Effect of Modified Peristaltic Phacoemulsification Device on Efficiency and Post-Occlusion Pressure Surge.

Purpose: To evaluate efficiency of grooving, nuclear fragment removal, and changes in pressure control in the Oertli Faros using traditional peristaltic and Speed and Precision (SPEEP) features. The SPEEP mode uses novel peristaltic technology permitting independent control of flow and vacuum. Methods: A porcine lens model was used with an enclosed chamber simulating the anterior segment. Grooving efficiency is evaluated with flow rates of 10, 30, and 50 mL/min using whole lenses. Lens cubes were emulsified at 20, 40, 60, 80, and 100% power with both SPEEP and non-SPEEP modes. Surge was evaluated with pressure gauges placed on the irrigation tubing and aspiration tubing. Pressure readings were recorded per the following: fluid and vacuum were initiated for 15 seconds, vacuum tubing was occluded for 5 seconds, tubing patency was then re-introduced for 15 seconds. Differences between sensors were recorded. Results: No significant increase in efficiency was seen with increasing flow rate from 30 to 50 mL/min using SPEEP. No significant differences were shown in lens fragment removal in SPEEP and non-SPEEP modes at any power tested. Pressure difference measurements were not significantly different with SPEEP and non-SPEEP modes. Conclusion: We showed that lower flow rates show comparable efficiency of grooving when using the SPEEP mode. The SPEEP function did not show increased efficiency in nuclear fragment removal when compared to traditional mode. Surge control was also comparable with both SPEEP and non-SPEEP modes. We suggest that the SPEEP function included in the Oertli Faros may have some advantages.

Efficiency of a polymer-coated phacoemulsification tip in cataract surgery.

PURPOSE: To determine whether there is a difference in efficiency during phacoemulsification when using the hybrid polymer tip compared with the metal balanced tip, as measured by cumulative dissipated energy (CDE) and total procedure time. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. DESIGN: Experimental study. METHODS: Phacoemulsification was performed with the Centurion Vision System and Infiniti OZil handpiece, with a 30-degree bevel metal balanced tip and hybrid polymer tip. The vacuum was set at 500 mm Hg and the aspiration flow rate at 50 mL/min. Power was changed for torsional and longitudinal ultrasound (US) at 20%, 40%, 60%, 80%, and 100%. Hardened porcine lenses were cut into 200 two mm cubes, 10 for each specified tip/power setting. They were placed into an artificial anterior chamber filled with a balanced salt solution, and phacoemulsification was performed. A second observer randomly assigned the US type and power. The same observer timed trials with a stopwatch, and CDE was recorded. RESULTS: There were no significant differences in time or CDE for any power levels or US modes when comparing the 2 tips. CONCLUSIONS: No significant difference in efficiency was observed when comparing the metal balanced tip with the hybrid polymer tip. Given the known improved safety profile and the overall equivalent efficiency of the hybrid tip, it could improve the performance of beginning and advanced surgeons in the future. Future study is needed to evaluate other setting combinations and to evaluate the hybrid tip in clinical settings.

Temperature Change of Ophthalmic Viscosurgical Devices in a Bi-Chamber Set-Up at a Flow of 0 and 20mL/min.

Purpose: To understand the role of ophthalmic viscosurgical devices (OVDs) in corneal incision contracture (CIC). Specifically, the aim was to evaluate with the tip of the phacoemulsification needle free of OVD, how various OVDs near the tip and sleeve may transmit thermal energy to the incision site. Methods: A small chamber was filled with balanced saline solution (BSS), and a thin membrane was placed on the surface. OVD was placed atop the membrane. A temperature probe was placed in the OVD, while the handpiece pierced the membrane. The experiment was run both with and without flow and vacuum. Temperature measurements were gathered for each of the OVDs at four separate time points at 0 and 20mL/min flow. Results: As expected, there was a more pronounced temperature increase in all test groups with no fluid flow. While the temperature increase was not significantly different from BSS for any of the OVDs tested at either 0 or 20mL/min, Viscoat showed the most variable results at both flow settings. Conclusion: As long as the phaco tip is not in OVD, residual OVD near the incision is not exothermic and so not an additional risk for CIC.

Comparison of Phacoemulsification Grooving Efficiency in Longitudinal vs Transversal Handpieces.

Purpose: To determine the difference, if any, in grooving efficiency at various settings on the Whitestar Signature Pro phacoemulsification (phaco) system. Methods: Cataractous lenses were simulated by exposing porcine lenses to formalin for 2 hours. A total of 120 lenses were analyzed at various power settings on both longitudinal and transversal handpieces. Twenty trials each were performed with power set to 25%, 50%, and 75% on both handpieces. A Whitestar Phaco Handpiece System was used to provide longitudinal power, and a Whitestar Signature Ellipsis Handpiece provided transversal power. Lenses were placed within a plastic chamber and grooved by an investigator blinded to settings. A second investigator recorded times and adjusted settings. The Whitestar Signature Pro phaco system was used for grooving. Results: There was no significant difference in grooving times between the longitudinal and transverse handpieces at any power setting (P > 0.05). There was a significant decrease in grooving times when comparing the 25% power setting with the 75% power setting for the transversal handpiece (P=0.021). Conclusion: Both longitudinal and transversal handpieces on the Whitestar Signature Pro phaco system produce similar results to one another at each power setting. There is a general trend toward shorter grooving times, reflecting greater efficiency, at higher power settings. Grooving efficiency on the transversal handpiece may be more affected by changes in the power settings as compared with the longitudinal settings.

Effect of low and passive flow on OVD thermal properties during phacoemulsification.

OBJECTIVE: To study the thermal properties and response magnitude of a forced-infusion phacoemulsification machine on 4 ophthalmic viscosurgical devices (OVDs). DESIGN: Experimental study. METHODS: A phacoemulsification tip, thermocouple, and gauge were placed into an artificial anterior chamber with balanced saline solution (BSS) or approximately 0.1 mL of OVD. Once the thermocouple measured a consistent temperature, the pedal was engaged for 60 seconds; then the tip was removed. The machine was cooled for 5 minutes and flushed with BSS to return to baseline. This was repeated 10 times for each OVD. The research consisted of 2 scenarios: vacuum-blocked flow rate and low aspiration flow rate. RESULTS: All OVDs showed greater temperature changes than BSS. In the vacuum-blocked scenario, these increases were statistically significant. The medium viscosity dispersive OVD (DiscoVisc) reached temperatures exceeding 60°C. In the low-flow scenario, HEALON5 and DisCoVisc were significantly different at 5 seconds and only HEALON5 at 10 seconds. No temperature increases over BSS were greater than 1.0°C. CONCLUSIONS: The dispersive, cohesive, and viscoadaptive OVDs demonstrated higher temperature changes than BSS but did not reach the threshold for corneal incision contracture. The study team verified the need for at least a minimal flow rate before ultrasound, which is especially evident in the first 10 seconds, because a flow rate of only 20 mL/minute mitigated OVD-related thermal effects. Understanding thermal responses enables corneal incision contracture risk reduction.

Corneal endothelium protection provided by ophthalmic viscosurgical devices during phacoemulsification: experimental study in rabbit eyes.

PURPOSE: To compare the protection of the corneal endothelium provided by a cohesive and a dispersive ophthalmic viscosurgical device (OVD) against damage from torsional ultrasound and simulated lenticular debris during phacoemulsification. SETTING: University setting, Salt Lake City, Utah. DESIGN: Experimental study. METHODS: 15 New Zealand rabbits were included. After incision, each eye received cohesive or dispersive OVD (ProVisc or Viscoat). 10 1.0 mm beads were injected to simulate lenticular debris. The Intrepid Balanced tip (Centurion Ozil handpiece) was inserted into the anterior chamber, and 60% torsional ultrasound with 50 mL/min flow, 70 mm Hg intraocular pressure, and 600 mm Hg vacuum was applied (20 seconds). Cumulative dissipated energy (CDE) was noted. After euthanasia and enucleation, corneas were removed, stained with trypan blue/alizarin red, and photographed (5 ×400 magnification photos and 1 overview photograph from each cornea). ImageJ was used to evaluate cell damage and loss. RESULTS: CDE was 4.70 ± 0.26 and 4.64 ± 0.10 in the cohesive and dispersive OVD groups, respectively ( P = .8647). The analysis of the ×400 photographs showed that the percentage of intact cells was statistically higher in the dispersive OVD group ( P = .0002), whereas the percentages of damaged and lost cells were statistically higher in the cohesive OVD group ( P = .0002 and .0059, respectively). Overview photographs revealed the presence of residual OVD on the endothelium, especially in the dispersive group. CONCLUSIONS: In this experimental study using a rabbit model, the corneal endothelium protection provided by the dispersive OVD was superior to that provided by the cohesive OVD.

Laser-Assisted In Situ Keratomileusis (LASIK) Enhancement for Residual Refractive Error after Primary LASIK.

Background: To evaluate the safety, efficacy, and predictability of laser-assisted in situ keratomileusis (LASIK) enhancement after primary LASIK and compare to Food and Drug Administration (FDA) criteria. Methods: Patients who underwent LASIK enhancement after primary LASIK between 2002 and 2019 were compared to those who underwent LASIK without retreatment. Patient demographics, preoperative characteristics, visual outcomes, and postoperative complications were compared between groups. Epithelial ingrowth (EI) development was stratified based on duration between primary and secondary procedures. Results: We compared 901 eyes with LASIK enhancement to 1127 eyes without retreatment. Age, sex, surgical eye, sphere, cylinder, and spherical equivalent (SE) were significantly different between groups (p < 0.05). At 12 months post-enhancement, 86% of the eyes had an uncorrected distance visual acuity of 20/20 or better and 93% of eyes were within ±0.50 D of the target. Development of EI (6.1%) demonstrated an odds ratio of 16.3 in the long-term compared to the short-term (95% CI: 5.9 to 45.18; p < 0.0001). Conclusions: Older age at primary LASIK, female sex, right eye, and larger sphere, cylinder and SE were risk factors for enhancement. Risk of EI significantly increased when duration between primary and enhancement procedures exceeded five years. LASIK enhancements produce favorable outcomes and meet FDA benchmarks for safety, efficacy, and predictability.

Effect of simulated lenticular debris on corneal endothelial cells: experimental study in rabbit eyes.

PURPOSE: To evaluate mechanical damage of simulated lenticular debris on corneal endothelial cells during phacoemulsification. SETTING: University setting, Salt Lake City, Utah. DESIGN: Experimental study. METHODS: 12 New Zealand rabbits underwent bilateral surgery. After incision, 10 1.0 mm beads were injected into the anterior chamber of test eyes to simulate lenticular debris. A balanced salt solution was injected into the contralateral eyes with the same injector. The Intrepid Balanced Tip of the Centurion Ozil handpiece was inserted into the anterior chamber, and 60% torsional ultrasound was applied for 20 seconds with 50 mL/min flow, 70 mm Hg intraocular pressure, and 600 mm Hg vacuum. Cumulative dissipated energy (CDE) was noted. After euthanasia and enucleation, the corneas were removed, stained with trypan blue/alizarin red, and photographed in a standardized manner (×400 photographs from 5 specific areas and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs. RESULTS: CDE was 4.64 ± 0.19 for test eyes with beads and 4.66 ± 0.17 for control eyes without beads ( P = .58). The percentage of intact cells was statistically higher in the control group ( P = .0005), whereas the percentages of damaged and lost cells were statistically higher in the test group ( P = .0010 and .0005, respectively). This was observed in the analysis of the ×400 photographs and overview photographs. CONCLUSIONS: This study suggests that lenticular debris swirling around the anterior chamber may cause significant damage to the corneal endothelium, providing further insight on mechanisms of damage during phacoemulsification.

Measurement of Phacoemulsification Vacuum Pressure in the Oertli CataRhex3.

Purpose: To determine the actual vacuum pressure generated by the Oertli CataRhex 3® (Oertli), using an external measuring system. Methods: The effective vacuum pressure created by the Oertli was measured with a pressure device that was continuous with the vacuum tubing system while closed to the external environment. Measurements were taken with the machine set to 300 and 500 mmHg at flow rates of 20, 35, and 50 mL/min and at bottle heights of 60, 80, and 100 cm. Pressures were recorded after the foot pedal was depressed to vacuum setting (second position), and the pressure was allowed to stabilize. Subsequently, it was compared to the pressure value displayed by the machine. Results: Externally measured vacuum pressure was on average 13.02% greater (39.05 mmHg) than displayed vacuum pressure at 300 mmHg (P < 0.005) and 8.60% greater (42.98 mmHg) than displayed vacuum at 500 mmHg (P < 0.005). The average difference between displayed and measured pressure increased with increasing bottle heights. Conclusion: On average, the vacuum pressure generated in the Oertli was found to be significantly higher than the machine's reading when the machine was set at 300 mmHg and 500 mmHg. Adjusting vacuum had variable effects on the measured versus displayed pressure readings.

Effect of longitudinal and torsional ultrasound on corneal endothelial cells: experimental study in rabbit eyes.

PURPOSE: To compare corneal endothelial damage from longitudinal and torsional ultrasound during phacoemulsification. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: 9 New Zealand white rabbits underwent bilateral surgery. After incision, the Intrepid Balanced Tip of the Centurion Ozil handpiece was inserted into the anterior chamber, and the following settings were used: 50 mL/min flow, 70 mm Hg intraocular pressure, 600 mm Hg vacuum, and 60% longitudinal (1 eye) or torsional (contralateral eye) ultrasound for 30 seconds. Cumulative dissipated energy (CDE) was noted. After euthanasia and enucleation, the corneas were removed, stained with trypan blue/alizarin red, and photographed (400× photographs from 5 specific areas and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs obtained from each cornea. RESULTS: Cavitation bubbles around the phacoemulsification tip were generally observed in the longitudinal group. CDE was 17.4 ± 0.58 and 6.93 ± 0.15 in the longitudinal and torsional groups, respectively (P = .003). The percentage of intact cells was statistically higher in the torsional group (94.22% ± 5.99% vs 56.85% ± 22.29%), and the percentage of lost cells was statistically higher in the longitudinal group (42.10% ± 22.02% vs 4.97% ± 6.23%) (P = .003). This was observed in the analysis of the 400× photographs and the overview photographs. CONCLUSIONS: This study suggests that torsional ultrasound was associated with significantly less corneal endothelial cell damage than classical longitudinal tip motion, providing further insight on mechanisms of corneal endothelial damage during phacoemulsification.

Effect of phacoemulsification fluid flow on the corneal endothelium: experimental study in rabbit eyes.

PURPOSE: To quantify the damage to the corneal endothelium from the flow of a balanced salt solution during phacoemulsification. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. DESIGN: Experimental study. METHODS: 12 New Zealand white rabbits received bilateral surgery. 6 eyes served as controls with no irrigation (incision only). In 18 eyes, the Intrepid Balanced tip of the Centurion Ozil (Alcon Laboratories, Inc.) handpiece was inserted into the anterior chamber for continuous irrigation at 50 mL/min with either 250 or 500 mL of balanced salt solution. After killing humanely and enucleation, the corneas were removed, stained with trypan blue-alizarin red, and photographed in a standardized manner (×400 photographs from 5 specific areas and 1 overview photograph from each corneal button). The ImageJ program was used to evaluate cell damage and loss in the photographs obtained from each cornea. RESULTS: Analysis of the ×400 photographs showed no statistically significant differences between control, 250 mL, and 500 mL groups in the percentage of intact, damaged, or lost cells (P = .896, .851, and .972 respectively). For the overview photographs, the differences in areas of intact and damaged cells among the groups were statistically significant, likely because of the peripheral areas of damage related to touches between the phacoemulsification tip and the endothelium during irrigation. CONCLUSIONS: The volume of balanced salt solution flow alone did not seem to be a major contributing source of endothelial cell damage and loss, providing further insight into mechanisms of corneal endothelium damage during phacoemulsification.