Preloaded injectors used in a clinical study: videographic assessment and laboratory analysis of injector nozzle damage

Characterisation of Intraocular Lens Injectors

In modern ophthalmic surgery, an intraocular lens (IOL) is commonly implanted into the patient's eye with an IOL injector. Many injectors are available, showing various technological differences, from the early manually loaded injector systems to the modern preloaded injectors. This review aims to give a concise overview of the defining characteristics of injector models and draws attention to complications that may occur during IOL implantation. One can differentiate injectors according to their preoperative preparation (manually loaded or preloaded), their implantation mechanism (push-type or screw-type or combined or automated), the size of the nozzle tip, the presence of an insertion depth control feature, and the injector's reusability. Potential complications are IOL misconfigurations such as a haptic-optic adhesion, adherence of the IOL to the injector plunger, an overriding plunger, uncontrolled IOL rotation, a trapped trailing haptic, or damage to the IOL. Additionally, during IOL implantation, the nozzle can become damaged with scratches, extensions, cracks, or bursts to the tip. While these complications rarely produce long-term consequences, manufacturers should try to prevent them by further improving their devices. Similarly, surgeons should evaluate new injectors carefully to ensure the highest possible surgical safety.

In vivo comparison of implantation behavior and laboratory analysis of two preloaded intraocular lens injectors

PURPOSE

We evaluated implantation behavior and injector damage of two different IOL injector systems, the Multisert and the AutonoMe.

DESIGN

Prospective, randomized, comparative study with laboratory investigation.

METHODS

We examined used injectors from 48 bilateral cataract cases and assessed video recordings of each Implantation. All eyes were intraindividually randomized for treatment with one of the two IOL injectors. Implantation videos were reviewed for inadvertent events and the time for different implantation steps was determined. The injector nozzle tips were examined using light and scanning electron microscopy (SEM). Damage was graded using the Heidelberg Score for IOL injector damage (HeiScore). Three months postoperatively, IOLs were assessed for material changes.

RESULTS

Implantation was without critical events in 96 of 96 eyes. Mean implantation time was 41.90 ± 7.11 s with the Multisert and 52.22 ± 12.06 s with the AutonoMe. In the AutonoMe group, we observed 4 eyes (8.3%) with a failed docking attempt, 28 eyes (58.3%) with a haptic adherence, one case (2.1%) of straight leading haptic and 2 cases (4.2%) of intrawound IOL manipulation. There were no events observed in the Multisert group. The mean HeiScore values were 0.87 ± 0.61 and 3.68 ± 0.47 for the AutonoMe and Multisert. 3 months postoperatively, IOL material changes were absent.

CONCLUSIONS

Both injectors allowed safe and controlled implantation. Using Multisert, implantation behavior was more consistent. The injectors showed different damage profiles with a higher damage score for the Multisert.The study is registered at the German Clinical Trials Register (Deutsches Register Klinischer Studien; reference number: DRKS00007837).

Laboratory Analysis of Causative Factors for the Final Incision Size due to Intraocular Lens Injector Insertion

Purpose

In intraocular lens (IOL) implantation, insertion of the IOL injector enlarges the clear corneal incision. A larger incision size (IS) is associated with a higher risk for surgically induced astigmatism and endophthalmitis. The goal of this study was to determine which parameters most influence the final IS.

Design

Experimental study.

Subjects

A total of 126 cadaver porcine eyes were included in this study.

Methods

We analyzed 409 clear corneal incisions made with 126 injectors from 13 injector models. We noted the vertical diameter and the tip angulation for every model. The corneal thickness of each incision location was measured using Scheimpflug tomography. The IS was measured before and after injector insertion and described as preoperative and final ISs, respectively. During surgery, the insertion depth and incision length were documented. A mixed effects model was applied to analyze the influence of the parameters on the final IS.

Main Outcome Measures

Influence on the final IS.

Results

Increases in the vertical diameter of the injector tip, the preoperative IS and the insertion depth, and a reduction of incision length were all significantly associated with increased final IS (P < 0.05). The conditional Pseudo-R2-Measure was 0.92. The preoperative IS had the largest standardized estimated effect on the final IS, followed by the vertical diameter of the injector tip, insertion depth, and lastly, incision length. Neither corneal thickness nor the tip angle of the injector had a significant effect on the final IS (P > 0.05).

Conclusions

The IOL injector's vertical diameter should be as small as possible to ensure a minimal final IS. The injector's insertion depth may be minimized, and the incision length should be long enough to reduce the final IS. Further studies are needed to confirm the findings in human autopsy eyes and in clinical practice.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references in the Footnotes and Disclosures at the end of this article..

Video analysis of optic-haptic-interaction during hydrophobic acrylic intraocular lens implantation using preloaded injectors

OBJECTIVE

To compare the optic-haptic interaction of different hydrophobic acrylic IOLs after using six preloaded injectors.

METHODS

We reviewed the video-recordings of procedures on a total of 388 eyes that underwent phacoemulsification and intraocular lens (IOL) implantation. For six preloaded injectors: multiSert (Hoya Surgical Optics) [System 1], TECNIS Simplicity (Johnson & Johnson Vision) [System 2], TECNIS iTec (Johnson & Johnson Vision) [System 3], AutonoMe (Alcon, Laboratories) [System 4], Bluesert (Carl Zeiss Meditec) [System 5], and Prosert (OphthalmoPro GmbH) [System 6], we noted in each case the time of IOL delivery and made a descriptive observation of IOL insertion and optic-haptic-interaction.

RESULTS

We defined standard haptic behavior where the haptics emerged "folded" from the injector and quickly recovered their pre-implantation appearance. The incidence where the leading haptic emerged in a deformed way for System 1 was 20%, System 2: 19%, System 3: 14%, System 4: 56%, System 5: 24% and System 6: 5%. For trailing haptic deformed behavior, the incidence was 36%, 6%, 4%, 8%, 18% and 2%, respectively for Systems 1 to 6. Optic-haptic adhesion occurred in 2% of cases for System 1, 44% for System 2, 52% for System 3, 48% for System 4, and 11% for System 6 (P < 0.05). Adhesion was not found with System 5.

CONCLUSIONS

We observed different deformed behavior for leading and trailing haptics in the six preloaded systems, some systems had as much as 52% optic-haptic adhesion.

Clinical Evaluation of a Hydrophobic Intraocular Lens Using a Preloaded Automated Injector in a Korean Population

Purpose

This study assessed post-market clinical outcomes of the Clareon monofocal intraocular lens (IOL) preloaded in the AutonoMe Delivery System in a real-world setting of Korean patients.

Methods

This prospective, multicenter, single-arm study in Korea was conducted from July 2020 to December 2021. Patients were ≥20 years old with unilateral or bilateral cataracts who received Clareon IOLs (CNA0T0) preloaded in an automated injector system. Best corrected distance visual acuity (BCDVA) and uncorrected distance visual acuity (UCDVA) were evaluated under photopic conditions. Surgeon delivery system preference was assessed using a survey questionnaire. Glistenings, surface haze, adverse events, posterior capsule opacification (PCO), and Nd:YAG capsulotomy rates were also assessed during the 12-month postoperative follow-up.

Results

Mean ± SD monocular BCDVA was 0.02 ± 0.11 and 0.00 ± 0.10 logMAR at 1 month and 12 months, respectively. BCDVA of 0.2 logMAR or better was achieved by 94.4% and 99.1% of eyes at 1 month and 12 months after implantation, respectively. Mean monocular UCDVA was 0.11 ± 0.14 and 0.07 ± 0.13 logMAR at 1 month and 12 months, respectively. UCDVA of 0.3 logMAR or better was achieved by 97.4% of eyes at 12 months after implantation. Preparation of the automated injector system was rated as "very easy" or "easy" and CNA0T0 IOL delivery was rated as "very controllable" or "controllable" by all surgeons. Only grade 0 glistenings and no surface haze were observed during the 12-month follow-up. No clinically significant PCO or Nd:YAG capsulotomy were reported throughout the study; clinically nonsignificant PCO was reported in 23% of eyes.

Conclusion

This 12-month real-world study of the CNA0T0 IOL and the automated injector system demonstrated excellent visual outcomes and high surgeon satisfaction.

Nano-Indentation to Determine Mechanical Properties of Intraocular Lenses: Evaluating Penetration Depth, Material Stiffness, and Elastic Moduli

INTRODUCTION

Intraocular lenses (IOL) should remain in the eye for life after implantation into the capsular bag during cataract surgery. The material must meet various requirements. It is crucial that the material has the best biocompatibility, and it should be flexible and soft for best possible implantation process but also sufficiently stable and stiff for good centering in the eye and posterior capsule opacification prevention.

METHODS

In this laboratory experiment, we used nano-indentation for the mechanical assessment of three hydrophobic acrylic (A, B, C), three hydrophilic acrylic (D, E, F), and one silicone (G) intraocular lens. We wanted to determine whether some react more sensitively to touching/handling than others. The indentation elastic modulus and the creep were obtained from the force displacement curve. For measuring penetration depth and testing of possible damage to the intraocular lenses, the samples were measured at room temperature. A 200-µm-diameter ruby spherical tipped indenter was used for all the tests. Indentations were made to three different maximum loads, namely 5 mN (milli Newton), 15 mN, and 30 mN and repeated three times.

RESULTS

The lowest penetration depth (12 µm) was observed with IOL B. However, IOL A, D, and F showed similar low penetration depths (20, 18, and 23 µm, respectively). Lenses C and E showed slightly higher penetration depths of 36 and 39 µm, respectively. The silicone lens (G) showed the greatest penetration depth of 54.6 µm at a maximum load of 5 mN. With higher maximal loads (15 and 30 mN) the penetration depth increased significantly. Lens C, however, showed the same results at both 15 and 30 mN with no increase of penetration depth. This seems to fit well with the material and manufacturing process of the lens (lathe-cut). During the holding time of 30 s at constant force all six acrylic lenses showed a significant increase of the creep (CIT 21-43%). Lens G showed the smallest creep with 14%. The mean indentation modulus (EIT) values ranged from 1 to 37 MPa. IOL B had the largest EIT of 37 MPa, which could be caused by the low water content.

CONCLUSION

It was found that results correlate very well with the water content of the material in the first place. The manufacturing process (molded versus lathe-cut) seems to play another important role. Since all included acrylic lenses are very similar, it was not surprising that the measured differences are marginal. Even though hydrophobic materials with lower water content showed higher relative stiffness, penetration and defects can also occur with these. The surgeon and scrub nurse should always be aware that macroscopic changes are difficult to detect but that defects could theoretically lead to clinical effects. The principle of not touching the center of the IOL optic at any time should be taken seriously.

How can clinical safety and efficacy concerns in stem cell therapy for spinal cord injury be overcome?

INTRODUCTION

Spinal cord injury (SCI) can lead to severe neurological dysfunction. Despite scientific and medical advances, clinically effective regenerative therapies including stem cells are lacking for SCI.

AREAS COVERED

This paper discusses translational challenges related to the safe, effective use of stem cells for SCI, with a focus on mesenchymal stem cells (MSCs), neural stem cells (NSCs), Schwann cells (SCs), olfactory ensheathing cells (OECs), oligodendrocyte precursor cells (OPCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs). We discuss approaches to enhance the efficacy of cell-based strategies by i) addressing patient heterogeneity and enhancing patient selection; ii) selecting cell type, cell source, cell developmental stage, and delivery technique; iii) enhancing graft integration and mitigating immune-mediated graft rejection; and iv) ensuring availability of cells. Additionally, we review strategies to optimize outcomes including combinatorial use of rehabilitation and discuss ways to mitigate potential risks of tumor formation associated with stem cell-based strategies.

EXPERT OPINION

Basic science research will drive translational advances to develop stem cell-based therapies for SCI. Genetic, serological, and imaging biomarkers may enable individualization of cell-based treatments. Moreover, combinatorial strategies will be required to enhance graft survival, migration and functional integration, to enable precision-based intervention.

Enlargement of main corneal incision: clinical intraindividual comparison of two preloaded intraocular lens injectors

PURPOSE

To compare the enlargement of the clear corneal incision from IOL implantation with 2 different intraocular lens (IOL) injectors: the AutonoMe preloaded with the Clareon IOL and the Multisert preloaded with the Vivinex IOL.

SETTING

The David J. Apple Center for Vision Research, Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.

DESIGN

Prospective randomized clinical comparative study.

METHODS

96 eyes of 48 patients with cataract were intraindividually randomized to treatment with 1 of the 2 injectors. For Multisert eyes, the insert shield (IS) was used in the advanced position in 23 eyes. The initial incision was 2.2 mm, and intraoperative measurements of the incision size were made before and after IOL injection. 3 months postoperatively, keratometry and uncorrected (UDVA) and corrected (CDVA) distance visual acuities were assessed.

RESULTS

Results are reported for 96 eyes of 48 patients. The mean incision enlargement was 0.213 ± 0.068 mm in the Multisert with the IS group, 0.265 ± 0.055 mm in the fellow eyes (AutonoMe) ( P < .05), 0.272 ± 0.060 mm in Multisert eyes treated without the IS, and 0.296 ± 0.066 mm for the fellow eyes (AutonoMe) ( P > .05). The mean absolute surgically induced astigmatism was 0.42 ± 0.23 diopters (D), 0.50 ± 0.25 D, and 0.44 ± 0.18 D in the Multisert with the IS, Multisert without the IS, and AutonoMe group, respectively ( P > .05). The UDVA and CDVA were comparable in all groups.

CONCLUSIONS

The Multisert was associated with less wound enlargement than the AutonoMe. All groups had comparable functional outcomes. Therefore, the observed difference in incision enlargement may be of limited clinical relevance.

Refractive Outcomes after Cataract Surgery

A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients’ vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients’ vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small “error budget” (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients’ refractory status after cataract surgery.