- Email: [email protected]
Comparative study of coaxial phacoemulsification and microincision cataract surgery
ARTICLE
Comparative study of coaxial phacoemulsification and microincision cataract surgery One-year follow-up Armando Stefano Crema, MD, Aileen Walsh, MD, Yoshifumi Yamane, MD, Walton Nose´, MD
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 G 0.33 (SD) and 0.82 G 0.39 minutes, respectively. The mean US power was similar between groups (mean 10.1% G 3.76% and 10.0% G 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% G 6.10% in the coaxial phacoemulsification group and 4.45% G 5.06% in the MICS group and at 1 year, 6.00% G 6.72% and 8.82% G 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. J Cataract Refract Surg 2007; 33:1014–1018 Q 2007 ASCRS and ESCRS
Many of the advantages of phacoemulsification are related to small incisions. Small incisions reduce tissue damage and postoperative inflammation and pain. They are also safer and provide faster and more stable postoperative visual and physical rehabilitation. Microincision cataract surgery (MICS) is performed through incisions of 1.5 mm or smaller.1 In MICS, irrigation is separated from aspiration and 2 incisions ranging from 1.2 to 1.5 mm are made to receive the sleeveless phacoemulsification tip and the irrigating chopper.1–3 Corneal burns had been a concern, but this complication was shown to be uncommon in vitro4–6 and in vivo.7,8 There are, however, some limitations related to MICS such as lower irrigation and therefore lower aspiration settings9 and the need to enlarge the incision for intraocular lens (IOL) implantation.10 The amount 1014
Q 2007 ASCRS and ESCRS Published by Elsevier Inc.
of ultrasound (US) energy used and corneal endothelial cell loss are other concerns. The purpose of this study was to evaluate the amount of US energy used at surgery, postoperative best corrected visual acuity (BCVA), and corneal endothelial cell loss with MICS and compare the results with those obtained with coaxial phacoemulsification. PATIENTS AND METHODS Thirty patients (60 eyes) with bilateral cataract were included in the study. All eyes were graded at the slitlamp using the Lens Opacity Classification System III.11 Exclusion criteria were previous significant other ophthalmic disease and complications during cataract surgery or postoperatively. Patients had coaxial phacoemulsification in 1 eye and MICS in the fellow eye. The operative technique used in the first eye was randomly selected. All surgeries used 0886-3350/07/$dsee front matter doi:10.1016/j.jcrs.2007.02.035
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
topical anesthesia, the soft-shell technique11 (sodium hyaluronate 3%–chondroitin sulfate 4% with sodium hyaluronate 1% [DuoVisc]), a 4.0 to 5.0 mm continuous curvilinear capsulorhexis, vertical chop technique, and 6.0 mm hydrophobic acrylic IOL (AcrySof SN60AT, Alcon) implantation in the capsular bag with a C cartridge and a Monarch II injector. The same surgeon (A.S.C.), who had performed 50 MICS cases before this study, performed all the operations. In the coaxial phacoemulsification group, a 0.8 mm sideport incision and 2.8 mm temporal clear corneal incision were created. In the MICS group, 2, 1.2 mm clear corneal incisions were created and the temporal incision was enlarged to 2.8 mm for IOL implantation. The Legacy 20000 unit (Alcon) was used in all patients. In the coaxial phacoemulsification group, the Aspiration Bypass System (ABS) was used with a ABS/straight, 30-degree, 1.1 mm flared tip; aspiration was 500 mm Hg/60 cc per minute and irrigation, at 110 cm. In the MICS group, the ABS with a straight, 30-degree microtip was used; aspiration was 350 mm Hg/35 cc per minute and irrigation, at 110 cm. A Crema/Nagahara irrigating chopper (Duet System, Micro Surgical Technology Inc.) was used in the MICS group. Measurements included US time and mean US power used during phacoemulsification, logMAR BCVA preoperatively and postoperatively at 2, 15, 30, and 90 days, and 1 year. Central corneal endothelial count (PRO CEM-4, Alcon) was performed preoperatively and postoperatively at 90 days and 1 year; a standard rectangle (2.0 mm 1.0 mm) was used. The mean of 3 images was used for cell density measurement. Endothelial cell loss was calculated as follows: Endothelial cell loss % Z (preoperative cell count – postoperative cell count) 100/preoperative cell count. The results were evaluated using paired t tests with SPSS statistical analysis software (version 11.0, SPSS Inc.). A P value less than 0.05 was considered significant. Four patients could not complete the 1-year follow-up; thus, the 1-year postoperative results are for 26 patients (52 eyes).
RESULTS
1015
classified as grade II, 16 (23.33%) as grade III, and 10 (16.66%) as grade I. Cataracts were classified as grade I in 6 eyes (20%) in the coaxial phacoemulsification group and 5 eyes (16.66%) in the MICS group; as grade II in 16 (53.33%) and 18 (60%), respectively; and as grade III in 8 (26.66%) and 7 (23.33%), respectively. The total US time during surgery was significantly lower in the coaxial phacoemulsification group (mean 0.50 G 0.33 minutes) than in the MICS group (mean 0.82 G 0.39 minutes) (P!.0001); however, there was no difference in mean US power used between the 2 groups (mean 10.1% G 3.76% and 10.0% G 4.0%, respectively) (PO.05). The frequency distribution showed logMAR BCVA was 0.3 or better in 80% of eyes in the coaxial phacoemulsification group and 70% in the MICS group at 24 hours and in all eyes in both group from 15 days to the last follow-up at 1 year. There was no difference in BCVA between groups at any measurement (PO.05). The means in the coaxial phacoemulsification group and MICS group were, respectively, as follows: 0.5500 and 0.4847 preoperatively, 0.2353 and 0.2113 at 24 hours, 0.0760 and 0.0573 at 15 days, 0.0440 and 0.0347 at 30 days, 0.0413 and 0.0347 at 90 days, and 0.0240 and 0.0160 at 1 year. The mean corneal endothelial cell counts in the coaxial phacoemulsification group and MICS group were, respectively, as follows: 2473.33 cells/mm2 and 2516.67 cells/mm2 preoperatively, 2353.33 cells/mm2 and 2400 cells/mm2 at 90 days, and 2304 cells/mm2 and 2280 cells/mm2 at 1 year; the difference between the preoperative and 90-day and 1-year postoperative values were significantly different in each group. The preoperative and 90-day and 1-year postoperative results were not significantly different between groups (PO.05) (Figure 1).
The mean age of 11 men (37%) and 19 women (63%) was 69.5 years G 11.1 (SD) (range 39 to 90 years; median 71.5 years). Thirty-four cataracts (66%) were
Accepted for publication February 5, 2007. From the Departments of Ophthalmology (Crema, Walsh, Yamane), Gama Filho University, Rio de Janeiro, and Paulista School of Medicine–UNIFESP (Crema, Nose´), Sa˜o Paulo, Brazil. No author has a financial or proprietary interest in any material or method mentioned. Presented in part at the XXIII Congress of the European Society of Cataract & Refractive Surgeons, Lisbon, Portugal, September 2005. Corresponding author: Armando Stefano Crema, MD, Rua Vinicius de Moraes 179, Rio de Janeiro, Brazil. E-mail: acrema@openlink. com.br.
Figure 1. Corneal endothelial cell count (Group 1 Z coaxial phacoemulsification; Group 2 Z MICS).
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
1016
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
The mean corneal endothelial cell loss in the coaxial phacoemulsification group and MICS group was, respectively, as follows: 4.66% G 6.10% and 4.45% G 5.06% at 90 days and 6.00% G 6.72% and 8.82% G 7.39% at 1 year. There was a significant difference between the 2 groups only at 1 year (P!.01) (Figure 2).
DISCUSSION We included 30 patients with bilateral cataract whose ages ranged from 39 to 90 years; because 1 eye of each patient with bilateral cataract was selected for each technique, the groups were very homogeneous. Nuclear hardness is an important factor when evaluating US use during phacoemulsification. We selected cataracts from grades I to III,11 and although there could have been a difference in the hardness of the cataract between the eyes of the same patient, the cataract grades were similar in both groups. We always operated on the eye with the worse BCVA first, which generally had a harder nucleus. However, we randomly selected the technique used in the first eye to have surgery; 18 first eyes had coaxial phacoemulsification and 12, MICS. The heat generated during phacoemulsification is proportional to the time US is on and to the length of the anteroposterior movement of the phaco tip (percentage of US)12; we used 5% to 30% panel US burst (90 ms) for chopping the nucleus and 60% linear pulses (15/second) for aspiration/emulsification of the pieces. The total US time was higher in the MICS group (0.82) than in the coaxial group (0.50); these results are not in agreement with other those in other studies13,14 and could be explained by the surgeon having less experience with the technique, by the
Figure 2. Corneal endothelial cell loss (Group 1 Z coaxial phacoemulsification; Group 2 Z MICS).
peristaltic pump of the Legacy (that is not ideal for MICS), and by the lower aspiration settings used in MICS. The mean US power was similar in the 2 groups, 10.1% G 3.76% in the coaxial phacoemulsification group and 10.0% G 4.0% in the MICS group. Good, fast, and stable visual rehabilitation is the goal of cataract surgery, and BCVA is one of the best parameters to evaluate the quality and efficiency of a surgical technique. The 24-hour BCVA was 0.3 or better in 80% in the coaxial phacoemulsification group and 70% in the MICS group. From 15 days to 1 year, all patients had a BCVA of 0.3 or better, showing that both techniques are efficient. Because the incisions in MICS are small and tight, they can be deformed at the end of surgery and some surgeons prefer to create a third incision for IOL implantation15 to ensure a good self-sealing wound. We enlarged the temporal clear corneal incision from 1.20 mm to 2.75 mm, in all 30 eyes in the MICS group, all incisions maintained their self-sealing ability. Central endothelial cell counts generally do not represent the entire cornea,16 especially after cataract surgery, after which the loss would always be greater near the incision.17 Thus, the endothelial cell population would be lower near the incision. Corneal endothelial cells take some time to migrate to this area; according to the literature, this period varies from 3 to 6 months to 1 year,18 2 years, and 10 years.16 It is also estimated that each year, between 0.5% and 0.8% of cells are lost due to physiological aging and that this rate is significantly higher 2 years after surgery (0.09% per year).17 Other authors estimate that 10 years after surgery, central endothelial cell loss continues at a rate of 2.5% per year.16 In our study, we measured central endothelial cell loss postoperatively at 3 months and 1 year. When evaluating the central endothelial cell count, especially without morphological analysis, bias can occur, generally because of the difficulty in repeating the same area evaluated in subsequent examinations and because of the larger or smaller amount of cells evaluated. We always used a standard rectangle (2.0 mm 1.0 mm) for the examination, counting all the cells inside it and all that touched the left and superior border. All measures were the mean of 3 different images. Although the central endothelial cell count showed no difference preoperatively or at 90 days and 1 year within the groups and the central endothelial cell count showed no difference at 90 days between groups, there was more central endothelial cell loss at 1 year with MICS. In uneventful surgery, endothelial cell loss is mainly related to the US time, amount of irrigation solutions, surgery time, and chattering of nuclear pieces
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
during phacoemulsification.19–21 In this study, we did not correlate the US time with endothelial cell loss; however, the results showed greater loss and more US energy in the MICS group than in the coaxial phacoemulsification group. Our results are similar to those in the literature evaluating endothelial cell counts at 3 months, with no differences between groups.13,14,22 However, in our study, the MICS group had more central cell loss at the 1-year follow-up; this difference could be because the surgeon was less experienced with the technique. Today, there is a clear trend toward smaller incisions and discussion that because of the small learning curve, better fluidics, same instrumentation, and same IOL inserted through a 2.0 mm incision, coaxial microphacoemulsification is the ideal surgery technique. Other authors use MICS as their routine phacoemulsification technique, especially because of the small amount of liquid and turbulence and because irrigation can be used as an instrument during surgery.3 Also, excellent outcomes are related to different IOLs for MICS,23–27 and IOLs that can be inserted through incisions smaller than 1.0 mm will probably soon be on the market.10 Although our results showed more central endothelial cell loss at 1 year with MICS than with coaxial phacoemulsification, we believe MICS is a safe and reliable technique, not only because there was no difference in the visual outcomes between the groups but also because the central endothelial cell loss was within the acceptable and safe rate cited in the literature with coaxial phacoemulsification.28–30 In conclusion, MICS required more US time than coaxial phacoemulsification; however, the mean US power was the same in the 2 groups. The BCVA was also similar in between the groups. There was more central endothelial cell loss in the MICS group than in the coaxial phacoemulsification group at the 1year follow-up. REFERENCES 1. Alio JL. What does MICS require? The transition to microincisional surgery. In: Alio JL, Rodriguez-Prats JL, Galal A, eds, MICS: Micro-Incision Cataract Surgery. El Dorado, Republic of Panama, Highlights of Ophthalmology International, 2004; 1–4 2. Agarwal A, Agarwal A, Agarwal S, et al. Phakonit: phacoemulsification through a 0.9 mm corneal incision. J Cataract Refract Surg 2001; 27:1548–1552 3. Olson RJ. Microphaco chop. Rationale and technique. In: Chang DF, ed, Phaco Chop; Mastering Techniques, Optimizing Technology, and Avoiding Complications. Thorofare, NJ, Slack, 2004; 227–237 4. Tsuneoka H, Shiba T, Takahashi Y. Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refract Surg 2001; 27:934–940 5. Soscia W, Howard JG, Olson RJ. Bimanual phacoemulsification through 2 stab incisions; a wound-temperature study. J Cataract Refract Surg 2002; 28:1039–1043
1017
6. Soscia W, Howard JG, Olson RJ. Microphacoemulsification with WhiteStar; a wound-temperature study. J Cataract Refract Surg 2002; 28:1044–1046 7. Tsuneoka H, Shiba T, Takahashi Y. Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results. J Cataract Refract Surg 2002; 28:82–86 8. Donnenfeld ED, Olson RJ, Solomon R, et al. Efficacy and woundtemperature gradient of WhiteStar phacoemulsification through a 1.2 mm incision. J Cataract Refract Surg 2003; 29:1097–1100 9. Chang DF. Bimanual phaco chop. Fluidic strategies. In: Chang DF, ed, Phaco Chop; Mastering Techniques, Optimizing Technology, and Avoiding Complications. Thorofare, NJ, Slack, 2004; 239–250 10. Paul T, Braga-Mele R. Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol 2005; 16:2–7 11. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III; the Longitudinal Study of Cataract Group. Arch Ophthalmol 1993; 111:831–836 12. Bissen-Miyajima H, Shimmura S, Tsubota K. Thermal effect on corneal incisions with different phacoemulsification ultrasonic tips. J Cataract Refract Surg 1999; 25:60–64 13. Alio´ J, Rodrı´guez-Prats JL, Galal A, Ramzy M. Outcomes of microincision cataract surgery versus coaxial phacoemulsification. Ophthalmology 2005; 112:1997–2003 14. Kurz S, Krummenauer F, Gabriel P, et al. Biaxial microincision versus coaxial small-incision clear cornea cataract surgery. Ophthalmology 2006; 113:1818–1826 15. Chang DF. 400 mm Hg high-vacuum bimanual phaco attainable with the Staar Cruise Control device [letter]. J Cataract Refract Surg 2004; 30:932–933 16. Bourne WM, Nelson LR, Hodge DO. Continued endothelial cell loss ten years after lens implantation. Ophthalmology 1994; 101:1014–1022; discussion by A Sugar, 1022–1023 17. Dick HB, Kohnen T, Jacobi FK, Jacobi KW. Long-term endothelial cell loss following phacoemulsification through temporal clear corneal incision. J Cataract Refract Surg 1996; 22:63–71 _ 18. Lesiewska-Junk H, Ka1uzny J, Malukiewicz-Wisniewska G. Long-term evaluation of endothelial cell loss after phacoemulsification. Eur J Ophthalmol 2002; 12:30–33 19. Hayashi K, Hayashi H, Nakao F, Hayashi F. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22:1079–1084 20. Walkow T, Anders N, Klebe S. Endothelial cell loss after phacoemulsification: relation to preoperative and intraoperative parameters. J. Cataract Refract Surg 2000; 26:727–732 21. Mencucci R, Ponchietti C, Virgili G, et al. Corneal endothelial damage after cataract surgery: microincision versus standard technique. J Cataract Refract Surg 2006; 32:1351–1354 22. Dogru M, Honda R, Omoto M, et al. Early visual results with the rollable ThinOptX intraocular lens. J Cataract Refract Surg 2004; 30:558–565 23. Pandey SK, Werner L, Agarwal A, et al. Phakonit: cataract removal through a sub-1.0 mm incision and implantation of the ThinOptX rollable intraocular lens. J Cataract Refract Surg 2002; 28:1710–1718 24. Agarwal A, Agarwal S, Agarwal A. Phakonit with an AcriTec IOL. J Cataract Refract Surg 2003; 29:854–855 25. Tsuneoka H, Hayama A, Takahama M. Ultrasmall-incision bimanual phacoemulsification and AcrySof SA30AL implantation through a 2.2 mm incision. J Cataract Refract Surg 2003; 29:1070–1076 26. Alio´ JL, Rodriguez-Prats JL, Vianello A, et al. Visual outcome of microincision cataract surgery with implantation of an Acri. Smart lens. J Cataract Refract Surg 2005; 31:1549–1556
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
1018
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
27. Alio´ JL, Schimchak P, Monte´s-Mico´ R, Galal A. Retinal image quality after microincision intraocular lens implantation. J Cataract Refract Surg 2005; 31:1557–1560 28. Bourne RRA, Minassian DC, Dart JKG, et al. Effect of cataract surgery on the corneal endothelium; modern phacoemulsification compared with extracapsular cataract surgery. Ophthalmology 2005; 111:679–685 29. Poyales-Galan F, Pirazzoli G. Clinical evaluation of endothelial cell decrease with visThesia in phacoemulsification surgery. J Cataract Refract Surg 2005; 31:2157–2161 30. Pereira ACA, Porfı´rio F Jr, Freitas LL, Belfort R Jr. Ultrasound energy and endothelial cell loss with stop-and-chop and nuclear
preslice phacoemulsification. J Cataract Refract Surg 2006; 32:1661–1666
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
First author: Armando Stefano Crema, MD Department of Ophthalmology, Gama Filho University, Rio de Janeiro, and Paulista School of Medicine–UNIFESP, Sa˜o Paulo, Brazil
Comparative study of coaxial phacoemulsification and microincision cataract surgery One-year follow-up Armando Stefano Crema, MD, Aileen Walsh, MD, Yoshifumi Yamane, MD, Walton Nose´, MD
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 G 0.33 (SD) and 0.82 G 0.39 minutes, respectively. The mean US power was similar between groups (mean 10.1% G 3.76% and 10.0% G 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% G 6.10% in the coaxial phacoemulsification group and 4.45% G 5.06% in the MICS group and at 1 year, 6.00% G 6.72% and 8.82% G 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. J Cataract Refract Surg 2007; 33:1014–1018 Q 2007 ASCRS and ESCRS
Many of the advantages of phacoemulsification are related to small incisions. Small incisions reduce tissue damage and postoperative inflammation and pain. They are also safer and provide faster and more stable postoperative visual and physical rehabilitation. Microincision cataract surgery (MICS) is performed through incisions of 1.5 mm or smaller.1 In MICS, irrigation is separated from aspiration and 2 incisions ranging from 1.2 to 1.5 mm are made to receive the sleeveless phacoemulsification tip and the irrigating chopper.1–3 Corneal burns had been a concern, but this complication was shown to be uncommon in vitro4–6 and in vivo.7,8 There are, however, some limitations related to MICS such as lower irrigation and therefore lower aspiration settings9 and the need to enlarge the incision for intraocular lens (IOL) implantation.10 The amount 1014
Q 2007 ASCRS and ESCRS Published by Elsevier Inc.
of ultrasound (US) energy used and corneal endothelial cell loss are other concerns. The purpose of this study was to evaluate the amount of US energy used at surgery, postoperative best corrected visual acuity (BCVA), and corneal endothelial cell loss with MICS and compare the results with those obtained with coaxial phacoemulsification. PATIENTS AND METHODS Thirty patients (60 eyes) with bilateral cataract were included in the study. All eyes were graded at the slitlamp using the Lens Opacity Classification System III.11 Exclusion criteria were previous significant other ophthalmic disease and complications during cataract surgery or postoperatively. Patients had coaxial phacoemulsification in 1 eye and MICS in the fellow eye. The operative technique used in the first eye was randomly selected. All surgeries used 0886-3350/07/$dsee front matter doi:10.1016/j.jcrs.2007.02.035
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
topical anesthesia, the soft-shell technique11 (sodium hyaluronate 3%–chondroitin sulfate 4% with sodium hyaluronate 1% [DuoVisc]), a 4.0 to 5.0 mm continuous curvilinear capsulorhexis, vertical chop technique, and 6.0 mm hydrophobic acrylic IOL (AcrySof SN60AT, Alcon) implantation in the capsular bag with a C cartridge and a Monarch II injector. The same surgeon (A.S.C.), who had performed 50 MICS cases before this study, performed all the operations. In the coaxial phacoemulsification group, a 0.8 mm sideport incision and 2.8 mm temporal clear corneal incision were created. In the MICS group, 2, 1.2 mm clear corneal incisions were created and the temporal incision was enlarged to 2.8 mm for IOL implantation. The Legacy 20000 unit (Alcon) was used in all patients. In the coaxial phacoemulsification group, the Aspiration Bypass System (ABS) was used with a ABS/straight, 30-degree, 1.1 mm flared tip; aspiration was 500 mm Hg/60 cc per minute and irrigation, at 110 cm. In the MICS group, the ABS with a straight, 30-degree microtip was used; aspiration was 350 mm Hg/35 cc per minute and irrigation, at 110 cm. A Crema/Nagahara irrigating chopper (Duet System, Micro Surgical Technology Inc.) was used in the MICS group. Measurements included US time and mean US power used during phacoemulsification, logMAR BCVA preoperatively and postoperatively at 2, 15, 30, and 90 days, and 1 year. Central corneal endothelial count (PRO CEM-4, Alcon) was performed preoperatively and postoperatively at 90 days and 1 year; a standard rectangle (2.0 mm 1.0 mm) was used. The mean of 3 images was used for cell density measurement. Endothelial cell loss was calculated as follows: Endothelial cell loss % Z (preoperative cell count – postoperative cell count) 100/preoperative cell count. The results were evaluated using paired t tests with SPSS statistical analysis software (version 11.0, SPSS Inc.). A P value less than 0.05 was considered significant. Four patients could not complete the 1-year follow-up; thus, the 1-year postoperative results are for 26 patients (52 eyes).
RESULTS
1015
classified as grade II, 16 (23.33%) as grade III, and 10 (16.66%) as grade I. Cataracts were classified as grade I in 6 eyes (20%) in the coaxial phacoemulsification group and 5 eyes (16.66%) in the MICS group; as grade II in 16 (53.33%) and 18 (60%), respectively; and as grade III in 8 (26.66%) and 7 (23.33%), respectively. The total US time during surgery was significantly lower in the coaxial phacoemulsification group (mean 0.50 G 0.33 minutes) than in the MICS group (mean 0.82 G 0.39 minutes) (P!.0001); however, there was no difference in mean US power used between the 2 groups (mean 10.1% G 3.76% and 10.0% G 4.0%, respectively) (PO.05). The frequency distribution showed logMAR BCVA was 0.3 or better in 80% of eyes in the coaxial phacoemulsification group and 70% in the MICS group at 24 hours and in all eyes in both group from 15 days to the last follow-up at 1 year. There was no difference in BCVA between groups at any measurement (PO.05). The means in the coaxial phacoemulsification group and MICS group were, respectively, as follows: 0.5500 and 0.4847 preoperatively, 0.2353 and 0.2113 at 24 hours, 0.0760 and 0.0573 at 15 days, 0.0440 and 0.0347 at 30 days, 0.0413 and 0.0347 at 90 days, and 0.0240 and 0.0160 at 1 year. The mean corneal endothelial cell counts in the coaxial phacoemulsification group and MICS group were, respectively, as follows: 2473.33 cells/mm2 and 2516.67 cells/mm2 preoperatively, 2353.33 cells/mm2 and 2400 cells/mm2 at 90 days, and 2304 cells/mm2 and 2280 cells/mm2 at 1 year; the difference between the preoperative and 90-day and 1-year postoperative values were significantly different in each group. The preoperative and 90-day and 1-year postoperative results were not significantly different between groups (PO.05) (Figure 1).
The mean age of 11 men (37%) and 19 women (63%) was 69.5 years G 11.1 (SD) (range 39 to 90 years; median 71.5 years). Thirty-four cataracts (66%) were
Accepted for publication February 5, 2007. From the Departments of Ophthalmology (Crema, Walsh, Yamane), Gama Filho University, Rio de Janeiro, and Paulista School of Medicine–UNIFESP (Crema, Nose´), Sa˜o Paulo, Brazil. No author has a financial or proprietary interest in any material or method mentioned. Presented in part at the XXIII Congress of the European Society of Cataract & Refractive Surgeons, Lisbon, Portugal, September 2005. Corresponding author: Armando Stefano Crema, MD, Rua Vinicius de Moraes 179, Rio de Janeiro, Brazil. E-mail: acrema@openlink. com.br.
Figure 1. Corneal endothelial cell count (Group 1 Z coaxial phacoemulsification; Group 2 Z MICS).
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
1016
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
The mean corneal endothelial cell loss in the coaxial phacoemulsification group and MICS group was, respectively, as follows: 4.66% G 6.10% and 4.45% G 5.06% at 90 days and 6.00% G 6.72% and 8.82% G 7.39% at 1 year. There was a significant difference between the 2 groups only at 1 year (P!.01) (Figure 2).
DISCUSSION We included 30 patients with bilateral cataract whose ages ranged from 39 to 90 years; because 1 eye of each patient with bilateral cataract was selected for each technique, the groups were very homogeneous. Nuclear hardness is an important factor when evaluating US use during phacoemulsification. We selected cataracts from grades I to III,11 and although there could have been a difference in the hardness of the cataract between the eyes of the same patient, the cataract grades were similar in both groups. We always operated on the eye with the worse BCVA first, which generally had a harder nucleus. However, we randomly selected the technique used in the first eye to have surgery; 18 first eyes had coaxial phacoemulsification and 12, MICS. The heat generated during phacoemulsification is proportional to the time US is on and to the length of the anteroposterior movement of the phaco tip (percentage of US)12; we used 5% to 30% panel US burst (90 ms) for chopping the nucleus and 60% linear pulses (15/second) for aspiration/emulsification of the pieces. The total US time was higher in the MICS group (0.82) than in the coaxial group (0.50); these results are not in agreement with other those in other studies13,14 and could be explained by the surgeon having less experience with the technique, by the
Figure 2. Corneal endothelial cell loss (Group 1 Z coaxial phacoemulsification; Group 2 Z MICS).
peristaltic pump of the Legacy (that is not ideal for MICS), and by the lower aspiration settings used in MICS. The mean US power was similar in the 2 groups, 10.1% G 3.76% in the coaxial phacoemulsification group and 10.0% G 4.0% in the MICS group. Good, fast, and stable visual rehabilitation is the goal of cataract surgery, and BCVA is one of the best parameters to evaluate the quality and efficiency of a surgical technique. The 24-hour BCVA was 0.3 or better in 80% in the coaxial phacoemulsification group and 70% in the MICS group. From 15 days to 1 year, all patients had a BCVA of 0.3 or better, showing that both techniques are efficient. Because the incisions in MICS are small and tight, they can be deformed at the end of surgery and some surgeons prefer to create a third incision for IOL implantation15 to ensure a good self-sealing wound. We enlarged the temporal clear corneal incision from 1.20 mm to 2.75 mm, in all 30 eyes in the MICS group, all incisions maintained their self-sealing ability. Central endothelial cell counts generally do not represent the entire cornea,16 especially after cataract surgery, after which the loss would always be greater near the incision.17 Thus, the endothelial cell population would be lower near the incision. Corneal endothelial cells take some time to migrate to this area; according to the literature, this period varies from 3 to 6 months to 1 year,18 2 years, and 10 years.16 It is also estimated that each year, between 0.5% and 0.8% of cells are lost due to physiological aging and that this rate is significantly higher 2 years after surgery (0.09% per year).17 Other authors estimate that 10 years after surgery, central endothelial cell loss continues at a rate of 2.5% per year.16 In our study, we measured central endothelial cell loss postoperatively at 3 months and 1 year. When evaluating the central endothelial cell count, especially without morphological analysis, bias can occur, generally because of the difficulty in repeating the same area evaluated in subsequent examinations and because of the larger or smaller amount of cells evaluated. We always used a standard rectangle (2.0 mm 1.0 mm) for the examination, counting all the cells inside it and all that touched the left and superior border. All measures were the mean of 3 different images. Although the central endothelial cell count showed no difference preoperatively or at 90 days and 1 year within the groups and the central endothelial cell count showed no difference at 90 days between groups, there was more central endothelial cell loss at 1 year with MICS. In uneventful surgery, endothelial cell loss is mainly related to the US time, amount of irrigation solutions, surgery time, and chattering of nuclear pieces
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
during phacoemulsification.19–21 In this study, we did not correlate the US time with endothelial cell loss; however, the results showed greater loss and more US energy in the MICS group than in the coaxial phacoemulsification group. Our results are similar to those in the literature evaluating endothelial cell counts at 3 months, with no differences between groups.13,14,22 However, in our study, the MICS group had more central cell loss at the 1-year follow-up; this difference could be because the surgeon was less experienced with the technique. Today, there is a clear trend toward smaller incisions and discussion that because of the small learning curve, better fluidics, same instrumentation, and same IOL inserted through a 2.0 mm incision, coaxial microphacoemulsification is the ideal surgery technique. Other authors use MICS as their routine phacoemulsification technique, especially because of the small amount of liquid and turbulence and because irrigation can be used as an instrument during surgery.3 Also, excellent outcomes are related to different IOLs for MICS,23–27 and IOLs that can be inserted through incisions smaller than 1.0 mm will probably soon be on the market.10 Although our results showed more central endothelial cell loss at 1 year with MICS than with coaxial phacoemulsification, we believe MICS is a safe and reliable technique, not only because there was no difference in the visual outcomes between the groups but also because the central endothelial cell loss was within the acceptable and safe rate cited in the literature with coaxial phacoemulsification.28–30 In conclusion, MICS required more US time than coaxial phacoemulsification; however, the mean US power was the same in the 2 groups. The BCVA was also similar in between the groups. There was more central endothelial cell loss in the MICS group than in the coaxial phacoemulsification group at the 1year follow-up. REFERENCES 1. Alio JL. What does MICS require? The transition to microincisional surgery. In: Alio JL, Rodriguez-Prats JL, Galal A, eds, MICS: Micro-Incision Cataract Surgery. El Dorado, Republic of Panama, Highlights of Ophthalmology International, 2004; 1–4 2. Agarwal A, Agarwal A, Agarwal S, et al. Phakonit: phacoemulsification through a 0.9 mm corneal incision. J Cataract Refract Surg 2001; 27:1548–1552 3. Olson RJ. Microphaco chop. Rationale and technique. In: Chang DF, ed, Phaco Chop; Mastering Techniques, Optimizing Technology, and Avoiding Complications. Thorofare, NJ, Slack, 2004; 227–237 4. Tsuneoka H, Shiba T, Takahashi Y. Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refract Surg 2001; 27:934–940 5. Soscia W, Howard JG, Olson RJ. Bimanual phacoemulsification through 2 stab incisions; a wound-temperature study. J Cataract Refract Surg 2002; 28:1039–1043
1017
6. Soscia W, Howard JG, Olson RJ. Microphacoemulsification with WhiteStar; a wound-temperature study. J Cataract Refract Surg 2002; 28:1044–1046 7. Tsuneoka H, Shiba T, Takahashi Y. Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results. J Cataract Refract Surg 2002; 28:82–86 8. Donnenfeld ED, Olson RJ, Solomon R, et al. Efficacy and woundtemperature gradient of WhiteStar phacoemulsification through a 1.2 mm incision. J Cataract Refract Surg 2003; 29:1097–1100 9. Chang DF. Bimanual phaco chop. Fluidic strategies. In: Chang DF, ed, Phaco Chop; Mastering Techniques, Optimizing Technology, and Avoiding Complications. Thorofare, NJ, Slack, 2004; 239–250 10. Paul T, Braga-Mele R. Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol 2005; 16:2–7 11. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III; the Longitudinal Study of Cataract Group. Arch Ophthalmol 1993; 111:831–836 12. Bissen-Miyajima H, Shimmura S, Tsubota K. Thermal effect on corneal incisions with different phacoemulsification ultrasonic tips. J Cataract Refract Surg 1999; 25:60–64 13. Alio´ J, Rodrı´guez-Prats JL, Galal A, Ramzy M. Outcomes of microincision cataract surgery versus coaxial phacoemulsification. Ophthalmology 2005; 112:1997–2003 14. Kurz S, Krummenauer F, Gabriel P, et al. Biaxial microincision versus coaxial small-incision clear cornea cataract surgery. Ophthalmology 2006; 113:1818–1826 15. Chang DF. 400 mm Hg high-vacuum bimanual phaco attainable with the Staar Cruise Control device [letter]. J Cataract Refract Surg 2004; 30:932–933 16. Bourne WM, Nelson LR, Hodge DO. Continued endothelial cell loss ten years after lens implantation. Ophthalmology 1994; 101:1014–1022; discussion by A Sugar, 1022–1023 17. Dick HB, Kohnen T, Jacobi FK, Jacobi KW. Long-term endothelial cell loss following phacoemulsification through temporal clear corneal incision. J Cataract Refract Surg 1996; 22:63–71 _ 18. Lesiewska-Junk H, Ka1uzny J, Malukiewicz-Wisniewska G. Long-term evaluation of endothelial cell loss after phacoemulsification. Eur J Ophthalmol 2002; 12:30–33 19. Hayashi K, Hayashi H, Nakao F, Hayashi F. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22:1079–1084 20. Walkow T, Anders N, Klebe S. Endothelial cell loss after phacoemulsification: relation to preoperative and intraoperative parameters. J. Cataract Refract Surg 2000; 26:727–732 21. Mencucci R, Ponchietti C, Virgili G, et al. Corneal endothelial damage after cataract surgery: microincision versus standard technique. J Cataract Refract Surg 2006; 32:1351–1354 22. Dogru M, Honda R, Omoto M, et al. Early visual results with the rollable ThinOptX intraocular lens. J Cataract Refract Surg 2004; 30:558–565 23. Pandey SK, Werner L, Agarwal A, et al. Phakonit: cataract removal through a sub-1.0 mm incision and implantation of the ThinOptX rollable intraocular lens. J Cataract Refract Surg 2002; 28:1710–1718 24. Agarwal A, Agarwal S, Agarwal A. Phakonit with an AcriTec IOL. J Cataract Refract Surg 2003; 29:854–855 25. Tsuneoka H, Hayama A, Takahama M. Ultrasmall-incision bimanual phacoemulsification and AcrySof SA30AL implantation through a 2.2 mm incision. J Cataract Refract Surg 2003; 29:1070–1076 26. Alio´ JL, Rodriguez-Prats JL, Vianello A, et al. Visual outcome of microincision cataract surgery with implantation of an Acri. Smart lens. J Cataract Refract Surg 2005; 31:1549–1556
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
1018
COAXIAL PHACOEMULSIFICATION VERSUS MICROINCISION CATARACT SURGERY
27. Alio´ JL, Schimchak P, Monte´s-Mico´ R, Galal A. Retinal image quality after microincision intraocular lens implantation. J Cataract Refract Surg 2005; 31:1557–1560 28. Bourne RRA, Minassian DC, Dart JKG, et al. Effect of cataract surgery on the corneal endothelium; modern phacoemulsification compared with extracapsular cataract surgery. Ophthalmology 2005; 111:679–685 29. Poyales-Galan F, Pirazzoli G. Clinical evaluation of endothelial cell decrease with visThesia in phacoemulsification surgery. J Cataract Refract Surg 2005; 31:2157–2161 30. Pereira ACA, Porfı´rio F Jr, Freitas LL, Belfort R Jr. Ultrasound energy and endothelial cell loss with stop-and-chop and nuclear
preslice phacoemulsification. J Cataract Refract Surg 2006; 32:1661–1666
J CATARACT REFRACT SURG - VOL 33, JUNE 2007
First author: Armando Stefano Crema, MD Department of Ophthalmology, Gama Filho University, Rio de Janeiro, and Paulista School of Medicine–UNIFESP, Sa˜o Paulo, Brazil