLs used (AcrySof and TECNIS toric IOLs), with or without ophthalmic viscosurgical device, and for either clockwise or counterclockwise rotations.

CONCLUSIONS

A newly designed CTR prototype represents a new technology for improving the rotational stability of a TIOL in the capsular bag. Under all test conditions, the prototype performed significantly better than a standard CTR. The results support the use of this new CTR design to improve the accuracy and refractive success of TIOLs.

Anterior capsule coverage and rotational stability of an acrylic toric intraocular lens

PURPOSE

To investigate factors related to the rotational stability of an acrylic toric intraocular lens (IOL).

SETTING

Four ophthalmic surgical sites in Japan.

DESIGN

Prospective case series.

METHODS

The study included 120 eyes of 120 patients undergoing phacoemulsification and implantation of a toric IOL (AcrySof IQ, Alcon Laboratories, Inc.). At 1 hour postoperatively, the area of continuous curvilinear capsulorhexis (CCC) was measured, and the state of anterior capsule coverage on the IOL optic (total on or partial on) was recorded. The toric IOL axis orientation was assessed at the end of surgery and at 1 hour, 1 week, 1 month, and 6 months postoperatively. Multiple regression analysis was performed to explore any clinical factors relevant to IOL rotation from the end of surgery to 6 months postoperatively. The explanatory variables included age, anterior chamber depth preoperatively, axial length, type of corneal astigmatism (with-the-rule, against-the-rule, or oblique astigmatism), area of CCC, state of anterior capsule overlap on IOL optic (total coverage vs partial coverage), and surgical sites (surgeons).

RESULTS

The multiple regression analysis in 110 eyes of 110 patients indicated that anterior capsule overlap on the IOL optic was the only variable associated with IOL rotation at 6 months postoperatively (P = .0482). The mean absolute rotation at 6 months was 1.96 ± 1.81 degrees in the total on group and 3.79 ± 3.12 degrees in the partial on group (P = .0004).

CONCLUSIONS

Rotational stability of a single-piece, acrylic toric IOL was better in eyes with total anterior capsule coverage than that in those with partial anterior capsule coverage on the IOL optic.

Clinical outcomes, predictability and rotational stability following implantation of Eyecryl toric versus TECNIS toric intraocular lenses-A comparative study

PURPOSE

To compare the visual outcomes, predictability and rotational stability following implantation of Eyecryl toric versus TECNIS toric intraocular lenses.

METHODS

This retrospective study included 100 eyes of 78 eligible patients who underwent phacoemulsification followed by implantation of either Eyecryl Toric IOL or TECNIS Toric IOL (n = 50 eyes in each group), using an intraoperative image-guided marker less system. All toric IOL implantations were performed under balanced salt solution. At 2 weeks, 3 months and 6 months, uncorrected (UDVA) and corrected distance visual acuity (CDVA), spherical equivalent refraction, residual astigmatism, and rotational stability of the toric IOL was evaluated and compared. Rotational stability was assessed using ray tracing.

RESULTS

Mean age of the participants was 67.8 ± 9.26 years in Eyecryl toric group and 64 ± 11 years in TECNIS toric group. The mean pre-op corneal astigmatism was 1.75 ± 0.62 D and 2.00 ± 0.71 D in the Eyecryl and TECNIS group, respectively (p = 0.07). At 2 weeks and at 6 months post-op, there was no statistically significant difference between the UDVA, CDVA, and residual astigmatism between the two groups (p < 0.05). Mean post-operative toric IOL rotation was 3.94 ± 2.27 degrees in the Eyecryl Toric group, and 4.44 ± 2.77 degrees, in the TECNIS Toric group, respectively, the difference was not statistically significant (p = 0.32). One IOL in the Eyecryl group and two IOLs in the TECNIS group required re-positioning for significant post-op rotation at 1 week post-op.

CONCLUSION

At 6 months, both Eyecryl toric and TECNIS toric IOLs showed comparable post-operative outcomes in terms of UDVA, CDVA, residual astigmatism and rotational stability.

Comparison of the rotational stability between plate-haptic toric and C-loop haptic toric IOLs in myopic eyes

PURPOSE

To compare the rotational stability of a plate-haptic toric intraocular lens (IOL) vs a C-loop haptic toric IOL in myopic cataract eyes.

SETTING

Eye and Ear, Nose, and Throat Hospital of Fudan University, China.

DESIGN

Prospective, randomized, controlled study.

METHODS

Cataract eyes with axial length (AL) more than 24.5 mm were randomly assigned to receive implantation of a C-loop haptic toric IOL (AcrySof Toric IOL) (Group A) or a plate-haptic toric IOL (AT TORBI 709M IOL) (Group B). IOL rotation, residual astigmatism, visual acuity, and higher-order aberrations (HOAs) evaluated with OPD-Scan III aberrometer were compared at 3 months postoperatively.

RESULTS

In total, 62 eyes of 62 patients were eligible for analysis: 31 in Group A and 31 in Group B. The mean rotation of toric IOLs was greater in Group A than that in Group B (8.00 ± 3.60 degrees vs 4.42 ± 3.24 degrees, respectively, P < .001), especially when IOLs were vertically placed. IOL rotation was positively correlated with AL in Group A, whereas no such correlations were found in Group B. Residual astigmatism in Group A was greater than that in Group B (-0.76 ± 0.30 diopter [D] vs -0.51 ± 0.29 D, respectively, P = .001). Fewer eyes achieved residual astigmatism of 0.50 D or less in Group A than in Group B (38.71% vs 64.52%). Group A had worse postoperative uncorrected visual acuity and higher total HOAs and coma for a 6.0 mm pupil than Group B, whereas postoperative corrected visual acuity was not different between the 2 groups.

CONCLUSIONS

The plate-haptic toric IOL might be a better choice for myopic cataract eyes with corneal astigmatism because of reduced postoperative rotation.

Clinical outcomes and rotational stability following implantation of Eyecryl toric intraocular lens - Results of a 12-months prospective study

Purpose:

To evaluate the clinical performance and rotational stability after implantation of Eyecryl Toric monofocal IOL following cataract surgery.

Methods:

Patients undergoing phacoemulsification for age-related cataract and satisfying the eligibility criteria were implanted with Eyecryl Toric IOL. All implantations were done under balanced salt solution. A marker-less system Callisto Eye (Carl Zeiss Meditec, Germany) was used to guide the intra-operative alignment of the toric IOL.

Results:

A total of 50 eyes from 39 patients with mean age of 68.2 ± 8.7 years were included in the study. At 12 months, 82% (41) eyes had cumulative UDVA of 20/20 or better. Post-op SE refraction accuracy was within ± 0.50 D for 94% (n = 47) eyes and refractive cylinder accuracy was within ≤0.50 D in 98% (n = 49) eyes. Average post-op rotation at 1 year was 4.06 ± 2.15 degrees. Eighty-four percent of eyes were within 5 degrees and 16% were within 6-10 degrees of intended axis. Two eyes required IOL re-positioning due to significant rotation of the toric IOL (>10 degrees), identified within the 1^st week after surgery.

Conclusion:

Eyecryl toric IOL demonstrated the ability to achieve a significant reduction in astigmatism, improved UDVA outcomes, high levels of spectacle independence, low rates of intra-operative injector related complications and good rotational stability at 12 months post-op.

Preliminary Clinical Study of a LenSx Femtosecond Laser-Assisted Limbal Relaxing Incision for the Correction of High Myopia with Low to Moderate Astigmatism in Posterior Implantable Collamer Lens Implantation

Purpose. To evaluate the safety, efficacy, and predictability of implantable collamer lens (ICL) implantation combined with a LenSx femtosecond laser-assisted limbal relaxing incision (LRI) for the correction of corneal astigmatism. Methods. This prospective study enrolled 64 eyes (54 patients) with high myopia with low to moderate regular corneal astigmatism. They were divided into an ICL group with ICL implantation (18 patients, 20 eyes), a TICL group with toric ICL implantation (17 patients, 23 eyes), and a LenSx + ICL group with a LenSx femtosecond laser-assisted LRI and an ICL implantation (19 patients, 21 eyes). Visual acuity, astigmatism correction ability, and visual quality were measured before and 1, 3, and 6 months after surgery. Results. The postoperative visual acuity of the 3 groups was higher than the preoperative visual acuity ( $P<0.01$ ), and the improvements in the LenSx + ICL group and the TICL group were greater than those in the ICL group ( $P<0.01$ ). The LenSx + ICL and TICL groups had less residual astigmatism and a higher astigmatism correction index (CI) than the ICL group ( $P<0.01$ ). There was no significant difference among the three groups in total high-order aberrations (HOAs) before and after surgery ( $P>0.05$ ). Conclusion. LenSx femtosecond laser-assisted LRI can effectively correct low to moderate corneal astigmatism during ICL implantation surgery. It can achieve similar clinical effects in the short term compared with TICL implantation.

Biomechanical Stability of Three Intraocular Lenses With Different Haptic Designs: In Silico and In Vivo Evaluation

PURPOSE

To assess the biomechanical stability of three different marketed intraocular lenses (IOLs) with different haptic designs (four-loop IOL [Micro F FineVision model] and double C-loop IOL [POD F and POD FT models], all manufactured by PhysIOL), in silico (computer simulation) and in vivo (in the context of lens surgery).

METHODS

An in silico simulation investigation was performed using finite element modeling (FEM) software to reproduce the compression test defined by the International Organization for Standardization and in vivo implantation in patients in the context of lens surgery was evaluated 1 day and 3 months postoperatively. IOL decentration and rotation were tested. In addition, the stress and strains were analyzed with the finite element method.

RESULTS

In the in silico evaluation, the compression force for the POD F IOL was slightly lower than for the POD FT IOL and Micro F IOL for all compression diameters. The axial displacement was maximum for the POD FT IOL and the tilt, rotation, and lateral decentration were substantially lower than the acceptable tolerance limits established in ISO 11979-2. In the in vivo evaluation, a total of 45 eyes from 45 patients were selected, 15 eyes for each IOL model under assessment. Statistically significant differences were found between the Micro F and POD F IOLs for lateral decentration in x-direction (in absolute value) at 3 months postoperatively (P = .03).

CONCLUSIONS

Although statistically significant differences have been found when comparing the displacement, tilt, and rotation between the different lenses, these differences cannot be considered clinically relevant, which would suggest that all three IOL models yield excellent stability in those terms. FEM appears to be a powerful tool for numerical studies of the biomechanical properties of IOLs. [J Refract Surg. 2020;36(9):617-624.].

Comparative effects of various types of toric intraocular lenses on astigmatism correction

BACKGROUND

Currently, various types of toric intraocular lenses (IOL) have been manufactured and can be divided into three types according to the location of correction component; front-toric IOL (correction on anterior IOL surface), back-toric IOL (correction on posterior IOL surface), and bi-toric IOL (correction on both anterior and posterior IOL surfaces). In this study, we aimed to investigate the effectiveness of reducing corneal astigmatism of either normal or post-penetrating keratoplasty (PKP) corneas according to the type of implanted toric IOLs.

METHODS

Medical records were retrospectively reviewed in 370 patients who had undergone phacoemulsification with posterior chamber toric IOL insertion (front-toric IOL, back-toric IOL or bi-toric IOL). Subjects were divided into 2 groups; subjects who had no history of corneal disease with corneal astigmatism more than 1.00 diopters (D) (G1) and subjects who received previous PKP with all corneal sutures removed and had corneal astigmatism more than 1.25 D (G2). Preoperatively intended target from SRK/T was evaluated. Refractive astigmatism and its vector analysis (J0, J45), mean numerical error (MNE) and mean absolute error (MAE) were assessed at least a month after cataract surgery.

RESULTS

Mean preoperative corneal astigmatisms were 2.2 D and 4.0 D in G1 and G2, respectively. There was significant reduction of mean postoperative refractive astigmatism to 0.89 D in G1 and to 2.33 D in G2. In G1, bi-toric IOL showed significantly more improved refractive astigmatism than back-toric IOL. In G2, no difference in refractive astigmatism according to toric IOL type was observed. While G2 showed no difference in MNE among toric IOLs, in G1, bi-toric IOL showed significant hyperopic shift compared to back-toric IOL. In both groups, there was no significant difference in MAE according to type of IOL. No postoperative complications were observed.

CONCLUSION

Our study suggests that all types of toric IOL are beneficial in correcting astigmatism of normal and post-PKP corneas. Noticeably, bi-toric IOL showed significantly better results in refractive astigmatism than back-toric IOL in normal cornea. However, bi-toric IOL showed a more hyperopic shift compared to back-toric IOL. Among post-PKP corneas, all types of toric IOL showed similar results.

Systematic Study on the Biomechanical Stability of C-Loop Intraocular Lenses: Approach to an Optimal Design of the Haptics

To study the main design parameters that affect the mechanical stability of C-loop intraocular lenses, leading to an optimal design that minimizes the axial displacement, tilt and rotation. A total of 144 geometrical variations were studied on a 1-piece, non-angulated, C-loop hydrophobic acrylate intraocular lens. The study was performed in a finite element modeling simulation. The suitable set of variations was determined using a mixed-factorial analysis, allowing to analyse the impact of the different designs on the mechanical stability of the lens (compression force, axial displacement, tilt and rotation). The design parameters under study were: the length, width, thickness and opening angle of the haptic, the haptic-optic junction and the start of the haptic curvature. The compression (or reaction) force is affected by the haptic width, the haptic-optic junction, and the interaction between both. The axial displacement is mainly affected by the width and thickness of the haptic, and the size of the haptic-optic junction as well. The tilt is affected by the haptic thickness and the interaction between the haptic curvature and the haptic-optic junction. The rotation is affected by the start of the haptic curvature, the haptic-optic junction and the haptic width. The haptic-optic juntion is one of the most influential parameters affecting the four responses studied of the C-Loop IOL. The smaller the haptic-optic juntion, the better biomechanical stability.

Rotational stability of a new multicomponent intraocular lens

Purpose

To evaluate the rotational stability of the Precisight multicomponent intraocular lens (MCIOL) following primary implantation and after enhancement procedures.

Patients and methods

Prospective, single-center study of eyes that underwent routine cataract surgery with implantation of a non-toric MCIOL, (Precisight, InfiniteVision, Optics, Strasbourg, France). The axis of the MCIOL was measured with a line bisecting the two dialing holes in the front lens. Intraoperative orientation was determined using a digital surgical guidance system while the postoperative orientation was determined using slit-lamp imaging. Two populations were analyzed: eyes that only underwent cataract surgery (PRIM) and eyes that also underwent enhancement (ENH), consisting of surgical front optic exchange. Both populations had 3 observation visits: first implantation (P-Op); 3 months (3mo) and 6 months (6mo) after primary surgery. The ENH group had an additional fourth visit that corresponded to the enhancement surgery (E-Op). The main outcome measure was mean absolute change in MCIOL orientation (degrees). The effects of axial length (AL) and anterior chamber depth (ACD) on IOL rotational stability were examined.

Results

Thirty-three eyes received MCIOL of which 29 had usable orientation images. Of these, 12 were in the PRIM group and 17 underwent ENH. Regarding the mean absolute rotation, among PRIM eyes, P-Op to 3mo was 3.03±2.45 degrees; P-Op to 6mo, 2.28±1.54 degrees; and 3–6mo, 2.37±1.56 degrees. Among the ENH eyes, P-Op to 3mo was 3.09±1.68; E-Op to 6mo, 2.71±3.30 and P-Op to 6mo, 3.62±3.42. There were no significant differences in the IOL rotation. There were no statistical differences in rotational stability between the ENH and PRIM groups. There was no correlation between IOL rotation and AL or ACD.

Conclusion

Precisight appears to be rotationally stable. The enhancement procedure does not affect rotational stability.

Efficacy of 4-Haptic Bitoric Intraocular Lens Implantation in Asian Patients with Cataract and Astigmatism

PURPOSE

To determine the efficacy of 4-haptic bitoric intraocular lens (IOL) implantation in Asian patients with cataract and astigmatism.

METHODS

A total of 19 eyes with ≤25.0 mm axial length and ≥0.75 diopters (D) corneal astigmatism were included in this prospective non-comparative study. All subjects underwent phacoemulsification with implantation of an AT Torbi 709M IOL. Visual and refractive outcomes as well as toric IOL axis were evaluated during a 3-month follow-up. Errors in predicted residual spherical equivalent were calculated by subtracting predicted residual spherical equivalent from postoperative refraction.

RESULTS

Uncorrected and corrected distance visual acuity improved significantly 3 months after surgery, from 0.43 to 0.05 and from 0.24 to -0.05, respectively. Mean refractive cylinders also decreased significantly, from -1.91 preoperatively to -0.54 D 3 months after surgery. Mean J0 and J45 decreased 3 months postoperatively, from 0.26 to 0.03 D and from 0.24 to -0.06 D, respectively. After 3 months, mean absolute IOL rotation was 1.81°. Errors in predicted residual spherical equivalent showed a hyperopic shift of 0.35 D.

CONCLUSIONS

Implantation of 4-haptic bitoric IOL proved to be effective for correcting astigmatism in Asian eyes during cataract surgery.

Consensus on the management of astigmatism in cataract surgery

This project was aimed at achieving consensus on the management of astigmatism during cataract surgery by ophthalmologists from Latin America using modified Delphi technique. Relevant peer-reviewed literature was identified, and 21 clinical research questions associated with the definition, classification, measurement, and treatment of astigmatism during cataract surgery were formulated. Twenty participants were divided into seven groups, and each group was assigned three questions to which they had to respond in written form, after thoroughly reviewing the literature. The assigned questions with corresponding responses by each group were discussed with other participants in round 4 – presentation of findings. The consensus was achieved if approval was obtained from at least 80% of participants. The present paper provides several agreements and recommendations for management of astigmatism during cataract surgery, which could potentially minimize the variability in practice patterns and help ophthalmologists adopt optimal practices for cataract patients with astigmatism and improve patient satisfaction.

Image-guided lens extraction surgery: a systematic review

A systematic review of the recent literature regarding the current image-guided systems used for cataract surgery or refractive lens exchange was performed based on the PubMed and Google Scholar databases in March 2018. Literature review returned 21 eligible studies. These studies compared image-guided systems with other keratometric devices regarding their accuracy, repeatability and reproducibility in measurement of keratometric values, astigmatism magnitude and axis, as well as in IOL power calculation. Additionally, the image-guided systems were compared with conventional manual ink-marking techniques for the alignment of toric IOLs. In conclusion, image-guided systems seem to be an accurate and reliable technology with measurements of high repeatability and reproducibility regarding the keratometry and IOL power calculation, but not yet interchangeable with the current established and validated keratometric devices. However, they are superior over the conventional manual ink-marking techniques for toric IOL alignment.

Comparative evaluation of two toric intraocular lenses for correcting astigmatism in patients undergoing phacoemulsification

Purpose:

To compare the efficacy of AT-TORBI plate haptic toric intraocular lens (IOL) (Carl Zeiss Meditec AG, Jena, Germany) and AcrySof loop haptic toric IOL (Alcon Laboratories, Inc., Fort Worth, TX, USA) for correcting preexisting astigmatism of ≥1 diopters (D) in patients undergoing phacoemulsification and to compare the rotational stability of these two toric IOLs.

Methods:

In this prospective randomized controlled trial. Forty-two eyes of 42 cataract patients with preexisting astigmatism of 1 D or more were randomized to receive plate haptic toric (AT TORBI) or loop haptic toric (AcrySof) IOLs, with 21 in each group. Postoperative evaluation was done at day 1, 1 week, 1 month, and 3 months. Uncorrected distance visual acuity (UDVA), best corrected visual acuity (VA), and IOL position were noted in both the groups.

Results:

At 3 months postoperatively, the mean log MAR UDVA was 0.23 ± 0.20 and 0.20 ± 0.13 in Groups I and II, respectively (P = 0.7), the mean residual cylindrical refractive error in plate haptic toric group was 0.40 ± 0.31 D and in loop haptic group was 0.45 ± 0.33 D (P = 0.64). The mean IOL rotation at 3 months follow-up in plate haptic group was found to be 3.52 ± 3.84° and in loop haptic group was 2.05 ± 2.56° (P = 0.25).

Conclusion:

Both types of toric IOLs were equally efficacious for attaining good uncorrected VA and correcting preexisting astigmatism between 1–5 D. Both of them were rotationally stable at 3 months follow-up.

Comparative evaluation of rotational stability and visual outcome of toric intraocular lenses with and without a capsular tension ring

Purpose:

To evaluate the rotational stability of toric intraocular lens (IOL) when co-implanted with a capsular tension ring (CTR) as compared to that of a toric IOL without a CTR.

Methods:

This was a prospective randomized clinical trial performed in a tertiary care centre in India. Fifty adult human eyes with visually significant cataract and regular corneal astigmatism ≥1.5D divided into two groups of 25 eyes each, A and B by simple randomization. Eyes with corneal pathology, lens subluxation, and a specular endothelial cell count <2000/mm² were excluded from the study. The eyes in both the groups underwent standard phacoemulsification and were implanted with a toric IOL. In Group A, a CTR was put in the bag before IOL implantation. The groups were called for follow-up on day 1, 1 week, 1 month, and 3 months, postoperatively. The axis of the toric IOL on each visit was measured by slit lamp imaging in retroillumination and analyzed digitally.

Results:

Mean rotation of toric IOL at 3 months postoperatively was 1.85 ± 1.72° in Group A and 4.02 ± 2.04° in Group B. The difference was statistically significant (P = 0.003).

Conclusion:

Coimplantation of a CTR is a safe and effective technique for ensuring better rotational stability of toric IOLs.

True rotational stability of a single-piece hydrophobic intraocular lens

BACKGROUND

To evaluate rotation and its influencing factors of an aspheric one-piece hydrophobic acrylic intraocular lens (IOL) Vivinex XY1 during 6 months after operation.

METHODS

In this institutional trial, 122 eyes of 66 patients were implanted with a non-toric aspheric IOL Vivinex XY1 (Hoya Corporation, Tokyo, Japan). IOL alignment was assessed at the end of surgery, 1 hour, 1 week, 1 month and 6 months after implantation. Confounding factors such as axial length, presence of anterior fibrosis and randomised implantation in four different intended axes (0°, 45°, 90°, 135°) were evaluated. Decentration and tilt were measured using a Purkinje metre.

RESULTS

Assessment of rotational stability was possible for 103 of 122 implanted IOLs 6 months after eye surgery. The median absolute rotation was 1.1° (range: 0°-5°). Rotation was significantly increased within the first hour after operation compared with later time-points (p<0.001). No correlation was found with axial length and rotation (Spearman's r=0.048, p=0.63). No significant difference was observed regarding different implantation axes (p=0.75). Rotation was not influenced by the presence of anterior fibrosis (p=0.98).

CONCLUSION

Assessing the true IOL position at the end of surgery is crucial for the evaluation of rotational stability of IOLs. No IOL rotation exceeding 5° could be detected 6 months after surgery.

Influence of material and haptic design on the mechanical stability of intraocular lenses by means of finite-element modeling

Intraocular lenses (IOLs) are used in the cataract treatment for surgical replacement of the opacified crystalline lens. Before being implanted they have to pass the strict quality control to guarantee a good biomechanical stability inside the capsular bag, avoiding the rotation, and to provide a good optical quality. The goal of this study was to investigate the influence of the material and haptic design on the behavior of the IOLs under dynamic compression condition. For this purpose, the strain-stress characteristics of the hydrophobic and hydrophilic materials were estimated experimentally. Next, these data were used as the input for a finite-element model (FEM) to analyze the stability of different IOL haptic designs, according to the procedure described by the ISO standards. Finally, the simulations of the effect of IOL tilt and decentration on the optical performance were performed in an eye model using a ray-tracing software. The results suggest the major importance of the haptic design rather than the material on the postoperative behavior of an IOL. FEM appears to be a powerful tool for numerical studies of the biomechanical properties of IOLs and it allows one to help in the design phase to the manufacturers.

Comparison of Two Toric IOLs with Different Haptic Design: Optical Quality after 1 Year

Background

The purpose of this prospective, randomised study was to interocularly compare the visual performance after implantation of two different toric IOLs with different haptic design.

Methods

59 subjects with corneal astigmatism greater than 1.25 diopter (D) were implanted with an AT TORBI 709M IOL (Carl Zeiss Meditec AG) in one eye and with a Tecnis toric aspheric IOL (Abbot Medical Optics) in the other eye. Observation procedure was performed 12 months postoperatively. Main outcome measures included uncorrected distance visual acuity (UDVA), manifest refraction, IOL rotation, and IOL position.

Results

Mean UCDVA was 0.04 ± 0.14 logMAR for AT TORBI eyes and 0.06 ± 0.15 logMAR for Tecnis eyes (p = 0.3). The postoperative spherical equivalent values were significantly lower in the AT TORBI group. Mean toric IOL axis rotation was 3.0 ± 2.26 degrees for AT TORBI eyes and 3.27 ± 2.37 for Tecnis eyes (p = 0.5). The mean vertical IOL tilt and vertical decentration values measured with the Visante OCT were significantly larger in the AT TORBI group (p < 0.05).

Conclusions

Both the Tecnis and the AT TORBI toric IOLs successfully reduced ocular astigmatism. Emmetropia could be better achieved with the AT TORBI IOL, whereas the Tecnis showed better positional stability. This trial is registered with ICMJE NCT03371576.

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.

Bilateral implantation of +3.0 D multifocal toric intraocular lenses: results of a US Food and Drug Administration clinical trial

Purpose

The purpose of this study was to evaluate the clinical outcomes of apodized diffractive +3.0 D multifocal toric intraocular lens (IOL) implantations in subjects with preoperative corneal astigmatism.

Patients and methods

This was a prospective cohort study conducted at 21 US sites. The study population consisted of 574 subjects, aged ≥21 years, with preoperative astigmatism 0.75–2.82 D, and potential postoperative visual acuity (VA) ≥0.2 logMAR, undergoing bilateral cataract removal by phacoemulsification. The intervention was bilateral implantation of aspheric apodized diffractive +3.0 D multifocal toric or spherical multifocal nontoric IOLs. The main outcome measures were monocular uncorrected near and distance VA and safety at 12 months.

Results

A total of 373/386 and 182/188 subjects implanted with multifocal toric and nontoric IOLs, respectively, completed 12-month follow-up after the second implantation. Toric IOLs were nonin-ferior in monocular uncorrected distance (4 m) and near (40 cm) VA but had >1 line better binocular uncorrected intermediate VA (50, 60, and 70 cm) than nontoric IOLs. Toric IOLs reduced cylinder to within 0.50 D and 1.0 D of target in 278 (74.5%) and 351 (94.1%) subjects, respectively. Mean ± standard deviation (SD) differences between intended and achieved axis orientation in the first and second implanted eyes were 5.0°±6.1° and 4.7°±4.0°, respectively. Mean ± SD 12-month IOL rotations in the first and second implanted eyes were 2.7°±5.8° and 2.2°±2.7°, respectively. No subject receiving toric IOLs required secondary surgical intervention due to optical lens properties.

Conclusion

Multifocal toric IOLs were noninferior to multifocal nontoric IOLs in uncorrected distance and near VAs in subjects with preexisting corneal astigmatism and effectively corrected astigmatism of 0.75–2.82 D.

Introduction of a Toric Intraocular Lens to a Non-Refractive Cataract Practice: Challenges and Outcomes

AIM

To identify challenges inherent in introducing a toric intraocular lens (IOL) to a non-refractive cataract practice, and evaluate residual astigmatism achieved and its impact on patient satisfaction.

METHODS

Following introduction of a toric IOL to a cataract practice with all procedures undertaken by a single, non-refractive, surgeon (SB), pre-operative, intra-operative and post-operative data was analysed. Attenuation of anticipated post-operative astigmatism was examined, and subjectively perceived visual functioning was assessed using validated questionnaires.

RESULTS

Median difference vector (DV, the induced astigmatic change [by magnitude and axis] that would enable the initial surgery to achieve intended target) was 0.93D; median anticipated DV with a non-toric IOL was 2.38D. One eye exhibited 0.75D residual astigmatism, compared to 3.8D anticipated residual astigmatism with a non-toric IOL. 100% of respondents reported satisfaction of ≥ 6/10, with 37.84% of respondents entirely satisfied (10/10). 17 patients (38.63%) reported no symptoms of dysphotopsia (dysphoptosia score 0/10), only 3 respondents (6.8%) reported a clinically meaningful level of dysphotopsia (≥ 4/10). Mean post-operative NEI VF-11 score was 0.54 (+/-0.83; scale 0 - 4).

CONCLUSION

Use of a toric IOL to manage astigmatism during cataract surgery results in less post-operative astigmatism than a non-toric IOL, resulting in avoidance of unacceptable post-operative astigmatism.

Astigmatism management in cataract surgery with Precizon(®) toric intraocular lens: a prospective study

Purpose

The purpose of this study was to evaluate the visual and refractive outcomes and rotational stability of the new aspheric Precizon^® toric intraocular lens (IOL) for the correction of corneal astigmatism in cataract surgery.

Setting

Department of Ophthalmology, Hospital Geral de Santo António – Centro Hospitalar do Porto, EPE and Hospital de Pedro Hispano, Matosinhos, Portugal.

Design

This was a prospective clinical study.

Patients and methods

A total of 40 eyes of 27 patients with corneal astigmatism greater than 1.0 diopter (D) underwent cataract surgery with implantation of Precizon^® toric IOL. IOL power calculation was performed using optical coherence biometry (IOLMaster^®). Outcomes of uncorrected (UDVA) and best-spectacle corrected distance visual acuities (BCDVA), refraction, and IOL rotation were analyzed at the 1st week, 1st, 3rd, and 6th month’s evaluations.

Results

The median postoperative UDVA was better than preoperative best-spectacle corrected distance visual acuity (0.02 [0.06] logMAR vs 0.19 [0.20] logMAR, P<0.001). At 6 months, postoperative UDVA was 0.1 logMAR or better in 95% of the eyes. At last follow-up, the mean spherical equivalent was reduced from −3.35±3.10 D to −0.02±0.30 D (P<0.001) with 97.5% of the eyes within ±0.50 D of emmetropia. The mean preoperative keratometric cylinder was 2.34±0.95 D and the mean postoperative refractive cylinder was 0.24±0.27 D (P<0.001). The mean IOL rotation was 2.43°±1.55°. None of the IOLs required realignment.

Conclusion

Precizon^® toric IOL revealed very good rotational stability and performance regarding predictability, efficacy, and safety in the correction of preexisting regular corneal astigmatism associated with cataract surgery.