The Efficacy of Low-Energy Selective Laser Trabeculoplasty

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1 c l i n i c l s c i e n c e The Efficcy of Low-Energy Selective Lser Treculoplsty Min Tng, MD; Yng Fu, MD; Ming-shui Fu, MD; Ying Fn, MD; Hi-dong Zou, MD; Xio-dong Sun, MD; Xun Xu, MD n BACKGROUND AND OBJECTIVE: To nlyze the efficcy of low-energy selective lser treculoplsty (SLT) in ptients. n PATIENTS AND METHODS: In 74 ptients (74 eyes) with oculr hypertension, suspected glucom, or primry open-ngle glucom, SLT ws the firstchoice tretment. Thirty-nine ptients in the low-energy group received tretment using hlf of conventionl lser energy over 360 of the treculr meshwork (t 100 points). Thirty-five ptients in the control group received conventionl lser energy. Ptients were oserved for 1 yer. Complictions nd introculr pressure (IOP) were oserved. n RESULTS: Postopertive trnsient IOP spike (> 3 mm Hg) occurred in three eyes on the dy of tretment nd prtil peripherl nterior synechie occurred in one eye 1 month fter tretment only in the control group. Effective rtes of tretment (> 20% IOP reduction) t week 2 nd month 1, 3, 6, nd 12 fter tretment were 69.23%, 64.10%, 61.54%, 53.85%, nd 48.72% in the low-energy group nd 71.43%, 71.43%, 60%, 51.43%, nd 48.57% in the control group, respectively. There ws no sttisticlly significnt difference etween the two groups t vrious time points (P =.836,.501,.892,.835,.990). n CONCLUSION: Compred with SLT using conventionl lser energy, low-energy SLT lowers IOP with fewer complictions, mking it sfe nd effective option. [Ophthlmic Surg Lsers Imging 2011;42:59-63.] INTRODUCTION Glucom is the second leding cuse of lindness worldwide. Estlishing sfe nd effective tretment for glucom remins chllenge in clinicl ophthlmology. Since lser treculoplsty ws dopted in 1974, 1 its effectiveness hs een widely recognized for open-ngle glucom, pigmentry glucom, nd exfolition syndrome. 2-4 With continuous improvement, this technique hs grdully ecome one of the firstline tretments nd the first choices for ptients with open-ngle glucom. 5-8 Some clinicl studies show it From Shnghi Jiotong University Affilited First People s Hospitl, Ophthlmology, Shnghi, Chin. Originlly sumitted April 15, Accepted for puliction Septemer 26, Posted online Decemer 1, The uthors hve no finncil or proprietry interest in the mterils presented herein. The uthors thnk Medic Communicus Asi for trnsltion of prt of the mnuscript. Address correspondence to Ying Fn, MD, Shnghi Jiotong University Affilited First People s Hospitl, Ophthlmology, Shnghi, Chin, E-mil: tngminsmile@126.com doi: / Ophthlmic Surgery, Lsers & Imging Vol. 42, No. 1,

2 is more effective thn drug therpy. 9,10 In prticulr, since selective lser treculoplsty (SLT) ws pproved for clinicl use in 2001, it hs een cclimed s highly cell-specific nd le to chieve the therpeutic effects of trditionl lser with less energy nd less tissue dmge However, SLT lso hs certin shortcomings. Its therpeutic effect fter one-time ppliction grdully decreses over time, 16 nd complictions include severe trnsient introculr pressure (IOP) spike, requiring filtrtion tretment, peripherl nterior synechi (PAS), nd cornel edem, 17 limiting further lser tretment. Therefore, reducing complictions without compromising efficcy nd mking the tretment more repetle will spred the clinicl use of SLT. In this study, we compred the IOP-lowering efficcy nd compliction rte of low-energy SLT versus conventionl energy SLT. PATIENTS AND METHODS In this prospective descriptive cse series, 74 eyes of 74 ptients treted t the outptient deprtment of our hospitl nd receiving confirmed dignosis of oculr hypertension (OHT), suspected glucom, or primry open-ngle glucom (POAG) from My 2007 to Novemer 2008 were selected. OHT ws defined y n IOP greter thn 21 mm Hg without glucomtous optic nerve hed or nerve fier chnges. Suspected glucom ws defined y suspicious ut not definite optic nerve hed, nerve fier lyer, or visul field normlities suggesting glucom. POAG ws defined y definitely glucomtous optic nerve hed or nerve fier lyer normlities, with or without visul field defects. The study ws pproved y the hospitl ethics committee nd ll ptients provided signed informed consent. In ll, 32 men nd 42 women with n verge ge of ± yers (rnge: 32 to 79 yers) greed to ccept SLT s the first-choice tretment. None hd received ny relted tretment nd seline IOP rnged from 21 to 30 mm Hg. The ptients were rndomly divided into two groups: the low-energy group (39 ptients) nd the control group (35 ptients). Eyes were treted with rimonidine trtrte eye drops once efore tretment. The Q-switch frequencydouling Nd (GE Helthcre, Munich, Germny) ws used. The YAG lser (532 nm) pulse time ws 3 ns nd the spot size of the lser em ws 400 µm. Strting t 0.6 mj, lser energy ws incresed in 0.1 mj increments until chmpgne-like ules ppered. Tht energy ws reduced y 0.1 mj nd used s the therpeutic energy for the control group (usully rnging 0.6 to 1.0 mj). The treculr meshwork (360 ) ws treted t 100 points, 25 in ech qudrnt. In the lowenergy group, the lser energy ws hlf of the therpeutic energy used in the control group (usully rnging 0.3 to 0.5 mj) nd the SLT ws lso pplied over 360 of the treculr meshwork t 100 points, 25 in ech qudrnt. Ptients were instructed to pply diclofenc sodium eye drops three times dy for 3 dys. Bseline IOP ws tken s the verge of the lst three redings efore the tretment using Goldmnn tonometer. Ptients received eye exmintions on the dy of tretment nd t dys 1 nd 3; weeks 1 nd 2; nd months 1, 3, 6, nd 12 fter tretment. Postopertive IOP vlues nd effective rtes of tretment (IOP decrese > 20% seline IOP) for ech energy group t vrious time points were nlyzed using SAS sttisticl softwre (SAS, Inc., Cry, NC). For ptients with unstisfctory IOP control (IOP decrese < 20% seline IOP over preopertive vlue), drug therpy or surgicl tretment ws recommended. During follow-up, ptients who received drug therpy or treculectomy seceded from the tril. RESULTS Thirty-nine eyes of 39 ptients were included in the low-energy group nd 29 ptients finished the 1- yer follow-up. Thirty-five ptients were included in the control group nd 28 ptients finished the 1-yer follow-up. The two groups hd no significnt differences in gender, ge, seline IOP, or type of dignosis. Ptient demogrphics re shown in Tle 1. At follow-up, we found complictions tht occurred in the low-energy group were fewer thn those in the control group nd tht low-energy SLT cuses no reltively severe complictions, including trnsient IOP spike or peripherl nterior synechi. Lser-induced complictions re shown in Tle 2. The postopertive men IOPs re shown in Tles 3 nd 4. Ptients who seceded from the tril re lso listed. We found tht the men IOP decresed significntly in oth groups. Tle 5 shows the percentge of eyes tht qulified for the definition of success (> 20% IOP reduction) t ech time point. The difference etween the two groups did not rech sttisticl significnce. 60 Copyright SLACK Incorported

3 Tle 1 Bseline Chrcteristics of Ptients Chrcteristic Low-Energy Age (y) ± (35 73) DISCUSSION ± (32 79) The initil design of SLT ws sed on the hypothesis tht lser selectively cts on the pigmented treculr meshwork cells nd leds to micro-explosion of those cells, nd cytokines relesed from the collpsed treculr meshwork cells ttrct mcrophges, which engulf pigment nd tissue deris tht lock the treculr P.279 Gender.949 Totl Mle Femle Bseline IOP (mm Hg) Dignosis ± 2.24 ( ) ± 1.85 ( ).232 OHT Suspected glucom POAG IOP = introculr pressure; OHT = oculr hypertension; POAG = primry open-ngle glucom. Student t test. Chi-squre test. Compliction Tle 2 Postopertive Complictions meshwork, therey incresing the queous humor dringe. However, cliniclly, the continuous wve 514-nm rgon lser treculoplsty, the continuous wve 532- nm frequency-douling Nd:YAG lser treculoplsty, nd the micro-pulse 810-nm diode lser treculoplsty my chieve similr IOP-lowering effects. Therefore, we speculted tht different lsers work through the sme mechnisms wherey tissue cells produce stress response to non-lethl dmge, leding to series of chnges in the micro-environment: the cscding relese of cyto- Low- Energy Mild pin 0 4 (11.4%) Conjunctivl 8 (20.5%) 11 (31.4%).283 hyperemi Mild nterior uveitis 2 (5.13%) 5 (14.3%).174 Cornel edem 0 0 Introculr hemorrhge 0 0 Trnsient IOP spike 0 3 (8.57%) Peripherl nterior synechi 0 1 (2.86%) c IOP = introculr pressure. Chi-squre test. Likelihood rtio chi-squre test. c One month fter selective lser treculoplsty. P Tle 3 IOP Lowing in Low-Energy Time Period Men IOP (mm Hg) t c P Seceded From the Tril Pre-tretment ± 2.24 (n = 39) 2 w post-tretment ± 2.00 (n = 39) ptients 1 m post-tretment ± 2.01 (n = 37) ptients (received drug therpy) 3 m post-tretment ± 1.96 (n = 35) ptients (received drug therpy) 6 m post-tretment ± 1.93 (n = 32) ptients (received drug therpy) 12 m post-tretment ± 1.83 (n = 29) ptients (2 received drug therpy, 1 received treculectomy) IOP = introculr pressure. In the low-energy group, the lser energy ws hlf of the therpeutic energy used in the control group (usully 0.3 to 0.5 mj), nd the selective lser treculoplsty ws pplied over 360 of the treculr meshwork t 100 points, 25 in ech qudrnt. During follow-up, ptients who hd unstisfctory IOP control nd received drug therpy or treculectomy seceded from the tril. c Student t test (ech time point post-tretment vs pretretment). Ophthlmic Surgery, Lsers & Imging Vol. 42, No. 1,

4 Tle 4 IOP Lowing in the Time Period Men IOP (mm Hg) t P Seceded From Tril Pre-tretment ± 1.85 (n = 35) 2 w post-retment ± 2.03 (n = 35) ptients 1 m post-tretment ± 2.09 (n = 34) ptient (received drug therpy) 3 m post-tretment ± 2.18 (n = 33) ptient (received drug therpy) 6 m post-tretment ± 2.09 (n = 31) ptients (received drug therpy) 12 m post-tretment ± 1.98 (n = 28) ptients (received drug therpy) IOP = introculr pressure. In the control group, the routine therpeutic energy of selective lser treculoplsty is used (usully 0.6 to 1.0 mj) nd the selective lser treculoplsty ws pplied over 360 of the treculr meshwork t 100 points, 25 in ech qudrnt. Student t test (ech time point post-tretment vs pretretment). Tle 5 Effective Rte in Low-Energy Versus Time After Tretment Low-Energy 2 w 69.23% (27/39) 1 m 64.10% (25/39) 3 m 61.54% (24/39) 6 m 53.85% (21/39) 12 m 48.72% (19/39) C2 P 71.43% (25/35) 71.43% (25/35) 60% (21/35) 51.43% (18/35) 48.57% (17/35) If introculr pressure decresed 20% or greter seline IOP, the tretment ws considered effective (chi-squre test). kines, metlloproteinse (MMP-3) upregultion, 18 nd incresed expressions of the treculr meshwork glycosylted protein. 19 Currently, scholrs elieve IOP-lowering effects re derived from injured treculr meshwork cells, not ded ones. 20 In this cse, the previously recommended energy threshold for SLT my e set too high. The routine therpeutic energy of SLT is often 0.1 mj less thn the lest energy cple of producing chmpgne-like ules on the surfce of the treculr meshwork. If the focusing fctor of the opertor is not considered, tht energy will e siclly stle for ech individul during tretment. In this study, good IOP-lowering effects were chieved in ptients in the control group nd the IOP decrese nd efficcy rte were close to those of relted reports. 21,22 However, we lso found in clinicl prctice tht some ptients with POAG otined lower IOP y SLT, ut in their tretment we did not lwys produce chmpgne-like ules. Therefore, sometimes their therpeutic energy should not rech the routine energy. This result prompted us to try lower energy in clinicl tretment. In the low-energy group, reltively high effective rte ws chieved using only hlf the lser energy of conventionl SLT. Although the erly effective rte in the low-energy group ws slightly lower thn tht in the control group (difference not sttisticlly significnt), the effective rtes in the two groups grdully ecme closer over time. Low-energy SLT lso seems to trigger iologicl effects in the treculr meshwork tht lower IOP nd this effect hs long-term stility. Bsed on this result, we posit individul vritions in sensitivity to SLT nd tht low-energy SLT cn chieve significnt effects in SLT-sensitive ptients. In clinicl ppliction of SLT, continuous nonoverlpping lser is often imed t 180 or 360 of the treculr meshwork to pproximtely 25 points in ech qudrnt. Studies suggest tht the IOP-lowering effects of SLT t 180 of the treculr meshwork were similr to those of SLT over 360 of the treculr meshwork, 23 ut incresed lser shot points in ech qudrnt (from 25 to 50 points) lowered SLT efficcy. 24 Therefore, simple increse in intensity of lser tretment does not improve the curtive effect. Some studies even suggest good IOP-lowering effects when treting only 90 of the treculr meshwork. 25 Together, these results seem to suggest series of iologicl rections in the treculr meshwork re triggered when the lser stimulus reches certin threshold, de- 62 Copyright SLACK Incorported

5 cresing IOP, ut further increses provide no enefit. Therefore, determining this threshold is importnt for clinicl ppliction. In this study, we treted 360 of the treculr meshwork (t 100 points) using continuous non-overlpping lser for the control group nd 360 of the treculr meshwork (t 100 points) for the low-energy group to oserve the efficcy etween the two groups. This prctice should not e tken to indicte tht we think tht 360 is the optiml tretment rnge for the low-energy group. The tretment rnge nd optiml numer of shot points will e the direction of our future reserch. Most SLT tretments re sfe nd considered repetle. 26 However, we must e cutious out the occurrence of serious complictions in clinicl prctice. Low-energy SLT cuses fewer complictions thn control SLT, nd its ppliction is sfer. Moreover, it uses less energy, interfering less with the structure of the treculr meshwork. Therefore, the lser tretment cycle cn e extended nd indictions for lser tretment cn e rodened. These re the gretest potentil dvntges of low-energy SLT tretment. The optiml energy prmeters of low-energy SLT nd its long-term efficcy re yet to e determined in lrge smple-sized controlled clinicl studies nd verified y relted sic reserch. Nevertheless, low-energy SLT shows promise s new clinicl ppliction of SLT. Compred with control SLT, low-energy (using hlf the conventionl energy) SLT hs similr IOPlowering effect nd cuses fewer complictions, mking it sfe nd effective lterntive for lowering IOP. REFERENCES 1. Worthen DM, Wickm MG. Argon lser treculotomy. Trns Am Acd Ophthlmol Otolryngol. 1974;78: Brncto R, Crss R, Trucchi G. Diode lser compred with rgon lser treculoplsty. Am J Ophthlmol. 1991;112: Morirty AP, McHugh JD, Splton DJ, Ffytche TJ, Shh SM, Mrshll J. Comprison of the nterior chmer inflmmtory response to diode nd rgon lser treculoplsty using lser flre meter. Ophthlmology. 1993;100: Andreic V, Miljkovic A, Bic N. 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