Intraindividual comparison of surgical trauma after bimanual microincision and conventional small-incision coaxial phacoemulsification

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1 ARTICLE Intraindividual comparison of surgical trauma after bimanual microincision and conventional small-incision coaxial phacoemulsification Günal Kahraman, MD, Michael Amon, MD, Carmen Franz, MD, Anna Prinz, MD, Claudette Abela-Formanek, MD PURPOSE: To compare the surgical trauma after microincision phacoemulsification and smallincision coaxial phacoemulsification after implantation of conventional, foldable, hydrophobic acrylic intraocular lenses (IOLs). SETTING: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS: A prospective investigator-masked case series comprised patients with bilateral cataract who had cataract surgery on the same day. Thirty-three patients (66 eyes) were randomized. Microincision cataract surgery (MICS) was performed through 2, 1.4 mm clear corneal incisions (CCIs) using bimanual sleeveless phacoemulsification (cool phaco) in 1 eye. Small-incision cataract surgery (SICS) was performed on the other eye through a 3.2 mm CCI. In all cases, an AcrySof SA60AT IOL was inserted, in the MICS group after the CCI was enlarged. Laser flare photometry, specular microscopy, corneal endothelial cell density, and pachymetry were evaluated preoperatively and postoperatively. Intraindividual comparison and statistical analyses were performed. RESULTS: There were no relevant clinical differences or perioperative complications in either group. There were no statistically significant differences between preoperative and postoperative anterior chamber flare or endothelial cell loss. On the first postoperative day, the MICS group had statistically significantly increased corneal swelling (P Z.008). Postoperatively, the mean endothelial cell density loss was higher in the MICS group (6.2%) than in the SICS group (3.10%); however, the difference between groups was not significant (P Z.08) CONCLUSIONS: Microincision cataract surgery was a safe and reproducible technique. The postoperative results in the MICS group were comparable to those in the SICS group. J Cataract Refract Surg 2007; 33: Q 2007 ASCRS and ESCRS Modern phacoemulsification techniques have made cataract surgery safe and efficient over the past several decades. Although the phacoemulsification procedure has improved greatly, cataract surgery still involves surgical trauma. It has been reported that all cataract surgery techniques cause corneal endothelial cell loss. 1 3 Several morphologic features of the endothelium are important for assessing the physiologic health of the cornea. Changes in endothelial cell density, coefficient of variation of cell area (variation in cell size), and percentage of hexagonal cells (variation in cell shape from 6-sided endothelial cells) occur after surgical procedures, in disease states, and in the normal aging process. 4 The corneal endothelial cell layer cannot regenerate after injury. Trauma to the endothelium leads to a reduction in cell density, a proportional increase in mean cell size and corneal thickness, and disruption of the normal hexagonal cell pattern. The widespread use of foldable intraocular lenses (IOLs) and advances in modern phaco machines and tips have allowed the size of clear corneal incisions (CCIs) to be less than 3.0 mm. Further reduction in the size of the CCI has several advantages such as rapid visual restoration with minimum postoperative inflammation, lower surgically induced corneal astigmatism, and less iatrogenic corneal damage. 5,6 Smaller wounds may heal more rapidly with less risk for leakage and endophthalmitis. 7 Theoretically, among other factors, the smaller the incision, the more stable the anterior chamber with improved surgical control during capsulorhexis, hydrodissection, and phacoemulsification. 8,9 618 Q 2007 ASCRS and ESCRS Published by Elsevier Inc /07/$dsee front matter doi: /j.jcrs

2 INTRAINDIVIDUAL COMPARISON OF SURGICAL TRAUMA: MICS VERSUS SICS 619 Compared to conventional phacoemulsification, the microincision cataract surgery (MICS) procedure uses a bimanual technique with a separate irrigation instrument and a sleeveless phaco tip to remove the cataract. The phaco tip has a small diameter, and incisions smaller than 1.5 mm are typically used to insert the tip into the anterior chamber. During the MICS procedure, the phaco tip is used in the micropulse mode. The pulse is set between 8 pulses and 10 pulses per second with a rest period of 90% or above. This means that when phaco power is used, there is a rest or cooling period for 90% of the time, which allows rapid dispersion of heat at the ultrasound tip with minimization of the thermal effects on the cornea. With this power delivery, cool phaco is possible. This allows a bimanual phacoemulsification technique using sleeveless phacoaspiration. Increasing the effectiveness of phacoemulsification reduces the total ultrasound power delivered to the anterior segment, which leads to less surgical tissue damage 10 and less corneal edema. 11 Documentation of postoperative endothelial alterations is essential to estimate the safety of new cataract surgery techniques. The purpose of this study was to compare surgical trauma quantitatively, expressed by flare and corneal parameters, after phacoemulsification by bimanual MICS and conventional small-incision coaxial phacoemulsification (SICS) techniques. PATIENTS AND METHODS A prospective investigator-masked intraindividual comparative study comprised 33 consecutive patients (66 eyes) with bilateral age-related cataract who had phacoemulsification cataract surgery between January and July 2005 at the Department of Ophthalmology, Medical University of Vienna, Austria. The cataracts were graded according to the Lens Opacities Classification System III (LOCS III) grading scale. 12,13 Inclusion criteria included a nucleus hardness of LOCS III grade 2 or 3. Exclusion criteria were corneal pathology, inflammatory eye disease, glaucoma, endothelial cell density less than 1500 cells/mm 2, previous ocular surgery or trauma, and diabetes mellitus. The patients were randomly assigned to have MICS in 1 eye and SICS in the other eye. Informed consent Accepted for publication January 8, From the Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. No author has a financial or proprietary interest in any material or method mentioned. Presented at the XXIV Congress of the European Society of Cataract & Refractive Surgeons, London, England, September Corresponding author: Dr. Günal Kahraman, Department of Ophthalmology, Medical University of Wien, Waeringer Guertel Vienna, Austria. guenal.kahraman@meduniwien.ac.at. was obtained after both surgical methods were explained to the patient. Cataract surgery was performed by 1 of 2 experienced surgeons (C.A.F., M.A.) using a standardized surgical protocol. The same surgeon operated on both eyes of a patient. Before surgery, the pupils were dilated with tropicamide (Mydriaticum), phenylephrine hydrochloride 2.5%, cyclopentolate 1%, and diclofenac sodium 0.1% (Voltaren). In all cases, topical anesthesia (oxybuprocaine 1%) was administered. The same irrigating solution (balanced salt solution [BSS]) and ophthalmic viscoelastic device (OVD) (sodium hyaluronate 1% [Healon]) were used in both groups. The OS3-Ophthalmic Small Incision Surgery System (Oertli Instruments) was used for phacoemulsification. Microincision Cataract Surgery Two 1.4 mm clear corneal incisions were created temporally 90 degrees apart with a 1.4 mm trapezoid knife (Sharp Point). The OVD was injected, and a continuous curvilinear capsulorhexis with a diameter of approximately 5.0 mm was created with a bent 26-gauge needle. After hydrodissection, bimanual sleeveless phacoemulsification was performed using the Cool Micro-Pulsed Ultrasound setting (CMP, Oertli Instruments). The CMP setting uses extremely brief microbursts of energy with 10/90 burst/rest periods, which reduces the final amount of ultrasound energy used. A 20-gauge, 30-degree angled sleeveless microincision tip and an irrigating chopper (Oertli Instruments) were used to remove the nucleus. The surgeon performed bimanual phacoemulsification using the divide-and-conquer method. Irrigation/aspiration (I/A) was performed bimanually using separate cannulas with diameters of 0.8 mm. The capsular bag was filled with OVD, and the temporal incision was enlarged to 3.2 mm for IOL implantation. Small-Incision Cataract Surgery A temporal clear corneal incision was placed with a calibrated 3.2 mm knife. A 1.2 mm blade was used to create a paracentesis 90 degrees apart. Capsulorhexis and hydrodissection were done using a technique similar to that used in the MICS group. The nucleus was emulsified and removed with a 45-degree angled phaco tip. Coaxial phacoemulsification was performed using standard pulse mode with fixed 50/50 burst/rest periods. Cortical remnants were removed with a 1.8 mm diameter, 45-degree angled I/A tip. Both Groups In both groups, a foldable hydrophobic acrylic IOL with an optic diameter of 6.0 mm (AcrySof SA60AT, Alcon Surgical) was loaded in a Monarch injector and inserted in the bag. No corneal sutures were required in any case. All patients received topical gentamicin dexamethasone eyedrops (Dexagenta-POS) 3 times daily for 4 weeks after the operation. Evaluations In addition to a complete ocular examination, ultrasound corneal pachymetry and anterior chamber flare measurements were performed preoperatively and postoperatively on the first day and at 3 months. Central corneal thickness was assessed using a DGH 500 ultrasonic pachymetry (DGH Technology, Inc.) set at a velocity of 1640 m/sec. An FC-1000 laser flare cell meter (Kowa Co. Ltd.) was used to measure anterior chamber inflammation. The percentage of corneal endothelial cell loss 3 months after surgery was quantified using specular microscopy. A noncontact specular microscope (Noncon Robo SP 8000, Konan Medical Inc.) was used to determine the endothelial cell density, cell size variation coefficient (an

3 620 INTRAINDIVIDUAL COMPARISON OF SURGICAL TRAUMA: MICS VERSUS SICS objective measure of polymegathism), and percentage of hexagonality (an index of pleomorphism) at the corneal center. More than 60 endothelial cells were evaluated at each examination. Endothelial cell loss was expressed as a percentage of the preoperative cell density as follows: endothelial cell loss (%) Z (preoperative cell count postoperative cell count)/(preoperative cell count 100). Endothelial cell counts were done on the day before surgery and 3 months after surgery. Statistical Analysis Data are presented as mean values G SD and range. The 2-tailed t test was used for statistical comparisons between groups. A P value less than 0.05 was considered statistically significant for all study outcome measures. Table 1. Operative parameters. Parameter MICS SICS P Value Mean ultrasound time (sec) 9.70 G G * Mean balanced salt solution volume G G Mean operation time (min) G G * Means G SD MICS Z microincision cataract surgery; SICSZ small-incision cataract surgery *Statistically significant, P!.05 RESULTS The patient cohort comprised 15 men and 18 women with a mean age of 71 years (range 55 to 86 years). Cataract surgery was uneventful in all eyes. There were no postoperative complications. No patient had signs of corneal burn. The estimated mean cataract grade (LOCS III) was 2.28 G 0.45 in the MICS group and 2.24 G 0.44 in the SICS group; the difference between groups was not statistically significant (P Z.57). Table 1 shows the results for the operative variables. The mean effective ultrasound time was statistically significantly higher in the SICS group than in the MICS group (P!.01). There were no statistically significant differences in mean irrigation volumes (P Z.33). The mean surgery time was longer in the MICS group than in the SICS group, and the difference was statistically significant (P Z.004). Table 2 shows the results for the preoperative and postoperative variables. Preoperatively, there were no statistically significant differences in mean flare (P Z.73). In both groups, the change in flare trend did not differ (P Z.46). The mean preoperative pachymetry was G mm in the SICS group and G in the MICS group; the difference was not significant (P Z.82). Postoperatively, both groups had an increase in central corneal thickness, with the MICS group having more corneal swelling than in the SICS group. The increase was statistically significant on the first postoperative day (P Z.008). The mean pachymetry was G mm and G mm in the MICS group and SICS group respectively. Three months after surgery, there was no statistical difference in central pachymetry values (Figure 1). Preoperatively, the mean endothelial cell density was G 288 cells/mm 2 (range 1663 to 2793 cells/mm 2 ) in the MICS group and G 329 cells/mm 2 (range 1542 to 2849 cells/mm 2 ) in the SICS group. There were no statistically significant differences between groups in mean endothelial cell density (P Z.41). Postoperatively, the mean endothelial cell density loss was higher in the MICS group than in the SICS group; however, the difference was not significant (P Z.08). There was a significant decrease in mean cell density between the preoperative and 3-month postoperative endothelial cell density values in both groups. The percentage loss was 6.20% G 5.07% and 3.10% G 6.24% in the MICS group and SICS group, respectively. At baseline, the mean coefficient of variation was G 9.77 SD/mm 2 in the MICS group and G SD/mm 2 in the SICS group (P Z.87). Preoperatively, there was no difference in the percentage of hexagonal cells (P Z.64). There was no statistically significant difference in the coefficient of variation of cell area (P Z.92) or percentage of hexagonal cells after 3 months (P Z.08) in both groups. There was also no statistical difference between the preoperative and postoperative values in either group. DISCUSSION The trend in modern cataract surgery is to minimize surgical trauma. The primary objective of this study was to compare the amount of surgical trauma caused by phacoemulsification, intraindividually. Both bimanual microincision and coaxial small-incision procedures offered highly satisfactory clinical results. Postoperative flare values give a general impression of the level of anterior chamber inflammation. 14 In our study, there was no difference in laser flare values between the groups at any time point. This indicates that both surgical approaches were associated with relatively low postoperative inflammation as measured by laser flare photometry. Kruger et al. 14 found that longer phaco time increases postoperative flare values. Although MICS eyes had significantly less phaco time than SICS eyes, we did not observe reduced inflammation in MICS eyes.

4 INTRAINDIVIDUAL COMPARISON OF SURGICAL TRAUMA: MICS VERSUS SICS 621 Table 2. Preoperative and postoperative parameters. Parameter MICS SICS P Value Mean cataract grade (LOCS III) 2.28 G G Mean flare value Preoperative 5.78 G G Day G G Month G G Mean pachymetry (mm) Preoperative G G Day G G * Month G G Mean loss of endothelial cells (%) 6.20 G G Mean endothelial cell density (cells/mm 2 ) Preoperative G G Month G G Mean coefficient of variation of cell area Preoperative G G Month G G Mean percentage hexagonal cells Preoperative G G Month G G Means G SD LOCS Z Lens Opacities Classification System; MICS Z microincision cataract surgery; SICSZ small-incision cataract surgery *Statistically significant, P!.05 Alió et al. 15 recently published early results of MICS, comparing them with results of coaxial phacoemulsification. In contrast to the results in our study, the authors found no differences in mean change in central corneal thickness on the first postoperative day. However, in our study, the differences between the 2 groups in mean change in pachymetry were statistically significant only on the first postoperative day. The SICS group had less central swelling than the MICS group. However, the difference was too small to be of clinical relevance in either group. As both techniques are similar and have important mean Pachymetry(µ) ,93 540,03 Pre-operative 568,69 MICS Day1 Visit 553,93 SICS 550,1 547,9 Day 90 Figure 1. Corneal thickness change over time (MICS Z microincision cataract surgery; SICSZ small-incision cataract surgery). differences only in incision size and total ultrasound energy used, the increased corneal thickness in the MICS group was probably related to the prolonged surgery time and mechanical corneal trauma due to tight corneal tunnels. In addition, the reduced freedom of surgical manipulation through the tight corneal tunnels is the reason for prolonged surgery time in the MICS group. The immediate postoperative corneal edema in the MICS eyes was thought to be the result of longer surgery time with prolonged aspiration and mechanical trauma due to a smaller CCI, although less total phacoemulsification energy was used. There is physiological endothelial cell loss with age, and this rate is significantly higher after surgical procedures such as phacoemulsification. 16 Endothelial cell loss after cataract surgery seems to be independent of preoperative endothelial cell density, and postoperative endothelial cell loss occurs as a result of many factors. These include longer phacoemulsification time, high ultrasound energy, cataract density, age, mechanical trauma by instruments, and corneal manipulation. 14,17,18 In the current study, the postoperative mean endothelial cell loss was 6.20% in the MICS group and 3.10% in the SICS group. We found no statistical difference in endothelial cell loss between groups (P Z.08). Although the difference did not reach statistical significance, MICS eyes had a greater loss of endothelial cells than SICS eyes and it is likely that the equivalent difference in a larger study

5 622 INTRAINDIVIDUAL COMPARISON OF SURGICAL TRAUMA: MICS VERSUS SICS population would be significant. This finding probably correlates with the increased corneal swelling on the first postoperative day in the MICS group. In addition, it took longer to remove the cataract with the MICS technique. Our data support findings in previous studies that found a significant correlation between postoperative corneal swelling and total surgical time. 17,19 In the current study, no change in cell hexagonality or the coefficient of variation occurred postoperatively. Endothelial cell loss after phacoemulsification in this study was comparable to that in other studies. 15,19 In our series, we did not observe a reduction in the total BSS volume used in the MICS group. Therefore, total volumes of fluids circulating inside the eye remain similar in both groups. In conclusion, the bimanual technique seems to be less traumatic because of the smaller incision size, low energy delivery to the eye, and low heat generation. In our study, the increase in corneal thickness was greater in the MICS group than in the SICS group on the first postoperative day; this difference was not clinically relevant because corneal thickness in the MICS group returned to values similar that in the SICS group. However, compared with conventional phacoemulsification, we could not prove there are advantages of MICS over SICS. REFERENCES 1. Bourne RRA, Minassian DC, Dart JK, et al. Effect of cataract surgery on the corneal endothelium; modern phacoemulsification compared with extracapsular cataract surgery. Ophthalmology 2004; 111: Walkow T, Anders N, Klebe S. Endothelial cell loss after phacoemulsification: relation to preoperative and intraoperative parameters. J Cataract Refract Surg 2000; 26: Binder PS, Sternberg H, Wickham MG, Worthen DM. Corneal endothelial damage associated with phacoemulsification. Am J Ophthalmol 1976; 82: Bourne WM, Nelson LR, Hodge DO. Central corneal endothelial cell changes over a ten-year period. Invest Ophthalmol Vis Sci 1997; 38: Tsuneoka H, Shiba T, Takahashi Y. Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results. J Cataract Refract Surg 2002; 28: Soscia W, Howard JG, Olson RJ. Bimanual phacoemulsification through 2 stab incisions; a wound-temperature study. J Cataract Refract Surg 2002; 28: Lundström M. Endophthalmitis and incision construction. Curr Opin Ophthalmol 2006; 17: Tsuneoka H, Shiba T, Takahashi Y. Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refract Surg 2001; 27: Jeng BH, Huang D. Anterior chamber stability during bimanual irrigation and aspiration; theoretical and experimental analysis. J Cataract Refract Surg 2001; 27: Takahashi H. Free radical development in phacoemulsification cataract surgery. J Nippon Med Sch 2005; 72: Fine IH, Packer M, Hoffman RS. Use of power modulations in phacoemulsification; choo-choo chop and flip phacoemulsification. J Cataract Refract Surg 2001; 27: 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: Smith JMA, El-Brawany M, Nassiri D, et al. The relationship between nuclear colour and opalescence on the LOCSIII scale and physical characteristics of cataract nuclei. Eye 2002; 16: Kruger AJ, Schauersberger J, Abela-Formanek C, et al. Einfluss der Dauer der Phakoemulsifikation auf die postoperative Inflammation d eine retrospektive Studie. Klin Monatsbl Augenheilkd 2001; 218: Alió J, Rodríguez-Prats JL, Galal A, Ramzy M. Outcomes of microincision cataract surgery versus coaxial phacoemulsification. Ophthalmology 2005; 112: Lesiewska-Junk H, Ka1u_zny J, Malukiewicz-Wisniewska G. Long-term evaluation of endothelial cell loss after phacoemulsification. Eur J Ophthalmol 2002; 12: Hayashi K, Hayashi H, Nakao F, Hayashi F. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22: O Brien PD, Fitzpatrick P, Kilmartin DJ, Beatty S. Risk factors for endothelial cell loss after phacoemulsification surgery by a junior resident. J Cataract Refract Surg 2004; 30: Zetterström C, Laurell C-G. Comparison of endothelial cell loss and phacoemulsification energy during endocapsular phacoemulsification surgery. J Cataract Refract Surg 1995; 21:55 58 First author: Günal Kahraman, MD