History

The LASIK technique was made possible by Dr Jose Barraquer (Colombia), who around 1960 developed the first microkeratome, used to cut thin flaps in the cornea and alter its shape, in a procedure called keratomileusis. This procedure was developed and pioneered by the world leading Barraquer Clinic, based in Bogota, Colombia.

LASIK surgery was developed in 1990 by Dr. Lucio Buratto (Italy) and Dr. Ioannis Pallikaris (Greece) as a melding of two prior techniques, keratomileusis and photorefractive keratectomy. It quickly became popular because of its greater precision and lower frequency of complications in comparison with these former two techniques.[1]

In 1991, LASIK was performed for the first time in the United States by Drs. Stephen Brint and Stephen Slade [2]. The same year, Drs. Thomas and Tobias Neuhann successfully treated the first German LASIK patients with an automated microkeratome.

Patients wearing soft contact lenses typically are instructed to stop wearing them approximately 7 to 10 days before surgery. One industry body recommends that patients wearing hard contact lenses should stop wearing them for a minimum of six weeks plus another six weeks for every three years the hard contacts had been worn. [3] Before the surgery, the surfaces of the patient’s corneas are examined with a computer-controlled scanning device to determine their exact shape. Using low-power lasers, it creates a topographic map of the cornea. This process also detects astigmatism and other irregularities in the shape of the cornea. Using this information, the surgeon calculates the amount and locations of corneal tissue to be removed during the operation. The patient typically is prescribed an antibiotic to start taking beforehand, to minimize the risk of infection after the procedure.

The operation is performed with the patient awake and mobile; however, the patient typically is given a mild sedative (such as Valium or diazepam) and anesthetic eye drops.

Lasik is performed in two steps. The initial step is to create a flap of corneal tissue. This process is achieved with a mechanical microkeratome using a metal blade, or a femtosecond laser microkeratome that creates a series of tiny closely arranged bubbles within the cornea.[4] A hinge is left at one end of this flap. The flap is folded back, revealing the stroma, the middle section of the cornea. The process of lifting and folding back the flap can be uncomfortable.

The second step of the procedure is to use an excimer laser (193 nm) to remodel the corneal stroma. The laser vaporizes tissue in a finely controlled manner without damaging adjacent stroma by releasing the molecular bonds that hold the cells together. No burning with heat or actual cutting is required to ablate the tissue. The layers of tissue removed are tens of micrometers thick.

During the second step, the patient’s vision will become very blurry once the flap is lifted. He/she will be able to see only white light surrounding the orange light of the laser. This can be disorienting.

Currently manufactured excimer lasers use a computer system that tracks the patient’s eye position up to 4,000 times per second, redirecting laser pulses for precise placement. After the laser has reshaped the cornea, the Lasik flap is repositioned over the treatment area by the surgeon. The flap remains in position by natural adhesion until healing is completed.

Performing the laser ablation in the deeper corneal stroma typically provides for more rapid visual recovery and less pain.

Wavefront-guided LASIK is a variation of LASIK surgery where, rather than apply a simple correction of focusing power to the cornea (as in traditional LASIK), an ophthalmologist applies a spatially varying correction, using a computer-controlled high-power UV laser guided by measurements from a wavefront sensor. The goal is to achieve a more optically perfect eye, though the final result still depends on the physician’s success at predicting changes which occur during healing. Nor are wavefront aberrations the factor to degrade vision; especially in older patients, scattering from microscopic particles plays a major role. Hence, patients expecting so-called “super vision” from such procedures may be disappointed. However, surgeons claim patients are generally more satisfied with this technique than with previous methods, particularly regarding lowered incidence of “halos”, the visual artifact caused by spherical aberration induced in the eye by earlier methods.

A subconjunctival hemorrhage is a common and minor post-LASIK complication.

The incidence of refractive surgery patients having unresolved complications six months after surgery has been estimated from 3%^[1] to 6%^[2]. The following are some of the more frequently reported complications of LASIK^[1][5]:

• Dry eyes
• Overcorrection or undercorrection
• Visual acuity fluctuation
• Halos or starbursts around light sources at night
• Light sensitivity
• Ghosts or double vision
• Wrinkles in flap (striae)
• Decentered ablation
• Debris or growth under flap
• Thin or buttonhole flap
• Induced astigmatism
• Epithelium erosion
• Posterior vitreous detachment^[3]
• Macular hole^[4]

Complications due to LASIK have been classified as those that occur due to preoperative, intraoperative, early postoperative, or late postoperative sources^[5]:

The incidence of flap complications has been estimated to be 0.244%[6]. 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 [6] but rarely lead to permanent visual acuity loss; the incidence of these microkeratome-related complications decreases with increased physician experience [7] [8].

A slipped flap (a corneal flap that detaches from the rest of the cornea) is one of the most common complications. The chances of this are greatest immediately after surgery, so patients typically are advised to go home and sleep, to let the flap heal.

Flap interface particles are another finding whose clinical significance is undetermined^[7]. A Finnish study found that particles of various sizes and reflectivity were clinically visible in 38.7% of eyes examined via slit lamp biomicroscopy, but apparent in 100% of eyes using confocal microscopy^[7].

The incidence of diffuse lamellar keratits (DLK)[9], also known as the Sands of Sahara syndrome, has been estimated at 2.3%^[8]. When diagnosed and appropriately treated, DLK resolves with no lasting vision limitation.

The incidence of infection responsive to treatment has been estimated at 0.4%^[8]. Infection under the corneal flap is possible. It is also possible that a patient has the genetic condition keratoconus that causes the cornea to thin after surgery. Although this condition is screened in the preoperative exam, it is possible in rare cases (about 1 in 5,000) for the condition to remain dormant until later in life (the mid-40s). If this occurs, the patient may need rigid gas permeable contact lenses, Intrastromal Corneal Ring Segments (Intacs)[10], Corneal Collagen Crosslinking with Riboflavin[11] or a corneal transplant.

The incidence of persistent dry eye has been estimated to be as high as 28% in Asian eyes and 5% in Caucasian eyes^[2]. Nerve fibers in the cornea are important for stimulating tear production. A year after LASIK subbasal nerve fiber bundles remain reduced by more than half ^[9].

The incidence of subconjunctival hemorrhage has been estimated at 10.5%^[8].

The incidence of epithelial ingrowth has been estimated at 0.1%[8].

Glare is another commonly reportedly complication of those who have had LASIK^[10]. Halos or starbursts around bright lights at night are caused by the irregularity between the lasered part and the untouched part. It is not practical to perform the surgery so that it covers the width of the pupil at full dilation at night, and the pupil may expand so that light passes through the edge of the flap into the pupil. In daytime, the pupil is smaller than the edge. Newer equipment is available to properly treat those with large pupils, and responsible physicians will check for them during examination.

Although there have been a number of improvements in LASIK technology [12][13] [14] , a large body of conclusive evidence on the chances of long-term complications is not yet in place. Also, there is a small chance of complications, such as slipped flap, corneal infection, haziness, halo, or glare. The procedure is irreversible.

The incidence of macular hole has been estimated at 0.2%^[4] to 0.3% ^[11].

The incidence of retinal detachment has been estimated at 0.36%^[11].

The incidence of choroidal neovascularization has been estimated at 0.33%^[11].

The incidence of uveitis has been estimated at 0.18%^[12]

Although the cornea usually is thinner after LASIK because of the removal of part of the stroma, refractive surgeons strive to maintain a minimum thickness in order to not structurally weaken the cornea. Decreased atmospheric pressure at higher altitudes has not been shown to be extremely dangerous to the eyes of LASIK patients. However, some mountain climbers have experienced a myopic shift at extreme altitudes [15] [16]. There are no published reports documenting diving-related complications after LASIK [http://www.scuba-doc.com/diveye.htm.

Laser in situ keratomileusis increases higher order wavefront aberrations of the cornea^{[13] [14]}. Glasses do not correct higher order aberrations.

Microfolding has been reported as “an almost unavoidable complication of LASIK” whose “clinical significance appears negligible” ^[7].

The cornea typically is avascular because it must be transparent to function normally. Its cells absorb oxygen from the tear film. Low oxygen-permeable contact lenses reduce the cornea’s absorption of oxygen, which sometimes results in the growth of blood vessels into the cornea, a process known as corneal neovascularization. This can cause a mild increase in inflammation and healing time and some discomfort during the surgery because of augmented bleeding. Although some contact lenses, notably modern RGP and soft silicone hydrogel lenses, are made of materials with higher oxygen permeability that help reduce the risk of corneal neovascularization, patients considering LASIK are cautioned to avoid overwearing their lenses. It is usually recommended that contact lens use be discontinued several days or weeks before the LASIK procedure.

A 2004 Wake Forest University study found that LASIK results are affected by heat and humidity, both during the procedure and in the two weeks before surgery[17].

Various surveys have been performed to determine patient satisfaction with LASIK. Most of these surveys have found patients to be very satisfied, with anywhere from 92-98% of respondents describing themselves as satisfied[10] ^{[15] [16] [17]}. Those who are unsatisfied tend to be those who have had some of the above-described complications.

The reported figures for safety and efficacy are open to interpretation. In 2003, the Medical Defence Union (MDU), the largest insurer for doctors in the United Kingdom, reported a 166% increase in claims involving laser eye surgery; however, the MDU averred that these claims resulted primarily from patients’ “unrealistic expectations” of LASIK rather than “faulty surgery” [18]. A 2003 study reported in the medical journal Ophthalmology found that nearly 18% of treated patients and 12% of treated eyes needed retreatment [19]. The authors concluded that “higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment.”

In 2004, the British National Health Service’s National Institute for Health and Clinical Excellence (NICE) considered a systematic review of four randomized controlled trials [20] [21] before issuing guidance for the use of LASIK within the NHS[22]. Regarding the procedure’s efficacy, NICE reported, “Current evidence on LASIK for the treatment of refractive errors suggests that it is effective in selected patients with mild or moderate short-sightedness” but that “evidence is weaker for its effectiveness in severe short-sightedness and long-sightedness.” Regarding the procedure’s safety, NICE reported that “there are concerns about the procedure’s safety in the long term and current evidence does not appear adequate to support its use within the NHS without special arrangements for consent and for audit or research.” Leading refractive surgeons in the United Kingdom and United States, including at least one author of a study cited in the report, believe NICE relied on information that is severely dated and weakly researched[23] [24].