Comparison of Conventional Phacoemulsification Technique VS. Cool Phacoemulsification Technique with the Importance of Phacoemulsification Variables

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1 ORIGINAL ARTICLE Comparison of Conventional Phacoemulsification Technique VS. Cool Phacoemulsification Technique with the Importance of Phacoemulsification Variables Shahid Wahab, Khowaja Faiz-ur-Rub and Lakhani Das Hargun ABSTRACT Objective: To compare the efficacy and outcome after cool phacoemulsification with conventional phacoemulsification techniques in terms of effective phacoemulsification time (EPT), wound size and operative complications along with other variables used for the technique. Study Design: Randomized controlled clinical trial (RCCT). Place and Duration of Study: Ophthalmology Unit III, Sindh Government Lyari General Hospital and DUHS and Al-Noor Eye Hospital, Karachi, from January to December Methodology: One hundred eyes with nuclear/cortico-nuclear cataract on LOCS III (Lens Opacities Classification System III) underwent phacoemulsification. Fifty eyes were randomized to have surgery by standard phacoemulsification technique and the other 50 eyes by cool phacoemulsification technique. Efficacy and outcomes were judged in terms of variables like effective phaco time, vacuum and power used, quantity of Ringer's lactate solution used and corneal burn. The results between the two groups were compared. Results: Among the phaco variables, the vacuum used in all cases ranged from 100 to 200 mmhg in group A with mean vacuum of and 300 to 350 mmhg with mean value of in group B at phaco II (p < 0.001). There was a significant difference in amount of Ringer s lactate used during surgery with ml in conventional phacotechnique as opposed to ml in cool phacoemulsification (p < 0.001). EPT in group A was between 30 to 180 seconds with mean of seconds while in group B, it ranged between 2 to 12 seconds with mean of seconds (p < 0.001). Rate of intra operative complications was lower in cool phacoemulsification (2%) as compared with conventional technique (18%, p=0.008). Conclusion: Cool phacoemulsification is a safe technique to operate cataract of all grades. It seems to be superior as it reduces effective phaco time, less operative and postoperative complications and is, therefore, safer for the cornea especially with regard to corneal wound burn. However, significantly greater amount of vacuum is needed. Key words: Cool phacoemulsification. Conventional phacoemulsification. Effective phaco time. Vacuum. Complication. INTRODUCTION Department of Ophthalmology, Lyari General Hospital, DUHS, Karachi. Correspondence: Prof. Shahid Wahab, 45-B, Sindhi Muslim Cooperating Housing Society, Karachi. nosherwan@cyber.net.pk Received Jun 25, 2009; accepted May 18, Cataract is the leading cause of reversible blindness worldwide, as it accounts for almost 16 million cases of blindness and 50 million patients of low vision. 1 Cataract accounts for 66% cases of blindness in Pakistan. 2 About 2.5 million people are blind due to cataract in one eye and another 1.5 million in both eyes. 3 Cool phacoemulsification is an effective and safe technique to manage all types of cataract. 4 During cool phacoemulsification, phaco tip is used in the micro-pulse mode, where the pulse is set between 8-10 pulses of phaco power per second, with the rest period of 90% or above which allows rapid dispersion of heat at ultrasound tip with minimization of thermal effect on cornea, hence the term cool. 5 During traditional phacoemulsification the probe operates at a frequency of Hz while in the burst or micropulse sonic mode it operates at 400 Hz. 6 The potential advantages of this technique are the reduction of total ultrasound power to anterior segment leading to less surgical tissue damage and less postoperative corneal edema. 7,8 The purpose of this study was to compare the efficacy and outcomes of cool phacoemulsification and conventional phacoemulsification in terms of effective phacoemulsification time (EPT), wound size and operative complications other variables used for the phaco-techniques. METHODOLOGY This study comprised of data of 100 eyes, which underwent phacoemulsification surgery between January and December 2008 at Ophthalmology Department, Unit III, Sindh Government Lyari General Hospital, DUHS and Al-Noor Eye Hospital, Karachi. Patients of either gender and age group between years having nuclear cataract grade II-IV according to Lens Opacification Classification System III (LOCS III), 9 Journal of the College of Physicians and Surgeons Pakistan 2010, Vol. 20 (7):

2 Shahid Wahab, Khowaja Faiz-ur-Rub and Lakhani Das Hargun were included in this study. Myopic (up to 6.0D) and deep seated/sunken eyes were also included. Patients having corneal and vitreo-retinal pathology, glaucoma, traumatic cataract, cataract with pseudoexfoliation and posterior synechiae, and eyes with previous intra-ocular surgeries were excluded. The principal author performed all surgeries with uniform parameters already defined in proforma. Patients were randomly divided in two groups comprising 50 cases in each group. Group A underwent standard phacoemulsification technique (incision size 3.2 mm, continuous mode) and Group B underwent cool phacoemulsification technique (incision size 2.75 mm, pulse mode). Bimanual phaco was done with irrigating chopper, 30 o phaco tips of the size 0.9 mm. Phacoemulsification was done with and without sleeve. Wound size was enlarged to 5.25 mm for rigid IOLs (intra-ocular lenses) only. Patients were explained about the pros and cons of both techniques and were randomly assigned to either group after obtaining an informed and written consent. All surgical events were noted carefully and subsequent amendments made in parameters to meet efficient results. Interplay of variables was noted for surgeon s guideline. Per-operative complications were noted between the two techniques. Efficacy and out comes were judged in terms of phaco variables like effective phaco time, vacuum and power used, amount of Ringer's lactate solution used and corneal burn. Followup was maintained strictly. SPSS version 15.0 was employed for data analysis. All continuous response variables like patients age, EPT, vacuum and quantity of Ringer s lactate were presented by mean+sd and were compared by applying student s t-test. Qualitative response variables like gender, laterality, cataract grading, Best Corrected Visual Acuity (BCVA) and operative complications were compared between two groups by applying chi-square test. Fisher s exact test was used if any variable count was less than 5, where as p-value < 0.05 was considered significant. RESULTS In group A (conventional phacoemulsification), there were more males (56%) than females (44%), while there were more females (52%) than males (48%) in group B (cool phacoemulsification). Mean age of patients in group A was years while that in group B was years. Thirty four patients in group A had grade II cataract as opposed to only 27 patients in group B. Fourteen patients in group A and 18 in group B had grade III cataract. There were 02 patients in group A and 05 patients in group B with grade IV cataract. There were 07 myopic eyes in group A as opposed to 06 in group B. Phacoemulsification was technically difficult due to deep-seated or sunken eyes in 06 patients in group A and 09 patients in group B. Among the phaco variables, the power setting in group A at phaco II ranged from 30-60% with mean value of , while in group B it ranged from 30-80% with mean value of which was statistically significant (p < 0.001). The vacuum used at phaco I ranged from 5-20 mmhg in group A with mean value of and mm Hg with mean value of in group B. The vacuum used at phaco II ranged from mm Hg in group A with mean vacuum of and mmhg with mean value of in group B. This shows that a significantly greater amount of vacuum was needed during cool phaco at phaco I (p < 0.001) and at phaco II (p < 0.001) as compared to conventional phaco. Flow rate in both groups was insignificantly different. There was a statistically significant difference (p < 0.001) of amount of Ringer s lactate used during surgery with ml in conventional phaco as opposed to ml in cool phaco. EPT in group A was between seconds with mean of seconds while in group B, it ranged between 2-12 seconds with mean of (p < 0.001, Table I). Table I: Surgical parameters. Parameters Group A (n=50) Group B (n=50) p-value Bottle height (cm) 63.3± ± (50-70) (50-70) Power setting (%) Phaco-I 67.4±7.4 (30-70) 66.9±7.7 (30-70) Phaco-II 57.2±6.7 (30-60) 73.3±11.5 (30-80)* < Vacuum (mm Hg) Phaco-I 16.1±5.3 (5-20) 45.8±6.1 (30-50)* < Phaco-II 145.3±29.6 ( ) 325.8±14.5 ( )* < Flow rate (cm 3 /min) Phaco-I 23.7±0.6 (22-24) 23.9±1.2 (20-25) Phaco-II 23.5±0.9 (22-24) 23.8±1.3 (20-25) Quantity of Ringer s 158.2±24.8 ( )* 123.3±23.0 (75-150) < lactate used (ml) Phaco mode Continuous Pulse Effective phaco time 111.3±40.4 (30-180)* 6.1±2.92 (2.0-12) < EPT (seconds) Values given in Column-II and III are Mean±SD (Range). *Shows significantly higher average of the group at p 0.05 level of significance. Thirty eight patients in group A received rigid Poly Methyl Meth Acrylate (PMMA), 5.2 mm diameter optic IOL, while 12 patients were implanted foldable acrylic IOL. All IOLs were implanted in the capsular bag except one, which was implanted in the ciliary sulcus. All those patients who received PMMA IOLs recieved one suture to close the wound. In group B, there was only 01 rigid PMMA IOL implanted and one suture was applied. All other IOL implantation in this group was in the capsular bag with no suture. Rate of intra operative complications were lower in cool phacoemulsification (2%) as compared with conventional technique (18%, p=0.008). Only 01 eye out of 50 patients in group A had posterior capsular rent during surgery, which was managed successfully, and PMMA 450 Journal of the College of Physicians and Surgeons Pakistan 2010, Vol. 20 (7):

3 Conventional phacoemulsification technique vs. cool phacoemulsification technique IOL was implanted within the sulcus. In this group, phaco tip was blocked/choked in 01 case. Mild phaco wound burn was noted in 03 cases and moderate wound burn occurred in 02 cases in group A. Iris damage was noted in 01 eye, in which pupil became smaller during surgery in group A. Posterior capsular rent occurred in 01 case which was managed with anterior vitrectomy and PMMA IOL was implanted in the sulcus (Table II). Table II: Per-operative complications. Complications Group A (n=50) Group B (n=50) p-value Incomplete capsulorrhexis Nil Nil -- Extension of capsulorrhexis Nil Nil -- Anterior chamber collapse Nil Nil -- Phaco tip blocked/choked One Nil -- Wound burn Mild-moderate-severe Nil Nil Iris chef Nil Nil Small pupil One Nil -- Posterior capsule rent One (vitreous show) One (no show) -- with or without vitreous show Anterior vitrectomy One Nil -- Total No. of complications 09 (18%) One (02%) Postoperatively in group A, BCVA at day 01 was 6/6 in 20 (40%) eyes, 6/9 in 10 (20%) eyes, 6/12 in 13 (26%) eyes and 6/18 in 07 (14%) eyes. In group B, visual outcome at day 01 was slightly better with 25 (50%) eyes having BCVA of 6/6, 13 (26%) with 6/9, 09 (18%) with 6/12 and 03 (06%) with 6/18. There was no significant difference in postoperative visual outcome in both groups at the first week and first month follow-up. There was greater incidence of striate keratitis on the first postoperative day in group A (14%) as opposed to group B (04%). DISCUSSION The trend in modern cataract surgery is towards the evolution of techniques that permit cataract extraction through smaller incisions. The smaller incision makes the surgery less invasive and safer, resulting in less postoperative inflammation, fewer incision-related complications, lower surgical induced astigmatism and shorter or total surgical time. This study objectively analyzed the different variables of phacoemulsification between the 2 techniques. It showed that the 2 techniques are safe for all grades of cataract and produce excellent visual results after the surgery. The cool phacoemulsification technique is associated with lower incidence of per operative complications but the small difference is not a clear-cut advantage. Nawrocki et al. compared cool phaco with conventional phaco and showed good anatomical and functional results in all cases of cool phaco. 10 The bimanual technique shortens the time of ultrasound usage and reduces postoperative astigmatism. This study also confirms the same observations with regard to EPT and less number of complications in cool phaco. There was also a statistically significant difference in the quantity of Ringer s lactate used during surgery, with lesser amounts during cool phacoemulsification. This difference is explainable on the basis that a larger bore (19 gauge) needle used in conventional technique aspirates more fluids during surgery and also port-site leakage through a larger incision is more likely. Effective phaco time (EPT) is equivalent time to 100% of phaco power. It is calculated by multiplying total phaco time in seconds by the average power percent used. 11 Kahraman et al. compared small incision cataract surgery (SICS) with micro-incision cataract surgery (MICS) and observed that mean EPT was significantly higher in SICS. 5 Shoaib observed that EPT in MICS was less as compared to conventional coaxial phaco. 11 This study also revealed that the mean EPT was significantly less in cool phaco as compared to conventional phaco. The interplay of various parameters of phaco power, aspiration flow rate and vacuum is similar to the interactions in a Rubik cube where even one move impacts on whole setting and creates a totally different scenario. In phacoemulsification there are more than 50 static and dynamic variables with different combinations. Before embarking upon phaco surgery, one should have theoretical knowledge of these variables and constant attention required during surgery. The surgeon has to anticipate these interactions and react accordingly. The different phacoemulsification related variables that can have impact on the eventual outcome of surgery are detailed in Table III. For cool phacoemulsification, temperature of phaco tip is an important factor that must be well addressed. Several studies have evaluated the thermal impact of a vibrating needle Other studies assessed temperature at incision site using a bare ultrasound tip. 17,18 Some studies show the benefits of reducing delivered thermal energy by using various surgical techniques. 19,20 For discussion of variables we need to recapitulate essential phacoemulsification terminologies. The basic power modes are continuous, pulse and burst. 21 Continuous power setting delivers power continuously depending upon how long the foot pedal is depressed. During pulse mode, intermittent ultrasound power is delivered in duty cycles i.e. after each pulse of energy delivered (on-period) there is a period during which no energy is supplied (off-period). 21 During burst mode, each burst of energy has the same amount of power but the interval between each burst decreases, as the foot pedal is depressed. 22 The combination of pulse and burst modes makes the use of ultrasound energy more efficient. Fluidics is a science or technology dealing with control of flow of fluid or air through a system. 23 The fluid inflow and outflow from the eye is determined by bottle height, pump speed, size of tubing and additional flow such as Journal of the College of Physicians and Surgeons Pakistan 2010, Vol. 20 (7):

4 Shahid Wahab, Khowaja Faiz-ur-Rub and Lakhani Das Hargun Table III: Interplay of variables. Patient State of orbit like deep sunken eye Depth of anterior chamber Refractive state like high myopia State of zonules Nervous/anxious patient Density of cataract Chronic obstructive lung disease Polar cataract High astigmatism Operated eye Vitrectomized eye Laterality (right or left eye) Technique Anaesthesia Capsulorrehexis Retrobulbar Small or Large Peribulbar Methylene Blue for hypermature Sub-tenon Needle or Forceps Topical Hydrodissection/Hydrodelineation Type and site of incision Technique Scleral Sculpting Limbal Divide and Conquer Corneal Stop and Chop Superotemporal or temporal Pre Chop Multiple ports Bimanual Construction of wound MICS Viscoelastic Separate infusion/dual infusion/irrigating chopper Methylcellulose Irrigation/aspiration Sodium hyaluronate Simcoe cannula Chondroitin sulphate Separate infusion/active suction Fluids IOL implantation BSS Forceps Ringer s lactate Injector Machine and technology Probe Fluidics Proper tuning Free flow Proper tightness of tip Flow rate Proper tubing Follow ability Tip bevel (0 o, 15 o, 30 o, 45 o ) Bottle height Kelman tip Mode Neosonix/ozil Continuous Sleeve Pulse Pump Burst Peristaltic Power setting Venturi Chatter Diaphragmatic Vacuum Surge Holdability Chamber maintainer Occlusion Sound (created sound not an ultrasound) Foot pedal Irrigation/aspiration Linear Occlusion Preset phaco Resistance Reflux Operation theatre Microscope (red reflex) Machine (all machines behave differently) Instruments OT technicians (experience and knowledge) Surgeon s chair (working distance) Operation table (working distance) Skill Stereopsis Dexterity Capsulorrhexis (skill) Good use of technique and technology Change technique with change of parameters Knows when to stop Knows when to convert Knows when to refer Should not copy other surgeons Good control on foot pedal in all three positions Recognizes sounds in different modes 452 Journal of the College of Physicians and Surgeons Pakistan 2010, Vol. 20 (7):

5 Conventional phacoemulsification technique vs. cool phacoemulsification technique an irrigating chopper. Irrigation is the flow of fluid into the eye and is dependent and determined by above factors. 23 Aspiration flow rate (AFR), often referred as flow rate, is the rate at which fluid is removed from the eye. It is controlled by pump speed and measured in cc/minute. Rise time is the rate at which vacuum builds once the aspiration port has been occluded. 23 Followability is the tendency of the nucleus or its fragments to be attracted to and stay on the phaco tip. 23 Shoaib showed high vacuum and high flow levels are required in bimanual phaco. 11 Chatter occurs when the ultrasonic stroke overcomes the vacuum or holding power and causes the nuclear fragments to be repelled from the ultrasonic tip. 8 Surge occurs when vacuum has built up because of an occlusion and the occlusion is suddenly broken, leading to the fluid in the higherpressure (positive) anterior chamber tending to rush into the lower-pressure (negative) phaco tip. 24 Knowledge of all above discussed variables is important to use in the technology and skill of the surgeon to give the best results to the patient. Endothelial cell count gives useful information where specular microscope is available. CONCLUSION Cool phacoemulsification is a safe technique to operate cataract of all grades. It is superior in reducing effective phaco time and having, less operative and postoperative complications. It is, therefore, safer for the cornea, especially with regard to corneal wound burn. Acknowledgement: We are thankful to Mr. Intisar Ahmad Siddiqui, Senior instructor-hcsm Program Coordinator, Department of Medical Education, CPSP, Karachi for his guidance in statistical data analysis. REFERENCES 1. Resnikoff S, Pascolini D, Etya'ale D, Kocur I, Pararajasegaram R, Pokharel GP, et al. Global data on visual impairment in the year Bull World Health Organ 2004; 82: Epub 2004 Dec Memon MS. Prevalence and causes of blindness in Pakistan. J Pak Med Assoc 1992; 42: Ahmad K, Khan MD, Qureshi MB, Munami S, Shah RA, Rasheed H, et al. Prevalence and causes of blindness and low vision in a rural setting in Pakistan. Ophthalmic Epidemiol 2005; 12: Olson RJ. Clinical experience with 21-gauge manual microphacoemulsification using Sovereign White Star Technology in eyes with dense cataract. J Cataract Refract Surg 2004; 30: Kahraman G, Amon M, Franz C, Prinz A, Abela-Formanek C. Intraindividual comparison of surgical trauma after bimanual microincision and conventional small-incision co-axial phacoemulsification. J Cataract Refract Surg 2007; 33: Comment in: J Cataract Refract Surg 2007; 33(12):2007; author reply Verges C, Cazal J, Lavin C. Bimanual cataract surgery with micropulsed ultrasound. Highlights Ophthalmol 2005; 33: 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: Comment in: J Cataract Refract Surg 2001; 27(2): Chylack LT Jr, Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, et al. Lens opacities classification system III; the longitudinal study of cataract study group. Arch Ophthalmol 1993; 111: Nawrocki J, Michalewski J, Michalewska Z, Cisiecki S. Cool phaco-new option in cataract surgery. Klin Oczna 2005; 107: Shoaib KK. Micro Incision cataract surgery (MICS)/bimanual phacoemulsification. Initial problems and the solutions. Pak J Ophthalmol 2009; 25: Osher RH, Injev VP. Thermal study of bare tips with various system parameters and incision sizes. J Cataract Refract Surg 2006; 32: Olson MD, Miller KM. In-air thermal imaging comparison of Legacy AdvanTec, Millennium, and Sovereign WhiteStar phacoemulsification systems. J Cataract Refract Surg 2005; 31: Mackool RJ, Sirota MA. Thermal comparison of the AdvanTec Legacy, Sovereign WhiteStar, and Millennium phaco-emulsification systems. J Cataract Refract Surg 2005; 31: Comment in: J Cataract Refract Surg 2006; 32:1896-7; author reply Bissen-Miyajima H, Shimmura S, Tsubota K. Thermal effect on corneal incisions with different phacoemulsification ultrasonic tips. J Cataract Refract Surg 1999; 25: Majid MA, Sharma MK, Harding SP. Corneoscleral burn during phacoemulsification surgery. J Cataract Refract Surg 1998; 24: Tsuneoka H, Shiba T, Takahashi Y. Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refract Surg 2001; 27: Comment in: J Cataract Refract Surg 2001; 27(10): Soscia W, Howard JG, Olson RJ. Bimanual phacoemulsification through 2 stab incisions; a wound temperature study. J Cataract Refract Surg 2002; 28: Comment in: J Cataract Refract Surg 2003; 29:233-5; author reply DeBry P, Olson RJ, Crandall AS. Comparison of energy required for phaco-chop and divide and conquer phacoemulsification. J Cataract Refract Surg 1998; 24: Wong T, Hingorani M, Lee V. Phacoemulsification time and power requirements in phaco-chop and divide and conquer nucleofractis techniques. J Cataract Refract Surg 2000; 26: Devgan U. Phaco fluidics and phaco ultrasound power modulations. Ophthalmol Clin N Am 2006; 19: Boyd BF. Cool phacoemulsification with micro incisions - New dynamics. Highlights Ophthalmol 2003; 31: Coombes AG, Gartry DS. Fundamentals of clinical ophthalmology: cataract Surgery. London: BMJ Publishing Group; Seibel BS. Phacodynamics: mastering the tools and techniques of phacoemulsification. 3rd ed. Thorofare (NJ):Slack Inc.; Journal of the College of Physicians and Surgeons Pakistan 2010, Vol. 20 (7):