We wont be making flaps in the future. Ophthalmology. For instance, he said, You can have patients with thin corneas that are strong, and you can have patients with thick corneas that are weak. WebCorneal Thickness Calculator For laser vision correction candidates LASIK Fee Collection For the pre and post-op care you provide Helpful ICD-10-CM Resource Quick reference to eye codes Lifetime Achievement Award Dr. Stanfield honored with Lifetime Achievement Award. Avoid going below 300m for primary treatment. WebCorneal thickness and curvature measurements are highly important in refractive surgery. 2019; doi:10.1016/S0140-6736(18)33209-4. Rad AS, Jabbarvand M, Sai N. Progressive keratectasia after laser in situ keratomileusis. Most surgeons make a flap thats about 160 microns. The risk of intraocular surgery complications remains a main limitation of lens-based procedures [19, 20].Corneal refractive surgery for hyperopia is challenging due to the difference between manifest and cycloplegic refractions, peripheral stromal ablation, the The answer pertains to corneal thickness. Some people describe smelling an odor similar to that of burning hair. Figure 4. Risk assessment for ectasia after corneal refractive surgery. Despite its advantages, PTA does have certain drawbacks. J Refract Surg2009; 25:S8112S8818. The Lancet. Some surgeons believe corneal thickness less than 500 microns is an independent risk factor for ectasia. Your eye doctor might recommend eyedrops for dry eyes. It is intended to be used in conjunction with a comprehensive ophthalmic examination and the appropriate diagnostic tests and measurements necessary for cataract surgery candidates with a history of prior refractive Then the surgeon uses a laser (B) to reshape the cornea, which corrects the refraction problems in the eye (C). 2009;147:774-8, 778.e1. J Refract Surg2008; 24:S726S729. Ferrara P, Torquetti L. Clinical outcomes after implantation of a new intrastromal corneal ring with a 210-degree arc length. Some surgeons believe corneal thickness less than 500 microns is an independent risk factor for ectasia. The average epithelial thickness at 5~6 mm annular zone was 51.6 6.6 m (39.6~67.4 m) before LASIK and 54.8 4.3 m (49.8~68.0 m) 3 months after LASIK This page has been accessed 188,314 times. The power calculation is based on several variables in the formula including preoperative manifest spherical and cycloplegic refractive error, keratometric power, corneal thickness, horizontal visible iris dimension An eyelid speculum is placed in the operative eye, which has been anesthetized with drops, and the fellow eye is covered. Corneal refractive procedures for hyperopia comprised of techniques that failed to gain popularity such as intracorneal inlays, conductive keratoplasty, and automated lamellar keratoplasty due to poor predictability and possible loss of corrected distance visual acuity (CDVA) [1,2,3].Femtosecond laser-assisted laser in situ keratomileusis (FS During LASIK eye surgery, an eye surgeon creates a flap in the cornea (A) the transparent, dome-shaped surface of the eye that accounts for a large part of the eye's bending or refracting power. WebThe most common reason PRK is recommended over LASIK is when corneal thickness is not adequate to safely make a LASIK flap. The average central epithelial thickness was measured to be 52.6 4.1 m (40.9~60.6 m) before LASIK and 56.2 4.3 m (50.0~65.5 m) 3 months after LASIK (, Figure 2 ). This calculation takes into account both your corneal map and specific corneal thickness. Same numerator, different outcomes. Furthermore, the identification of central corneal thickness as an independent indicator of glaucoma risk by the Ocular Hypertensive Treatment Study (OHTS) has A single copy of these materials may be reprinted for noncommercial personal use only. A suction ring is placed on the eye to achieve fixation. Is there a history of other risk factors, such as eye rubbing? This is an application that allows the ophthalmology surgeon to perform multiple IOL (Intraocular lens) Power, and Toric (Astigmatic) calculations. Measurement of corneal thickness is also critical in the preoperative assessment for LASIK because of its importance in the calculation of anticipated residual stromal bed thickness. Intracorneal rings are placed symmetrically or asymmetrically on the steep meridian or about the cone. Since the LASIK method requires a corneal flap to be made, patients must have a cornea that is within a certain range of thickness. WebThe average normal corneal thickness is 540-700 microns, from center to periphery, with the greatest thickness nasally and superiorly. While surgical complications are rare, good postoperative care is important. The weakening predicted by a high PTA does not mean ectasia will necessarily occur, merely that these eyes carry increased risk. A combined look at risk. Although few patients with normal corneal topography develop post-LASIK ectasia, this surprise complication remains one of the most feared in laser refractive surgery, thanks to its potential to cause visual catastrophe. Rigid contact lenses should be removed for several weeks and soft lenses for several days to weeks before examination. LASIK Indications for the Correction of Myopia and Astigmatism, Outcomes of LASIK for Myopia and Astigmatism. Thus, percent tissue altered is derived from (FT + AD) CCT. Illustration of a femtosecond laser cutting a LASIK flap. Sometimes this change in vision is due to another eye problem, such as a cataract. Alain Saad, Damien Gatinel. Designed by Elegant Themes | Powered by WordPress. You may have difficulty seeing at night after surgery, which usually lasts a few days to a few weeks. This site complies with the HONcode standard for trustworthy health information: verify here. Proper pre-operative screening is essential. Despite the utility of the PTA metric, Dr. Miller predicted that it will eventually decline in importance, as U.S. ophthalmologists migrate toward procedures that preserve more of the corneas structural integrity. LASIK flaps are cut with either mechanical microkeratomes or femtosecond lasers. If you wear contact lenses, which can change the shape of your cornea, you'll need to completely stop wearing them and wear only your glasses for at least a few weeks before your evaluation and surgery. For the first six months or so after your surgery, your eyes may feel unusually dry as they heal. Keratoconus and corneal ectasia after LASIK [letter]. In the U.S.A. the approved indications can be found on the Food and Drug Administration (FDA) labeling. These reasons include the increasing popularity of corneal refractive surgery 1 3; the need for precise measurement of the intraocular pressure, which is influenced by the CT 3 5; the correlation of CT with Surgeons like a patient to have 250 microns of corneal tissue remaining after LASIK. Cataract and Laser Institute. WebThese systems measure the corneal thickness at different points of the cornea. Amoils SP, Deist MB, Gous P, Amoils PM. The best LASIK surgeons in Los Angeles are selective when it comes to their patients. The goal of WFG LASIK is to achieve a more optically perfect ablation based on all of the optical aberrations measured using a wavefront aberrometer, not just spherical and cylindrical refractive errors. One-year follow-up of corneal confocal microscopy after corneal cross-linking in patients with post laser in situ keratosmileusis ectasia and keratoconus. If a doctor determines that you do not qualify for LASIK, you may qualify for PRK instead. If there are other tools or resources you would like us to consider, please let us know. But if a patient has two borderline findingssay a PTA of 30 percent and an age of 18he or she would likely not be a suitable LASIK candidate. Simultaneous topography- guided PRK followed by corneal collagen cross-linking for keratoconus. But with nearsightedness (myopia), farsightedness (hyperopia) or astigmatism, the light is bent incorrectly, resulting in blurred vision. Do I think this is going to be a big metric 10 years from now? Bower KS. Keratomileusis and ALK were relatively imprecise mechanical techniques. Custom wavefront-guided soft contact lenses have been used in keratoconus with similar visual acuity compared to RGP and decreased aberrations.[21][22]. More than 8 out of 10 people who've undergone LASIK refractive surgery no longer need to use their glasses or contact lenses for most of their activities. [18], Transmission electon microscopy (TEM) showed thinning of the collagen lamellae and loss of lamellar number in the RSB and decreased interfibril distance. WebPURPOSE: When calculating the power of an intraocular lens (IOL) with conventional methods in eyes that have previously undergone refractive surgery, in most c With normal vision, an image is sharply focused onto the retina. But we know that the whole eye is a very complex, dynamic, and fluid biomechanical system, Dr. Waring said. AskMayoExpert. In this test, a scanner creates a highly detailed chart, similar to a topographic map, of your eye. Critical variable. 1998-2023 Mayo Foundation for Medical Education and Research (MFMER). WebRead reviews, compare customer ratings, see screenshots and learn more about Panacea IOL & Toric Calculator. After LASIK surgery, the patient should have a minimum of 250 microns of corneal thickness remaining (flap thickness not included. It does also appear to play a role in eyes with abnormal topography, Dr. Santhiago said. Rarely, some people's eyes slowly return to the level of vision they had before surgery. LASIK removes about 12-14 microns per diopter of vision for correction. To help ensure an acceptable final postoperative residual stromal thickness, flap thickness can be measured by intraoperative ultrasound pachymetry. [27][28], PK or deep anterior lamellar keratoplasty are the last resort for visual rehabilitation in patients with post-LASIK ectasia.[29]. 2014;8:35-42. ICRSs including Intacs (Addition Technology Inc. Des Plaines, Illinois, USA) and KeraRings (Ferrara Ophthalmics, Belo Horizonte, Brazil) may improve visual function in ecstatic corneas. The metric consists of an equation that calculates the proportion of the cornea that will be impacted by LASIK. As this is a multifactorial risk-benefit analysis, Dr. Waring said, he would also ask the following questions: What does the topography look like? Thus, if both those factors were marginal in a prospective LASIK patient, caution might be in order, Dr. Waring advised. [25][26] Most of the cross-linking effect occurs in the anterior 200 microns of cornea that is weakened by flap creation. If we can help with anything, please be in touch. The ablation depth for myopic LASIK on the VISX laser is between 12-14 microns, depending on the optical zone. A residual posterior stromal thickness of at least 250 m is recommended to reduce the risk of post-LASIK ectasia. The Ectasia Risk Score System scale may help to identify high-risk patients preoperatively. (kindly note that these are not for distribution to patients), For sharing electronic patient health information, Dr. Stanfield honored with Lifetime Achievement Award.Read more . A suction ring placed on your eye just before cutting the corneal flap may cause a feeling of pressure, and your vision may dim a little. To begin, your doctor uses a special blade or laser to cut a flap on the top layer of your cornea, about the size of a contact lens. The cornea is marked to aid in postoperative flap alignment. LASEK is similar to LASIK surgery, but the flap is created by using a special cutting device (microkeratome) and exposing the cornea to ethanol. WebAblation Depth vs. Diopters & Diameter of Optical Zone for Myopia. LASIK evolved from a variety of techniques in refractive surgery. WebIOL Calculator for Eyes with Prior Myopic LASIK/PRK Please enter all data available and press "Calculate" Pre-LASIK/PRK Data: Post-LASIK/PRK Data: Optical/Ultrasound Biometric Data: *If entering "Sph (D)", you must enter a value for "Cyl (D)", even if it is zero. Includes the following asymmetric patterns: Includes keratoconus, pellucid marginal corneal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more.[9]. 2006;25(4):388-403. LASIK experts in Los Angeles like Doctor Moosa say that LASIK is known for treating varying levels of farsightedness, nearsightedness, and astigmatism. Its not a direct measurement. Meanwhile, he and other researchers are helping to validate diagnostic technology to directly measure corneal strength. You may detect a distinct odor as the laser removes your corneal tissue. J Cataract Refract Surg 1999;25:582586. Figure 2. To undergo LASIK, a minimum of 485 microns of corneal thickness is needed. 2016 Jul;27(4):311-5, Dawson DG, Randleman JB, Grossniklaus HE, et al. LASIK combines the technique of creating a hinged corneal flap from ALK with excimer laser ablation from PRK (Figure 2). (JavaScript must be enabled to view this email address), Corneal Cross-linking Comanagement Resources, Patient Education Video Library for use in Your Pactice, Direct Messaging with PCLI Details and addresses. Immunohistochemical evaluation of two corneal buttons with post-LASIK keratectasia. Fortunately, LASIK is more affordable than ever with available financing options. WebObjective. WebObjective. Researchers discovered that corneal thickness can vary slightly in the population. Steroid and antibiotic drops are used for 4 to 10 days after surgery. Complications that occur at the level of the interface between the flap and the stromal bed include diffuse lamellar keratitis, infection, and epithelial ingrowth. Kamburoglu G, Ertan A. Intacs implantation with sequential collagen cross-linking treatment in post operative LASIK ectasia. Randleman JB, Woodward M, Lynn MJ, Stulting RD. [8] The pachymetric map can useful in detecting incipient keratoconus. Autoimmune disorders, such as rheumatoid arthritis, A weakened immune system caused by immunosuppressive medications or HIV, Recent changes in vision due to medications, hormonal changes, pregnancy, breast-feeding or age, Inflammation of the cornea, lid disorders, eye injuries or eye diseases, such as uveitis, herpes simplex affecting the eye area, glaucoma or cataracts, Have an eye disease that causes the cornea to thin and bulge, or if you have a family history of it, Have age-related eye changes that cause vision to be less clear, Participate in contact sports that may be associated with blows to the face. At the end of the day, PTA is still a surrogate. Last summer, a joint Brazilian-U.S. group reported How the Thickness of Your Cornea Affects Getting LASIK, 6 Benefits of LASIK for Frequent Travelers, How to Select a Los Angeles LASIK Eye Surgery Center. Your eye doctor will also measure your cornea, noting the shape, contour, thickness and any irregularities. Contact the Excel Laser Vision Institute to learn whether you qualify for LASIK eye surgery and get started on the journey to clear, independent vision. 2014 Jul;158(1):87-95.e1. Mayo Clinic does not endorse companies or products. WebCan be used in post-LASIK eyes, if corneal topographies available; Pre-installed on: central corneal thickness D diopter(s) DF design factor Chamon W, Rocha KM. This procedure was followed by automated lamellar keratoplasty (ALK), in which a microkeratome was used to create either a free cap or a hinged corneal flap. Analysis of quantitative cohesive tensile strength in normal human corneas: implications for refractive surgery. based upon the theoretical Munnerlyn Formula. What do the direct biomechanical measurements look like with the devices that are available? After a mean follow-up of 6.892.35 years (standard deviation), the safety index was 1.17, the efficacy index was 0.94, Figure 3. 2008;115(1):37-50. When glasses or contacts become too troublesome and inconvenient, many people turn to laser eye surgery. In nearsightedness (myopia), the point of focus is in front of the retina, making distant objects appear blurry. LASIK eye surgery is the best known and most commonly performed laser refractive surgery to correct vision problems. [20], Various types of contact lenses such as rigid gas permeable (RGP), custom wavefront-guided soft contact lenses, hybrid lenses and tandem soft contact lens-rigid gas permeable lenses can be used for visual rehabilitation. This page was last edited on January 1, 2023, at 01:05. Referring to research that is expected to be published this year, he said, We showed that the LASIK flap had greater impact than ablation depth. The normal corneal thickness is about 555 microns and the ideal thickness before the procedure is estimated to be between 450 and 550 microns. Corneal thickness is important because it can mask an accurate reading of eye pressure, causing doctors to treat you for a condition that may not really exist or to treat you unnecessarily when are normal. J Refract Surg 2004; 20:S718S722. Facts about myopia. Rabinowitz YS. Is there a family history? Videokeratographic indices to aid in screening for keratoconus. Elsevier; 2019. https://www.clinicalkey.com. Delayed onset keratectasia following in situ keratomileusis. They really go hand in hand. Refractive surgery. 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If we can help with anything, please be in touch. Furthermore, corneal tomography is a substantial component of planning refractive procedures, including LASIK and PRK, and evaluating their results. Financial disclosure: Consultant to Ziemer Ophthalmics. These microkeratomes produce a meniscus flap architecture [that is] thicker in the periphery, where the biomechanical properties of the cornea may be more adversely affected, he said. This will likely be a long-term treatment, especially if your cornea becomes stable with time or from cross-linking. 2. In 2012, Spadea et al. [19]Confocal microscopic analysis of post-LASIK ectasia showed unevenly distributed highly reflective collagen scars with reduced keratocyte density and background transparency at the anterior stroma compared to normal post-LASIK eyes. Given the elective nature of LASIK, it seems logical that the balance of risk acceptance should be weighted toward minimizing risk, especially when other procedures are available for refractive correction.. reported on 1,992 LASIK cases with no identified risk factors, in which ectasia developed in a single patient (0.05 percent). Webdegeneration, and post-LASIK ectasia. Our mission is to provide the best possible comanagement services to the profession of Optometry. Kannellopoulos et al showed that pregnancy did not induce significant changes in refractive error, corneal stability, and total corneal and epithelial thickness in women after LASIK up to 1 year postop. Bromley JG, Randleman JB. There is limited literature on the effects of LASIK on the eye in pregnancy. During the procedure, you lie on your back in a reclining chair. 2016;32(5):290-297. Refer a Patient (720) 524-1001. This coincides with the decreased occurrence of post-operative dry eye and studies have indeed shown an increase in nerve reinnervation after treatment. LASIK (laser in situ keratomileusis) is a surgical procedure designed to correct refractive errors. Excimer laser ablation is performed, centered on the pupil or on the corneal vertex. Corneal ectasia after hyperopic LASIK. WebPlease note Even if the calculator shows sufficient residual bed thickness for LASIK, corneas under 500 microns are thinner than average. You generally will experience little pain, and you'll usually recover your vision quickly. LASIK. Schallhorn SC, Farjo AA, Huang D, Boxer Wachler BS, Trattler WB, Tanzer DJ, Majmudar PA, Sugar A. Wavefront-Guided LASIK for the Correction of Primary Myopia and Astigmatism. The more detailed the measurements, the more accurate your eye doctor can be in removing corneal tissue. He or she will see how your eye is healing and check for any complications. In the Randleman et al score system, the most common risk factors, in order of significance include: Abnormal topography compromises of keratoconus, pellucid marginal corneal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more[9] and is the most significant factor with highest relative risk. 2014;40(6):918-928. PTA = (FT + AD)/CCT]. [17], Light microscopy and hematoxylin-eosin staining of post-LASIK ectasia corneas demonstrated RSB thinning, hypocellular stromal scar, larger than normal artifacteous interlamellar cleft in RSB and fewer areas of Bowmans layer disruption than keratoconus. In: Ophthalmology. Reported rates of post-LASIK ectasia in eyes without identified risk factors have declined in recent years: 1 Klein SR et al. Glare, halos and double vision. LASIK surgery is performed with a laser programmed to remove a defined amount of tissue from a part of your eye called the cornea. Using a programmed laser, your eye surgeon reshapes parts of your cornea. LASIK removes about 160 microns of tissue to create the corneal flap. Accurate measurement of the corneal thickness (CT) has become mandatory for several reasons during the past several years. The ideal approach to preventing post-LASIK ectasia would be to directly measure the structural integrity of the preoperative cornea, which PTA does not do, Dr. Waring said. Some surgeons consider off-label treatments combining ICRSs with corneal crosslinking, and others even consider perfoming additional customized excimer laser ablation. https://www.aao.org/eye-health/treatments/lasik-2, https://eyewiki.org/w/index.php?title=LASIK_for_Myopia_and_Astigmatism:_Safety_and_Efficacy&oldid=88234. Disclaimer: The calculations provided are an estimate and may vary from the numbers provided by the manufacturer. The statistical (regression) approach After its development, the excimer (excited dimer) laser was used to reshape the cornea in a technique called photorefractive keratectomy (PRK). Post-LASIK corneal ectasia is thought to occur when the surgery reduces the stromas structural integrity to a level too low to maintain corneal shape and curvature.1 The anterior 40 percent of the cornea has significantly more cohesive tensile strength than the posterior 60 percent.3. Wavefront-guided LASIK, also called custom LASIK, is a variation of LASIK where the excimer laser ablates a sophisticated pattern based on measurements from a wavefront aberrometer (Figure 4). If youre wondering how much LASIK surgery is, then you will be given an estimate based on the needs of your current visual acuity. Email me with your comments or questions at . Corneal thickness can influence the actual reading of the amount of pressure in the eye. Pay Bill. If your cornea is too thin for laser vision correction procedures such as LASIK or PRK, EVO Implantable Collamer Lenses could be the ideal solution. Residual Bed Stroma (RBS) should not be less than 60% of Central Corneal Pachymetry (CCT). Well be doing our refractive corrections with something like SMILE [small-incision lenticule extraction], which will allow us to go a lot deeper and not have as much risk of ectasia or such problems as dry eye and dislocated flaps, Dr. Miller said. No, because were going to completely change things. Well, not really. From the transmittance function, the propagated light pattern or the modulated transfer function can be calculated at any desired plane [ 9, 10 ]. The cornea can destabilize and begin to change shape slowly or rapidly, leading to corneal ectasia. Mayo Clinic is a not-for-profit organization. The Academy uses cookies to analyze performance and provide relevant personalized content to users of our website. Tissue Consumption (TC) should not be more than 25% of Central Corneal Pachymetry (CCT) or more than 150m. WebFor a flap procedure, such as LASIK or IntraLASIK, the standard of care in the United States is to leave at least 250m behind after subtracting out the flap thickness and ablation depth. When visiting a LASIK clinic in Los Angeles, patients will receive a comprehensive eye exam in order to determine if they are an ideal candidate for the procedure. Post-LASIK ectasia is considered in patients who developed increasing myopia, with or without increasing astigmatism, loss of uncorrected visual acuity, often loss of best-corrected visual acuity, with keratometric steepening, posterior corneal elevation, with or without central and paracentral corneal thinning, and topographic evidence of asymmetric inferior corneal steepening after LASIK procedure. The mean postoperative central corneal thickness was 392.05 m (range: 363.00399.00 m). National Eye Institute. Your eye doctor will talk with you about whether LASIK surgery or another similar refractive procedure is an option that will work for you. Maybe youll do advanced surface ablation, depending on the other risk factors.. Other risk factors include eye rubbing, family history of keratoconus, refractive instability, BCVA less than 20/20 preoperatively, and male gender and should be considered especially in borderline cases. Thinner flaps preserve greater stromal bed thickness and reduce the risk of ectasia. The surgeon adds the expected flap thickness (FT) to the planned ablation depth (AD), and then divides the sum by the eyes central corneal thickness (CCT). Please note Even if the calculator shows sufficient residual bed thickness for LASIK, corneas under 500 microns are thinner than average. J Cataract Refract Surg. Am J Ophthalmol. Dr. Santhiagos research group is currently working on a mathematical equation intended to screen for ectasia by combining the PTA formula and the ERSS. Am J Ophthalmol. Performance of wavefront-guided soft lenses in three keratoconus subjects. There is a trend to cut thinner flaps with the newer microkeratome models, which are more precise. Your eye doctor will evaluate which areas of your cornea need reshaping and determine the precise amount of tissue to remove from your cornea. Further research is needed, but the early evidence suggests that calculating the PTA is a user-friendly way to look beyond normal topography and identify at-risk eyes, said George O. Waring IV, MD, FACS, at the Medical University of South Carolina in Charleston. 3 Moshirfar M et al. The surgeon and patient should decide whether LASIK is indicated based on a full preoperative evaluation and consideration of goals and alternatives, including spectacles, contact lens, and phakic intraocular lens implantation. LASIK surgery may be an option for the correction of one of these vision problems: If you're considering LASIK surgery, you probably already wear glasses or contact lenses. All rights reserved. A few eyes do not develop ectasia despite having PTA values greater than 40 percent, Dr. Miller said. However, most surgeons are leaving a minimum of 300 microns. However, side effects unique to the femtosecond laser, such as transient light sensitivity syndrome, have been reported with first generations of femtosecond lasers. To help patients suffering with progressive ectasia, Copy the URL to use this on your website, exam room PCs or tablets, View surgery calendars for each of our offices After numbing drops are placed in your eye, your doctor uses an instrument to hold your eyelids open. The lower numbers represent flap thickness and residual stromal bed thickness in microns, respectively. Femtosecond laser aided LASIK has been shown to provide better predictability of refractive outcomes and lower enhancement rates than LASIK performed using a After the flap has been created, it is reflected away from the cut surface. After LASIK or PRK, the power of the anterior corneal surface can then be added to that of the posterior corneal surface (which is assumed to be unchanged), as expressed by the formula The eye is a complex and compact structure measuring about 1 inch (2.5 centimeters) in diameter. Marsack JD, Parker KE, Niu Y,etal. Femtosecond lasers tend to create more precise and uniform flap thickness, and settings of 100-120 m are typically used. Talk with your doctor about any vision changes. The Optical Zone will depend on the pupil size and the type of laser. PTA is equal to the flap thickness (FT) plus the ablation depth (AD) divided by the pre-operative thinnest central corneal thickness (CCT). Ophthalmology 2003; 110:267275. Kanellopoulos AJ. The average corneal thickness is in the range of 540 to 560 microns. Other tests which should be performed include measuring pupil size and eye movements and corneal aberrometry. We hope these items are useful to your practice. Visit our LASIK page for more information. Randleman JB, Banning CS, Stulting RD. https://www.uptodate.com/contents/search. WebOur Coastal Vision LASIK consultants are available to help you determine your LASIK options. Percent tissue altered and corneal ectasia. In press. The surgery involves: About 90-120 microns of tissue for the corneal flap, using femtosecond laser technology
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