Thermal effect on corneal incisions with different phacoemulsification ultrasonic tips

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.

Effect of surgical microscope and illuminated chopper on anterior chamber temperature

BACKGROUND

To evaluate the effect of the light intensity of the surgical microscope and illuminated chopper on the anterior chamber temperature.

STUDY DESIGN

Experimental study.

METHODS

A model eye (Kitaro WetLab System; FCI Ophthalmics, Pembroke, MA, USA) was used in this experimental study. The illuminance of a surgical microscope (Leica M300; Leica Microsystems, Wetzlar, Germany) and illuminated chopper (iChopper NAM-25 GB; Oculight, Korea) with a light source (iVision; Oculight) was measured using an illuminometer. In addition, the temperature in the anterior chamber of the model eye filled with balanced salt solution when using the surgical microscope with a light intensity from level 1 to level 6 and the illuminated chopper at 99% light intensity was measured for 10 min.

RESULTS

The anterior chamber temperature was increased by 0.2, 0.5, 1.0, and 1.4 ℃ when using the surgical microscope at level 3 (10050 lux), 4 (16490 lux), 5 (24900 lux), and 6 (32500 lux), respectively, for 10 min. The illuminated chopper at 99% light intensity (14893 lux) positioned in the anterior chamber increased the anterior chamber temperature by 0.2° C after 10 min, which was equal to the increase in the temperature caused by the surgical microscope at level 3.

CONCLUSION

The photothermal effect of the illuminated chopper directly positioned in the anterior chamber appeared to be similar to that of a microscope with similar illuminance. Therefore, the illuminated chopper is safe in terms of anterior chamber temperature changes in cataract surgery.

Autologous tenon plug and patch in phacoburn

This 75-year-old woman had phacomorphic angle closure, dense nuclear sclerosis, deep set eye, miotic pupil and tight corneal wound during phacoemulsification. Phacoemulsification wound burn was noted at the end of surgery. Tenon was harvested from the inferior conjunctiva, placed over the gape and anchored by two radial corneoscleral 10-0 nylon. Ten days later, anterior optical coherence tomography showed good wound apposition and sutures were removed with visual recovery to 20/25 (6/7.5) without astigmatism.

Effect of hypothermic perfusion on phacoemulsification in eyes with hard nuclear cataract: randomized trial

PURPOSE

To evaluate the effectiveness and safety of hypothermic perfusion in the phacoemulsification of hard nuclear cataract.

SETTING

Tertiary opthalmology center, China.

DESIGN

Laboratory study and prospective randomized clinical trial.

METHODS

Rabbits and patients with hard nuclear cataract underwent phacoemulsification with perfusion temperatures at 4°C or 24°C. Anterior segment optical coherence tomography (AS-OCT), corneal endothelial cell count (ECC), and cornea sections were observed before the rabbits' operation and 1 day and 7 days postoperatively. AS-OCT, corneal ECC, and anterior chamber (AC) inflammation were observed before the patients' operation and 1 day, 7 days, and 30 days postoperatively.

RESULTS

The study comprised 40 rabbits and 80 patients. In the animal models, the mean central corneal thickness (CCT) in the 4°C group (370.4 μm ± 45.5 [SD]) was thinner than in the 24°C group (496.7 ± 121.5 μm) 1 day postoperatively (P < .001). The mean AC inflammation reaction grade in the 4°C group (1.1 ± 0.9) was lower than in the 24°C group (2.2 ± 0.8) (P = .0333). In clinical trials, the mean CCT and incisional corneal thicknesses in the 4°C group (600.7 ± 51.8 μm and 859.2 ± 177.8 μm, respectively) were thinner than in the 24°C group (655.3 ± 85.0 μm and 955.9 ± 196.7 μm, respectively) (P < .001). The endothelial cell density (P = .036) and hexagonality (P = .001) were higher in the 4°C group. The mean AC inflammation reaction grade in the 4°C group (0.6 ± 0.6) was lower than in the 24°C group (1.3 ± 1.0) 1 day postoperatively (P = .004).

CONCLUSIONS

Hypothermic perfusion in phacoemulsification of hard nuclear cataract is safe and it can effectively protect corneal endothelium, decrease corneal edema, and reduce AC inflammation in the early postoperative stage.

Investigation of scleral thermal injuries caused by ultrasonic pars plana phacoemulsification and aspiration using pig eyes

PURPOSE

The purpose of this study was to investigate the thermal injuries caused by ultrasonic pars plana phacoemulsification and aspiration (PPPEA) using pig eyes.

METHOD

Using a 20-gauge (G) vitrectomy system (Accurus^®, Fragmatome; Alcon Laboratories) in both the 'open-tip' and 'closed-tip' techniques, PPPEA was performed in pig eyes and the subsequent thermal injuries generated around the scleral wound were measured by infrared thermal imaging (thermography). Post surgery, the state of the scleral wound was observed under a microscope, and a tissue slice containing the scleral wound was then prepared and observed under an optical microscope.

RESULTS

Thermography measurements revealed a slight temperature rise around the scleral wound in the open-tip case, yet a marked temperature rise in the closed-tip case. The scleral wound incision produced by the open tip was linear, while that produced by the closed tip was expanded. Histological examination revealed mild degeneration of the sclera around the wound in the open-tip case, yet marked tissue degeneration by thermal injuries in the closed-tip case.

CONCLUSION

Our findings showed that in PPPEA, the temperature of the tip of a 20G vitrectomy system rapidly increases due to the closed-tip technique, thus producing obvious thermal damage to the scleral wound. In order to prevent thermal injuries to the scleral wound during PPPEA, it is important to shorten the time of ultrasonic oscillation during surgery as much as possible while the tip is occluded with nuclear fragments.

[Use of infrared thermography in ophthalmology]

Thermoregulation disorders are associated with Body temperature fluctuation. Both hyper- and hypothermia are evidence of an ongoing pathological process. Contralateral symmetry in the Body heat spread is considered normal, while asymmetry, if above a certain level, implies an underlying pathology. Infrared thermography (IRT) is employed in many medical fields including ophthalmology. The earliest attempts of eye surface temperature evaluation were made in the 19^th century. Over the last 50 years, different authors have been using this method to assess ocular adnexa, however, the technique remains insufficiently studied. The reported IRT data is often contradictory, which may be due to heterogeneity (in terms of severity) of patient groups and disparities between research parameters.

Laboratory assessment of thermal characteristics of three phacoemulsification tip designs operated using torsional ultrasound

Purpose

Ultrasound activation of phacoemulsification (phaco) tips can create considerable thermal energy that may increase the risk of tissue damage during cataract surgery. The purpose of this study was to define the thermal profiles of three phaco tip designs in simulated surgical conditions.

Methods

In this laboratory investigation, sleeved phaco tips (mini-flared Kelman^® tip with aspiration bypass port and Intrepid^® Balanced Tip with aspiration bypass port, and MST A1 bent-mini phaco tip (without aspiration bypass) were tested using an ultrasonic phaco device operated in torsional mode at power levels of 50%, 75%, and 100% amplitude. An automated fixture applied a 30 g load to simulate compression against the incision site, leading to friction between the silicone sleeve and the titanium tip. Temperature was recorded by high rate infrared imaging under conditions of free flow and occlusion, which was simulated by clamping the aspiration line. Data were summarized using descriptive statistics.

Results

Baseline temperatures of ~26°C were observed for all tips. During ultrasonic operation at 50%, 75%, and 100% amplitude, temperatures were lower for the mini-flared and balanced tips versus the bent-mini tip, both when load was applied and during occlusion. The bent-mini tip reached temperatures as high as 70°C during occlusion with load when operated at 100% amplitude, whereas the mini-flared tip remained <50°C, and the balanced tip remained <36°C in all test conditions. For the mini-flared and balanced tips, temperature increases during operation were not markedly different from free flow and no-load conditions when occlusion or frictional events were simulated.

Conclusion

In all experiments for each tip design, increasing ultrasound power was associated with greater increases in tip temperature. Tip temperatures increased with applied load, but marked temperature increases during occlusion were observed only with the bent-mini tip. The balanced tip produced minimal thermal peaks in all tests.

Thermal evaluation of two phacoemulsification systems

OBJECTIVE

To compare thermal profiles of new transversal ultrasound power modulation to torsional ultrasound in an artificial chamber and cadaver eye.

DESIGN

Laboratory investigation.

METHODS

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Temperature increase after 30 seconds was measured at the needle midshaft in an artificial chamber and at maximal friction point in a cadaver eye. Ellips FX (transverse) was tested at 100% power, as was Signature with micropulse settings (6 milliseconds on and off). OZil (torsional only) was tested at 100% power in the artificial chamber and cadaver eye. Runs were completed with aspiration blocked. Temperature was continuously measured on the phacoemulsification sleeve using a microthermistor probe connected to the BAT-10 multipurpose thermometer, with an accuracy of ±0.1°C.

RESULTS

Transversal FX had a greater temperature increase than micropulse (p < 0.001) and torsional (p < 0.001). Micropulse had a greater temperature increase than torsional (p < 0.001). The cadaver eye had a greater temperature increase than the artificial chamber for torsional (p < 0.001).

CONCLUSIONS

Higher heat accumulation and potential for incisional burn occurred with the cadaver model than with the artificial chamber, suggesting the need for caution when using 100% torsional ultrasound with aspiration blocked. Transversal FX generated more heat than was reported originally. Further study is needed to determine the incidence of incisional burn with varied power settings for this new model. Micropulse generated more heat than previous reports, but the increased efficiency is likely to negate potentially increased incisional burn risk.

The Ultrachopper tip: a wound temperature study

PURPOSE

To determine the thermal characteristics of the Ultrachopper and its thermal properties in varied viscosurgical substances.

DESIGN

Experimental study.

PARTICIPANTS

Not applicable.

METHODS

The Ultrachopper (Alcon, Inc) tip with the Infiniti (Alcon, Inc) handpiece was attached to a thermistor and placed in a test chamber filled with either an ophthalmic viscosurgical device (OVD) or balanced salt solution (BSS). The thermistor allowed for continuous monitoring of temperature from baseline and the change that occurred over 60 seconds of continuous run time.

RESULTS

Mean maximum temperature in each OVD exceeded 50°C over the first 25 seconds of continuous run time. The mean maximum temperature was statistically significantly higher with all OVDs (p < 0.0001) when compared with BSS. A small but statistically significant difference in mean maximum temperature was shown between Healon 5 (AMO, Inc) and Viscoat (Alcon, Inc) (p < 0.05). The linear increase in temperature was statistically significantly different with all OVDs compared with BSS (p < 0.0001).

CONCLUSIONS

The thermal properties of the Ultrachopper tip demonstrate a heat-generating capacity that achieves published thresholds for risk for wound burn.

Temperature profiles of sleeveless and coaxial phacoemulsification

PURPOSE

To study the temperature profile at the corneal wound during 2 sleeveless techniques versus 2 coaxial phacoemulsification techniques.

SETTING

Department of Ophthalmology, Meir Medical Center, Kfar Saba and Ein-Tal Eye Center, Tel-Aviv, Israel.

DESIGN

Experimental study.

METHODS

Thirty-six porcine eyes were randomized into 4 groups: Group 1: conventional coaxial system (3.0 mm incision); Group 2: coaxial microincision cataract surgery (MICS) system (2.2 mm incision); Group 3: bimanual MICS (1.1 mm incision); Group 4: sleeveless tri-MICS (1.1 mm incision) using a 19-gauge anterior chamber maintainer as the sole fluid source. Temperature measurements were taken using a thermocouple and an infrared thermal imaging system. Measurements were taken in 2 settings; that is, with and without occlusion.

RESULTS

With no occlusion, corneal burns did not occur in any group. However, corneal temperatures were lower with the sleeveless systems (Groups 3 and 4) than with the coaxial systems (Groups 1 and 2) (P=.0003). When occlusion was induced, temperatures were kept constantly low in the sleeveless groups, whereas in the coaxial groups, temperatures increased rapidly, causing corneal burns within seconds. The mean temperature elevations at the incision sites were 39 °C, 48.5 °C, 13.6 °C, and 11.3 °C in Groups 1, 2, 3, and 4, respectively (P<.0001).

CONCLUSIONS

Sleeveless phacoemulsification maintained lower tissue temperatures than sleeved coaxial methods. During occlusion, fluid flow around the naked tip of the sleeveless systems prevented heat accumulation and corneal burns.

Heat profiling of phacoemulsification tip using a thermal scanning camera

An experimental study to measure the heat profile of the phacoemulsification (phaco) tip using standard continuous phaco and hyperpulse phaco with and without waveform power modulation in the Millennium Microsurgical System with Custom Control Software (CCS). The phaco tip was imaged in air using a thermal camera. The highest temperature was measured 15 s after application of phaco power. Continuous, hyperpulse and waveform power modulations of the Millennium Microsurgical System were used with different power settings (20, 50 and 100 %) and duty cycles (40, 60 and 90 %), with the irrigation turned on and off. Using continuous phaco with the irrigation on, the phaco tip temperature remains <28.0 °C. With irrigation off, the temperature is higher compared to irrigation on but still remains <45.0 °C. Comparing the temperatures for all three power modulations when irrigation is on, at each phaco power and duty cycle setting, the temperature of the phaco tip is highest with continuous phaco, followed by hyperpulse with rise time 1, then hyperpulse with rise time 2. When irrigation is off, the highest temperatures are recorded using the hyperpulse with rise time 2, followed by continuous phaco, then hyperpulse with rise time 1. Hyperpulse and waveform modulations reduce heat generation compared to the continuous mode when irrigation is turned on. Lower duty cycles and lower ultrasound power produce less heat at the phaco tip.

Thermal study of longitudinal and torsional ultrasound phacoemulsification: tracking the temperature of the corneal surface, incision, and handpiece

PURPOSE

To evaluate the change and difference in the corneal surface, incision, and handpiece temperatures during longitudinal and torsional ultrasound (US) phacoemulsification with standard incisions (2.75 mm) and microincisions (2.20 mm) and the thermal effect on wounds.

SETTING

Department of Ophthalmology, Duke University, Durham, North Carolina, USA.

METHODS

In this prospective study, human cadaver eyes had simulated phacoemulsification. Group 1 had a 2.75 mm incision with 100% longitudinal US; Group 2, a 2.20 mm incision with 100% longitudinal US; Group 3, a 2.75 mm incision with 100% torsional US; and Group 4, a 2.20 mm incision with 100% torsional US. During phacoemulsification, the corneal incision was evaluated by surgical microscopy and scanning electron microscopy (SEM) and images of the corneal surface, incision, and handpiece were captured with an infrared camera.

RESULTS

Twelve eyes (3 each group) were evaluated. The maximum incision temperature was higher in the longitudinal groups than in the torsional groups. With the same US modality, the maximum microincision temperature was higher than the maximum standard incision temperature. After application of full power for 40 seconds, wound burn was observed in all eyes in the longitudinal groups and no eyes in the torsional groups. On SEM, there was more extensive loss of Descemet membrane in the longitudinal groups than in the torsional groups.

CONCLUSION

Incision temperature was influenced by US modality and was significantly lower with torsional US than with longitudinal US. Using torsional US with smaller incisions may decrease the risk for wound burn in eyes with denser cataracts.

Thermal comparison of Infiniti OZil and Signature Ellips phacoemulsification systems

PURPOSE

To determine thermal characteristics of Signature Ellips (Abbott Medical Optics) and Infiniti OZil (Alcon, Inc.) transverse ultrasound and compare both with longitudinal ultrasound in clinically relevant scenarios.

DESIGN

Laboratory investigation.

METHODS

Temperature increase over baseline after 60 seconds was measured in water at positions in 90-degree increments around the sleeve near the proximal needle shaft in an artificial chamber for Ellips and OZil on continuous ultrasound with aspiration blocked and unblocked. This was also done with Signature using longitudinal ultrasound, with and without micropulse (6 ms on, 12 ms off), with aspiration blocked and unblocked, and at the OZil sleeve tip on continuous transverse mode with aspiration unblocked.

RESULTS

OZil (8.1 +/- 0.3 C) had greater temperature increase than Ellips (5.2 +/- 0.3 C; P < .0001) with aspiration unblocked and blocked (29.3 +/- 1.0 C vs 12.2 +/- 0.7 C; P < .0001). OZil had uneven distribution of heat around the shaft (30.1 +/- 0.5 C vs 28.5 +/- 0.6 C; P < .0001), whereas Ellips did not (P = .57). OZil was cooler at the tip (6.6 +/- 0.2 C; P < .0001). Friction in a cadaver eye incision only increased these numbers by 10% (OZil, irrigation blocked).

CONCLUSIONS

Metal stress probably creates heat at the proximal needle junction for both transverse methods. Heat generation differences between OZil and Ellips result from the manner in which they create needle motion. Incision burns may occur, especially for OZil, under nonpulsed settings during fragment removal with occlusion when reaching across the anterior chamber such that the proximal needle shaft came near the wound.

Heat production: Longitudinal versus torsional phacoemulsification

PURPOSE

To compare the heat production of longitudinal versus torsional phacoemulsification under strict laboratory test conditions.

SETTING

Department of Ophthalmology, David Geffen School of Medicine at UCLA, and Jules Stein Eye Institute, Los Angeles, California, USA.

METHODS

Two Infiniti phacoemulsification handpieces were inserted into silicone test chambers filled with a balanced salt solution and imaged serially using a thermal camera. Incision compression was simulated by suspending 25.3 g weights from the silicone chambers. To simulate occlusion of the phacoemulsification tip, the aspiration line was clamped. Peak temperatures were measured 0, 10, 30, 60, and 120 seconds after the commencement of continuous ultrasound power. The 2 handpieces, operating exclusively in longitudinal or torsional modes, were compared 3 ways: (1) using the same power displayed on the instrument console, (2) using identical stroke lengths, and (3) using the same applied energy, a product of stroke length and frequency.

RESULTS

For all 3 comparisons, torsional phacoemulsification resulted in lower temperatures at each time point. At the same displayed power setting, the scenario most familiar to cataract surgeons, longitudinal phacoemulsification elevated temperatures up to 41.5 degrees C more than torsional phacoemulsification.

CONCLUSIONS

Torsional phacoemulsification generated less heat than longitudinal phacoemulsification in all 3 comparison tests. Lower operating temperatures indicate lower heat generation within the same volume of fluid, and this may provide additional thermal protection during cataract surgery.

Comparison of peristaltic and Venturi pumps in bimanual microincisional cataract surgery

Comparison of peristaltic and Venturi pumps in bimanual microincision phacoemulsification on the success of the cataract surgery by using sleeveless phaco tip. Bimanual microincision phacoemulsification was done in 49 eyes using a 1.4-mm temporal clear corneal incision. A peristaltic pump was used in 23 eyes, and a Venturi pump was used in 26 eyes for phacoemulsification. Intraoperative complications, anterior chamber stability, and mean duration of surgery were recorded. Duration of surgery was shorter in the Venturi pump group. Anterior chamber stability could not be established in 17 eyes in the peristaltic pump group; it was established in all eyes in the Venturi pump group. Corneal burns were observed in two eyes in the peristaltic pump group and no eyes in the Venturi pump group. Use of a Venturi pump system and a vented gas-forced infusion system can significantly shorten surgery time and reduce risk of thermal burns.

AquaLase versus NeoSoniX--a comparison study

AIMS

To compare the metrics and surgical outcome when using Infiniti AquaLase and NeoSoniX cataract removal modalities.

METHODS

This prospective clinical study involved 50 patients with bilateral cataracts and lens removal using AquaLase in the right eye and NeoSoniX in the left eye. Best corrected visual acuity (BCVA), endothelial cell density and pachymetry were evaluted pre- and postoperatively. Statistical analysis was performed using the Wilcoxon Signed- Rank Test.

RESULTS

Preoperative mean pachymetry was 569 +/- 31 mu in the right eye (RE) and 560 +/- 37 mu in the left eye (LE), mean endothelial cell density 2744 +/- 418 cells/mm(2) (RE) and 2730 +/- 472 cells/mm(2) (LE). One week after operation pachymetry was 576 +/- 52 mu (RE) and 583 +/- 72 mu (LE) and endothelial cell density 2388 +/- 586 cells/mm(2) (RE) and 2463 +/- 615 cells/mm(2) (LE). One month after surgery pachymetry was 556 +/- 43 mu (RE) and 559 +/- 44 mu (LE) and endothelial cell density 2368 +/- 52 cells/mm(2) (RE) and 2495 +/- 548 cells/mm(2) (LE). BCVA improved in all eyes and was 0.8 or better on the first postoperative day.

CONCLUSIONS

Both the NeosoniX and AquaLase minimize intraoperative damage to ocular structures.

Comparison of the effect of AquaLase and NeoSoniX phacoemulsification on the corneal endothelium

PURPOSE

To compare the extent of corneal endothelial cell loss and pachymetry changes in 2 age-based groups of patients who had cataract removal by AquaLase (Alcon) phacoemulsification in 1 eye and NeoSoniX (Alcon) phacoemulsification in the contralateral eye.

SETTING

Department of Ophthalmology, University Hospital, Hradec Králové, Czech Republic.

METHODS

This prospective clinical study comprised 28 patients younger than 80 years (Group A) and 28 patients 80 years or older (Group B) with bilateral cataract having lens removal using AquaLase in the right eye and NeoSoniX in the left eye. The nuclei were graded clinically on the basis of hardness. The endothelial cell count (ECC), pachymetry, and best corrected visual acuity (BCVA) were evaluated preoperatively and postoperatively. The mean ECC and pachymetry values (+/-SD) were calculated in each group, with differences between right and left eyes analyzed using the paired t test.

RESULTS

In Group A, the differences in the postoperative changes in ECC and pachymetry between AquaLase and NeoSoniX were not statistically significant. In Group B, there were statistically significant differences in postoperative changes in ECC and pachymetry, with the results better in the AquaLase eyes. The BCVA immediately after surgery was better than preoperatively in all eyes.

CONCLUSION

The results suggest that AquaLase cataract extraction is safe for the endothelium, even in older patients with harder cataracts and a lower ECC count preoperatively.

In water thermal imaging comparison of the Alcon legacy and AMO sovereign phacoemulsification systems

Purpose:

To compare the temperature profiles of 2 popular phacoemulsification units under similar operating conditions in water.

Methods:

The phacoemulsification probes of the Sovereign WhiteStar and Legacy AdvanTec were capped with water-filled test chambers and imaged side-by-side using a thermal camera. The highest temperature of each chamber was measured at several time points after power application. Testing was performed under conditions capable of producing a corneal burn. The Legacy was operated in pulse mode at 15 Hz; a 50% duty cycle; and console power settings of 10, 30, 50 and 100%. The Sovereign was operated at the same console settings in WhiteStar C/F pulse mode at 56 Hz and a 33% duty cycle.

Results:

Under all conditions (powers of 10, 30, 50 and 100%; with or without irrigation/aspiration flow; and with or without sleeve compression), the Sovereign generated higher temperatures than the Legacy. At irrigation/aspiration flow rates ≥ 5 cc/min, the temperature profiles of the 2 units were indistinguishable.

Conclusion:

The Sovereign WhiteStar ran hotter than the Legacy AdvanTec under a variety of controlled low flow operating conditions. The Sovereign WhiteStar is more likely than the Legacy AdvanTec to produce a corneal burn under low flow conditions.

Comparative study of coaxial phacoemulsification and microincision cataract surgery. One-year follow-up

PURPOSE

To evaluate the amount of ultrasound (US) used, best corrected visual acuity (BCVA), and corneal endothelial cell loss in bimanual microincision cataract surgery (MICS) and coaxial phacoemulsification.

SETTING

Department of Ophthalmology, Universidade Gama Filho, Rio de Janeiro, Brazil.

METHODS

A prospective randomized study included 30 patients (60 eyes) with bilateral cataract. All patients had coaxial phacoemulsification in 1 eye and MICS in the fellow eye. The US time and the effective US time were measured intraoperatively. The BCVA and central endothelial cell loss were evaluated in both groups over a 1-year follow-up. The results between the 2 groups were compared.

RESULTS

The total US time was lower in the coaxial phacoemulsification group than in the MICS group; the means were 0.50 minutes +/- 0.33 (SD) and 0.82 +/- 0.39 minutes, respectively. The mean US power was similar between groups (mean 10.1% +/- 3.76% and 10.0% +/- 4.0%, respectively). The BCVA was similar between the groups from 24 hours to 1 year. The mean central corneal endothelial cell loss at 3 months was 4.66% +/- 6.10% in the coaxial phacoemulsification group and 4.45% +/- 5.06% in the MICS group and at 1 year, 6.00% +/- 6.72% and 8.82% +/- 7.39%, respectively. The only significant difference in the postoperative results between the 2 groups was central endothelial cell loss at the 1-year follow-up.

CONCLUSIONS

The US time was longer in the MICS group than in the in the coaxial phacoemulsification group, but the mean US power was similar between groups. The BCVA was also similar between groups; however, the MICS group had more central endothelial cell loss at the 1-year follow-up.

Microcoaxial phacoemulsification

PURPOSE

To examine and compare the fluidic, thermal, and incision behaviors of 2.2 mm microcoaxial and sleeveless bimanual phacoemulsification.

SETTING

Private practice, Cincinnati, Ohio, USA.

METHOD

Fluidic performance of microcoaxial phacoemulsification and sleeveless bimanual microphacoemulsification was examined using a reduced-size irrigating sleeve and numerous irrigating choppers, respectively. Incision temperature during phacoemulsification, incision sealability after phacoemulsification, and incision leak were compared in cadaver eyes. Porcine eyes were used to determine whether a full-sized single-piece SN60AT intraocular lens (IOL) (AcrySof) could be inserted through a 2.2 mm incision.

RESULTS

Fluidic comparison indicated greater irrigation flow and a more stable occlusion break response with the microcoaxial setup than with the sleeveless bimanual setup under the same test conditions. Incision temperature during phacoemulsification, incision sealability after phacoemulsification, and incision leakage tests indicated that the microcoaxial setup produced less temperature rise, better incision sealability, and less incision leakage. A full-sized SN60AT IOL could be inserted through a 2.2 mm incision.

CONCLUSIONS

Laboratory results indicate that microcoaxial phacoemulsification through a 2.2 mm incision offers fluidic-, thermal-, and incision-related benefits over sleeveless bimanual microphacoemulsification. Moreover, a full-sized single-piece acrylic IOL could be safely implanted without enlarging the 2.2 mm incision.

Effect of incisional friction and ophthalmic viscosurgical devices on the heat generation of ultrasound during cataract surgery

PURPOSE

To determine the thermal features of the Legacy (Alcon) and Sovereign (Advanced Medical Optics) phacoemulsification machines in a cadaver eye and with 7 ophthalmic viscosurgical devices (OVDs).

SETTING

In situ and in vitro study.

METHODS

Temperature without occlusion was recorded at the sleeve placed in the wound of a cadaver eye, and temperature over baseline was determined after 60 seconds. The result was then compared with the results in a previous study that used balanced salt solution (BSS) in artificial chambers. In the second portion of the experiment, with irrigation and aspiration lines occluded, temperature was recorded at the sleeve placed in an artificial chamber filled with sodium hyaluronate 2.3% (Healon5), sodium hyaluronate 1.4% (Healon GV), sodium hyaluronate 1.0% (Healon), sodium hyaluronate 1.6% (Amvisc Plus), sodium hyaluronate 1.0% (Provisc), sodium hyaluronate 3.0%-chondroitin sulfate 4.0% (Viscoat), or hyaluronate 3.0% (Vitrax). Temperature over baseline was also determined after 60 seconds. These results were compared with each set of OVD data and with the results in the prior BSS study.

RESULTS

In the eye-bank model, the Legacy machine had a 62% temperature increase from incisional friction and the Sovereign machine had a decrease of 8.6% over results in an artificial anterior chamber. The OVD temperature increases were greater for the Sovereign (P<.001) and followed the same general trend for the Legacy. The least temperature increase was with Amvisc Plus, Healon, and Healon GV; the intermediate increases were with Provisc and Vitrax; and the greatest increases were with Viscoat and Healon5. The OVD findings did not correlate with viscosity or pseudoplasticity.

CONCLUSIONS

Incisional friction alone increased heat generation in the Legacy, a stroke-length driven instrument, more than in the Sovereign, a power-driven instrument. Ophthalmic viscosurgical devices are not only a concern due to outflow occlusion but can also add up to 6 times the heat in comparison with BSS. The need to aspirate the OVD before using ultrasound is thus verified.

Thermal study of bare tips with various system parameters and incision sizes

PURPOSE

To identify major and minor surgeon-controlled parameters that affect incision temperature when performing microincision lens removal using the Alcon Infiniti Vision System.

SETTING

In vitro research and development laboratory, Alcon Research, Irvine, California, USA.

METHOD

Phacoemulsification was performed in eye-bank cadaver eyes and the following parameters evaluated: incision, duty cycle, ultrasound (US) power, aspiration flow rate (AFR), vacuum, pulse, bottle height and balanced salt solution temperature, and tip design/size. Each parameter was varied while the others remained constant. The resulting temperature of the incision and US tip was measured using a thermal camera.

RESULTS

Major contributors to elevated incision temperature included incision size, US power, duty cycle, AFR, vacuum setting, tip design, and presence of an ophthalmic viscosurgical device (OVD). Minor contributors included pulse frequency, bottle height, and temperature of the infusate.

CONCLUSION

Microincision lens removal can be performed at safe temperatures with the knowledgeable selection of surgeon-controlled parameters.

Thermal effect of microburst and hyperpulse settings during sleeveless bimanual phacoemulsification with advanced power modulations

PURPOSE

To assess wound temperature during bimanual sleeveless phacoemulsification using customizable power modulations such as hyperpulse and microburst technology.

SETTING

In vitro laboratory.

METHODS

The Millennium Microsurgical System (Bausch & Lomb) with custom control software (CCS) was used to perform phacoemulsification in 5 porcine eyes with MicroFlow needles (Bausch & Lomb) and with power varied from 20% to 80% in 10% increments. Pulse modes were set for fixed microburst (4 ms on, 4 ms off; and 6 ms on, 12 or 24 ms off) and for hyperpulse (30% duty cycle with 8 or 75 pulses per second [pps]), with and without aspiration-line occlusion. Wound temperatures were measured 3 times per second.

RESULTS

Using 80% total power, the wound temperature during 3 minutes of occlusion did not exceed 39.0 degrees C. The maximum temperature with fixed microbursts of 4 ms on, 4 ms off was 29.0 degrees C without occlusion and 37.8 degrees C with occlusion (duration 3 minutes). At 6 ms on, 12 ms off, the maximum temperatures were 28.1 degrees C and 38.7 degrees C, respectively. At 6 ms on, 24 ms off, peak temperatures were 24 degrees C and 23.6 degrees C, respectively. The hyperpulse mode of 30% duty cycle and 8 pps produced maximum temperatures of 25.5 degrees C nonoccluded and 33.4 degrees C occluded. With 30% duty cycle, 75 pps, temperatures were 28 degrees C and 38.0 degrees C, respectively. For all power below 80%, temperatures were lower.

CONCLUSIONS

Customizable power modulation with microburst and hyperpulse technology further reduced wound temperatures during bimanual sleeveless phacoemulsification. This enhances the safety and effectiveness of phacoemulsification through a sleeveless needle and a small stab incision.

Thermography used for analysis and comparison of different cataract surgery procedures based on phacoemulsification

Thermography has been employed to analyze and compare three cataract surgery procedures performed in vivo with phacoemulsification, namely, the Sovereign phacoemulsification system with a traditional technique, the Sovereign WhiteStar phacoemulsification system with a traditional technique and the Sovereign WhiteStar phacoemulsification system with a bimanual technique. During the entire surgical procedure, the temperature of the ocular surface was monitored. The temperature values in the area where the phaco probe was inserted in the eye were measured, and the quantities of heat transmitted to the eye in the different procedures were assessed through suitable indices. In this study the highest temperature measured for each procedure during the surgical operation was 44.9 degrees C for the Sovereign phacoemulsification system with a traditional technique, 41 degrees C for the Sovereign WhiteStar phacoemulsification system with a traditional technique and 39.5 degrees C for the Sovereign WhiteStar phacoemulsification system with a bimanual technique, which is also the surgical procedure having the lowest thermal impact on the eye, i.e., the one in which the temperature peaks are lowest in amplitude and the least amount of heat is transmitted to the eye. Thermography, used in this study as a temperature monitoring instrument, has allowed analysis to be effected through a useful and advantageous methodology, totally non-invasive as regards both surgeon and patient, and has been applied in vivo without requiring any change in the surgical procedure.

Thermal imaging study comparing phacoemulsification with the Sovereign with WhiteStar system to the Legacy with AdvanTec and NeoSoniX system

PURPOSE

To assess intraoperative thermal levels at the wound site during divide-and-conquer phacoemulsification with the Sovereign with WhiteStar (SWS) system or the Legacy with AdvanTec and NeoSoniX (LAD) system.

DESIGN

Prospective, randomized, parallel-group, comparative study.

METHODS

Twenty-six subjects from a private clinical practice underwent divide-and-conquer phacoemulsification with either the SWS system or the LAD system. CB/CF settings (60%/33% duty cycles) were utilized with SWS and 12 pulses per second with the LAD system. Key criteria assessed were peak wound-site temperature, mean temperature change at the wound site, effective phaco time, average phaco power, procedure time, amount of BSS used, and surgical complications.

RESULTS

Mean temperature change at the wound site was greater for the LAD than the SWS group. There was a statistically significant difference (P=.0002) in mean peak wound temperatures, with the LAD group having higher mean peak temperatures (42.47+/-5.33 degrees C) than the SWS group (36.59+/-1.33 degrees C). Highest wound-site temperature was 51 degrees C for the LAD group and 39.3 degrees C for the SWS group. A statistically significant difference (P=.0031) in mean peak temperature was found between the LAD and SWS systems for subjects with a cataract density of 4: higher mean peak temperatures were observed for LAD patients with a cataract density of 4.

CONCLUSIONS

Our findings show that phacoemulsification using the SWS system results in lower peak temperatures and less temperature change at the phaco wound site compared with the LAD system.

Comparison of thermal features associated with 2 phacoemulsification machines

PURPOSE

To determine the thermal characteristics of the Legacy Advantec and Sovereign WhiteStar phacoemulsification machines during different clinically relevant scenarios.

SETTING

In vitro study.

METHODS

In water, temperature was recorded continuously on the sleeve in an artificial chamber, and the increase in temperature over baseline after 60 seconds of ultrasound was determined. This was done for continuous ultrasound, 50 ms on and 50 ms off (pulse), 6 ms on and 12 ms off (WhiteStar; Sovereign only) with aspiration blocked and not blocked, and with 100 g and 200 g weights suspended from the sleeve.

RESULTS

Comparing temperature increase per 20% machine power increments, Sovereign ran hotter than Legacy Advantec for continuous ultrasound (2.31x) and pulse (2.23x). Blocking aspiration increased temperature over the unblocked state. Pulsing decreased temperature by 51% (Legacy Advantec, pulse), 52% (Sovereign, pulse), and 64% (WhiteStar). Weights had much more effect on the Legacy Advantec: 3.5 times more going from baseline to 100 g weights and 3.2 times more going from 100 to 200 g weights. For all these comparisons, the P value was less than 0.0001.

CONCLUSIONS

The machines behaved fundamentally differently, with the Legacy Advantec controlling stroke length and Sovereign controlling a fixed power at any setting. Therefore, workload had a much bigger impact on Legacy Advantec thermal characteristics. Pulsing decreased heat produced directly related to the duty cycle. The most dangerous incision burn scenario is with continuous ultrasound, aspiration blocked, and a heavy workload.

Aqualase for cataract extraction

PURPOSE

To report our experience of using Aqualase technology for cataract extraction.

METHODS

In total, 33 patients (20 females; mean age 71.4 years) underwent cataract surgery using Aqualase through a 3.2-mm corneal incision. Grade of nucleus, nuclear removal technique, and intraoperative complications were noted. Clinical parameters from postoperative visits were collected.

RESULTS

Aqualase is capable of removing cataracts up to nuclear sclerosis 2+ (out of 4) with relative ease. Nuclei graded 2+ or greater were technically more difficult and conversion to ultrasound phacoemulsification was required in one case. Two posterior capsule ruptures occurred: one during nucleus removal (contact with the tip while aspirating without Aqualase) and one unrelated to Aqualase during aspiration of cortex. Of 25 patients seen on the first postoperative day, 22 had a clear cornea. A total of 96% patients without preoperative comorbidity achieved 6/9 or better postoperatively. One patient had transient postoperative uveitis.

CONCLUSIONS

Removal of softer cataracts with Aqualase has the theoretical advantage over phacoemulsification, by carrying less risk to the posterior capsule, since the handpiece has a smooth polymer tip that has no mechanical motion inside the eye. However, the tip should not be considered entirely capsule-friendly, as rupture is possible with the foot-pedal in position two (aspiration only). Although certain adjustments to the technique are required, the method is similar enough to phacoemulsification to ensure a brief learning curve. With increasingly firm cataracts, Aqualase becomes less effective and ultrasound phacoemulsification is still superior for such cases, in our experience.

In-air thermal imaging comparison of Legacy AdvanTec, Millennium, and Sovereign WhiteStar phacoemulsification systems

PURPOSE

To compare the temperature profiles of 3 popular phacoemulsification units (Alcon Legacy AdvanTec, Bausch & Lomb Millennium, and AMO Sovereign WhiteStar) under similar operating conditions in air.

SETTING

Jules Stein Eye Institute and the Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.

METHODS

Phacoemulsification probes from the 3 units were placed side by side in air and imaged in the infrared region using model P60 ThermaCAM (Flir Systems). The highest temperature produced by each probe was measured 10 seconds and 30 seconds after power application. Testing was performed under conditions that might produce a corneal burn during cataract surgery. Irrigation flow was set at the low rate of 1 cc/min to simulate a tight incision. Aspiration flow was set at 0 cc/min to simulate occlusion of the needle lumen. Wound compression was simulated in some tests by suspending 22.6 g weights by rubber bands from the silicone sleeves. Manufacturers' specific and identical silicone sleeves were used to evaluate possible variations in thermal conductivity. The AdvanTec Legacy and Millennium were operated in pulse mode at 15 Hertz; 50% duty cycle; and 10%, 30%, and 50% power. The Sovereign WhiteStar was operated in both C/F (56 Hz, 33% duty cycle) and C/L (33 Hz, 20% duty cycle) modes at the same console power settings. Temperature profiles were determined at a variety of power settings with each system operating in continuous and pulse mode.

RESULTS

Under all experimental conditions (at 10%, 30%, and 50% powers; with and without external weights suspended from the phacoemulsification probes; with manufacturers' and identical silicone sleeves; and in continuous and pulse modes), the Millennium and the Sovereign WhiteStar generated higher temperatures than the Legacy AdvanTec.

CONCLUSIONS

Under controlled operating conditions in air and under a variety of power, load, and duty-cycle settings, the Millennium and the Sovereign WhiteStar, operating in both pulse and continuous modes, generated higher peak temperatures than the Legacy AdvanTec.

Thermal comparison of the AdvanTec Legacy, Sovereign WhiteStar, and Millennium phacoemulsification systems

PURPOSE

To determine the operating temperature of ultrasonic tips used with the Alcon AdvanTec Legacy, AMO Sovereign WhiteStar, and Bausch & Lomb Millennium phacoemulsification systems.

SETTING

Mackool Eye Institute, Astoria, New York, New York, USA.

METHODS

Thermal imaging of ultrasonic tips (Legacy, WhiteStar, and Millennium) was performed in air and in human cadaver eyes using a duty cycle of 33% (WhiteStar) and 50% (Millennium and Legacy). In vitro temperatures were measured with the tip centered in the incision and intentionally decentered against the side of the incision. The stroke length of each instrument was also measured, and the operating frequency of the Legacy was evaluated with the addition of a tangential load.

RESULTS

Open air and in vitro testing demonstrated that tip temperatures with the Legacy were consistently the lowest. Temperatures measured with the WhiteStar and Millennium systems were higher and generally similar to each other. At identical console power settings, the stroke length of the WhiteStar and Millennium tips was longer than that of the Legacy. The frequency of the Legacy handpiece did not change significantly (less than 200 Hz) under conditions of tangential tip loading.

CONCLUSIONS

At identical console power settings and similar console duty cycles, the temperature elevation of ultrasonic tips was least for the Legacy and greater for the WhiteStar and Millennium under all conditions. The causes of these findings appear to be the longer stroke length of the WhiteStar and Millennium and the underestimation of the duty cycle with the WhiteStar.

Legacy AdvanTec and Sovereign WhiteStar

PURPOSE

To assess the wound temperature of the Sovereign WhiteStar (S-WS) (AMO) and Legacy AdvanTec (L-ADV) (Alcon) phacoemulsification systems.

SETTING

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

METHODS

Phacoemulsification using 20-gauge, 30-degree straight tips with the L-ADV and S-WS systems was performed in fresh cadaver eyes. The power was set at 50%, and aspiration was 12 mL/min; the L-ADV was run at 15 pulses per second (pps) and the S-WS at WS CF (6 milliseconds on, 12 milliseconds off). Temperature was measured at 5-second intervals for 60 seconds using a microthermistor placed in the wound. The phaco tip was angled 30 degrees to increase wound-tissue contact. At 10 seconds, the flow was clamped to simulate occlusion. Five runs, sleeved and unsleeved, were averaged for the phaco tip.

RESULTS

The mean temperature was significantly higher with L-ADV than with S-WS (from 10 seconds on in the sleeved condition and from 5 seconds on in the unsleeved condition after the aspiration line was clamped). In 2 of 5 sleeved runs and 4 of 5 unsleeved runs, the L-ADV handpiece decreased power as the temperature increased. One run with the L-ADV with sleeve showed signs of wound burn. There were no signs of wound burn with the S-WS. The highest temperature recorded was 57.5 degrees C with the L-ADV and 38.6 degrees C with the S-WS. Power tests showed L-ADV protected the stroke length and S-WS had constant power except in air where it increased power.

CONCLUSIONS

There was less increase in wound temperature over time with the S-WS than with the L-ADV system in sleeved and unsleeved simulated surgery in human eye-bank eyes. Because the ultrasound handpieces respond differently under different load scenarios, meaningful comparisons of pulsing features are difficult to create.

AquaLase: a new technology for cataract extraction

PURPOSE OF REVIEW

This review describes a completely new technology for removal of the crystalline lens and compares it to currently available instruments. The AquaLase option on the Infiniti Vision System (Alcon Laboratories, Fort Worth, Texas) delivers unique advantages over conventional ultrasound phacoemulsification.

RECENT FINDINGS

Incremental improvements have made ultrasonic phacoemulsification safer to the posterior capsule and less likely to create wound burn. AquaLase uses a fundamentally different technology that eliminates the risk of incision burn, is probably less likely to cause posterior capsule rupture than ultrasonic phacoemulsification needles, and is more efficient than laser-based lens removal instruments.

SUMMARY

AquaLase is a new technology that offers significant advantages and is likely to find wider application as clinical experience accumulates.

Feasibility of sleeveless bimanual phacoemulsification with the Millennium microsurgical system

PURPOSE

To assess the feasibility of sleeveless bimanual phacoemulsification using the Millennium Microsurgical System (Bausch and Lomb Surgical) by measuring wound temperature during phacoemulsification.

SETTING

In vitro laboratory.

METHODS

The Millennium system was used in 6 eye-bank eyes using pulse mode and 80-milllisecond and 160-millisecond phaco burst mode width intervals. Wound temperatures were measured, and the wounds were observed for thermal injury.

RESULTS

In pulse mode and the nonoccluded state at 100% power, the maximum temperature was 43.8 degrees C. In the occluded state at 30% power, the maximum temperature was 51.7 degrees C after 70 seconds of occlusion. In phaco burst mode with a 160-millisecond burst-width interval, the maximum temperature was 41.4 degrees C (nonoccluded at 100% power). At 80% power, the maximum temperature was 53.2 degrees C within 60 seconds of full aspiration occlusion with the footpedal fully depressed. With an 80-millisecond burst-width interval in the nonoccluded and occluded states (100% power, footpedal fully depressed for 3 minutes), there was no significant temperature rise. The maximum temperature was 33.6 degrees C in the nonoccluded state and 41.8 degrees C in the occluded state. In all instances, the corneal wound remained clear. No wound burn or contracture was noted.

CONCLUSIONS

The demonstrated temperature rises were under clinically unusual parameters. Phacoemulsification with a sleeveless needle through a small stab incision can be safely performed with the Millennium system using conventional phaco burst mode settings within certain parameters.

Phacoemulsification and thermal wound injury

The technique of lens nucleus phacoemulsification has revolutionized cataract surgery. However, the production of ultrasound energy is associated with heat generation that can result in damage to ocular tissue, in particular the corneoscleral wound site. Thermal damage to the corneoscleral wound site may result in difficulty with wound closure and consequent risk of wound leakage, as well as damage to the adjacent corneal stroma and endothelium, fistula formation, and the induction of high degrees of post-operative astigmatism. The loss of adequate flow of irrigation fluid around the phacoemulsification tip is the key factor in the development of phacoemulsification-induced thermal injury. Use of excessive ultrasound power and production of excessive frictional forces generated by contact of the vibrating phacoemulsification needle with the irrigation sleeve are also factors involved. In the event of a "phacoburn," a specialized "gape suture" may help minimize surgically-induced astigmatism. The degree of induced astigmatism tends to wane over time; astigmatic keratotomy is an option in the setting of high degrees of residual astigmatism.

Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results

PURPOSE

To evaluate the intraoperative complications and postoperative results of bimanual phacoemulsification and aspiration using a sleeveless phaco tip inserted through an ultra-small incision.

SETTING

Department of Ophthalmology, Jikei University, Tokyo, Japan.

METHODS

This study comprised 637 eyes having cataract extraction using conventional phacoemulsification equipment. A 20-gauge phaco tip with the sleeve removed was inserted through a 19-gauge corneal incision. A 20-gauge hooked cannula with the wall thinned to increase the inner diameter was used for infusion. After the crystalline lens was removed, the incision was widened to 2.8 to 4.1 mm and and an intraocular lens (IOL) was implanted. Study parameters were operating time, amount of infusion solution used, incidence of intraoperative complications, and early postoperative results.

RESULTS

The mean operating time was 8 minutes 42 seconds. Although the nuclear hardness was grade 4 or above in 35 eyes, there were no cases of thermal burn. The amount of infusion solution and the rate of postoperative decrease in corneal endothelial cell density did not differ greatly from results of conventional methods. This technique induced considerably less corneal astigmatism than surgery using conventional corneal incisions.

CONCLUSIONS

A sleeveless phaco tip was used to perform successful bimanual phacoemulsification using conventional phaco machines and familiar surgical techniques. The cataracts were safely removed through an incision of 1.4 mm or smaller that was widened for IOL insertion.

Phacoemulsification of brunescent and black cataracts

PURPOSE

To evaluate the efficacy and safety of a step-by-step, chop in situ, lateral separation technique to remove brunescent and black cataracts.

SETTING

Iladevi Cataract and IOL Research Center, Ahmedabad, India.

METHODS

In this prospective study conducted between May 1997 and June 1998, 167 consecutive eyes were divided into 2 groups: Group 1, brunescent cataract (n = 123), and Group 2, black cataract (n = 44). Preoperative assessment included axial length (AL), slitlamp examination, corneal pachymetry, tonometry, and specular microscopy. During phacoemulsification performed by a single surgeon, a step-by-step, chop in situ, lateral separation technique was used to divide the nucleus. Intraoperatively, hydroxypropyl methylcellulose 2% was used and irrigation was by balanced salt solution (BSS). Postoperatively, all eyes were assessed at 1, 7, 30, 90, 180, and 360 days. The results were evaluated using regression analysis, the chi-square test, and the Student t test.

RESULTS

The mean follow-up was 14.4 months (range 6 to 35 months) in Group 1 and 13.0 months (range 6 to 32 months) in Group 2. The AL was significantly greater in Group 2 (P =.02). Corticapsular adhesions were present in 17.82% in Group 1 and 31.82% in Group 2. The mean cumulative dissipated energy was 2.03 and 3.12, respectively (P =.0005). Wound site thermal injury occurred in 16 eyes (13.01%) in Group 1 and 4 eyes (9.09%) in Group 2. No serious intraoperative or postoperative complications were noted. One day postoperatively, the mean rise in intraocular pressure was 1.76 mm Hg in Group 1 and 4.15 mm Hg in Group 2 (P =.012), and transient corneal edema was present in 24.40% and 34.10%, respectively. At 1 month, the endothelial cell loss was 10.06% in Group 1 and 9.22% in Group 2.

CONCLUSION

The step-by-step, chop in situ, lateral separation technique was effective and did not produce serious complications such as zonulysis or posterior capsule rupture. However, the incidence of wound site thermal injury and endothelial cell loss was greater than after emulsification of standard cataracts.

Feasibility of ultrasound cataract surgery with a 1.4 mm incision

PURPOSE

To study the feasibility of performing ultrasound (US) phacoemulsification cataract surgery through a 1.4 mm incision using conventional phacoemulsification equipment but removing the infusion sleeve from the US tip.

SETTING

Department of Ophthalmology, Jikei University, Tokyo, Japan.

METHODS

The infusion sleeve was removed from a 20 gauge US tip, and the sleeveless tip was inserted in a 1.4 mm incision in a postmortem porcine eye, providing infusion through a side port; phacoemulsification was performed with the US tip occluded. Temperature at the incision site was measured with a thermometer to determine whether a thermal burn occurred during the process. A hooked infusion cannula with a widened inner channel and 3 apertures was used to stabilize the anterior chamber depth.

RESULTS

Ultrasound phacoemulsification produced almost no temperature elevation at the incision site as long as the infusion liquid was adequately circulated around the US tip. With the 20 gauge US tip, an adequate volume of leakage was maintained through the 1.4 mm incision; no thermal burns developed at the incision site. The use of a hooked infusion cannula made it possible to stabilize the anterior chamber and to apply the bimanual nucleofractis technique to emulsify and aspirate the lens nucleus.

CONCLUSION

Using a sleeveless 20 gauge US tip, US cataract surgery was safely performed through a 1.4 mm incision without producing thermal burns at the incision site.

Pilot study on erbium laser phacoemulsification

PURPOSE

To investigate the suitability of erbium laser phacoemulsification for cataract surgery using a prospective pilot study.

DESIGN

Prospective, single-center, nonrandomized clinical trial.

PATIENTS AND METHODS

Slit-lamp microscopy, keratometry, best-corrected visual acuity, refraction, pachymetric corneal thickness, endothelial cell density, and intraocular pressure were assessed before surgery and on the first, fourth, fourteenth, and the sixtieth day after surgery in 40 eyes of 34 patients with senile cataract (17 males with a mean age of 67.3 years; 17 females with a mean age of 73.2 years). All operations were performed by one surgeon (HH) using the MCL-29 erbium laser (Aesculap-Meditec, Jena, Germany). The nuclear sclerosis grade ranged from 0 to 4.

MAIN OUTCOME MEASURES

Primary outcome measures were defined as the ability to emulsify the lens nucleus under clinical conditions and the occurrence of side effects. Secondary outcome measures included the change in visual acuity, refraction, intraocular pressure, corneal thickness, and endothelial cell density.

RESULTS

Complete emulsification of the lens nucleus using the erbium laser was achieved in 36 of 40 eyes (90%; nuclear sclerosis grade, 0-3). Partial emulsification of the nucleus was possible in two cases with grade 3 nuclear sclerosis, in one case of grade 2 nuclear sclerosis, and in one case of cataract with grade 4 nuclear sclerosis. Mean phacoemulsification time was 3 minutes, and the total applied energy equaled 38.5 J. The postoperative changes in visual acuity, spherical and astigmatic refraction, and intraocular pressure were found to be the same as with ultrasonic phacoemulsification. The decrease in the density of endothelial cells (by 0.96%) was not statistically significant. Posterior capsule ruptures occurred in three eyes early in the series. There were no further vision-threatening complications.

CONCLUSIONS

Erbium laser phacoemulsification is effective for lenses with mild to moderate nuclear sclerosis. For higher grades of nuclear sclerosis, further improvements in technical and surgery-related parameters are required.