Introduction

Phacoemulsification is the gold standard method to remove the natural lens during cataract surgery. An important facet for safety and good postoperative outcomes is the phacoemulsification tip, with differences in design or materials reportedly influencing surgical outcomes.¹ Traditional tips have used a metal cutting edge at the distal end of the phacoemulsification handpiece. In contrast, the Intrepid hybrid tip (Alcon Vision, LLC) utilizes a soft polymer on the metal tip, which is designed to reduce posterior capsular rupture (PCR) compared to a conventional tip.^2–4

Cataract surgery is typically performed with intraocular pressure (IOP) settings much higher than physiological IOP. Using these high IOP settings may increase the risk of postoperative complications such as corneal edema (including epithelial edema, stromal edema, and endothelial edema) and endothelial cell loss.^5,6 Studies have reported a correlation between increased postoperative central corneal thickness and endothelial cell loss.^7,8

Active Sentry technology (Alcon Vision, LLC) has an integrated pressure sensor in the handpiece, which can detect the onset of post-occlusion surge, and a Quickvalve within the cassette that can supply solution into the aspiration line when a surge event occurs.⁹ Combined with Active Fluidics, which adjusts flow to maintain target IOP, Active Sentry can provide a stable target IOP.⁹ This handpiece also facilitates operation at lower IOP settings, which may reduce the risk of postoperative complications.

The use of Centurion with Active Sentry handpiece and the Intrepid hybrid tip has been reported to potentially improve clinical safety.¹⁰ However, to date there is minimal data on the cutting efficiency when using IOP settings that are closer to physiological IOP. The purpose of this study was to assess the efficiency (as measured by phaco time, aspiration time, and fluid use) of a hybrid tip in removing cataract grades 3 and 4 in high and low IOP settings.

Methods

This prospective, observational, randomized, contralateral eye study enrolled was reviewed and approved by an independent institutional review board (Salus IRB, approval JS-22-001). An independent IRB was used as this study was conducted in private practice. All participants gave written informed consent, and the study was registered in a clinical trials registry (NCT05868772). The study followed good clinical practice, the tenets of the Declaration of Helsinki, and International Harmonization (ICH) guidelines.

Inclusion criteria were adults (age 50 years or older), who were candidates for uncomplicated bilateral cataract surgery with IOL implantation and had a grade 3 or 4 cataract (classified using LOCS III). Exclusion criteria were pseudoexfoliation syndrome, zonular dehiscence, history of eye trauma, rheumatoid arthritis, prior refractive surgery, or posterior capsular tear.

One experienced surgeon performed all surgeries (JS). The Centurion Vision System with Active Sentry Handpiece and hybrid tip (Alcon Vision, LLC) were used in all eyes. One eye was randomized (using simple randomization) to have phacoemulsification using high IOP settings (50 mmHg), and the other eye had phacoemulsification using low IOP settings (20 mmHg). Aspiration and vacuum settings were also different for each group. A summary of the settings used for each group is shown in Table 1.

Table 1 Settings for High and Low Intraocular Pressure Groups

The primary endpoint was to compare efficiency (as measured by phaco time, aspiration time, and fluid use) of the hybrid tip in removing cataract grades 3 and 4 using high and low IOP settings. The secondary endpoint was to compare changes in central corneal thickness (CCT). Exploratory endpoints included cumulative dissipated energy (which is a measure of ultrasonic exposure during surgery), total case time, total torsional time, total longitudinal time, and IOP.

We estimated that the study would require 54 eyes, assuming a pooled standard deviation of 10.3 mL, difference in means between the high and lower IOP groups of 7.8 mL, power of 80% and a level of significance of 5% (two sided). For additional power, a total of 100 eyes was targeted. The software environment R (version 4.3.1; The R Foundation for Statistical Computing, Vienna, Austria) was used for statistical analysis. An analysis of variance model, adjusted for any bias when using 2 eyes from the same patient, was used for comparisons between groups. A p ≤ 0.05 was considered significant.

Results

A total of 51 subjects (102 eyes) completed the study. Demographic and preoperative data are summarized in Table 2. Preoperative CCT and IOP were similar between groups. Three adverse events occurred relating to the surgery. Each was related to elevated IOP and resolved within a week.

Table 2 Preoperative Patient Demographics

The efficiency of removing cataracts grade 3 and 4 is summarized in Table 3. The efficiencies (as measured by phaco time, aspiration time, and fluid use) under high and low IOP settings were similar overall, and when specifically comparing grade 3 and grade 4 cataracts (p > 0.05). Other operative data are also summarized in Table 3. The results for high and low IOP settings were similar for cumulative dissipated energy, torsional time, and longitudinal time (p > 0.05). Total case time appears lower for the high IOP settings group compared to the low IOP settings group, but this difference was not significant (p > 0.05).

Table 3 Efficiency of Cataract Removal and Other Operative Data

Table 4 summarizes the postoperative data. At day 1 and day 7, IOP was similar for eyes in the high IOP settings group compared to the low IOP settings group. Change in central corneal thickness compared to preoperative appeared slightly elevated in the low IOP settings group at both postoperative days, but this was not significant (p > 0.05).

Table 4 Postoperative Data

Discussion

In this study, we compared the efficiency of a hybrid tip in removing cataract grades 3 and 4 using high and low IOP settings. To the best of our knowledge, this is the first study to compare efficiency of the hybrid tip in high and lower IOP settings. The efficiency (as measured by phaco time, aspiration time, and fluid use) was similar between the two groups, with no significant differences identified overall or in grade 3 or 4 cataracts. Sabur and Unsal¹⁰ reported similar efficiency results to ours for Active Sentry and the Intrepid hybrid tip in eyes (62% of which were grade 3 or 4 cataract) with high IOP settings. Minor differences between their results and ours may be explained by surgical technique, settings on the Centurion Vision System, and the differences in cataract grade. The results of our study suggest that there is no significant loss in efficiency of grade 3 or 4 cataract removal with lower IOP settings when using the hybrid tip.

Using lower IOP settings may decrease the risks of postoperative complications.^5,6 One indicator of corneal endothelial damage is an increase in CCT postoperatively. We observed no significant differences in postoperative CCT between high and low IOP settings overall or in grade 3 or grade 4 cataracts. This could be due in part to the differences in vacuum and aspiration flow rate used between the groups. Indeed, Liu et al⁹ reported lower postoperative day 1 CCT using low IOP settings with an Active Sentry handpiece compared to high IOP settings with a handpiece that does not have an integrated pressure sensor (Ozil), with the vacuum and aspiration flow rate kept constant between groups. Though it is not clear whether the difference is from the IOP settings, the handpieces, surgical technique or a combination of these. However, Cyril et al¹¹ observed no significant differences in corneal edema (percentage of none, mild, moderate) using an Active Sentry handpiece compared to an Ozil handpiece, both with high IOP settings.

The findings from this study have important implications for surgical practice and patient safety in cataract surgery. The demonstrated efficiency of the hybrid tip at both high and low IOP settings suggests that surgeons may safely employ lower IOP levels during phacoemulsification without sacrificing operational efficiency. The high IOP settings group used higher vacuum and aspiration flow rate, which could decrease the total case time and potential stress to ocular structures. Despite this, the low IOP settings group was similarly efficient and did not significantly increase CCT from baseline at days 1 or 7 postoperatively. This is particularly relevant in the context of minimizing postoperative complications associated with elevated IOP, such as corneal edema and endothelial cell loss, which can significantly affect long-term visual outcomes. In our study, there were 3 instances of IOP spikes immediately postoperatively (which all resolved within a week). Elevated IOP can be influenced by various factors, including but not limited to residual viscoelastic at the end of the procedure, over-infiltration of balanced salt solution, and steroid response. However, we do not believe that the choice of handpiece or the intraocular pressure (IOP) settings significantly contributed to postoperative spikes in IOP.

Future studies should aim to explore the long-term effects of using lower IOP settings, including the impact on endothelial health and visual acuity over extended follow-up periods. Additionally, investigating the performance of the hybrid tip across a broader spectrum of cataract grades and varying surgical conditions could further clarify its role in enhancing safety and efficacy in cataract surgery. Ultimately, optimizing IOP settings alongside advancements in phacoemulsification technology may contribute to improved patient outcomes in cataract surgery.

A limitation of this study of this study was the relatively short follow-up period. We are not able to draw conclusions about the long-term outcomes between the two IOP settings; however, the primary outcome for the study was to measure the efficiency of cataract removal. The follow-up period was sufficient to accomplish this goal. In addition, the vacuum and aspiration flow rate settings were different between the groups. The high IOP settings group used higher vacuum and aspiration flow rate, which would decrease the total case time and potential stress to ocular structures. Despite this, the low IOP settings group was similarly efficient.

In conclusion, the results of this study suggest that a Hybrid tip was efficient (as measured by phaco time, aspiration time, and fluid use) in removing grade 3 and grade 4 cataracts with high and low IOP settings.