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Outcomes of coaxial microincision cataract surgery versus conventional coaxial cataract surgery
ARTICLE
Outcomes of coaxial microincision cataract surgery versus conventional coaxial cataract surgery Andre´ Alexandre Dosso, MD, Laura Cottet, Nathalie Dang Burgener, MD, Silvio Di Nardo, PhD
PURPOSE: To compare the outcomes of coaxial microincision cataract surgery (MICS) with those of conventional coaxial cataract surgery. SETTING: University Eye Clinic, Geneva, Switzerland. METHODS: In a prospective study, 50 eyes of 50 patients with nuclear or corticonuclear cataract (grades 2 to 4 on the Lens Opacities Classification System III) were randomly selected to have cataract extraction through a temporal clear corneal incision using 1 of 2 techniques: coaxial MICS (25 eyes) or conventional coaxial cataract surgery (25 eyes). Coaxial MICS was performed through a 1.6 mm incision and conventional coaxial cataract surgery, through a 2.8 mm incision. In all cases, a flexible hydrophobic acrylic intraocular lens (Lentis L-303, WaveLight GmbH) was implanted. Intraoperative parameters were ultrasound time, surgical time, and total volume of balanced salt solution used. The best corrected visual acuity, corneal thickness, and endothelial cell count were evaluated preoperatively and postoperatively. RESULTS: There were no relevant clinical differences between groups or perioperative complications in either group. The only statistically significant differences between the 2 groups were ultrasound time (P Z .0002) and surgical time (P Z .005). CONCLUSIONS: Coaxial microincision cataract surgery was a safe and effective technique. Although ultrasound and surgical time were significantly higher with coaxial MICS than with conventional coaxial cataract surgery, the postoperative results in the 2 techniques were comparable. J Cataract Refract Surg 2008; 34:284–288 Q 2008 ASCRS and ESCRS
Improvements in cataract surgery technique over the past decades have made it possible to decrease the size of the incision through which surgery is performed. This results in an improved prognosis for visual acuity, less risk for surgically induced
Accepted for publication September 30, 2007. From University Eye Clinic (Dosso, Cottet, Burgener), Geneva, and Oertli Instrumente AG (Nardo), Berneck, Switzerland. Dr. Di Nardo is an employee of Oertli Instrument. No other author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Andre´ Alexandre Dosso, University Eye Clinic, 22, rue Alcide Jentzer, 1211 Geneva 14, Switzerland. E-mail: [email protected].
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Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
astigmatism (SIA), a reduced incidence of postoperative inflammation, and shorter postoperative rehabilitation.1,2 Moreover, smaller wounds may heal more rapidly, with less risk for leakage and endophthalmitis.3 Conventional coaxial phacoemulsification requires corneal incisions ranging from 2.5 to 3.2 mm to accommodate infusion sleeves that are large enough to provide adequate inflow. Although these incisions are significantly smaller than those in earlier techniques, they are still large enough to carry risks, such as intraoperative anterior chamber instability, astigmatism induction, and postoperative endophthalmitis. The microincision cataract surgery (MICS) technique permits cataract removal through incisions ranging from 1.0 to 1.5 mm. In bimanual MICS, the instruments for anterior chamber infusion and phacoemulsification/aspiration are separate4; ultrasound 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.09.037
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power is provided by a sleeveless phaco tip used in the micropulse mode, and the infusion line is connected to an irrigating chopper. Notwithstanding the increasing success of MICS, scepticism remains. Perhaps this is related to the difficulty of using sleeveless tips and 2 hands and to the considerably altered fluidic conditions in the anterior chamber. Recently, we started performing coaxial MICS through 1.6 mm incisions, allowing us to use the same surgical approach as for conventional coaxial phacoemulsification. The aim of this study was to quantitatively compare surgical trauma, expressed by corneal parameters, after phacoemulsification by coaxial MICS and by conventional coaxial phacoemulsification. PATIENTS AND METHODS A prospective study comprised 50 eyes of 50 patients who had phacoemulsification between January 2007 and March 2007 at the University Eye Clinic of Geneva. The patients had nuclear or corticonuclear cataract of grade 2 to 4 according to the Lens Opacities Classification System III (LOCS III) scale.5 Exclusion criteria were corneal pathology, inflammatory eye disease, glaucoma, previous ocular surgery or trauma, and endothelial cell density less than 1500 cells/mm2. The patients were randomly assigned to have coaxial MICS or conventional coaxial phacoemulsification. Informed consent was obtained after both surgical techniques had been explained to the patient. In addition to a complete ocular examination, biometry for intraocular lens (IOL) power calculation (IOLMaster, Zeiss), corneal pachymetry (Visante OCT, Zeiss), and endothelial cell counts (Heidelberg Retina Tomograph II, Rostock Cornea Module, Heidelberg Engineering GmbH) were performed preoperatively and postoperatively at 1 week and 2 months. Corneal thickness was assessed in 4 areas (0 to 2.0 mm, 2.0 to 5.0 mm, 5.0 to 7.0 mm, and 7.0 to 10.0 mm), and the mean was calculated. Images of the endothelial cell layer were captured in the central cornea area, and all measures were the mean of 3 images. All cell counts were performed manually. Endothelial cell loss was expressed as a percentage of the preoperative cell density as follows: endothelial cell loss Z (preoperative postoperative)/ preoperative 100.
Table 1. Settings used with the OS3 surgery system. Parameter Pump Ultrasound power (%) Mode Aspiration flow (mL/min) Vacuum (mm Hg) Irrigation/aspiration (mm Hg)
Coaxial MICS
CCCS
Peristaltic 70 Continuous 22 300 300
Peristaltic 70 Continuous 22 150 300
CCCS Z conventional coaxial cataract surgery; MICS Z microincision cataract surgery
WaveLight GmbH) was implanted using a 1.8 mm Viscojet injector (Medicel) for coaxial MICS and a 2.0 mm Viscojet injector for the conventional coaxial surgery. In both groups, postoperative therapy included a topical combination of tobramycin and dexamethasone (TobraDex) 4 times a day for 2 weeks.
Coaxial Microincision Group A 1.6 mm clear corneal incision was made temporally with a precalibrated trapezoid knife (Figure 1). Two 0.8 mm paracenteses were created 180 degrees apart with a 20-gauge knife. The OVD was injected, and a continuous curvilinear capsulorhexis with a diameter of approximately 5.0 mm was created. After hydrodissection, phacoemulsification was performed with a 0.7 mm 30-degree-angled tip with a sleeve using a continuous ultrasound setting (Figure 2). The nucleus was grooved by the divide-and-conquer technique using a 20-gauge chopper. Irrigation/aspiration was performed bimanually using separate cannulas with
Surgical Technique All surgeries were performed by the same surgeon (A.D.). Before surgery, the pupils were dilated with tropicamide (Mydriaticum), phenylephrine hydrochloride 2.5%, and diclofenac sodium 0.1% (Voltare`ne). In all cases, topical anesthesia (cocaine 5%) was used. The same irrigating solution (balanced salt solution [BSS]) and ophthalmic viscosurgical device (OVD) (sodium hyaluronate 1% [Healon]) were used in both groups. The OS3 surgery system (Oertli Instruments) and the coaxial MICS phaco tip and sleeve from the same manufacturer were used for phacoemulsification. Surgical settings were identical in both groups (Table 1) except for a higher vacuum limit for coaxial MICS. In all eyes, the incision was made in the temporal clear cornea and a flexible hydrophobic acrylic IOL (Lentis L-303,
Figure 1. Coaxial microincision technique. The phaco tip with a sleeve is inserted through a 1.6 mm clear corneal incision created temporally with a precalibrated trapezoid knife.
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ultrasound setting. The nucleus was grooved by the stopand-chop technique using a 20-gauge chopper. Irrigation/ aspiration was performed bimanually using separate cannulas with diameters of 0.8 mm. The capsular bag was filled with OVD, and the IOL was inserted.
Intraoperative Parameters The mean phacoemulsification time, total surgical time (from first corneal incision to hydration of wounds), and total volume of BSS used (initial volume in infusion bottle minus residual BSS volume) were recorded.
Statistical Analysis Data are expressed as mean values G standard deviation. A 2-tailed Student t test was used for statistical comparisons between groups. A P value less than 0.05 was considered statistically significant. Figure 2. Coaxial microincision technique. Phacoemulsification is performed with a 0.7 mm 30-degree-angled probe with a sleeve and a 20-gauge chopper.
diameters of 0.8 mm. The capsular bag was filled with OVD, the incision was enlarged to 1.8 mm, and the IOL was inserted (Figure 3).
Conventional Coaxial Group A 2.8 mm clear corneal incision was made temporally with a precalibrated trapezoid knife. Two 0.8 mm paracentesis incisions were made 180 degrees apart with a 20-gauge knife, and capsulorhexis and hydrodissection were performed using the same technique as in the coaxial MICS group. Phacoemulsification was performed with a 1.12 mm 30 degree-angled tip with a sleeve using a continuous
RESULTS The mean age of the patients was 75 years (range 60 to 87 years; 68% women) in the coaxial MICS group and 75 years (range 60 to 89 years; 47% women) in the conventional surgery group. There were no statistically significant differences between the 2 groups in baseline best corrected visual acuity (mean in both groups 20/40). The estimated mean cataract grade (LOCS III) was 2.32 G 0.43 in the coaxial MICS group and 2.30 G 0.42 in the conventional surgery group; the difference between groups was not statistically significant (P Z .65). No intraoperative or postoperative complications occurred. Table 2 shows the results for the operative variables. The mean ultrasound time was statistically significantly higher in the coaxial MICS group than in the conventional surgery group (P!.0002). There were no statistically significant differences in mean irrigation volumes (P Z .12). The mean surgery time was significantly longer in the coaxial MICS group than in the conventional surgery group (P!.005). Table 3 shows the results of the statistical analysis of the preoperative and postoperative variables in both groups. No statistically significant differences between the 2 groups were observed. Table 2. Intraoperative parameters. Mean G SD Parameter Ultrasound time (sec) BSS volume (mL) Surgical time (mn)
Figure 3. Injection of a Lentis L-303 IOL through the microincision. Note the injector is not introduced in the eye but rather only in the external lips of the corneal incision.
Coaxial MICS
CCCS
P Value
49.6 G 19 122.1 G 37 13.09 G 2.3
24.4 G 7 104.3 G 16 11.1 G 1.8
.0002* .12 .005*
BSS Z balanced salt solution; CCCS Z conventional coaxial cataract surgery; MICS Z microincision cataract surgery *Statistically significant
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Table 3. Preoperative and postoperative parameters. Mean G SD Parameter Cataract grade (LOCS III) Postop endothelial cell loss (%) 1 wk 8 wk Endothelial cell density (cells/mm2) Preop Postop 1 wk Postop 8 wk Pachymetry (mm) Preop 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop 1 wk 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop 8 wk 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop BCVA 1 wk 8 wk
Coaxial MICS
CCCS
2.32 G 0.43 2.30 G 0.42
3.2 5.6
4.1 6.5
3266 G 668 3221 G 686 3162 G 633 3088 G 619 3044 G 638 3077 G 606
P Value .6
.7 .9
.8 .8 .9
526 G 38 547 G 38 584 G 40 629 G 43
531 G 38 555 G 37 595 G 39 640 G 46
.6 .5 .3 .4
546 G 45 570 G 47 611 G 50 661 G 48
548 G 43 560 G 54 621 G 49 682 G 52
.7 .6 .5 .2
532 G 19 565 G 33 602 G 36 659 G 36
545 G 41 568 G 41 614 G 46 669 G 56
.2 .7 .4 .5
0.86 G 0.1 0.95 G 0.1
0.84 G 0.1 0.94 G 0.08
.6 .8
BCVA Z best corrected visual acuity; CCCS Z conventional coaxial cataract surgery; LOCS Z Lens Opacities Classification System; MICS Z microincision cataract surgery
DISCUSSION The main evolution in cataract surgery during the past decades has been paralleled by a decrease in the size of the incision, with the potential benefits of reduced SIA, shorter recovery time, and less propensity for wound leakage. At present, 2 methods of phacoemulsification that use smaller incisions are available: bimanual MICS and coaxial MICS. Despite the advantages of MICS,6 as with any surgical technique, the method has disadvantages. Fluid leakage through the paracenteses can produce anterior chamber instability during phacoemulsification, infusion is limited by the smaller gauge instruments, and the relatively tight incisions, combined with exposure to the unprotected phaco tip, may predispose to increased wound trauma.6 The main advantage of coaxial MICS is that it uses the same methods as the conventional technique but with
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smaller incisions. As the surgeon does not need to change his or her technique, the learning curve is short. The only small difficulty encountered was the use of the forceps during capsulorhexis due to the smaller range of motion for maneuvering the instrument. Phacoemulsification performed through incisions as small as 1.6 mm and the use of a sleeved phaco tip of 0.7 mm diameter fully preserve anterior chamber stability and wound tightness. These observations were confirmed in a recent study, which showed that coaxial MICS and standard coaxial phacoemulsification induce less wound stress and wound morphology alteration leading to wound leakage than MICS.7 The main objective of our study was to compare the amount of surgical trauma caused by phacoemulsification by coaxial MICS and conventional coaxial cataract surgery. There were no significant differences between the techniques in postoperative visual acuity, endothelial cell loss, or corneal thickness. However, we observed that during coaxial MICS, irrigation turbulence and mechanical trauma by the phaco tip were less than with conventional phacoemulsification. This might suggest less overall intraoperative trauma in coaxial MICS. Therefore, we conclude that the 2 techniques offered highly satisfactory clinical results. The difference between the 2 techniques clinically was not relevant, and visual rehabilitation was quick and satisfactory in both groups. The only significant differences between the techniques were the surgery time and ultrasound time. Although the coaxial MICS technique involves statistically significantly longer phacoemulsification and surgery times than the conventional technique, this was not clinically relevant and did not affect endothelial cell loss or pachymetry. This may be because a phaco tip with a smaller tip area creates less acoustic power than a larger tip.8,9 It can be calculated that the acoustic power generated by the coaxial MICS tip used in this study was 20% of that of a conventional 19-gauge phaco tip (same ultrasound settings on the phaco machine). Thus, a longer phacoemulsification time does not imply that the total amount of energy created in the anterior chamber is increased as well. In conclusion, coaxial MICS is an effective and safe technique for cataract surgery. It offers the advantages of negligible to no wound leakage, good anterior chamber stability, and improved visibility during surgery in eyes with small pupils. REFERENCES 1. Linebarger EJ, Hardten DR, Shah GK, Lindstrom RL. Phacoemulsification and modern cataract surgery. Surv Ophthalmol 1999; 44:123–147 2. Dick HB, Schwenn O, Krummenauer F, et al. Inflammation after sclerocorneal versus clear corneal tunnel phacoemulsification. Ophthalmology 2000; 107:241–247
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3. Lundstro¨m M. Endophthalmitis and incision construction. Curr Opin Ophthalmol 2006; 17:68–71 4. Paul T, Braga-Mele R. Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol 2005; 16:2–7 5. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III; the Longitudinal Study of Cataract Study Group. Arch Ophthalmol 1993; 111:831–836 6. Weikert MP. Update on bimanual microincisional cataract surgery. Curr Opin Ophthalmol 2006; 17:62–67 7. Berdahl JP, DeStefeno JJ, Kim T. Corneal wound architecture and integrity after phacoemulsification; evaluation of coaxial, microincision coaxial, and microincision bimanual techniques. J Cataract Refract Surg 2007; 33:510–515 8. Schafer ME, Broadwin A. Acoustical characterization of ultrasonic surgical devices. Proceedings of the IEEE Ultrasonics Symposium. New York, NY, Institute of Electrical and Electronics Engineers, 1994; 1903–1906. Abstract available at: http://
ieeexplore.ieee.org/xpls/abs_all.jsp?arnumberZ401963. Accessed November 9, 2007 9. Schafer ME, Arbisser LB. Quantification of acoustic exposure during cataract surgery. Proceedings of the IEEE Ultrasonics Symposium, 2004. New York, NY, Institute of Electrical and Electronics Engineers, 2004; 1828–1831. Abstract available at: http:// ieeexplore.ieee.org/xpls/abs_all.jsp?arnumberZ1418184. Accessed November 9, 2007
First author: Andre´ Alexandre Dosso, MD University Eye Clinic, Geneva, Switzerland
J CATARACT REFRACT SURG - VOL 34, FEBRUARY 2008
Outcomes of coaxial microincision cataract surgery versus conventional coaxial cataract surgery Andre´ Alexandre Dosso, MD, Laura Cottet, Nathalie Dang Burgener, MD, Silvio Di Nardo, PhD
PURPOSE: To compare the outcomes of coaxial microincision cataract surgery (MICS) with those of conventional coaxial cataract surgery. SETTING: University Eye Clinic, Geneva, Switzerland. METHODS: In a prospective study, 50 eyes of 50 patients with nuclear or corticonuclear cataract (grades 2 to 4 on the Lens Opacities Classification System III) were randomly selected to have cataract extraction through a temporal clear corneal incision using 1 of 2 techniques: coaxial MICS (25 eyes) or conventional coaxial cataract surgery (25 eyes). Coaxial MICS was performed through a 1.6 mm incision and conventional coaxial cataract surgery, through a 2.8 mm incision. In all cases, a flexible hydrophobic acrylic intraocular lens (Lentis L-303, WaveLight GmbH) was implanted. Intraoperative parameters were ultrasound time, surgical time, and total volume of balanced salt solution used. The best corrected visual acuity, corneal thickness, and endothelial cell count were evaluated preoperatively and postoperatively. RESULTS: There were no relevant clinical differences between groups or perioperative complications in either group. The only statistically significant differences between the 2 groups were ultrasound time (P Z .0002) and surgical time (P Z .005). CONCLUSIONS: Coaxial microincision cataract surgery was a safe and effective technique. Although ultrasound and surgical time were significantly higher with coaxial MICS than with conventional coaxial cataract surgery, the postoperative results in the 2 techniques were comparable. J Cataract Refract Surg 2008; 34:284–288 Q 2008 ASCRS and ESCRS
Improvements in cataract surgery technique over the past decades have made it possible to decrease the size of the incision through which surgery is performed. This results in an improved prognosis for visual acuity, less risk for surgically induced
Accepted for publication September 30, 2007. From University Eye Clinic (Dosso, Cottet, Burgener), Geneva, and Oertli Instrumente AG (Nardo), Berneck, Switzerland. Dr. Di Nardo is an employee of Oertli Instrument. No other author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Andre´ Alexandre Dosso, University Eye Clinic, 22, rue Alcide Jentzer, 1211 Geneva 14, Switzerland. E-mail: [email protected].
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Q 2008 ASCRS and ESCRS Published by Elsevier Inc.
astigmatism (SIA), a reduced incidence of postoperative inflammation, and shorter postoperative rehabilitation.1,2 Moreover, smaller wounds may heal more rapidly, with less risk for leakage and endophthalmitis.3 Conventional coaxial phacoemulsification requires corneal incisions ranging from 2.5 to 3.2 mm to accommodate infusion sleeves that are large enough to provide adequate inflow. Although these incisions are significantly smaller than those in earlier techniques, they are still large enough to carry risks, such as intraoperative anterior chamber instability, astigmatism induction, and postoperative endophthalmitis. The microincision cataract surgery (MICS) technique permits cataract removal through incisions ranging from 1.0 to 1.5 mm. In bimanual MICS, the instruments for anterior chamber infusion and phacoemulsification/aspiration are separate4; ultrasound 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.09.037
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COAXIAL MICS VERSUS CONVENTIONAL COAXIAL CATARACT SURGERY
power is provided by a sleeveless phaco tip used in the micropulse mode, and the infusion line is connected to an irrigating chopper. Notwithstanding the increasing success of MICS, scepticism remains. Perhaps this is related to the difficulty of using sleeveless tips and 2 hands and to the considerably altered fluidic conditions in the anterior chamber. Recently, we started performing coaxial MICS through 1.6 mm incisions, allowing us to use the same surgical approach as for conventional coaxial phacoemulsification. The aim of this study was to quantitatively compare surgical trauma, expressed by corneal parameters, after phacoemulsification by coaxial MICS and by conventional coaxial phacoemulsification. PATIENTS AND METHODS A prospective study comprised 50 eyes of 50 patients who had phacoemulsification between January 2007 and March 2007 at the University Eye Clinic of Geneva. The patients had nuclear or corticonuclear cataract of grade 2 to 4 according to the Lens Opacities Classification System III (LOCS III) scale.5 Exclusion criteria were corneal pathology, inflammatory eye disease, glaucoma, previous ocular surgery or trauma, and endothelial cell density less than 1500 cells/mm2. The patients were randomly assigned to have coaxial MICS or conventional coaxial phacoemulsification. Informed consent was obtained after both surgical techniques had been explained to the patient. In addition to a complete ocular examination, biometry for intraocular lens (IOL) power calculation (IOLMaster, Zeiss), corneal pachymetry (Visante OCT, Zeiss), and endothelial cell counts (Heidelberg Retina Tomograph II, Rostock Cornea Module, Heidelberg Engineering GmbH) were performed preoperatively and postoperatively at 1 week and 2 months. Corneal thickness was assessed in 4 areas (0 to 2.0 mm, 2.0 to 5.0 mm, 5.0 to 7.0 mm, and 7.0 to 10.0 mm), and the mean was calculated. Images of the endothelial cell layer were captured in the central cornea area, and all measures were the mean of 3 images. All cell counts were performed manually. Endothelial cell loss was expressed as a percentage of the preoperative cell density as follows: endothelial cell loss Z (preoperative postoperative)/ preoperative 100.
Table 1. Settings used with the OS3 surgery system. Parameter Pump Ultrasound power (%) Mode Aspiration flow (mL/min) Vacuum (mm Hg) Irrigation/aspiration (mm Hg)
Coaxial MICS
CCCS
Peristaltic 70 Continuous 22 300 300
Peristaltic 70 Continuous 22 150 300
CCCS Z conventional coaxial cataract surgery; MICS Z microincision cataract surgery
WaveLight GmbH) was implanted using a 1.8 mm Viscojet injector (Medicel) for coaxial MICS and a 2.0 mm Viscojet injector for the conventional coaxial surgery. In both groups, postoperative therapy included a topical combination of tobramycin and dexamethasone (TobraDex) 4 times a day for 2 weeks.
Coaxial Microincision Group A 1.6 mm clear corneal incision was made temporally with a precalibrated trapezoid knife (Figure 1). Two 0.8 mm paracenteses were created 180 degrees apart with a 20-gauge knife. The OVD was injected, and a continuous curvilinear capsulorhexis with a diameter of approximately 5.0 mm was created. After hydrodissection, phacoemulsification was performed with a 0.7 mm 30-degree-angled tip with a sleeve using a continuous ultrasound setting (Figure 2). The nucleus was grooved by the divide-and-conquer technique using a 20-gauge chopper. Irrigation/aspiration was performed bimanually using separate cannulas with
Surgical Technique All surgeries were performed by the same surgeon (A.D.). Before surgery, the pupils were dilated with tropicamide (Mydriaticum), phenylephrine hydrochloride 2.5%, and diclofenac sodium 0.1% (Voltare`ne). In all cases, topical anesthesia (cocaine 5%) was used. The same irrigating solution (balanced salt solution [BSS]) and ophthalmic viscosurgical device (OVD) (sodium hyaluronate 1% [Healon]) were used in both groups. The OS3 surgery system (Oertli Instruments) and the coaxial MICS phaco tip and sleeve from the same manufacturer were used for phacoemulsification. Surgical settings were identical in both groups (Table 1) except for a higher vacuum limit for coaxial MICS. In all eyes, the incision was made in the temporal clear cornea and a flexible hydrophobic acrylic IOL (Lentis L-303,
Figure 1. Coaxial microincision technique. The phaco tip with a sleeve is inserted through a 1.6 mm clear corneal incision created temporally with a precalibrated trapezoid knife.
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COAXIAL MICS VERSUS CONVENTIONAL COAXIAL CATARACT SURGERY
ultrasound setting. The nucleus was grooved by the stopand-chop technique using a 20-gauge chopper. Irrigation/ aspiration was performed bimanually using separate cannulas with diameters of 0.8 mm. The capsular bag was filled with OVD, and the IOL was inserted.
Intraoperative Parameters The mean phacoemulsification time, total surgical time (from first corneal incision to hydration of wounds), and total volume of BSS used (initial volume in infusion bottle minus residual BSS volume) were recorded.
Statistical Analysis Data are expressed as mean values G standard deviation. A 2-tailed Student t test was used for statistical comparisons between groups. A P value less than 0.05 was considered statistically significant. Figure 2. Coaxial microincision technique. Phacoemulsification is performed with a 0.7 mm 30-degree-angled probe with a sleeve and a 20-gauge chopper.
diameters of 0.8 mm. The capsular bag was filled with OVD, the incision was enlarged to 1.8 mm, and the IOL was inserted (Figure 3).
Conventional Coaxial Group A 2.8 mm clear corneal incision was made temporally with a precalibrated trapezoid knife. Two 0.8 mm paracentesis incisions were made 180 degrees apart with a 20-gauge knife, and capsulorhexis and hydrodissection were performed using the same technique as in the coaxial MICS group. Phacoemulsification was performed with a 1.12 mm 30 degree-angled tip with a sleeve using a continuous
RESULTS The mean age of the patients was 75 years (range 60 to 87 years; 68% women) in the coaxial MICS group and 75 years (range 60 to 89 years; 47% women) in the conventional surgery group. There were no statistically significant differences between the 2 groups in baseline best corrected visual acuity (mean in both groups 20/40). The estimated mean cataract grade (LOCS III) was 2.32 G 0.43 in the coaxial MICS group and 2.30 G 0.42 in the conventional surgery group; the difference between groups was not statistically significant (P Z .65). No intraoperative or postoperative complications occurred. Table 2 shows the results for the operative variables. The mean ultrasound time was statistically significantly higher in the coaxial MICS group than in the conventional surgery group (P!.0002). There were no statistically significant differences in mean irrigation volumes (P Z .12). The mean surgery time was significantly longer in the coaxial MICS group than in the conventional surgery group (P!.005). Table 3 shows the results of the statistical analysis of the preoperative and postoperative variables in both groups. No statistically significant differences between the 2 groups were observed. Table 2. Intraoperative parameters. Mean G SD Parameter Ultrasound time (sec) BSS volume (mL) Surgical time (mn)
Figure 3. Injection of a Lentis L-303 IOL through the microincision. Note the injector is not introduced in the eye but rather only in the external lips of the corneal incision.
Coaxial MICS
CCCS
P Value
49.6 G 19 122.1 G 37 13.09 G 2.3
24.4 G 7 104.3 G 16 11.1 G 1.8
.0002* .12 .005*
BSS Z balanced salt solution; CCCS Z conventional coaxial cataract surgery; MICS Z microincision cataract surgery *Statistically significant
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COAXIAL MICS VERSUS CONVENTIONAL COAXIAL CATARACT SURGERY
Table 3. Preoperative and postoperative parameters. Mean G SD Parameter Cataract grade (LOCS III) Postop endothelial cell loss (%) 1 wk 8 wk Endothelial cell density (cells/mm2) Preop Postop 1 wk Postop 8 wk Pachymetry (mm) Preop 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop 1 wk 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop 8 wk 0.0–2.0 2.0–5.0 5.0–7.0 7.0–10.0 Postop BCVA 1 wk 8 wk
Coaxial MICS
CCCS
2.32 G 0.43 2.30 G 0.42
3.2 5.6
4.1 6.5
3266 G 668 3221 G 686 3162 G 633 3088 G 619 3044 G 638 3077 G 606
P Value .6
.7 .9
.8 .8 .9
526 G 38 547 G 38 584 G 40 629 G 43
531 G 38 555 G 37 595 G 39 640 G 46
.6 .5 .3 .4
546 G 45 570 G 47 611 G 50 661 G 48
548 G 43 560 G 54 621 G 49 682 G 52
.7 .6 .5 .2
532 G 19 565 G 33 602 G 36 659 G 36
545 G 41 568 G 41 614 G 46 669 G 56
.2 .7 .4 .5
0.86 G 0.1 0.95 G 0.1
0.84 G 0.1 0.94 G 0.08
.6 .8
BCVA Z best corrected visual acuity; CCCS Z conventional coaxial cataract surgery; LOCS Z Lens Opacities Classification System; MICS Z microincision cataract surgery
DISCUSSION The main evolution in cataract surgery during the past decades has been paralleled by a decrease in the size of the incision, with the potential benefits of reduced SIA, shorter recovery time, and less propensity for wound leakage. At present, 2 methods of phacoemulsification that use smaller incisions are available: bimanual MICS and coaxial MICS. Despite the advantages of MICS,6 as with any surgical technique, the method has disadvantages. Fluid leakage through the paracenteses can produce anterior chamber instability during phacoemulsification, infusion is limited by the smaller gauge instruments, and the relatively tight incisions, combined with exposure to the unprotected phaco tip, may predispose to increased wound trauma.6 The main advantage of coaxial MICS is that it uses the same methods as the conventional technique but with
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smaller incisions. As the surgeon does not need to change his or her technique, the learning curve is short. The only small difficulty encountered was the use of the forceps during capsulorhexis due to the smaller range of motion for maneuvering the instrument. Phacoemulsification performed through incisions as small as 1.6 mm and the use of a sleeved phaco tip of 0.7 mm diameter fully preserve anterior chamber stability and wound tightness. These observations were confirmed in a recent study, which showed that coaxial MICS and standard coaxial phacoemulsification induce less wound stress and wound morphology alteration leading to wound leakage than MICS.7 The main objective of our study was to compare the amount of surgical trauma caused by phacoemulsification by coaxial MICS and conventional coaxial cataract surgery. There were no significant differences between the techniques in postoperative visual acuity, endothelial cell loss, or corneal thickness. However, we observed that during coaxial MICS, irrigation turbulence and mechanical trauma by the phaco tip were less than with conventional phacoemulsification. This might suggest less overall intraoperative trauma in coaxial MICS. Therefore, we conclude that the 2 techniques offered highly satisfactory clinical results. The difference between the 2 techniques clinically was not relevant, and visual rehabilitation was quick and satisfactory in both groups. The only significant differences between the techniques were the surgery time and ultrasound time. Although the coaxial MICS technique involves statistically significantly longer phacoemulsification and surgery times than the conventional technique, this was not clinically relevant and did not affect endothelial cell loss or pachymetry. This may be because a phaco tip with a smaller tip area creates less acoustic power than a larger tip.8,9 It can be calculated that the acoustic power generated by the coaxial MICS tip used in this study was 20% of that of a conventional 19-gauge phaco tip (same ultrasound settings on the phaco machine). Thus, a longer phacoemulsification time does not imply that the total amount of energy created in the anterior chamber is increased as well. In conclusion, coaxial MICS is an effective and safe technique for cataract surgery. It offers the advantages of negligible to no wound leakage, good anterior chamber stability, and improved visibility during surgery in eyes with small pupils. REFERENCES 1. Linebarger EJ, Hardten DR, Shah GK, Lindstrom RL. Phacoemulsification and modern cataract surgery. Surv Ophthalmol 1999; 44:123–147 2. Dick HB, Schwenn O, Krummenauer F, et al. Inflammation after sclerocorneal versus clear corneal tunnel phacoemulsification. Ophthalmology 2000; 107:241–247
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COAXIAL MICS VERSUS CONVENTIONAL COAXIAL CATARACT SURGERY
3. Lundstro¨m M. Endophthalmitis and incision construction. Curr Opin Ophthalmol 2006; 17:68–71 4. Paul T, Braga-Mele R. Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol 2005; 16:2–7 5. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III; the Longitudinal Study of Cataract Study Group. Arch Ophthalmol 1993; 111:831–836 6. Weikert MP. Update on bimanual microincisional cataract surgery. Curr Opin Ophthalmol 2006; 17:62–67 7. Berdahl JP, DeStefeno JJ, Kim T. Corneal wound architecture and integrity after phacoemulsification; evaluation of coaxial, microincision coaxial, and microincision bimanual techniques. J Cataract Refract Surg 2007; 33:510–515 8. Schafer ME, Broadwin A. Acoustical characterization of ultrasonic surgical devices. Proceedings of the IEEE Ultrasonics Symposium. New York, NY, Institute of Electrical and Electronics Engineers, 1994; 1903–1906. Abstract available at: http://
ieeexplore.ieee.org/xpls/abs_all.jsp?arnumberZ401963. Accessed November 9, 2007 9. Schafer ME, Arbisser LB. Quantification of acoustic exposure during cataract surgery. Proceedings of the IEEE Ultrasonics Symposium, 2004. New York, NY, Institute of Electrical and Electronics Engineers, 2004; 1828–1831. Abstract available at: http:// ieeexplore.ieee.org/xpls/abs_all.jsp?arnumberZ1418184. Accessed November 9, 2007
First author: Andre´ Alexandre Dosso, MD University Eye Clinic, Geneva, Switzerland
J CATARACT REFRACT SURG - VOL 34, FEBRUARY 2008