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

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.

Transient temperature distribution on the corneal endothelium during ophthalmic phacoemulsification: a numerical simulation using the nodeless variable element

Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into the anterior chamber of eye. Then, heat is generated by the oscillation of the phaco needle, which may injury the corneal endothelial cells. There are no data available for temperature responses at the corneal endothelium to heat from the phaco needle during phacoemulsification. Objective: Investigate temperature distribution on the corneal endothelium during ophthalmic phacoemulsification using numerical simulation, and compare the transient temperature response to heat between balanced salt solution (BSS) and ophthalmic viscoelastic device (OVD), Viscoat®. Methods: Heat flux from a phaco needle was measured with thermal properties of BSS and AVS in an experimental setting. Then, nodeless variable finite element method was applied to predict temperature changes in the eye by the phaco needle inserted into the anterior chamber. The transient temperature distribution on the corneal endothelium was calculated at 10, 20, and 30 seconds after heat generation by the needle. Results: The heat generation of phaco needle without sleeve cover was 1.6 kW/m2. The numerical simulation showed that the maximum temperature occurs on the wound location at all times after heat generation by the phaco needle. Especially, at time 30 seconds, it was 49.2 and 41.7°C in BSS and OVD, respectively. The temperature elevation by the phaco needle was lower in OVD than BSS. Conclusion: Phacoemulsification is a heat-generating procedure performed between the anterior chamber structures of eye. During this procedure, OVD may protect the corneal endothelium against heat better than BSS.

Comparative analysis of coaxial phacoemulsification with 2.2- and 2.8-mm clear corneal incisions

PURPOSE

To compare the intraoperative efficiency and postoperative visual outcome of coaxial phacoemulsification using 2.2- and 2.8-mm clear corneal incision coaxial phacoemulsification.

SETTING

The study was conducted at Vardhaman Mahavir Medical College and Safdarjung Hospital, New Delhi which is a tertiary health care centre.

STUDY DESIGN

This is a prospective, randomized, comparative interventional study.

MATERIALS AND METHODS

A total of 140 eyes of patients undergoing cataract surgery were enrolled according to the inclusion-exclusion criteria and randomly divided in two groups of 70 such that Group I-Patients underwent phacoemulsification through 2.8-mm clear corneal incision. Group II-Patients underwent phacoemulsification through 2.2-mm clear corneal incision.Postoperative assessment was done at 1 day, 1 and 6 weeks to note best-corrected visual acuity (BCVA), ophthalmic examination, corneal topography, central corneal thickness and corneal endothelial cell count.

STATISTICS

1. Quantitative variables were compared using Mann-Whitney test and Wilcoxon ranked-sum test. 2. Qualitative variables were compared using Fisher's exact test. p value of <0.05 was considered statistically significant.

RESULTS

There is steady trend in decrease in postoperative astigmatism with time, more so in 2.8 mm group; however, differences were not found to be statistically significant. 2.2 mm group had larger increase in CCT and ECC compared to 2.8 mm group which was not statistically significant (p = 0.296).

CONCLUSION

Reducing the incision size from 2.8 to 2.2 mm does not result in any significant reduction in the amount of surgically induced astigmatism. Also, both the incision sizes have similar intraoperative efficacy when compared in terms of postoperative decrease in corneal endothelial cell count and increase in central corneal thickness.

Wound and surface temperatures in vivo in torsional and longitudinal modalities of ultrasound in coaxial microincisional cataract surgery

BACKGROUND

To study phacoemulsification probe shaft/wound and corneal surface/tip temperatures in vivo during longitudinal, torsional and combined phacoemulsification modes and their relationship to machine parameters.

DESIGN

This was a prospective study at Chaithanya Eye Hospital and Research Institute, Trivandrum, India (tertiary).

PARTICIPANTS

Twenty-two eyes of 22 patients were randomized into six groups depending on the grade of nuclear sclerosis (NS) and the type of ultrasound used: Group 1, torsional in NS2; Group 2, torsional in NS3; Group 3, torsional with intermittent longitudinal in NS2; Group 4, torsional with intermittent longitudinal in NS3; Group 5, longitudinal in NS2; Group 6, longitudinal in NS3.

METHODS

Patients underwent phacoemulsification by torsional, longitudinal or combined modalities. A thermal camera was used to measure phaco probe temperatures.

MAIN OUTCOME MEASURES

The mean probe shaft and tip temperatures were documented for different ultrasound modalities.

RESULTS

The mean shaft and tip temperatures were: Group 1, 29.22°C±0.71°C and 28.4°C±0.88°C; Group 2, 32.12°C±0.62°C and 31.88°C±0.84°C; Group 3, 30.25°C±0.71°C and 29.35°C±0.62°C; Group 4, 31.95°C±0.65°C and 32.01°C±1.31°C; Group 5, 23°C and 27.6°C and Group 6, 23°C and 29.68°C, respectively. In all groups using longitudinal ultrasound, the phaco tip surface temperatures were higher than the shaft temperatures, except in Group 3. Shaft temperatures were higher than tip temperatures in cases using torsional phaco, except in Group 4. The mean temperature difference between groups was significant only for shaft temperatures (P=0.001). On thermal imaging, for torsional phaco, the rise in temperature of the probe from shaft to tip was dependent on the amplitude of ultrasound applied (P=0.009).

CONCLUSION

The shaft temperatures were higher than over the phaco tip during torsional phacoemulsification.

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.

Comparison of macular thickness and inflammatory cytokine levels after microincision versus small incision coaxial cataract surgery

PURPOSE

To compare the macular thickness and volume change, and inflammatory cytokine levels after cataract surgery performed using two different sizes of incision (microincision versus small incision).

METHODS

In this randomized, comparative clinical trial, 84 eyes with nuclear density from Grade 3-4 were randomly divided into two groups (microincision, 2.2 mm; and small incision, 2.75 mm). Forty-two patients underwent phacoemulsification with microincision coaxial cataract surgery and 42 patients underwent phacoemulsification with small incision coaxial cataract surgery. Clinical measurements included preoperative, 1-week, 1-month and 2-month postoperative best corrected visual acuity, central corneal thickness (CCT) and endothelial cell count. ELISA and RT-PCR were performed for IL-1β, IL-6, VEGF and PGE2 preoperatively and at 1 week postoperatively.

RESULTS

The percentage increase in CCT in the microincision group was significantly higher than that in the small incision group at 1 week after cataract surgery (p = 0.01). The increase in macular thickness in the microincision group was significantly higher than that in small incision group at 1 month after cataract operation (p = 0.04). Also, IL-1β, IL-6, VEGF and PGE2 concentrations and their expression ratio in the microincision group were significantly higher than those in the small incision group at 1 week after cataract surgery compared to the preoperative period (p < 0.05).

CONCLUSIONS

Phacoemulsification with microincision coaxial cataract surgery may increase the macular thickness compared to phacoemulsification with small incision coaxial cataract surgery. Blood-aqueous barrier breakdown may occur more frequently after microincision cataract surgery than after small incision cataract surgery.

Changes in Aqueous Humor pH After Femtosecond Laser-Assisted Cataract Surgery

PURPOSE

To compare aqueous humor pH values in patients during femtosecond laser-assisted cataract surgery with patients during conventional phacoemulsification.

METHODS

A prospective clinical study was conducted in 29 eyes of 29 patients who underwent cataract surgery by a single surgeon. The femtosecond laser group included 15 eyes operated on with a femtosecond laser platform (Catalys; Abbott Medical Optics, Santa Ana, CA) and the phacoemulsification group included 14 eyes that were operated on with conventional phacoemulsification. The femtosecond laser group was subdivided into low, medium, and high level of cavitation gas bubbles after docking and the femtosecond laser procedure, according to the judgment of the surgeon. Aqueous humor samples (0.10 to 0.15 mL) were collected through a paracentesis from each patient after docking, corneal incisions, and nucleus fragmentation in the femtosecond laser group and after corneal incisions but before injection of viscoelastic in the phacoemulsification group, then analyzed with a pH meter.

RESULTS

The mean pH was 6.53 ± 0.09 (range: 6.42 to 6.70) and 7.42 ± 0.07 (range: 7.28 to 7.48) in the femtosecond laser and phacoemulsification groups, respectively (P < .001). In the femtosecond laser group, no significant differences in pH were observed between the three subgroups after docking and the femtosecond laser surgical procedure: low (6.55 ± 0.09 [range: 6.53 to 6.57]), medium (6.54 ± 0.07 [range: 6.52 to 6.55]), and high (6.42 ± 0.00 [range: 6.40 to 6.44]) level of gas bubbles.

CONCLUSIONS

Cavitation bubbles derived from the photodisruption process in femtosecond laser-assisted cataract surgery lead to an acidic shift of the aqueous humor pH as a result of the transformation of carbon dioxide to carbonic acid. The level of gas bubbles visible after the laser photodisruption does not seem to correlate with this pH shift. Further analysis of femtosecond laser-assisted cataract surgery is necessary.

Experimental and Numerical Determination of the Local Temperature Distribution during Phacoemulsification and Comparison of Different Surgery Situations within Enucleated Porcine Eyes

Phacoemulsification, a common treatment for cataract, is accompanied by cell damage at the corneal endothelium. Thermal exposure during treatment has been considered a reason for this damage, but a thorough experimental and theoretical assessment of the local temperature distribution inside the eye had not yet been conducted. Measurements in porcine eyes and a finite-element simulation enabled such an assessment and localized the highest temperature rise very close to the probe. The results described in this study indicate that a distance of 1 mm between the probe and the endothelium should be maintained during treatment as a safety margin, especially when fluid flow is blocked. The highest measured temperature rise with surgically reasonable system settings and unblocked fluid flow was 1.11°C. The finite-element simulation described here is able to calculate the temperature rise at the endothelium and could serve as a tool for comparing arbitrary surgical situations with respect to thermal exposure of the endothelium.

Structural analysis of different incision sizes and stromal hydration in cataract surgery using anterior segment optical coherence tomography

Purpose

To analyze healing changes of corneal wounds of different corneal incision sizes with or without stromal hydration in cataract surgery using anterior segment optical coherence tomography.

Methods

Cataract surgeries were performed by a single surgeon and 2.2- and 2.8-mm corneal incisions were made using a diamond blade (ME-759; Meyco, Biel-Bienne, Swiss). Patients were divided into four groups according to incision size (2.2 and 2.8 mm), and with/without stromal hydration. Fifteen eyes were assigned to each group and incision wounds were measured using anterior segment optical coherence tomography at 2 hours, 1 day, 1 week, 1 month, and 3 months postoperatively. Corneal thickness, incision length and incision angle were measured and existence of epithelial, endothelial gaping and Descemet's membrane detachment was evaluated.

Results

Incision thickness was greater in the group with stromal hydration than in the group without on operation day (p < 0.05). Stromal hydration exerted greater influence in the 2.2-mm incision group than in the 2.8-mm incision group. Corneal thickness decreased more rapidly in the stromal hydration group than in the group with no hydration (p = 0.022). Endothelial gaping was greater in the 2.2-mm incision group than in the 2.8-mm incision group 1 day, 1 month, and 3 months after surgery (p = 0.035, p = 0.009, and p = 0.008, respectively). No other statistical significance was observed between the two groups (2.2 and 2.8 mm) during follow-up regarding corneal thickness, epithelial gaping and Descemet's membrane detachment.

Conclusions

Corneal wounds with a smaller incision could be more vulnerable to external stimuli such as stromal hydration and are less stable than those with a larger incision.

Computation of the temperature rise at the corneal endothelium during cataract surgery by modeling of heat generation inside the anterior chamber

The corneal endothelium sustaining the transparency of the cornea is a vulnerable cell layer. Thermal exposure during phacoemulsification is considered to be a potential cause of post-operative cell loss. Knowledge of the temperature rise and particularly of its dependence on region and system settings could deliver useful information about a potential correlation with cell damage. However, there exists a lack of understanding of the process and location of heat generation. Analytical calculations and experiments enabled the quantification of different mechanisms acting as heat sources during phacoemulsification. Heat generation caused by viscous friction was estimated using both an analytical approach and a numerical simulation. In contrast to absorption of sound and self-heating of the probe, this effect was ascertained to be the main heat source. Calorimetric measurement of the power input verified this modeling. On the basis of these results, the local temperature distribution inside a porcine eye was computed time dependently using the finite-element method. Two different amplitude settings were compared with respect to the temperature increase at the corneal endothelium. Various conclusions on the mitigation of thermal exposure during treatment can be drawn from this finite-element simulation.

Thermal imaging comparison of Signature, Infiniti, and Stellaris phacoemulsification systems

Background

To compare the heat production of 3 different phacoemulsification machines under strict laboratory test conditions. More specifically, the thermal behavior was analyzed between the torsional modality of the Infiniti system and longitudinal modalities of the Abbot WhiteStar Signature Phacoemulsification system and Bausch and Lomb Stellaris system.

Methods

Experiments were performed under in-vitro conditions in this study.

Three phacoemulsification handpieces (Infiniti, Signature, and Stellaris) were inserted into balanced salt solution-filled silicone test chambers and were imaged side-by-side by using a thermal camera. Incision compression was simulated by suspending 30.66-gram weights from the silicone chambers. The irrigation flow rate was set at 0, 1, 2, 3, 4, and 5 cc/min and the phacoemulsification power on the instrument consoles was set at 40, 60, 80, and 100%. The highest temperatures generated from each handpiece around the point of compression were measured at 0, 10, 30, and 60 seconds.

Results

Under the same displayed phacoemulsification power settings, the peak temperatures measured when using the Infiniti were lower than when using the other two machines, and the Signature was cooler than the Stellaris. At 10 seconds, torsional phacoemulsification with Infiniti at 100% power showed data comparable to that of the Signature at 80% and the Stellaris at 60%. At 30 seconds, the temperature from the Infiniti at 100% power was lower than the Signature at 60% and the Stellaris at 40%.

Conclusions

Torsional phacoemulsification with the Infiniti generates less heat than longitudinal phacoemulsification with the Signature and the Stellaris. Lower operating temperatures indicate lower heat generation within the same fluid volume, which may provide additional thermal protection during cataract surgery.

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.

Smaller Incision Size Leads to Higher Predictability in Microcoaxial Cataract Surgery

Purpose.

The aim of the study was to compare the clinical outcomes of a 1.8 mm, 2.2 mm, and 2.75 mm microcoaxial cataract surgery system.

Methods.

In this retrospective study, 129 eyes of 129 patients were included. Patients underwent phacoemulsification using a Stellaris system or an Infiniti system. The incision size was 1.8 mm, 2.2 mm, or 2.75 mm, respectively. Subjects were examined before surgery and 4 weeks after. The surgically induced astigmatism (SIA) was examined.

Results.

The SIA in the 1.8 mm group was statistically lower compared to the 2.2 mm group (p=0.046) and the 2.75 mm group (p=0.017). There was no significant difference between the 2.2 mm group and the 2.75 mm group.

Conclusions.

With the use of appropriate support systems, 1.8 mm incisions appear to result in less SIA than 2.2 mm and 2.75 mm incisions. Advantages may arise from this, especially in the implantation of aspheric, toric, or multifocal lenses.

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.

Incision sizes at different stages of phacoemulsification with foldable intraocular lens implantation

PURPOSE

To evaluate incision sizes during different stages of phacoemulsification and after implantation of a foldable acrylic intraocular lens (IOL).

SETTING

Private eye center, Manila, Philippines.

METHODS

In this prospective observational case series, incision widths were measured before and after microcoaxial phacoemulsification (2.2 mm), after cortical removal, and after implantation of a 6.0 mm optic, foldable, single-piece aspheric hydrophobic acrylic IOL using a D cartridge and a Monarch III injector.

RESULTS

The incision width increased in 101 (93.5%) of the 108 eyes; the enlargement was 0.1 mm in 78 eyes (77.2%) and 0.2 mm in 23 eyes (22.8%). The final incision width was 2.3 mm in 78 eyes (72.2%), 2.2 mm in 27 eyes (25.0%), 2.1 mm in 2 eyes, and 2.4 mm in 1 eye. Enlargement occurred during phacoemulsification in 39 eyes, during cortical removal in 33 eyes, and during IOL implantation in 52 eyes; 23 eyes had more than 1 enlargement. Before IOL implantation, the incision was smaller than 2.2 mm in 76 eyes (70.4%); after IOL implantation, the incision increased to 2.3 mm in 47 eyes (61.8%). Thirty-two eyes (29.6%) had a 2.3 mm incision before IOL implantation; the incision increased further (by 0.1 mm) after IOL implantation in 1 eye.

CONCLUSIONS

Incision enlargement occurred at different stages of phacoemulsification, mostly during IOL implantation. More than 72% of eyes had a final incision of 2.3 mm. Beginning with a 2.3 mm incision may prevent wound tears and surface irregularities.

The effect of micro-incision and small-incision coaxial phaco-emulsification on corneal astigmatism

PURPOSE

To evaluate the effect of micro-incision (2.2 mm) and small-incision (2.6 mm or 3.0 mm) coaxial phaco-emulsification on surgically induced astigmatism (SIA).

METHODS

Cataract patients (n = 83, 129 eyes) were randomized into three groups: 43 eyes in the 2.2-mm incision group, 42 eyes in the 2.6-mm group and 44 eyes in the 3.0-mm group. Torsional phaco-emulsification was followed by intraocular lens implantation via the Monarch II injector with the C cartridge (Alcon Laboratories Inc., Fort Worth, TX, USA). Corneal astigmatism, SIA and uncorrected distance visual acuity were assessed 30 and 90 days after cataract surgery.

RESULTS

At 30 and 90 days postoperative, SIA of the 3.0-mm group was greater than SIA of the 2.2-mm and 2.6-mm groups (P < or = 0.015), but SIA was similar between the 2.2-mm group and the 2.6-mm group. Timewise, mean SIA at 30 days was greater than SIA at 90 days in the 3.0-mm group (P = 0.04), while SIA did not change with time for the 2.2-mm and 2.6-mm groups. Postoperative uncorrected distance visual acuity tended to be better with the smaller incisions, but this trend did not reach statistical significance (P > or = 0.07).

CONCLUSION

Incision size contributed to postoperative corneal astigmatism. When incision size was reduced from 3.0 mm to 2.6 mm, SIA was reduced and refractive stabilization was faster. Reduction of incision size from 2.6 mm to 2.2 mm offered no greater reduction of SIA when using the C cartridge; however, the D cartridge (designed for 2.2-mm incisions) should be evaluated.

Intraoperative performance and postoperative outcomes of microcoaxial phacoemulsification

PURPOSE

To evaluate the intraoperative performance and postoperative outcomes after microcoaxial phacoemulsification.

SETTING

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

A prospective observational case series comprised 84 eyes with age-related uncomplicated cataract having microcoaxial phacoemulsification through a 2.2 mm clear corneal incision by a standard surgical technique. Phacoemulsification parameters (Infiniti Vision System, Alcon) were microburst width, 30 ms; preset power, 50%; vacuum, 650 mm Hg; aspiration flow rate, 25 cc/minute. A single-piece Alcon AcrySof intraocular lens was implanted with the C cartridge (Alcon) cartridge. The incision was measured at the end of surgery. Observations included surgical time (from commencement of sculpting to end of epinucleus removal), cumulative dissipated energy (CDE), wound burns, intraoperative complications, postoperative increase in mean central corneal thickness (CCT) at 1 day and 1 month, mean % decrease in endothelial cell density (ECD), absolute mean change in coefficient of variation (cv) 3 months, and uncorrected visual acuity (UCVA) at 1 day. Data were analyzed using a 1-sample t test with 95% confidence intervals (CIs).

RESULTS

The mean follow up was 3 months +/- 0.3 (SD). The mean incision size at the end of surgery was 2.3 +/- .09 mm; mean surgical time, 4.5 +/- 1.5 minutes; and mean CDE, 2.3 +/- 2.2 seconds. No wound burns or other intraoperative complications occurred. The postoperative CCT increased by a mean of 16 microm at 1 day (95% CI, 8-25; P = .66;) and by a mean of 3.14 microm at 1 month (95% CI, 2.26-4.05; P = .92). The ECD decreased by a mean of 5.8% (95% CI, 6.8-3.5; P = .82) and the mean coefficient of variation, by 3.3 (95% CI, 4.5-2.0; P = .65). At 1 day, the UCVA was 20/20 in 29% of cases, 20/20 to 20/40 in 58%, and 20/40 to 20/50 in 12%.

CONCLUSION

Microcoaxial phacoemulsification was safely and effectively performed, achieving consistent and satisfactory postoperative outcomes.

Mikroinzisionsintraokularlinse mit Plattenhaptik

BACKGROUND

Evaluation of rotational stability of a microincision intraocular lens with plate haptic design (*Acri. Smart 46S, *Acri.Tec AG) and its centering in the capsular bag after implantation.

MATERIAL AND METHOD

In a total of 43 eyes in 37 patients a foldable, spherical microincision cataract surgery (MICS) intraocular lens (IOL) with plate haptic design was implanted through a 1.4-mm microincision by means of an injector system. The IOL was marked prior to implantation to allow exact determination of its endocapsular position. After 1 1/2 years the best corrected visual acuity, refraction, centering and rotational stability of the IOL were determined.

RESULTS

No rotation or decentration was observed in any of the 42 eyes 12-19 months postoperatively. On the first postoperative day 1 IOL rotated in the counterclockwise direction by approx. 6 degrees as a result of flattening of the anterior chamber. Its position then remained stable. No unwanted complications occurred.

CONCLUSIONS

Conclusions: *Acri. Smart 46S is a safe, effective and stable IOL that can also be used as the basis of complex refractive optical systems, e.g. for correction of astigmatism.

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.

Innovations in phacoemulsification technology

PURPOSE OF REVIEW

A working knowledge of the principles guiding recent technologic upgrades in phacoemulsification units will help the surgeon to maximize clinical benefits from the latest machines.

RECENT FINDINGS

Reduced thermal energy combined with more efficient emulsification resulting from microfractionation of ultrasound energy, and improved chamber stability from automatic fluidic adjustments are achievable with the recent technological advances.

SUMMARY

Improved safety and efficiency can be achieved with the most current advances in phacoemulsification technology.