If we can help with anything, please be in touch. LASIK combines the technique of creating a hinged corneal flap from ALK with excimer laser ablation from PRK (Figure 2). This site complies with the HONcode standard for trustworthy health information: verify here. WebObjective. Pinero DP, Alio JL, Uceda-Montanes A, et al. To assess the posterior corneal power and asphericity changes after myopic laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. Doctors generally use wavefront-guided technology to evaluate your eye in detail before LASIK surgery. After reshaping the cornea, the surgeon lays the flap back into place. LASIK evolved from a variety of techniques in refractive surgery. Despite its advantages, PTA does have certain drawbacks. 2014 Jul;158(1):87-95. In nearsightedness (myopia), the point of focus is in front of the retina, making distant objects appear blurry. Refractive Accuracy of Barrett True-K vs Intraoperative Aberrometry for IOL Power Calculation in Post-Corneal Refractive Surgery Eyes. Mayo Clinic; 2019. This form of measurement gives the doctors an overall view of your corneal thickness across the entire cornea. This coincides with the decreased occurrence of post-operative dry eye and studies have indeed shown an increase in nerve reinnervation after treatment. Clin Ophthalmol. A combined look at risk. With normal vision, an image is sharply focused onto the retina. One-year follow-up of corneal confocal microscopy after corneal cross-linking in patients with post laser in situ keratosmileusis ectasia and keratoconus. Disclaimer: The calculations provided are an estimate and may vary from the numbers provided by the manufacturer. Biomechanical evidence of the distribution of cross-links in corneas treated with riboavin and ultraviolet A light. Figure 2. Your chances for improved vision are based, in part, on how good your vision was before surgery. Steps you can take to prepare for surgery include: Long-term results from LASIK tend to be best in people who are carefully evaluated before surgery to ensure that they are good candidates for the procedure. If you do not have pachymetry or topography instruments, patients can be scheduled with one of our techs for a 30-minute pachymetry/topography visit. This helps conserve corneal tissue. Immunohistochemical evaluation of two corneal buttons with post-LASIK keratectasia. Steroid and antibiotic drops are used for 4 to 10 days after surgery. https://eyewiki.org/w/index.php?title=Ectasia_After_LASIK&oldid=87816, Abnormal topography, RSB <240 microns, corneal thickness less than 450 microns and Manifest refraction spherical equivalent (MRSE)> -14 D, Inferior steepening pattern or skewed radial axis in topography, RSB between 240 to 259 microns, age between 18 to 21 years, corneal thickness between 451 to 480 microns, MRSE between -12 to -14 D, RSB between 260 and 279 microns, age between 22 to 25 years, corneal thickness between 481 to 510 microns and MRSE between -10 to -12 D, Asymmetric bowtie pattern in topography, RSB between 280 to 290 microns, age between 26 to 29 years, MRSE between -8 to -10 D, Normal pattern or symmetric bowtie, RSB more than 300 microns, age more than 30 years, corneal thickness more than 510 microns, MRSE less than -8 D, Chan CC, Sharma M, Wachler BS. Ophthalmology. The higher your prescription is, the more 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. This will likely be a long-term treatment, especially if your cornea becomes stable with time or from cross-linking. All rights reserved. Laser-assisted subepithelial keratectomy (LASEK). LASIK requires the creation of a tiny flap in order to access the stromal layers of the cornea. The app can be used by entering patients personal data, refraction of each eyes, keratectomy values, pachymetry of the cornea and type of refractive surgery. Translate: 720-524-1001 Cornea; Dry Eye; Glaucoma; Keratoconus; Retina; Uveitis; Corneal Cross-Linking; Clear Lens Exchange; EVO ICL; Patient Info. J Cataract Refract Surg 1999;25:582586. LASIK is also a better option than PRK for correcting more severe nearsightedness (myopia). reported on 1,992 LASIK cases with no identified risk factors, in which ectasia developed in a single patient (0.05 percent). If possible, they should be evaluated at one of our 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. The surgery involves: About 90-120 microns of tissue for the corneal flap, using femtosecond laser technology Clin Ophthalmol. Measurement of corneal topography is essential, and is used to screen for irregular astigmatism, keratoconus and forme fruste keratoconus which are associated with unpredictable refractive outcomes and progressive ectasia after LASIK. This totals 196 to 202 microns of corneal tissue. Researchers discovered that corneal thickness can vary slightly in the population. When youre ready, call (888) 501- 4496 to schedule a free consultation. From the transmittance function, the propagated light pattern or the modulated transfer function can be calculated at any desired plane [ 9, 10 ]. In such cases where the cornea is too thin, LASIK can do more harm than good. 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. 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. Use this tool to estimate if myopic patients have enough corneal thickness to proceed with laser vision correction. Santhiago MR, Smadja D, Gomes BF, Mello GR, Monteiro ML, Wilson SE, Randleman JB. What does the tomography look like? This page was last edited on January 1, 2023, at 01:05. Marsack JD, Parker KE, Applegate RA. 4. Your results depend on your specific refractive error and other factors. Elsevier; 2019. https://www.clinicalkey.com. Suite 310 Brea, CA 92821, 16130 Ventura Blvd., Suite #120 Encino, CA 91436. microkeratome. You may have difficulty seeing at night after surgery, which usually lasts a few days to a few weeks. Post-LASIK ectasia may occur when the biomechanical stability of the cornea is altered. Dan Z. Reinstein, MD, MA(Cantab), FT=flap thickness, AD=ablation depth CCT=preoperative central corneal thickness. 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. After measuring the thickness of your cornea, LASIK specialists will need to do some mathematical reasoning in order to determine if you are a safe candidate for the procedure. METALLIC PARTICLES AFTER PHACOMULSIFICATION. In 2014, Moshirfar et al. Designed by Elegant Themes | Powered by WordPress. J Cataract Refract Surg 2005; 31:20352038. In eyes with normal vision, the cornea bends (refracts) light precisely onto the retina at the back of the eye. 2016;32(5):290-297. PTA was still a more significant factor than the variables that comprise it., Some eyes dont fit the model. Ophthalmology 2002;109:175187. Anterior segment optical coherence tomography (OCT) can be used to measure flap and stromal bed thicknesses (Figure 3). It might be a few weeks before you can start to use cosmetics around your eyes again. WebLASIK in Pregnant Patients. 2007 Jan;2:98-102. Complications that occur at the level of the interface between the flap and the stromal bed include diffuse lamellar keratitis, infection, and epithelial ingrowth. We wont be making flaps in the future. Some surgeons also believe that the stromal bed should be at least half of the original corneal thickness. [18], Transmission electon microscopy (TEM) showed thinning of the collagen lamellae and loss of lamellar number in the RSB and decreased interfibril distance. Disclaimer: The calculations provided are an estimate and may vary from the numbers provided by the manufacturer. 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. Intracorneal rings are placed symmetrically or asymmetrically on the steep meridian or about the cone. The axial map placido disc-based topography pattern classification using in this score system consists of: Includes round, oval, or symmetric bowtie patterns. 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 ). LASEK is similar to LASIK surgery, but the flap is created by using a special cutting device (microkeratome) and exposing the cornea to ethanol. There is a trend to cut thinner flaps with the newer microkeratome models, which are more precise. You might also have to wait several weeks before resuming strenuous contact sports, swimming or using hot tubs. Dr. Miller said that he is generally in agreement with the PTA concept because it can enable surgeons to recognize corneas in which the usual minimum values for RSB and CCT values would not suffice. Less serious side effects such as dry eyes, night time starbursts, and/or reduced contrast sensitivity occur relatively frequently. 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. Amoils SP, Deist MB, Gous P, Amoils PM. No, because were going to completely change things. Thinner flaps preserve greater stromal bed thickness and reduce the risk of ectasia. Cataract surgery with a smartphone / tablet. WebOur Coastal Vision LASIK consultants are available to help you determine your LASIK options. WebExcimer Laser consumption calculator: After inserting the refraction intended to treat, you will see the Tissue Consumption (TC) for the different Optical Zones (OZ). In: Ophthalmology. LASIK is an excellent procedure for most patients with myopia and astigmatism. 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 2009;147:774-8, 778.e1. 1998-2023 Mayo Foundation for Medical Education and Research (MFMER). Our mission is to provide the best possible comanagement services to the profession of Optometry. With each pulse of the laser beam, a tiny amount of corneal tissue is removed. If the flap created during the LASIK procedure is irregular, incomplete, or buttonholed, laser treatment cannot safely be performed in the same session. Refractive stabilization for myopes take up to 3 months depending on the amount of treatment performed. ICRSs including Intacs (Addition Technology Inc. Des Plaines, Illinois, USA) and KeraRings (Ferrara Ophthalmics, Belo Horizonte, Brazil) may improve visual function in ecstatic corneas. Webdegeneration, and post-LASIK ectasia. 2021 Oct Following the excimer laser, the flap is replaced. It receives millions of pieces of information about the outside world, which are quickly processed by the brain. The mean postoperative central corneal thickness was 392.05 m (range: 363.00399.00 m). https://www.uptodate.com/contents/search. 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). Vincigeurra P,Camesasca FI,Albe E,Trazza S.Corneal collagen cross-linking for ectasia after excimer laser refractive surgery:1-year results. Kanellopoulos AJ. To assess the posterior corneal power and asphericity changes after myopic laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. Kim TI, et al. At the end of the day, PTA is still a surrogate. However, side effects unique to the femtosecond laser, such as transient light sensitivity syndrome, have been reported with first generations of femtosecond lasers. J Cataract Refract Surg 2000;26: 96777. George O. Waring IV, MD, FACS, is director of refractive surgery and assistant professor of ophthalmology at the Medical University of South Carolina in Charleston and adjunct assistant professor of bioengineering at Clemson University in Clemson, S.C. Financial disclosure: No related interests. Ischemic optic neuropathy is a rare complication that has been reported following LASIK. Preservative-free tears may be used for weeks to months depending on dry eye symptoms and corneal punctate staining. 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. For the first six months or so after your surgery, your eyes may feel unusually dry as they heal. In farsightedness (hyperopia), your cornea doesn't refract light properly, so the point of focus falls behind the retina. Rad AS, Jabbarvand M, Sai N. Progressive keratectasia after laser in situ keratomileusis. Critical variable. Sometimes this change in vision is due to another eye problem, such as a cataract. 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 3. It is controversial in its utility because diagnostic methods of screening for preoperative ectasia have changed dramatically over the past 10 years, and now include possibly more sensitive techniques of corneal 'tomography' (Pentacam, Orbscan, Gallei) which can measure posterior corneal curvature rather than placido-disc based 'topography' which only measure anterior corneal curvatures. Dry and cycloplegic refraction should be performed for all patients. It does also appear to play a role in eyes with abnormal topography, Dr. Santhiago said. Residual refractive error can be corrected after stabilization, typically by relifting the flap and ablating the stromal bed in a retreatment procedure (also called an enhancement). Laser-assisted in situ keratomileusis (LASIK) can be an alternative to glasses or contact lenses. Portland, Tualatin, Yakima, Spokane,Bellevue, Bellingham, Web$ 62,250.00 USD Costs Savings is Calculated Using Your Annual Amount Spent on Glasses/Contacts (as provided above) and Adjusts for the Cost of LASIK Surgery You Select and Incoporates one Eye Exam Check Every 2 Years until Age 50 or About the Time You Will Require Treatment of Your "Presbyopia". 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). The typical pedestal thickness for PRK and LASIK is approximately 5 m, but this value may vary depending on the specific medical excimer laser device and even the profile type. https://nei.nih.gov/health/errors/myopia. A single copy of these materials may be reprinted for noncommercial personal use only. Ophthalmology 2008;115:3750. What should I expect before, during, and after surgery? It is uncertain if there is any relationship between LASIK and an increased incidence of postoperative retinal detachment. LASIK surgery is usually completed in 30 minutes or less. LASIK removes about 160 microns of tissue to create the corneal flap. [25] Accurate measurement of the corneal thickness (CT) has become mandatory for several reasons during the past several years. 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. However, after a healing period, a secondary LASIK or PRK procedure may be performed in some cases. With normal vision, an image is sharply focused onto the surface of the retina. Proper pre-operative screening is essential. Accessed Aug. 16, 2019. Critical variable. LASIK removes about 12-14 microns per diopter of vision for correction. The ablation depth for myopic LASIK on the VISX laser is between 12-14 microns, depending on the optical zone. 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 Well, not really. Critical variable. To help ensure an acceptable final postoperative residual stromal thickness, flap thickness can be measured by intraoperative ultrasound pachymetry. WebThe metric consists of an equation that calculates the proportion of the cornea that will be impacted by LASIK. While surgical complications are rare, good postoperative care is important. 2. 2019; doi:10.1016/S0140-6736(18)33209-4. Some surgeons also believe that the stromal bed should be at least half of the original corneal thickness. But a thick flap may bear a more significant effect on the resulting biomechanics of the cornea than a thin flap would. This would be particularly true in instances in which an older mechanical microkeratome was used. 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. One hypothesis is that some of these individuals would have developed delayed onset forme fruste or keratoconus even without LASIK procedure. After LASIK surgery, the patient should have a minimum of 250 microns of corneal thickness remaining (flap thickness not included. Marcony R. Santhiago, MD, PhD, is professor of ophthalmology and head of cataract and refractive surgery at the Federal University of Rio de Janeiro. 2022 Excel Laser Vision Institute. Corneal ectasia induced by laser in situ keratomileusis. As this is a multifactorial risk-benefit analysis, Dr. Waring said, he would also ask the following questions: What does the topography look like? The normal cornea is about 540 microns thick (a little more than half a millimeter), measured in the center. Rigid contact lenses should be removed for several weeks and soft lenses for several days to weeks before examination. Whether you qualify for LASIK or not, it is a good idea to visit a clinic to have the evaluation and determine the best way to reach your vision goals. Randleman JB, Dawson DG, Grossniklaus HE, McCarey BE, Edelhauser HF. The Lancet. Compared to conventional mechanical microkeratomes, femtosecond lasers create LASIK flaps with more predictable and uniform thickness, and fewer complications. Reported rates of post-LASIK ectasia in eyes without identified risk factors have declined in recent years: 1 Klein SR et al. National Eye Institute. When corneal thickness is unknown, this calculator defaults to the average corneal thickness of 540 microns. Talk with your doctor about any vision changes. No direct measurement of corneal strength. Using a programmed laser, your eye surgeon reshapes parts of your cornea. 2007 Sep;26:983-91. Facts about myopia. The cornea is marked to aid in postoperative flap alignment. Most recent stable refraction prior to development of a cataract. Beyond PTA. 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]. Your doctor will discuss whether you're a candidate for the procedure or other similar procedures. But we know that the whole eye is a very complex, dynamic, and fluid biomechanical system, Dr. Waring said. WebYour eye doctor will also measure your cornea, noting the shape, contour, thickness and any irregularities. Publication is expected this year. 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, The answer pertains to corneal thickness. Is there a history of other risk factors, such as eye rubbing? People with a low grade of nearsightedness tend to have the most success with refractive surgery. LASIK patients can achieve up to 20/20 vision or, in some cases, even better! Keratomileusis and ALK were relatively imprecise mechanical techniques. Mayo Clinic does not endorse companies or products. Chehalis, Kennewick, Olympia, Silverdale, Tacoma, and Vancouver. Am J Ophthalmol. Percent tissue altered and corneal ectasia. Chehalis, Kennewick, Olympia, Silverdale, Tacoma, and Vancouver, Serving Optometric Physicians in the Sprit of True reported eight cases (1.8 percent), out of 450 LASIK procedures. You may be given medicine to help you relax. 2. Immediately after surgery, your eye might itch, feel gritty, burn and be watery. What do the direct biomechanical measurements look like with the devices that are available? 2012;6:1801-1813. Certain health conditions can increase the risks associated with LASIK surgery or make the outcome less predictable. Figure 5. Rao SN, Epstein RJ. J Refract Surg2009; 25:S807S811. But certain side effects of LASIK eye surgery, particularly dry eyes and temporary visual problems such as glare, are fairly common. However, most surgeons are leaving a minimum of 300 microns. Glasses or contact lenses can correct vision, but reshaping the cornea itself also will provide the necessary refraction. Your eye doctor might also ask you to wear a shield over your eye at night until your eye heals. One significant criticism of the Risk Score System is that any individual less than 22 years old is automatically classified as at least 'Moderate Risk', despite the low incidence of ectasia in this age group. Results will be sent to you without interpretation. Investigative Ophthalmology & Visual ScienceNovember 2010, Vol.51, 5546-5555. OD News, where we share clinical updates and pearls that can directly enhance your patient care. For example, a patient with a 540m cornea, 160m flap thickness and a -6.00 D glasses prescription would calculate out as follows: =308m residual thickness. Against this backdrop, refractive surgeons are reacting positively to a proposed new formulathe percent tissue altered (PTA) metricfor identifying at-risk eyes. J Refract Surg. WebFor example, pre-treatment refractive power, as well as thickness and curvature changes following corneal incisions, are used to perform post-operative calculation of the total corneal refractive power (TCRP) after LASIK treatment. Mayo Clinic is a not-for-profit organization. J Cataract Refract Surg2007; 33:7580. Also, it is very easy to calculate. WHAT HAPPENED WITH THIS PATIENT?/QUE PAS CON ESTE PACIENTE? This page has been accessed 188,314 times. Make a donation. Therefore, before recommending LASIK, your LASIK surgeon will first perform an exam that includes a corneal pachymetry test to measure the thickness of the cornea. Randleman JB, Banning CS, Stulting RD. Serious adverse complications leading to significant permanent visual loss occur rarely. LASIK involves creating a corneal flap using a microkeratome (Figure 1) or a femtosecond laser, reshaping the cornea using an excimer laser to remove tissue from the underlying stromal bed and then replacing the flap. 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. Laser refractive surgery. Laser In Situ Keratomileusis for Myopia and Astigmatism: Safety and Efficacy. Patient eligibility, choice of surgical technique, risk for late complications,13 and the amount of ablation depend on accurate analysis of corneal topography. It also identifies the thinnest point in the cornea, both by value and location. Stonecipher K, Ignacio TS, and Stonecipher M. Advances in refractive surgery: microkeratome and femtosecond laser flap creation in relation to safety, efficacy, predictability, and biomechanical stability Curr Opin Ophthalmol 2006; 17:368372. The flap allows access to the deeper layers of your eye. User friendly. Figure 4. The cornea can destabilize and begin to change shape slowly or rapidly, leading to corneal ectasia. Femto lasik laser; It is one of the eyes treatment techniques used in the treatment of hyperopia, myopia and astigmatism.In this treatment, valve preparation is done with a laser called "Femtosecond laser". Webnea that will be impacted by LASIK. Am J Ophthalmol. Here are some of the qualifications and facts that LASIK specialists consider: After measuring the thickness of your cornea, LASIK specialists will need to do some mathematical reasoning in order to determine if you are a safe candidate for the procedure. Kymionis GD, Kontadakis GA, Kounis GA, et al. WebBecause a small incision (2-3 mm) is used in place of an entire flap, corneal nerve severance is minimal in comparison to LASIK. Mild to moderate keratoconus can be treated with eyeglasses or contact lenses. Complications that result in a loss of vision are very rare. WebRead reviews, compare customer ratings, see screenshots and learn more about Panacea IOL & Toric Calculator. Videokeratographic indices to aid in screening for keratoconus. WebLASIK is a combination of two refractive technologies: Use of a microkeratome, to create a thin flap of tissue (approximately 130 to 180 microns thick) followed by excimer laser ablation to reshape the stromal tissue beneath the flap. The statistical (regression) approach However, thicker flaps alone were insufficient to create ectasia unless coupled with greater ablation depthsand thus high PTA values. This content does not have an English version. Advertising revenue supports our not-for-profit mission. [25][26] Most of the cross-linking effect occurs in the anterior 200 microns of cornea that is weakened by flap creation. Laser Epithelial Keratomileusis (LASEK). Custom wavefront-guided soft contact lenses have been used in keratoconus with similar visual acuity compared to RGP and decreased aberrations.[21][22]. To undergo LASIK, a minimum of 485 microns of corneal thickness is needed. Your eye doctor will talk with you about whether LASIK surgery or another similar refractive procedure is an option that will work for you. If we can help with anything, please be in touch. J Cataract Refract Surg 2009; 35:16041608. He or she will see how your eye is healing and check for any complications. Paying For Your LASIK eye surgery is the best known and most commonly performed laser refractive surgery to correct vision problems. Comanagement, . But as it turned out, all of them had a high PTA. Some surgeons consider off-label treatments combining ICRSs with corneal crosslinking, and others even consider perfoming additional customized excimer laser ablation. You may detect a distinct odor as the laser removes your corneal tissue. Any use of this site constitutes your agreement to the Terms and Conditions and Privacy Policy linked below. Thus, if both those factors were marginal in a prospective LASIK patient, caution might be in order, Dr. Waring advised. Doctors generally use wavefront-guided technology to evaluate your eye in detail before LASIK surgery. Figure 3. The most common complication or side effect following LASIK is dry eyes. Comanagement, . The procedure allows the surgeon J Refract Surg2008; 24:S726S729. Bower KS. J Cataract Refract Surg2001; 27:17961802. WebUse ICON Eyecare's LASIK calculator to estimate your lifetime savings in vision health. DipCompSci(Cantab); Tariq A. Lewis, MSci, ARCS, OMT; Marine Gobbe, MSTOptom, PhD; Johnny Moore, FRCOphth, PhD, MD; Tara Moore, BSc, PhD Long-term Visual and Refractive Outcomes After Instead, SMILE uses one laser to create a small incision through the corneas surface. In this test, a scanner creates a highly detailed chart, similar to a topographic map, of your eye. [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. Rarely, some people's eyes slowly return to the level of vision they had before surgery. 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. Illustration of a femtosecond laser cutting a LASIK flap. You'll probably have blurred vision. 2010;21:255-8. 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.