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LASIK surgery: Say goodbye to your glasses
These days, when someone I have been introduced to finds out that I am an ophthalmologist, the almost inevitable question that follows is: "Do you perform LASIK?" LASIK, the acronym for "laser in-situ keratomileusis", is a type of refractive surgery that has become the most popular procedure performed today for correcting refractive errors such as myopia, hyperopia, and astigmatism
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These days, when someone I have been introduced to finds out that I am an ophthalmologist, the almost inevitable question that follows is: "Do you perform LASIK?"
LASIK, the acronym for "laser in-situ keratomileusis", is a type of refractive surgery that has become the most popular procedure performed today for correcting refractive errors such as myopia, hyperopia, and astigmatism.
Its success is largely attributed to its safety, efficacy, rapid visual recovery and minimal discomfort to patients. This surgical phenomenon has swept across many developed countries around the globe in just one decade.
Singapore, with its high prevalence of myopia, is witnessing an ever increasing demand for LASIK.
Although much has been written about LASIK, there remains -- to the general public and even to eye doctors who do not perform LASIK -- many misperceptions, myths and misgivings. Some of the confusion arises from, ironically, the advances in LASIK and refractive surgery as well as the marketing hype associated with it.
LASIK has evolved from a variety of techniques in refractive surgery. Essentially, it is a two-stage procedure, the first of which involves creating a thin corneal flap and the second involves remodeling of the exposed cornea bed by removal of tissue with an excimer laser. The flap is then repositioned and it remains in position by natural adhesion until healing is completed.
The ground work for creating the LASIK flap was laid in the 1950s with the invention of the microkeratome, a fine mechanical metal blade used to cut the cornea. Each successive generation of microkeratome has made the creation of the corneal flap safer and more predictable.
The technological breakthrough for the second stage of LASIK occurred in 1980, when it was discovered that an ultraviolet excimer laser could etch living tissue in a precise manner with no thermal damage to the surrounding area. Two years later, a paper outlining the potential of using the excimer laser in refractive surgeries was published.
The first form of refractive surgery to employ the excimer laser was photorefractive keratectomy (PRK). However, the limitations of PRK, such as postoperative pain and corneal scarring, led to a search for a better procedure. LASIK was thus introduced in the early 1990s.
The cornea plays a central role in LASIK, as it accounts for about two-thirds of the overall refractive power of the eye -- the remaining of which comes from the natural crystalline lens. Consequently, modifying the shape of the cornea changes the refractive status of the eye. This forms the underlying principle behind LASIK and all other forms of corneal refractive surgery.
In treating myopia, the cornea is flattened centrally to reduce the refractive power of the cornea. To correct hyperopia, the cornea is steepened to increase the refractive power of the cornea. To treat astigmatism, the curvatures of the cornea in two axes 90 degrees apart are made equal.
Bladeless, all-laser LASIK refers to the use of a femtosecond laser to create the corneal flap. With the mechanical microkeratome, the incidence of flap complications has been estimated to be about 3 in 1000. Flaps that are too small, irregular or with button-holes mean that the second stage of LASIK cannot be performed and patients will be left disappointed.
A newer technique of creating the flap with a femtosecond laser was then developed: Tiny, ultrashort (femtosecond) pulses of infra-red laser that target a specific depth and position within the cornea to produce a uniform layer of microscopic bubbles. Because of the unique way in which the femtosecond laser creates a precisely positioned layer of bubbles just beneath the surface of the cornea, it creates a smooth even surface after the flap is lifted. Some studies have shown that this method of creating the flap produces better quality of vision.
Myopic people who require reading glasses or bifocals after reaching their mid-to-late forties, may find that they still require reading glasses despite having undergone LASIK. Myopic people generally require reading glasses or bifocal eyeglasses at a later age than people who are emmetropic (those who see without eyeglasses), but this benefit is lost if they undergo LASIK. This is not a complication, but an expected result of the physical laws of optics.
Although there is currently no method to completely eradicate the need for reading glasses in this group, it may be minimized by performing a variation of the LASIK procedure called "slight monovision". In this procedure, which is performed exactly like distance-vision-correction LASIK, the dominant eye is set for distance vision, while the non-dominant eye is set to the prescription of the patient's reading glasses. This allows the patient to achieve a similar effect as wearing bifocals.
The majority of patients tolerate this procedure very well and do not notice any shift between near and distance viewing -- although a small portion of the population has trouble adjusting to the monovision effect. This can be tested for several days prior to surgery by wearing contact lenses that mimic the monovision effect.
For almost two decades now, The Singapore National Eye Center (SNEC) has been treating cases of poor eyesight in local patients as well as those from overseas. Cases range from cataract to LASIK surgeries to potentially blinding conditions such as cornea and retinal diseases.
The SNEC now attends to 250,000 outpatient visits, including 16,000 foreign patient visits, and performs 14,000 major eye surgeries and 13,000 laser procedures annually. The high quality and volume of SNEC's services place the institution as a leading eye center in the Asia-Pacific region and beyond.
Articles in this biweekly column are provided by a panel of health professionals from www.flyfreeforhealth.com, a leading multimedia medical tourism platform dedicated to providing travel and lifestyle incentives for those adopting a healthy lifestyle.
Our health service providers include Dr Chua Wei Han, M Med (Ophth), FRCSEd (Ophth), FAMS Consultant Ophthalmologist, Refractive Surgery Service, Singapore National Eye Center; Prof. Sriprasit Boonvisut, MD, Chief of the Phyathai Beauty Center 2, Phyathai Plastic Surgery Center, Phyathai 2 Hospital, Thailand; Dr.Thanainit Chotanaphuti, Chief of Musculoskeletal Centre, Phyathai Hospital, Thailand. Email us at info@flyfreeforhealth.com.
