1 LASIK Michael Lawless, MBBS Christopher Hodge, BAppSc(Orth) Introduction History and Definitions Myopia and myopic astigmatism are complex eye conditions that affect an estimated 1.6 billion people worldwide. In western populations, it is thought to be approximately 25% and the prevalence is much higher (70% to 90%) in selected regions of Asia. 1,2 The excimer laser was introduced as an experimental device with Trokel s first article in Twenty-nine years later laser in situ keratomileusis (LASIK) is the most frequently performed elective surgical procedure in the world. It is used to treat refractive errors such as myopia, hyperopia, and astigmatism, in both normal eyes and in eyes after corneal transplantation and cataract and lens surgery among others. Initially excimer lasers were used to perform photorefractive keratectomy. The impediments to the widespread use of photorefractive keratectomy were postoperative pain and delayed visual recovery, and also the greater incidence of corneal haze and night glare symptoms with higher myopic corrections. LASIK overcame the issues of pain and delayed healing and expanded the range to include higher myopic corrections. 4 Building on the concepts of in situ keratomileusis from Barraquer and automated lamellar keratoplasty, LASIK as a concept was first described by Gholam Peyman in 1985 and later patented in Lucio Buratto from Italy described the creation of a free cap of cornea made by a mechanical microkeratome, followed by excimer laser ablation on the back surface of the cap. 5,6 There were problems centering the ablation on the back of the cap; so, Pallikaris in Greece in 1988 described the creation of a lamellar corneal flap with the INTERNATIONAL OPHTHALMOLOGY CLINICS Volume 53, Number 1, r 2013, Lippincott Williams & Wilkins 111
2 112 Lawless and Hodge microkeratome and then applying the excimer laser to the host stromal bed under the flap. 7,8 It was Pallikaris who coined the term laser in situ keratomileusis (LASIK). LASIK Technique LASIK involves the creation of a lamellar corneal flap, lifting of the flap, and ablation of the underlying stromal bed. When LASIK began the flap was created with a mechanical microkeratome and the use of a femtosecond laser to create the corneal flap was first described by Ratkay-Traub in Our technique could be considered representative and is described as follows: Upon admission the patient is provided with the opportunity to take an oral sedative (Valium 5 mg, etc.). Once the sedative has taken effect the patient will be prepped for surgery. Topical anesthetic (BNX, Benoxinate Minims; Chauvin Pharmaceuticals, UK), antibiotic [ciprofloxacin (Ciloxan); Alcon Laboratories Inc., Ft Worth, TX], and antiinflammatory drops [dexamethasone (Maxidex); Alcon Laboratories Inc.] are instilled 1 minute apart. The operated eye/s are then swabbed with betadine (PVP iodine prep and scrub swabsticks; PDI Inc., Orangeburg, NY) immediately before entry in the room for the femtosecond laser (Intralase; AMO Abbott, Santa Ana, CA) procedure. The patient lies on the bed while the surgeon orientates the laser. A suction ring is applied to the patients eye taking care to center the ring over the eye. The use of a speculum is optional and depends on surgeon preference and/or patient anatomy. The patient interface is inserted into the laser arm and this is brought down to connect with the suction ring to form a complete set. At this point, the surgeon will verify the laser settings and position of the intended ablation. When satisfied, the surgeon will apply the footswitch to begin the ablation. Once complete, the suction ring will be removed and the patient interface withdrawn. The patient is then moved to the excimer laser. A further drop of anesthetic is instilled before the surgical drapes being applied to the lids. The speculum is then inserted. The laser-created hinged flap is lifted with the aid of a disposable LASIK cannula (Lindstrom LASIK Cannula; Oasis Medical, CA). A sterile swab may be used to remove any excess moisture or particles from the stromal bed immediately before the laser. After the excimer ablation, the flap is replaced and balanced salt solution (Alcon Laboratories Inc.) is used to irrigate the interface. Once the surgeon confirms the position of the flap, ciprofloxacin and dexamethasone are applied before the speculum and drapes being removed. The patient is then viewed on the slit-lamp microscope before discharge.
3 LASIK 113 Panadeine tablets given to aid pain relief over the initial 24 hours after surgery are provided. Techniques vary widely and one interesting approach is that taken by Probst. 10 His view is that as femtosecond LASIK eliminates the need for a blade to create the LASIK flap, the procedure can reasonably be performed as a completely disposable operation. He uses a disposable lid speculum and then creates the LASIK flap with an IntraLase laser that uses a disposable applanation cone. Disposable sponges are used during the procedure to control hydration and eye movement. Given that the only step that could reasonably prevent LASIK from being completely disposable is lifting the flap after the IntraLase flap creation, Probst uses a disposable 27-G hydrodissection cannula, which is commonly used in cataract surgery for this part of the procedure. Probst s rationale for introducing all disposable LASIK is to try and avoid the 2 potentially serious, but rare, complications diffuse lamellar keratitis (DLK) and infectious keratitis. The disposable approach would not eliminate the risks of these but would reduce the risk of contamination in a significant way. He also believes that disposable instruments also improve the surgical efficiency of LASIK as surgical assistants are no longer required to move instruments in and out of autoclaves and surgical trays can be set up in advance of the procedure without waiting for the sterilization of instruments. Mechanical Microkeratome Versus Femtosecond Flap Creation What began with a single model (IntraLase) to create a femtosecond LASIK flap has gone through many developments with multiple competing technologies available around the world. The proportion of LASIK performed with femtosecond lasers continues to increase with over 50% of LASIK procedures in the United States performed using femtosecond lasers. 11 The Market Scope second quarter survey in 2010 revealed that 69.5% of LASIK flaps were created with a femtosecond laser. The femtosecond laser photo disrupts tissue at a set depth producing small bubbles consisting of water and carbon dioxide. These bubbles expand and separate the corneal lamellae, which then creates a resection plane. 12 A high-quality corneal flap is critical to an accurate visual result and also to prevent complications. In 2000 IntraLase (Abbott Medical Optics Inc.) became the first clinical femtosecond laser to be approved by the US Food and Drug Administration (FDA) for creating lamellar corneal flaps. There are now 4 further FDA-approved femtosecond laser systems the Femtec (2010: Technolas Perfect Vision GMBH), the FemtoLDV (previously Da Vinci Ziemer Ophthalmic Systems), the
4 114 Lawless and Hodge Visumax (Carl Zeiss and Meditec AG), and the WaveLight FS 200 (Alcon Laboratories Inc.). A summary of current femtosecond laser platforms is provided in Table 1. Two recent articles attempt to objectively analyze whether femtosecond LASIK flap creation is superior to mechanical microkeratome flap creation. 13,14 Zhang and colleagues attempted to evaluate and compare refractive outcomes, corneal higher-order aberrations, and early postoperative complications with the femtosecond laser and mechanical microkeratome for myopic LASIK. They used data sourced articles limited to randomized controlled trials from January 2000 to July Of the 139 potential relevant studies, 7 prospective randomized controlled trials published between 2005 and 2010 were included in their meta-analysis. IntraLase was the femtosecond laser used in all 7 trials. (Table 2). In terms of efficacy, in 2 of the trials all eyes achieved uncorrected distance visual acuity of 20/20 or better. One trial favored the femtosecond laser group and 2 other trials favored neither group. For 6 months or longer data, which was available in 3 of the trials, no group had a better efficacy outcome (P = 0.78). For higher-order aberrations derived from the anterior corneal surface, the mechanical microkeratome group was associated with greater total and spherical aberration values than the femtosecond laser group with a statistically significant difference between groups in favor of the femtosecond laser. Complications were evenly divided with DLK more likely in the femtosecond group (P = 0.01), epithelial ingrowth at 1% the same in both groups, and buttonhole formation more likely in the mechanical microkeratome group. The pooled results showed no significant difference in the proportion of eyes with uncorrected distance vision of 20/20 or better, or within a target of ± 0.5 D. The safety measure loss of 2 or more lines of corrected distance visual acuity was less conclusive, because only one of the trials was considered robust enough to analyze and no sensitivity analysis could be performed. Because poor visual outcomes are very rare, it requires a large sample size to detect potential differences in safety. Zhang s analysis showed that total higher-order aberrations and spherical aberrations were higher with the mechanical microkeratome group than with femtosecond LASIK. The nonuniform meniscusshaped flap created by mechanical microkeratomes as compared with the more planar femtosecond flap could disrupt more anterior peripheral collagen lamellar, resulting in peripheral steepening, central corneal flattening, and consequently an increase in spherical aberration. Zhang concluded that because of the differing methods of testing they felt that these aberration results should be interpreted with caution. Javaloy et al 15 attributed the higher incidence of DLK to the greater inflammation induced by femtosecond energy at the interface. In
5 LASIK 115 Table 1. Summary of Current Femtosecond Platform Data Laser Platform Pulse Repetition Rate (khz) Laser Pulse Duration (fs) Wavelength (nm) Pulse Energy (nj) Spot Size (mm) Flap Diameter (mm) Flap Thickness (mm) Docking Interface Capabilities AMO Intralase Zeiss Visumax Technolas 520F < Flat LASIK Corneal Applications Intracorneal rings Max: Curved LASIK Corneal Applications Intracorneal rings ReLex FLEX Curved LASIK Intracorneal rings Intracor Arcuate incisions Ziemer LDV 20, , 9, 9.5, Flat LASIK Corneal Applications Intracorneal rings Wavelight FS mm in 0.5 mm steps LASIK indicates laser in situ keratomileusis Flat LASIK Corneal Applications Intracorneal rings Pockets
6 116 Lawless and Hodge Table 2. Main Characteristics and Quality Score of the Included Trials in Meta-analysis (Zhang et al 14 ) Mean Age (y) ± SD (Range) Mean Preop SE (D) ± SD Device Studyw (Year) Country FU (mo) Pts/Eyes (n) FS MM FS MM FS Laser MM Ablation Laser Outcome Assessor Masked Loss to FU (mo) Quality Score Calvo (2010)z 16 USA 36 21/42 38 ± 10 (22,54) 3.67 ± ± 1.69 Intralase* 15 khz Chan USA 12 51/ ± 7.8 (25/59) 3.76 ± ± 1.40 Intralase (2008)z,} khz Alió (2008) 18 Spain 3 33/ ± 6.32(19,43) 4.11 ± ± Intralase 4.01 ± 1.18z 30 khz Buzzonetti Hansatome* Star S4* Yes 0 3 Hansatome Star S4 NA 4 3 M2 or Carriazo* pendular (2008) * Italy 12 28/47 39 ± ± ± ± 3.30 Intralase Hansatome Technolas Montés-Mico Esiris* Yes 0 3 NA NA 1 Spain 6 100/ ± ± ± ± 1.63 Intralase CB* Visx S2 Yes 0 2 Durrie Yes 0 3 (2005)z,} * USA 3 51/ ± Intralase Hansatome Ladarvision Tran (2005) 22 USA 3 9/18 37 ± 9.5 (23,50) 2.58 ( 1.37, 4.00) 2.58 ( 1.25, 4.12) Intralase 10 khz Hansatome Technolas 217A* NA 0 2 *Manufacturers: Intralase, Intralase Corp.; Hansatome, Bausch & Lomb; Star S4 and S2, Visx; M2, Moria; Carriazo pendular, Schwind; Technolas 217, Bausch & Lomb; Carriazo-Barraquer, Moria; Ladarvision 4000, Alcon Laboratories Inc.; Technolas 217A, Bausch & Lomb. wfirst author. zpaired-eye study. }Wavefront-guided ablation. 8M2 mechanical microkeratome. zcarriazo pendular microkeratome. CB indicates Carriazo-Barraquer; FS, femtosecond laser; FU, follow-up; MM, mechanical microkeratome; NA, not available; Preop, preoperative; Pts, patients; SE, spherical equivalent.
7 LASIK 117 essence, the sample size for complications such as DLK, buttonhole, and epithelial ingrowth was too small to determine statistical differences between the femtosecond and mechanical microkeratome groups. Pooled data also showed a lower mean deviation from the intended flap thickness and a smaller SD of flap thickness in the femtosecond laser group. It is worth noting that newer generation mechanical microkeratomes such as the Carriazo pendulum (Schwind) can make thin flaps with relatively homogenous profiles that may rival those of the femtosecond laser. 18,23 Zhang s meta-analysis by their own admission has benefits and limitations. There are a relatively small number of cases in each trial so the analysis has relatively low power, especially for events with low incidence rates. That said, meta-analysis does provide more powerful evidence than individual reports alone. An inherent problem with metaanalysis is that they are trying to analyze a technique in evolution; for example the femtosecond laser has moved from 16 khz to regularly 60 khz and over 200 khz models providing less pulse energy and shorter flap cutting times. 24 With higher pulse rate modes providing tighter line separation, smoother corneal beds are produced. The assumption is that this will produce better visual and refractive outcomes. 25 Given more modern femtosecond laser platforms also allows less energy to be transmitted, this may result in a lower rate of DLK and transient light sensitivity syndrome. Thin-Flap LASIK Thin-flap LASIK was conceived to conserve stromal bed tissue, the suggestion being that this would decrease the risk of ectasia, and expand the ability to treat higher levels of myopia. The question mark over thinflap LASIK is whether a thin flap of approximately 90 mm would be as safely created as a flap of 110 to 120 mm. Very thin flaps can lead to gas breakthrough, microwrinkles, and subflap haze. Moshirfar and colleagues used an IntraLase FS60 to compare flaps of intended thickness of 120 versus 90 mm. They used the Visx Star SF Customvue excimer laser and in a prospective study at 6-month visual acuity of 20/20 or better was achieved in 98% of eyes with 120 mm, and 95% of eyes with 90-mm flaps and 20/15 uncorrected acuity was achieved in 50% of eyes with 120 mm and 45% of eyes with 90-mm flaps. 26 This was not a statistically significant difference. Both groups had significant increases in total higher-order aberrations (Pr0.003). There were no significant differences found between the groups in contrast sensitivity (PZ0.258) or corrected distance visual acuity (PZ0.726). Their conclusion was that thin-flap LASIK at 90 mm achieved similar results to 120-mm flap LASIK.
8 118 Lawless and Hodge Azar et al 27 analyzed what they called thin-flap or sub-bowman s keratomileusis (SBK) versus thick-flap LASIK for moderate to high myopia. This reflects the confusion in terminology. Thin-flap LASIK by their definition was flap thicknesses between 82 and 120 mm and thickflap LASIK were those >160 mm. The mean flap thickness in the SBK group was ± 9.2 mm SD and in the thick-flap group was mm with a SD of ± There were no differences in visual outcomes and their conclusion was that the safety, efficacy, and predictability of the SBK was similar to those of conventional thick-flap LASIK on corneas with equivalent residual stromal bed thickness. Complications of LASIK Yuen et al in published a 10-year prospective audit of LASIK for myopia in 38,000 eyes at the Singapore National Eye Centre. This was a prospective nonrandomized single-center multisurgeon study with patients undergoing LASIK between 1998 and They separated out intraoperative problems, which included flap complications (incomplete, dislodged, eccentric, or buttonhole flaps), decentered ablation zones, and loose epithelium. These accounted for 0.3% and 0.7% of total complications annually over the 10 years. Postoperative complications included flap striae, epithelial ingrowth, infection, DLK, and debris at the interface. They had 3 confirmed cased of infection during the 10- year period (0.008%). Their data were confused by an outbreak of DLK in 2007 because of the use of a Gentian Violet ink marker, which was promptly identified and controlled. There were 8 known cases (0.02%) of post-lasik ectasia. Totaling all the above complications, both intraoperative and postoperative, the annual complication rate ranged from 0.66% in 2003 up to 2.8% in Removing the DLK outbreak, the complication rate in 2007 would have been 1.19%. Most cases were performed with a mechanical microkeratome with the femtosecond laser being used relatively infrequently, and only in the later years. Of the 3 confirmed cases of infectious keratitis, these were all managed with flap lift and antibiotic washout and all recovered with good best corrected visual acuity without the need for further surgery. The incidence of complications may have been further reduced by the introduction of femtosecond laser technology. Binder and Sutton indicate in their respective papers a flap-related complication rate of between 0.7% and 0.8%. 29,30 Davison and Johnson 31 report a rate of 0.37% across 3009 consecutive cases from 2002 to All cases utilized the Intralase laser (AMO Abbott). The complications included 8 suction breaks, 1 incomplete flap, and 2 adherent flaps. All cases of the suction breaks continued immediately with a reapplication of a new patient interface. The remaining 3 cases were completed at a later date without incident. All
9 LASIK 119 patients achieved normal uncorrected and corrected visual acuity results. Dry eye is the most common surgical-related complication with an estimated 20% to 50% of patients suffering some mild form of discomfort during the short-term to mid-term postoperative period Levinson et al 35 describe dry eye as the major contributor to patient dissatisfaction after LASIK. Patients with existing dry eye conditions, females, patients with high laser corrections (or deeper ablation depth), thick flaps, and/or superior hinges seem to be at higher risk for developing significant dry eye It has been suggested that femtosecond lasers may induce less dry eye than mechanical microkeratomes. In a small, randomized control study Golas and Manche 40 demonstrated no significant statistical difference in self-reported dry eye in patients undergoing LASIK with either femtosecond laser or microkeratomes. Interestingly there was no statistically significant effects related to age, central ablation depth, or flap thickness on dry eye scores seen in this study in apparent contradistinction with previous literature; however, because of the small numbers (n = 51) the authors do suggest that the results be interpreted with caution. It is recommended that all patients be thoroughly evaluated, and if necessary, treated before surgery to minimize the risk of severe dry eye related symptoms. Table 3 summarizes potential complications that may occur with the LASIK procedure. Ectasia and Its Prevention Ectasia is progressive corneal steepening and thinning associated with increasing myopic astigmatism and loss of best corrected vision after LASIK. 41,42 In 2003, a review of 85 published cases of ectasia documented that most had abnormal topography before LASIK and/or did not undergo intraoperative pachymetry so there was an unknown assumed residual stromal bed thickness. 43 In 2008, Randleman et al 44 developed an ectasia risk score system, which analyzed 5 criteria. This was an attempt to standardize risk factors and has been the subject of intense discussion as to its usefulness and validity. The Randleman system was developed from case reports of ectasia, many of which were operated on before The sensitivity and specificity of this scoring system was calculated at 91% and 92%. Since then, several authors have commented on cases that would have been excluded or regarded with caution in terms of LASIK being performed, and yet they did not develop ectasia and conversely cases which would have passed the Randleman criteria but which did develop ectasia. 45,46 The ectasia risk score system remains a useful tool because it
10 120 Lawless and Hodge Table 3. LASIK Complications Intraoperative complications Inability to obtain adequate suction/loss of suction Opaque bubble layer Gas bubble in anterior chamber Gas breakthrough at epithelium Irregular/thin flaps/buttonhole flaps Subconjunctival hemorrhage Epithelial defect Interface fluid syndrome Decentered flap/decentered ablation Immediate postoperative complications Epithelial defects Slipped/dislocated flap Flap debris Transient intraocular pressure rise (steroid induced) Transient light sensitivity syndrome Rainblow glare syndrome Infection Glare/haloes Mid-long-term postoperative complications Diffuse lamellar keratitis Epithelial ingrowth Corneal haze Dry eye Diplopia/stabismus Undercorrection/overcorrection Increase in higher-order aberrations Corneal ectasia LASIK indicates laser in situ keratomileusis. is a simple method of raising awareness of appropriate screening for LASIK. For surgeons who have extensive screening knowledge and understanding, it will not add anything other than perhaps reducing the percentage of eyes that are considered suitable for LASIK. For novice surgeons, it is a way to suggest a careful evaluation of all preoperative factors. Excluding eyes with abnormal preoperative topography and performing intraoperative pachymetry so that the true residual bed thickness is determined, are probably the most useful take-home messages. The main argument against the Randelman system is that it overestimates the risks that a given eye would develop ectasia when the preoperative topography does not suggest a preexisting ectatic condition. Visual Results Reported results vary depending on whether it is a single surgeon series, an FDA application or large multisurgeon pooled data. Accuracy is influenced by many variables including the quality of the preoperative
11 LASIK 121 data, the type of excimer laser used, and the experience and skill of the surgeon. There are individual patient variables as well related to age, tear quality, corneal anatomy, etc., which makes it difficult to give an overall impression of the accuracy of LASIK. One good start is the large 10-year study by Yuen et al. 28 They used a variety of algorithms including wavefront-guided (WFG) treatment, tissue saving treatments, and aspheric treatments and the data mixes these together. The mean spherical error treated was 5.90 D ( ± 2.57 D). Uncorrected visual acuity had a consistent rate above 90% achieving 20/40 unaided since the year 2000, with a positive trend achieving 98% in Uncorrected visual acuity of 20/20 or better improved for 5 consecutive years to 73% in Lower refractive predictability was observed with increasing amounts of preoperative myopia. There was a 2.2% to 6.2% retreatment range over the life of the study. Their efficacy results were comparable with those conducted by the FDA. 47,48 These studies generally show about 97% achieving uncorrected 20/40 or better and 62% 20/20 or better. The SNEC data showed similar outcomes in 2007 with 98% achieving 20/40 or better and 72.8% 20/20 or better. Visual results improved over the 10-year study representing a learning curve on the part of the surgeons, and improvements in laser and ablation nomograms. One of the common issues with conventional LASIK in its early days was reasonable uncorrected Snellen acuity but poor quality night vision primarily because of an increase in higher-order aberrations and in particular an induction of spherical aberration, which is pupil size dependent. Wavefront technology, which had been used in astronomy for many years to improve the image quality of telescopes, was applied to analyze the aberration profile of the eye and design treatments to improve on preexisting higher-order aberrations or at least minimize their induction. WFG LASIK is a variation of the surgery in which the excimer laser ablates a pattern based on measurements from an aberrometer. This is distinct from 3 other types of excimer laser treatment profiles: conventional, wavefront-optimized, and topography-guided. Conventional LASIK or standard LASIK was the first profile. Conventional LASIK applies a simple spherocylindrical correction based on the removal of tissue using Munnerlyn s equation. 49 Conventional LASIK to reduce myopia induces positive spherical aberrations and is dependent on the amount of attempted correction. Wavefront-optimized LASIK is a treatment profile designed to reduce or eliminate the induced spherical aberration of conventional LASIK. 50 Wavefront-optimized treatments are based on a spherocylindrical correction that is adjusted by an internal algorithm to remove additional tissue in the periphery of the ablation zone. Topography-guided LASIK uses information from the corneal shape and the spherocylindrical correction to determine the excimer laser ablation profile. Topography-guided LASIK is considered
12 122 Lawless and Hodge investigational in the United States but widely used elsewhere, mainly to improve irregular astigmatism or enlarge previous LASIK patients with small optical zones. WFG LASIK aims to achieve a more optically perfect ablation based on all of the optical aberrations measured with a wavefront aberrometer, not just sphere and cylinder. To achieve this goal would require appropriate patient selection, high-quality wavefront data, complication-free surgery and accurately predicting and managing the change that occurred during healing. Schallhorn et al 51 performed a literature search from 2004 to 2009 using 209 unique references. They attempted to grade the quality of the data; there were no studies rated as level 1 evidence in regard to WFG LASIK. There was substantial lower level evidence that WFG LASIK was safe and effective for the correction of primary myopia, or myopia and astigmatism with a high level of patient satisfaction. WFG LASIK seemed to have similar or better refractive accuracy and uncorrected visual acuity outcomes compared with conventional LASIK. There was evidence of improved contrast sensitivity and fewer visual symptoms, such as glare and halos at night, compared with conventional LASIK. It was noted that even though WFG LASIK aimed to treat higher-order aberrations, they are generally still increased after WFG LASIK, but this increase is typically less than that induced by conventional LASIK. Stonecipher compared the visual outcomes using the WaveLight Allegretto. This was a prospective open-labeled multicenter study conducted in the United States with 374 eyes randomized by alternating enrollment to either wavefront-optimized or WFG LASIK. 52 They used an IntraLase femtosecond laser to create the corneal flaps. Ninety-three percent of eyes at 3 months in both groups achieved uncorrected visual acuity of 20/20 or better. Seventy-six percent of eyes with wavefrontoptimized treatment and 64% of eyes with WFG treatment achieved uncorrected visual acuity of 20/16 or better. No eyes in either group lost 2 lines or more of best corrected visual acuity. Indeed 58% of eyes with wavefront-optimized treatment and 62% of eyes with WFG treatment gained 1 line or more of best spectacle corrected acuity. No statistically significant difference was found between WFG and wavefront-optimized treatments and their recommendation was that WFG treatments routinely not needed, but may be considered if the magnitude of preoperative root mean squared (RMS) higher-order aberration was >0.35 mm. In their study, 83% of eyes had preoperative RMS higherorder aberrations <0.30 mm. The consensus is that conventional LASIK does induce higher-order aberrations with a consequent increase in night vision symptoms. This can be significantly improved with either WFG or wavefront-optimized treatments. One is not superior to the other, but the convenience of wavefront optimized means that it is often the preferred method in
13 LASIK 123 clinical practice. WFG treatments tend to be reserved for those with a higher-order aberration profile >0.3 mm of RMS error. Vilaseca et al 53 attempted to objectively analyze visual quality in LASIK patients. Using a double pass technique, an image of a point source object is recorded after reflection on the retina and a double pass through the ocular media. The technique has been used to analyze retinal image quality in the normal population as a function of age, in contact lens wearers, in patients with monofocal or multifocal intraocular lenses and in LASIK patients Because the double pass technique provides complete information on aberrations and intraocular scattering, it is useful for evaluating optical quality in patients who have had ocular conditions such as cataract, as well as in older eyes and eyes that have had refractive surgery. 58 What this study showed was that some eyes, not unexpectedly, had better preoperative optical quality than others, possibly because of a combination of factors, such as the degree of ametropia, keratometry, irregular astigmatism, and corneal and intraocular higher order aberrations. There was no trend that was observable in corrected distance visual acuity before and after LASIK in their patient cohort, but what they did show was patients with low or moderate quality before LASIK generally had a relative improvement in optical quality after LASIK. Patients with high optical quality before surgery had similar optical quality after LASIK. Lastly patients with a very high optical quality before surgery had a decline in optical quality after LASIK. The reasons for this are unclear but it may help to explain why some patients with very high optical quality before surgery report being dissatisfied postoperatively despite a good refractive result. LASIK and Its Effect on Quality of Life and Patient Satisfaction Solomon et al 59 summarized the published literature on LASIK for the years 1988 to A total of 309 articles were incorporated into their data base. A level 1 rating was assigned to those properly conducted, well-designed, randomized clinical trials and level 2 rating to well-designed cohort and case-controlled studies. Of the 309 articles, 6.1% (19 articles) reported on both patient quality of life and satisfaction and together encompassed a total of 2198 subjects. The procedures were performed between 1995 and The overall patient satisfaction rate after primary LASIK surgery was 95.4%. Patient satisfaction rate after myopic LASIK was 95.3% and after hyperopic LASIK 96.3%. They made the point with over 16 million procedures performed worldwide at that time, LASIK surgery should be considered among the most successful elective surgical procedures.
14 124 Lawless and Hodge In a more recent study from 2012, Queros et al 60 used the National Eye Institute Refractive Error Quality of Life questionnaire to compare quality of life between normal emmetropes and those who had successful LASIK for myopia, those who used orthokeratology, spectacles, or soft contact lenses. Emmetropes rated the best in terms of quality and of the groups above, the average decrease in quality of life compared with emmetropes were 0.71% for LASIK, 13% for orthokeratology, 15.8% for spectacle correction, and 17.3% for soft contact lenses. All patients in each group were considered to be successfully visually corrected with whatever their method of correction was, but LASIK as a treatment option showed the lowest average decrease in quality of life compared with alternative nonsurgical treatments. Brown et al 61 used a computer-based interactive survey to query patients regarding their satisfaction with the service experience and the results of their LASIK procedure from a large data base. Responses from 13,655 consecutive patients were analyzed and a very high level of satisfaction was observed both for the quality of postoperative care (98.6%) and for visual results obtained (95.0%). Most patients (94.2%) indicated that LASIK improved their life and most would recommend laser vision correction (96.5%) to their friends and family. Lazon de la Jara 62 investigated how LASIK affects quality of life and attempted to identify factors that may affect satisfaction after LASIK. They used a multidimensional quality of life scale (Institute for Eye Research Multidimensional QOL Scale) which assesses psychological characteristics, personality traits, cosmesis and tolerance to disturbing visual and ocular symptoms as well as overall satisfaction with vision. In their cohort of 104 patients significant postoperative changes included increased satisfaction with their quality of life after LASIK (P<0.001), reduced frequency of visual and ocular symptoms (P<0.001), and change in psychological characteristics (P = 0.033). Satisfaction correlated with uncorrected visual acuity in agreement with other studies that demonstrate residual refractive error as a common reason for dissatisfaction. The closer we get patients to plano the better. In general, there was an increase in adaptability, sense of confidence, and sense of wellbeing in the group after LASIK with patients reporting a more positive or optimistic attitude to life after surgery. Although the overwhelming majority of papers suggest that LASIK surgery does provide excellent outcomes for patients, a small portion will remain unhappy with their result. These patients will be vocal and often require additional chair time during the visit. In response to such persistent requests by lobby groups unhappy with laser surgery results, the FDA launched a multisite, collaborative initiative (LASIK Quality of Life Collaboration Project) to better understand the quality of life results from patients undergoing LASIK and to further determine the incidence of patient-reported outcomes. 63 Although it was hoped
15 LASIK 125 that the initial findings may be available in 2012, the project has come against significant barriers, including slow recruitment and difficulty in agreeing to the study protocols. 64 The authors declare that they have no conflicts of interest to disclose. References 1. Kempen JH, Mitchell P, Lee KE, et al. The prevalence of refractive errors among adults in the United States, Western Europe and Australia. Arch Ophthalmol. 2004;122: Short AJ, Allan BDS. Photorefractive keratectomy (PRK) versus laser assisted in-situ keratomileusis (LASIK) for myopia. Cochrane Data Base Syst Rev. 2006:CD Trokel SL, Sirnavasan R, Braren B. Excimer laser surgery of the cornea. Am J Ophthalmol. 1983;96: Krueger RR, Rabinowitz YS, Binder PS. The twenty fifth anniversary of excimer lasers in refractive surgery: historical review. J Refract Surg. 2010;26: Peyman GA. Inventor. Method for Modifying Corneal Curvature. US Patent 4,840,175. June 20, Buratto L, Ferrari M, Rama P. Excimer laser intra-stromal keratomileusis. Am J Ophthalmol. 1992;113: Pallikaris I, Papatzanaki M, Stahi E. Laser in-situ keratomileusis. Lasers, Surgery, Medicine. 1990;10: Pallikaris I, Papatzanaki M, Siganos D. A corneal flap technique for laser in-situ keratomileusis. Human studies. Arch Ophthalmol. 1991;109: Ratkay-Traub I, Ferincz IE, Juhasz T, et al. First clinical results with a neodymium glass laser in refractive surgery. J Refract Surg. 2003;19: Probst LE. The optimisation of LASIK. Int Ophthalmol Clin. 2008;48: Randleman JB. Femtosecond LASIK flaps: excellent but superior? Editorial. J Refract Surg. 2012;28: Kurtz RM, Liu X, Elner VM, et al. Photodisruption in the human cornea as a function of laser pulse width. J Refract Surg. 1997;13: Chen S, Feng Y, Stojanovic A. IntraLase femtosecond laser versus mechanical microkeratomes in LASIK for myopia: a systematic review and meta-analysis. J Refract Surg. 2012;28: Zhang SH, Jin HY, Suo Y, et al. Femtosecond laser versus mechanical microkeratome laser in-situ keratomileusis for myopia. Meta-analysis of randomised controlled trials. J Cataract Refract Surg. 2011;37: Javaloy J, Vidal MT, Abdelrahm AM, et al. Confocal microscopy comparison of IntraLase femtosecond laser and moria M2 microkeratome in LASIK. J Refract Surg. 2007;23: Calvo R, McLaren JW, Hodge DO, et al. Corneal aberrations and visual acuity after laser in situ keratomileusis: femtosecond laser versus mechanical microkeratome. Am J Ophthalmol. 2010;149: Chan A, Ou J, Manche EE. Comparison of the femtosecond laser and mechanical keratome for laser in situ keratomileusis. Arch Ophthalmol. 2008;126:
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