1988. in 1989, gholam a. peyman was granted a us patent for using an excimer laser to modify corneal curvature. it was, "a method and apparatus for modifying the curvature of a live cornea via use of an excimer laser. the live cornea has a thin layer removed therefrom, leaving an exposed internal surface thereon. then, either the surface or thin layer is exposed to the laser beam along a predetermined pattern to ablate desired portions. the thin layer is then replaced onto the surface. ablating a central area of the surface or thin layer makes the cornea less curved, while ablating an annular area spaced from the center of the surface or layer makes the cornea more curved. the desired predetermined pattern is formed by use of a variable diaphragm, a rotating orifice of variable size, a movable mirror or a movable fiber optic cable through which the laser beam is directed towards the exposed internal surface or removed thin layer." the patents related to so-called broad-beam lasik and prk technologies were granted to us companies including visx and summit during 1990–1995 based on the fundamental us patent issued to ibm (1988) which claimed the use of uv laser for the ablation of organic tissues. implementation in the u.s. the lasik technique was implemented in the u.s. after its successful application elsewhere. the food and drug administration (fda) commenced a trial of the excimer laser in 1989. the first enterprise to receive fda approval to use an excimer laser for photo-refractive keratectomy was summit technology (founder and ceo, dr. david muller). in 1992, under the direction of the fda, greek ophthalmologist ioannis pallikaris introduced lasik to ten visx centers. in 1998, the "kremer excimer laser", serial number kea 940202, received fda approval for its singular use for performing lasik. subsequently, summit technology was the first company to receive fda approval to mass manufacture and distribute excimer lasers. visx and other companies followed. the excimer laser that was used for the first lasik surgeries by i. pallikaris pallikaris suggested a flap of cornea could be raised by microkeratome prior to the performing of prk with the excimer laser. the addition of a flap to prk became known as lasik. recent years the procedure seems to be a declining option for many in the united states, dropping more than 50 percent, from about 1.5 million surgeries in 2007 to 604,000 in 2015, according to the eye-care data source market scope. a study in the journal cornea determined the frequency with which lasik was searched on google from 2007 to 2011. within this time frame, lasik searches declined by 40% in the united states. countries such as the u.k. and india also showed a decline, 22% and 24% respectively. canada, however, showed an increase in lasik searches by 8%. this decrease in interest can be attributed to several factors: the emergence of refractive cataract surgery, the economic recession in 2008, and unfavorable media coverage from the fda's 2008 press release on lasik. effectiveness in 2006, the british national health service's national institute for health and clinical excellence (nice) considered evidence of the effectiveness and the potential risks of the laser surgery stating "current evidence suggests that photorefractive (laser) surgery for the correction of refractive errors is safe and effective for use in appropriately selected patients. clinicians undertaking photorefractive (laser) surgery for the correction of refractive errors should ensure that patients understand the benefits and potential risks of the procedure. risks include failure to achieve the expected improvement in unaided vision, development of new visual disturbances, corneal infection and flap complications. these risks should be weighed against those of wearing spectacles or contact lenses." the fda reports "the safety and effectiveness of refractive procedures has not been determined in patients with some diseases." satisfaction surveys of lasik surgery find rates of patient satisfaction between 92 and 98 percent. in march 2008, the american society of cataract and refractive surgery published a patient satisfaction meta-analysis of over 3,000 peer-reviewed articles from international clinical journals. data from a systematic literature review conducted from 1988 to 2008, consisting of 309 peer-reviewed articles about "properly conducted, well-designed, randomized clinical trials" found a 95.4 percent patient satisfaction rate among lasik patients. a 2017 jama study claims that overall, preoperative symptoms decreased significantly, and visual acuity excelled. a meta-analysis discovered that 97% of patients achieved uncorrected visual acuity (ucva) of 20/40, while 62% achieved 20/20. the increase in visual acuity allows individuals to enter occupations that were previously not an option due to their vision. dissatisfaction some people with poor outcomes from lasik surgical procedures report a significantly reduced quality of life because of vision problems or pain associated with the surgery. a small percentage of patients may need further surgery because their condition is over- or under-corrected. some patients need to wear contact lenses or glasses even after treatment. the most common reason for dissatisfaction in lasik patients is chronic severe dry eye. independent research indicates 95% of patients experience dry eye in the initial post-operative period. this number has been reported to up to 60% after one month. symptoms begin to improve in the vast majority of patients in the 6 to 12 months following the surgery. however, 30% of post-lasik referrals to tertiary ophthalmology care centers have been shown to be due to chronic dry eye. morris waxler, a former fda official who was involved in the approval of lasik, subsequently criticized its widespread use. in 2010, waxler made media appearances and claimed that the procedure had a failure rate greater than 50%. the fda responded that waxler's information was "filled with false statements, incorrect citations" and "mischaracterization of results". a 2016 jama study indicates that the prevalence of complications from lasik are higher than indicated, with the study indicating many patients experience glare, halos or other visual symptoms. forty-three percent of participants in a jama study (published in 2017) reported new visual symptoms they had not experienced before. presbyopia a type of lasik, known as presbylasik, may be used in presbyopia. results are, however, more variable and some people have a decrease in visual acuity. risks higher-order aberrations higher-order aberrations are visual problems that require special testing for diagnosis and are not corrected with normal spectacles (eyeglasses). these aberrations include 'starbursts', 'ghosting', 'halos' and others. some patients describe these symptoms post-operatively and associate them with the lasik technique including the formation of the flap and the tissue ablation. there is a correlation between pupil size and aberrations. this correlation may be the result of irregularity in the corneal tissue between the untouched part of the cornea and the reshaped part. daytime post-lasik vision is optimal, since the pupil size is smaller than the lasik flap. others propose that higher-order aberrations are present preoperatively. they can be measured in micrometers (µm) whereas the smallest laser-beam size approved by the fda is about 1000 times larger, at 0.65 mm. in situ keratomileusis effected at a later age increases the incidence of corneal higher-order wavefront aberrations. these factors demonstrate the importance of careful patient selection for lasik treatment. a subconjunctival hemorrhage is a common and minor post-lasik complication. dry eyes 95% of patients report dry-eye symptoms after lasik. although it is usually temporary, it can develop into chronic and severe dry eye syndrome. quality of life can be severely affected by dry-eye syndrome. underlying conditions with dry eye such as sjögren's syndrome are considered contraindications to lasik. treatments include artificial tears, prescription tears, and punctal occlusion. punctal occlusion is accomplished by placing a collagen or silicone plug in the tear duct, which normally drains fluid from the eye. some patients complain of ongoing dry-eye symptoms despite such treatments and the symptoms may be permanent. halos some post-lasik patients see halos and starbursts around bright lights at night. at night, the pupil may dilate to be larger than the flap leading to the edge of the flap or stromal changes causing visual distortion of light that does not occur during the day when the pupil is smaller. the eyes can be examined for large pupils pre-operatively and the risk of this symptom assessed. complications due to lasik have been classified as those that occur due to preoperative, intraoperative, early postoperative, or late postoperative sources: according to the uk national health service, complications occur in fewer than 5% of cases. other complications flap complications – the incidence of flap complications is about 0.244%. flap complications (such as displaced flaps or folds in the flaps that necessitate repositioning, diffuse lamellar keratitis, and epithelial ingrowth) are common in lamellar corneal surgeries but rarely lead to permanent loss of visual acuity. the incidence of these microkeratome-related complications decreases with increased physician experience. slipped flap – is a corneal flap that detaches from the rest of the cornea. the chances of this are greatest immediately after surgery, so patients typically are advised to go home and sleep to let the flap adhere and heal. patients are usually given sleep goggles or eye shields to wear for several nights to prevent them from dislodging the flap in their sleep. a short operation time may decrease the chance of this complication, as there is less time for the flap to dry. flap interface particles – are a finding whose clinical significance is undetermined. particles of various sizes and reflectivity are clinically visible in about 38.7% of eyes examined via slit lamp biomicroscopy and in 100% of eyes examined by confocal microscopy. diffuse lamellar keratitis – an inflammatory process that involves an accumulation of white blood cells at the interface between the lasik corneal flap and the underlying stroma. it is known colloquially as "sands of sahara syndrome" because on slit lamp exam, the inflammatory infiltrate appears similar to waves of sand. the usaeyes organisation reports an incidence of 2.3% after lasik. it is most commonly treated with steroid eye drops. sometimes it is necessary for the eye surgeon to lift the flap and manually remove the accumulated cells. dlk has not been reported with photorefractive keratectomy due to the absence of flap creation. infection – the incidence of infection responsive to treatment has been estimated at 0.04%. post-lasik corneal ectasia – a condition where the cornea starts to bulge forwards at a variable time after lasik, causing irregular astigmatism. the condition is similar to keratoconus. subconjunctival hemorrhage – a report shows the incidence of subconjunctival hemorrhage has been estimated at 10.5%. corneal scarring – or permanent problems with cornea's shape making it impossible to wear contact lenses. epithelial ingrowth – estimated at 0.01%. traumatic flap dislocations – cases of late traumatic flap dislocations have been reported up to thirteen years after lasik. retinal detachment: estimated at 0.36 percent. choroidal neovascularization: estimated at 0.33 percent. uveitis: estimated at 0.18 percent. for climbers – although the cornea usually is thinner after lasik, because of the removal of part of the stroma, refractive surgeons strive to maintain the maximum thickness to avoid structurally weakening the cornea. decreased atmospheric pressure at higher altitudes has not been demonstrated as extremely dangerous to the eyes of lasik patients. however, some mountain climbers have experienced a myopic shift at extreme altitudes. late postoperative complications – a large body of evidence on the chances of long-term complications is not yet established and may be changing due to advances in operator experience, instruments and techniques. potential best vision loss may occur a year after the surgery regardless of the use of eyewear. ocular neuropathic pain (corneal neuralgia); rare fda's position in october 2009, the fda, the national eye institute (nei), and the department of defense (dod) launched the lasik quality of life collaboration project (lqolcp) to help better understand the potential risk of severe problems that can result from lasik in response to widespread reports of problems experienced by patients after lasik laser eye surgery. this project examined patient-reported outcomes with lasik (prowl). the project consisted of three phases: pilot phase, phase i, phase ii (prowl-1) and phase iii (prowl-2). the last two phases were completed in 2014. the results of the lasik quality of life study were published in october 2014. based on our initial analyses of our studies: up to 46 percent of participants, who had no visual symptoms before surgery, reported at least one visual symptom at three months after