Ultrasound Energy in Phacoemulsification: A Comparative Analysis of Phaco-Chop and Stop-and-Chop Techniques According to the Degree of Nuclear Density

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1 c l i n c i l s c i e n c e Ultrsound Energy in Phcoemulsifiction: A Comprtive Anlysis of Phco-Chop nd Stop-nd-Chop Techniques According to the Degree of Nucler Density Jung Hyun Prk, MD; Sng Mok Lee, MD, PhD; Ji-Won Kwon, MD, PhD; Mee Kum Kim, MD, PhD; Joon Young Hyon, MD, PhD; Won Ryng Wee, MD, PhD; Jin Hk Lee, MD, PhD; Young Keun Hn, MD, PhD n BACKGROUND AND OBJECTIVE: To evlute the mount of ultrsound energy used, cornel endothelil cell loss, nd centrl cornel thickness using the phco-chop nd stop-nd-chop techniques for ctrcts with different degrees of nucler density. n PATIENTS AND METHODS: One hundred two eyes of 51 ptients with ilterl senile ctrct were included. Ech eye ws rndomly ssigned to hve either phco-chop or stop-nd-chop nucleofrctis during phcoemulsifiction. The groups were divided into two sugroups ccording to the nucler density. The effective phcoemulsifiction time, endothelil cell density, nd centrl cornel thickness were nlyzed. n RESULTS: The men effective phcoemulsifiction time ws similr etween the groups in modertely dense nuclei (2.17 ± 1.33 vs 1.33 ± 1.05 seconds; P =.41). However, the phco-chop technique required less effective phcoemulsifiction time thn the stop-ndchop technique in dense nuclei (3.86 ± 4.18 vs 6.70 ± 5.43 seconds; P =.01). The endothelil cell loss nd the centrl cornel thickness did not vry significntly etween the groups. n CONCLUSION: The phco-chop technique requires lower ultrsound energy for nucler mngement thn the stop-nd-chop technique in dense ctrcts nd the resulting endothelil loss ws similr in oth techniques. [Ophthlmic Surg Lsers Imging 2010;41: ] From the Deprtment of Ophthlmology (JHP), Seoul Pik Hospitl, Inje University College of Medicine, Busn; the Deprtment of Ophthlmology (JHP, SML, JWK, MKK, JYH, WRW, JHL, YKH), Seoul Ntionl University College of Medicine, Seoul; the Deprtment of Ophthlmology (SML, YKH), Seoul Municipl Borme Hospitl, Seoul; the Seoul Ntionl University Hospitl Helth Cre System Gngnm Center (JWK), Helthcre Reserch Institute, Seoul; nd the Deprtment of Ophthlmology (JYH, JHL), Seoul Ntionl University Bundng Hospitl, Seongnm, Kore. Accepted for puliction My 28, The uthors hve no finncil or proprietry interest in the mterils presented herein. Address correspondence to Young Keun Hn, MD, PhD, Deprtment of Ophthlmology, Seoul Ntionl University Borme Hospitl, #425 Shindeng-2- dong, Dongjk-gu, Seoul , Kore. doi: / Copyright SLACK Incorported

2 Introduction The cornel endothelil dmge during phcoemulsifiction cn e cused y fctors such s irrigtion flow, turulence nd movement of fluids, presence of ir ules, direct trum cused y the instruments or lens frgments, nd the phcoemulsifiction time nd power needed to chieve nucler emulsifiction. 1 Mny methods hve evolved in recent yers to enhnce the efficcy of nucler mngement during phcoemulsifiction. The min purpose of these techniques is to mechniclly rek the nucleus into smller frgments with the help of second instrument, which helps decrese the use of ultrsound power in nucler emulsifiction nd reduces surgicl time, limiting endothelil dmge. 2,3 Such techniques re especilly useful in the mngement of hrd nuclei. The phco-chop nd the stop-nd-chop techniques hve ecome populr. 4,5 Previous studies reported tht phco-chop nd stop-nd-chop nucleofrctis did not vry significntly in the ultrsound power used nd resulting endothelil loss. 6 However, to our knowledge there re no pulished prospective studies tht give n ccurte comprison of these two methods of nucleofrctis ccording to the grde of nucler density. Thus, we performed prospective study to compre the efficcy nd results of phcoemulsifiction using these techniques in ctrcts with different degrees of nucler density. Ptients nd Methods One hundred two eyes of 51 ptients with ilterl senile ctrcts who underwent phcoemulsifiction nd posterior chmer introculr lens implnttion t the Seoul Ntionl University Borme Hospitl etween Mrch nd Septemer 2006 were included. One eye of ech ptient ws rndomly ssigned to the phco-chop group nd the other eye ws ssigned to the stop-nd-chop group. Exclusion criteri included corne guttt, Fuchs dystrophy, pseudoexfolition, history of uveitis, previous introculr surgery, nd intropertive nd postopertive complictions such s posterior chmer rupture with vitreous loss, endothelil touch during introculr mnipultions, introculr lens decentrtion, Descemet s memrne detchment, or excerted postopertive inflmmtion with oculr hypertension. Ptients whose degree of nucler density ws different etween the two eyes were lso excluded. Preopertive ssessment included visul cuity, introculr pressure, nucler hrdness grding y slitlmp iomicroscopy, ultrsonic pchymetry of the centrl corne, nd cornel endothelil density y speculr microscopy. The nucler density ws grded sed on the Lens Opcities Clssifiction System III. 7 Ptients were divided into two groups: moderte nucler density (NO3 nd NO4) nd hrd nucleus (NO5 nd NO6). The prmeters evluted intropertively were phcoemulsifiction time nd men power nd the effective phcoemulsifiction time, which expresses how long phcoemulsifiction energy would hve een delivered if 100% power hd een used (effective phcoemulsifiction time = phcoemulsifiction time 3 phcoemulsifiction power). 3 The postopertive prmeters mesured t 1 dy nd 1, 4, nd 8 weeks fter surgery were visul cuity, introculr pressure, endothelil cell density, nd centrl cornel thickness. Phcoemulsifiction ws performed y single surgeon (YKH) using the Busch & Lom Millennium (Busch & Lom, Sn Dims, CA). A temporl cler cornel incision ws mde with crescent knife nd the nterior chmer ws entered with 2.75-mm steel kertome. Sodium hyluronte 1% (Hyl-2000; LG Chemicl, Seoul, Kore) ws used to fill the nterior chmer nd protect the cornel endothelium. A cpsulorhexis ws creted nd then hydrodissection nd hydrodelinetion were performed. In the phco-chop group, the superficil cortex nd the epinucler plte were removed. Next, the phcoemulsifiction proe ws used to hold the superior nucleus t high vcuum setting (100 to 120 mm Hg). The Nghr Nucleus chopper (Busch & Lom) ws then inserted through side-port incision nd plced opposite the min incision t the edge of the nucleus. The chopper ws moved towrd the phcoemulsifiction proe to initite nucler crcking. Both instruments were moved in opposite directions, dividing the nucleus into hlves. The nucleus ws then rotted 90, the phcoemulsifiction tip ws impled in hlf of the nucleus, nd the chopper ws used to rek this hlf into two smller frgments tht were then emulsified. The procedure ws repeted on the other hlf of the nucleus. In the stop-nd-chop group, the phcoemulsifiction proe ws used to sculpt centrl crter down to Ophthlmic Surgery, Lsers & Imging Vol 41, No 2,

3 Tle 1 Prmeters of the Phcoemulsifiction Mchine During Phco-Chop nd Sculpting Prmeter Phco-Chop Sculpting Mximum phcoemulsifiction power (%) 90% of nucler depth. The chopper nd the phcoemulsifiction proe were then inserted into the depth of the crter nd the posterior plte of the nucleus ws crcked in hlf y lterlly moving the two instruments in opposite directions. The rest of the procedure ws similr to tht used in phco-chop. The detiled prmeters of the phcoemulsifiction mchine during the phco-chop nd sculpting re summrized in Tle 1. In ll cses, corticl removl ws done fter the nucleus ws completely emulsified. A Sensr AR40e IOL (Advnced Medicl Optics, Snt An, CA) ws implnted in the cpsulr g. The smple size ws 16 ptients per group to detect difference on the effective phcoemulsifiction time of 1 stndrd devition with n vlue of.05 (two-sided) nd power 1-d of 0.8. The t test ws used to compre preopertive nd postopertive centrl cornel thickness nd endothelil cell density nd loss. The Mnn Whitney U test ws used in sugroup nlysis. Sttisticl significnce ws ccepted s P vlue of less thn.05. Sttisticl nlyses were performed using SPSS for Windows version 12.0 (SPSS Inc., Chicgo, IL). Results Modultion Continuous Continuous Vcuum power (mm Hg) 100 to Bottle height (cm) Of the 51 ptients, 22 were men nd 29 were women. The men ge ws 71.1 ± 6.77 yers, with rnge of 48 to 84 yers. The grde of nucler density ws NO3 or NO4 in 64 eyes of 32 ptients nd NO5 or NO6 in 38 eyes of 19 ptients. Tle 2 shows the prmeters evluted preopertively. Tle 3 shows the intropertive prmeters ccording to nucler density. No significnt differences were found in phcoemulsifiction times, phcoemulsifiction power, nd effective phcoemulsifiction Tle 2 Men Vlues of the Preopertive Prmeters Using the Phco-Chop nd Stop-nd-Chop Techniques Prmeter Visul cuity (LogMAR) Introculr pressure (mm Hg) Endothelil cell density (cells/ mm 2 ) Centrl cornel thickness (µm) Phco- Chop Stop-nd- Chop time in ctrcts with NO3 nd NO4 nucler density. In contrst, ctrcts with NO5 nd NO6 nucler density required significntly shorter phcoemulsifiction time nd lower phcoemulsifiction power when the phco-chop technique ws used. Effective phcoemulsifiction time, which is product of phcoemulsifiction time nd phcoemulsifiction power, ws lso shorter in the phco-chop group with denser ctrct (Figure). The men visul cuity t 1 week fter surgery ws 0.20 ± 0.31 logrithm of the minimum ngle of resolution (LogMAR) in the phco-chop group nd 0.19 ± 0.27 LogMAR in the stop-nd-chop group. Eight weeks fter surgery, visul cuity improved to 0.18 ± 0.33 LogMAR in the phco-chop group (P =.004) nd 0.15 ± 0.28 LogMAR in the stop-nd-chop group (P =.001). Introculr pressure remined unchnged t 1 dy fter surgery nd decresed 1 week fter surgery compred to the preopertive vlue. The introculr pressure chnge ws similr etween the phco-chop nd stop-nd-chop groups (Tle 4). Tle 5 shows endothelil cell densities preopertively nd postopertively. The men endothelil cell loss (% chnge) ws similr etween groups. There were no significnt differences in endothelil cell loss etween ctrcts of different densities with either technique. Although the centrl cornel thickness incresed fter phcoemulsifiction, the difference etween groups ws not significnt (Tle 6). P 0.52 ± ± ± ± ,794 ± 380 2,728 ± ± ± 38.9 LogMAR = logrithm of the minimum ngle of resolution Copyright SLACK Incorported

4 Figure. Intropertive phcoemulsifiction time, phcoemulsifiction power, nd effective phcoemulsifiction time using the phcochop versus stop-nd-chop technique in (A) modertely dense nuclei nd (B) hrd nuclei. Tle 3 Men Vlues of Intropertive Prmeters Evluted During Phco-Chop nd Stop-nd-Chop Techniques Moderte Nucler Density (n = 32) Hrd Nucleus (n = 19) Vrile Phco-Chop Stop-nd-Chop P Phco-Chop Stop-nd-Chop P Phcoemulsifiction time (sec) Phcoemulsifiction power (%) 30.9 ± ± ± ± ± ± ± ± EPT (s) 2.17 ± ± ± ± EPT = effective phcoemulsifiction time. Mnn Whitney U test. Exmintion Tle 4 Chnges in Introculr Pressure After Phcoemulsifiction Phco-Chop IOP (mm Hg) Stop-nd-Chop IOP (mm Hg) Preopertive 13.8 ± ± dy 13.3 ± ± week 13.3 ± ± weeks 11.7 ± ± weeks 11.5 ± ± 3.0 c.40 IOP = introculr pressure. P <.001. P <.05 versus preopertive introculr pressure. c P <.01. P Discussion Our study estlished tht phco-chop technique required lower ultrsound energy thn the stop-ndchop technique in crcking hrd nuclei. However, the phco-chop nd stop-nd-chop techniques re comprle in the spect of endothelil cell loss. In ctrcts with moderte nucler density, oth techniques re eqully efficcious in crcking the nucleus. Preventing cornel endothelil cell dmge during phcoemulsifiction surgery is crucil. Old ge, smll pupil, hrd or lrge nucleus, greter infusion volume, Ophthlmic Surgery, Lsers & Imging Vol 41, No 2,

5 Tle 5 Preopertive nd Postopertive Endothelil Cell Density nd Loss in Ctrct Surgeries Using the Phco-Chop nd Stop-nd-Chop Techniques Moderte Nucler Density (n = 32) Hrd Nucleus (n = 19) Exmintion Phco-Chop Stop-nd-Chop P Phco-Chop Stop-nd-Chop P c Preopertive 2,829 ± 405 2,750 ± ,768 ± 341 2,727 ± dy 2,492 ± 324 (-10.4) 2,475 ± 541 (-10.0).90 2,327 ± 504 (-12.8) 2,295 ± 569 (-8.8).47 1 week 2,406 ± 419 (-12.5) 2,338 ± 486 (-14.0).61 1,914 ± 725 (-31.0) 1,843 ± 514 (-25.5).63 4 weeks 2,334 ± 429 (-16.8) 2,339 ± 480 (-14.0).97 1,839 ± 675 (-33.0) 1,912 ± 441 (-32.2).95 8 weeks 2,356 ± 379 (-16.3) 2,379 ± 488 (-13.2).88 1,685 ± 625 (-40.1) 1,529 ± 537 (-33.2).43 Vlues re shown s cells/mm 2 ± stndrd devition (% chnge). c Mnn Whitney U test. Tle 6 Preopertive nd Postopertive Centrl Cornel Thickness in Ctrct Surgeries Using the Phco-Chop nd Stop-nd-Chop Techniques Exmintion Moderte Nucler Density (n = 32) Hrd Nucleus (n = 19) Phco-Chop (µm) Stop-nd-Chop Phco-Chop (µm) P (µm) Stop-nd-Chop (µm) Preopertive ± ± ± ± dy ± 37.6 (+7.8) ± 32.9 (+9.7) ± 43.4 (+8.5) ± 26.5 (+5.7).24 1 week ± 38.5 (+4.9) ± 34.5 (+4.9) ± 47.0 (+3.6) ± 48.0 (+3.9).84 4 weeks ± 32.8 (+2.5) ± 34.1 (+1.9) ± 38.6 (+1.2) ± 42.2 (+1.7).77 8 weeks ± 34.8 (-1.7) ± 34.0 (-0.6) ± 40.1 (+0.15) ± 47.6 (+0.9).95 Vlues re shown s µm ± stndrd devition (% chnge). c Mnn Whitney U test. P c nd greter totl emitted ultrsound energy were risk fctors for cornel endothelil injury during phcoemulsifiction. 8,9 When phcoemulsifiction ws first introduced, the nucleus ws not divided nd the phcoemulsifiction proe ws used to sculpt nd consume the nucleus. This resulted in significnt endothelil cell loss. 10 The divide-nd-conquer technique ws introduced to crck the nucleus nd fcilitte phcoemulsifiction. 11 However, severl studies found significnt endothelil cell loss, even with this procedure. 12 Some uthors even recommended tht extrcpsulr ctrct extrction ws etter option for nucler crcking thn phcoemulsifiction ecuse it ws sfer for the cornel endothelium. 13 Different nucler chopping techniques were introduced to further decrese endothelil cell dmge. 14,15 These chopping techniques mechniclly frgment the nucleus into smller pieces nd decrese the need for ultrsonic power to emulsify the nucleus. They lso decrese the effective phcoemulsifiction nd totl surgicl times, limiting the insult to the cornel endothelium. The phco-chop technique is more difficult, hs longer lerning curve, nd my e ssocited with higher incidence of ters in the continuous curviliner cpsulorhexis thn the stop-nd-chop technique. 6 The sic difference etween the phco-chop nd stop-nd-chop techniques is tht the ltter initilly uses ultrsonic energy to crete centrl groove in the nucleus. Although dditionl ultrsonic power is used to mke the initil trench, the resulting crter helps the surgeon rek the hrd posterior plte of the nucleus, which is crucil to the success of nucler chopping. 240 Copyright SLACK Incorported

6 Severl comprtive studies hve een reported using vrious chopping techniques. In rndomized prospective study, Wong et l. 2 used Legcy system nd found men phcoemulsifiction time of 1.2 minutes for phco-chop nd 2.4 minutes for divide-nd-conquer. Pereir et l. 16 reported tht phcoemulsifiction time nd power nd effective phcoemulsifiction time were significntly higher in the stop-nd-chop group compred to the nucler preslice group, lthough the decrese in endothelil cell density ws similr etween groups. Cn et l. 17 reported tht the men phcoemulsifiction time ws shorter nd the phcoemulsifiction power ws lower in the phco-chop group compred to the stop-nd-chop group. The men times to chieve mximum vision nd to return to preopertive pchymetry vlues were lso shorter in the phco-chop group. Contrrily, Vjpyee et l. 6 compred the phco-chop nd stop-nd-chop techniques nd reported men effective phcoemulsifiction time of 27 seconds for the phco-chop group nd 28 seconds for the stop-nd-chop group in grde 2 (yellow) nd 3 (mer) ctrcts. There were no significnt inter-group differences in effective phcoemulsifiction time, endothelil cell loss, nd centrl cornel thickness. However, ecuse they did not specify ctrct densities, the difference in phco-chop nd stop-nd-chop techniques ccording to the nucler density ws not estlished. Moreover, ecuse our study recruited ptients with ilterl ctrct with the sme degree of nucler density, the preopertive conditions were optimlly mtched etween the two groups. The literture reports positive correltion etween the use of ultrsound energy in surgery nd endothelil loss. 12,18 Our results show tht even though the stopnd-chop technique required longer phcoemulsifiction time nd higher phcoemulsifiction power thn the phco-chop technique in dense ctrcts, no significnt difference in endothelil loss occurred etween the two groups. Becuse centrl endothelil loss cn occur until 12 months fter surgery, 19 long-term evlution should e estlished. Our study showed tht ultrsound energy consumption ws lower (shorter phcoemulsifiction time nd lower phcoemulsifiction power) with the phcochop technique thn with the stop-nd-chop technique in denser ctrcts nd the resulting endothelil loss ws similr with oth techniques. References 1. Linerger EJ, Hrdten DR, Shh GK, Lindstrom RL. Phcoemulsifiction nd modern ctrct surgery. Surv Ophthlmol. 1999;44: Wong T, Hingorni M, Lee V. Phcoemulsifiction time nd power requirements in phco chop nd divide nd conquer nucleofrctis techniques. J Ctrct Refrct Surg. 2000;26: Fine IH, Pcker M, Hoffmn RS. Use of power modultions in phcoemulsifiction: choo-choo chop nd flip phcoemulsifiction. J Ctrct Refrct Surg. 2001;27: Koch PS. Techniques nd instruments for ctrct surgery. Current Opin Ophthlmol. 1994;5: Koch PS. Mstering Phcoemulsifiction: A Simplified Mnul of Strtegies for the Spring, Crck nd Stop & Chop Technique, 4th ed. Thorofre, NJ: SLACK Incorported; Vjpyee RB, Kumr A, Dd T, et l. Phco-chop versus stop-ndchop nucleotomy for phcoemulsifiction J Ctrct Refrct Surg. 2000;26: Chylck LT Jr, Wolfe JK, Singer DM, et l. The Lens Opcities Clssifiction System III. The Longitudinl Study of Ctrct Study Group. Arch Ophthlmol. 1993;111: Wong T, Hingorni M, Lee V. Phcoemulsifiction time nd power requirements in phco chop nd divide nd conquer nucleofrctis techniques. J Ctrct Refrct Surg. 2000;26: Hyshi K, Hyshi H, Nko F, Hyshi F. Risk fctors for cornel endothelil injury during phcoemulsifiction. J Ctrct Refrct Surg. 1996;22: Hyshi K, Nko F, Hyshi F. Cornel endothelil cell loss fter phcoemulsifiction using nucler crcking procedures. J Ctrct Refrct Surg. 1994;20: Gimel HV. Divide nd conquer nucleofrctis phcoemulsifiction: development nd vritions. J Ctrct Refrct Surg. 1991;17: Pirzzoli G, D Eliseo D, Ziosi M, Accirri R. Effects of phcoemulsifiction time on the cornel endothelium using phcofrcture nd phco chop techniques. J Ctrct Refrct Surg. 1996;22: Ogino K, Kohd F. Cornel endothelil dmge cused y phcoemulsifiction using the divide nd conquer nucleofrctis. Jpn J Ophthlmic Surg. 1992;5: Kohlhs M, Klemm M, Kmmnn J, Richrd G. Endothelil cell loss secondry to two different phcoemulsifiction techniques. Ophthlmic Surg Lsers. 1998;29: Rm J, Wesendhl TA, Auffrth GU, Apple DJ. Evlution of in situ frcture versus phco chop techniques. J Ctrct Refrct Surg. 1998;24: Pereir AC, Porfirio F Jr, Freits LL, Belfort R Jr. Ultrsound energy nd endothelil cell loss with stop-nd-chop nd nucler preslice phcoemulsifiction. J Ctrct Refrct Surg. 2006;32: Cn I, Tkmz T, Ckici F, Ozgul M. Comprison of Nghr phco-chop nd stop-nd-chop phcoemulsifiction nucleotomy techniques. J Ctrct Refrct Surg. 2004;30: Zetterstrom C, Lurell CG. Comprison of endothelil cell loss nd phcoemulsifiction energy during endocpsulr phcoemulsifiction surgery. J Ctrct Refrct Surg. 1995;21: Wlkow T, Anders N, Klee S. Endothelil cell loss fter phcoemulsifiction: reltion to preopertive nd intropertive prmeters. J Ctrct Refrct Surg. 2000;26: Ophthlmic Surgery, Lsers & Imging Vol 41, No 2,

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