History of Refractive Surgery
The History of Refractive Surgery
The Increasing popularity of laser vision correction and lasik eye surgery
Where did it all start?
How did refractive surgery elevate itself to such a popular level? Within recent years we have seen the rapid infusion of new technologies in eye care leading to the initial Radial Keratotomy (RK) and evolving towards wavefront driven lasik and then into refractive intraocular surgery. The ophthalmology community has been involved with refractive surgery for actually over a 100 years now, but it is these recent technogically driven times that have generated the most substantial results. Modern refractive surgery has been improving vision and improving the lifestyle of these patients. Many LASIK patients today do not require glasses of any type and sing the praises of LASIK eye surgery as "truly amazing". But how is it possible to actually shapely perform surgery on eyes? The answer to this question lies ahead in the text below.
Understanding Your Vision
Before you can understand refractive surgery you must understand the basics of vision disorders and refractive errors. Myopia (Nearsightedness), Hyperopia (Farsightedness), Presbyopia (Bifocals), and Astigmatism are the main refractive errors that cause people to need glasses, bifocals or contact lenses. Refractive can play a role in correcting these visual issues but each case brings separate issues and require specialized treatment. Technology has evolved to impact each of these refractive errors.
Nearsighted patients typically have trouble seeing at distances and often require glasses for driving or everyday functionality. Nearsighted patients are typically great candidates for Lasik eye surgery even if the patient has existing astigmatism. With a myopic patient, the excimer laser used to reshape the cornea will actual decrease the amount of corneal tissues, thus changing the shape of the cornea and the refraction.
Farsighted patients typically have trouble reading or seeing things up close and require reading glasses. Individuals over the age of 40 will often start to experience the first signs of naturally occurring loss of close vision. Refractive Surgery can correct farsightedness but the options will be different for nearsighted patients. Some modern refractive surgery for decreasing farsightedness would be hyperopic lasik, LTK (Laser Thermal Keratoplsyty) conductive keratolplasty (NearVision CK), or multifocal IOL refractive lensectomy.
Astigmatism is a common vision condition where the corneal surface is not evenly shaped, causing one to see ghosting or shadowing of images. With astigmatism, the cornea is not a perfect sphere, like a basketball, but is steeper in one direction and flatter in the other, like a football. Astigmatism can occur alone but is most often combined with nearsightedness or farsightedness.
Presbyopic patients suffer from both near and far vision loss. They typically use bifocals to function in everyday life. There are options for the correction of presbyopia to a certain extent. There is no definite correction to solve the entire presbyopic disorder but there are methods that can deal with near or far vision. Monovision is a type of correction that corrects one eye for close and the other for distance vision. There are also some new multifocal IOL lenses that correct both far and near vision but do not guarantee perfect 20/20 vision.
The Beginning of Refractive Surgery
The basic principles of keratotomy were specified by L.J. Lans, of The Netherlands in 1898. Keratotomy was further explored in a controlled clinical environment in the 1940s by T Sako and K Akiyam of Japan. The general concepts involved radial incisions on the surface of the cornea. In the 1960s in the USSR, Slava Fyodorov dramatically increased the safety of what was now called Radial Keratotomy (RK) by placing the multiple incisions on the anterior surface of the eye and leaving a clear central optical zone. He observed that predictable results could be obtained by using steel surgical blades and a standardized formula of correction. Interest in Radial Keratotomy spread to the United States in the late 1970s prompting the nationwide PERK study sanctioned by the National Eye Institute. Results of this study demonstrated the effectiveness of RK but also noted a disturbing percentage of patients with progressive surgical effect and fluctuating daily vision.
Introduction of refractive surgery in the United States
In 1978 a refractive procedure called Radial Keratotomy (RK) was introduced in the United States. RK involves making of a number of cuts in the cornea to change its shape and correct refractive errors. This was the same technique that Dr. Fyodorov had perfected in the Soviet Union and performed factory style state controlled eye surgery. Although RK was not a perfect procedure it quite routinely decreased the complete dependence on glasses. After the introduction of the RK and PERK study doctors corrected nearsightedness, farsightedness, and astigmatism using various applications of incisions on the cornea. In order to correct astigmatism doctors created AK (Astigmatic Keratotomy) with different nomogram patterns to deal with the irregularities. Improvements in RK surgical technology by the use of ultrathin diamond micrometer cutting blades, microscopic guidance systems and computer databases for results tracking and predictive nomograms helped the procedure to become increasing popular in the early 1990s. The Caspere Research foundation run by Dr. Charles Caspere helped educate practices throughout this time period and helped to increase the publics awareness of the procedure.
Making the Leap to PRK (photorefractive keratectomy)
In the 1980s a new type of laser called the excimer laser was developed. This revolutionary laser was originally used to work with the making of computer chips. Ophthalmologists began using the excimer laser successfully in refractive surgery techniques to remove very precise amounts of tissue from the eye's surface. Excimer lasers revolutionized refractive surgery by providing a degree of safety and precision that was previously unattainable with other techniques. During this time research into the use of the excimer laser was begun by Charles Brau and James Ewing in 1973. The first excimer laser action was produced by Stuart Searles in 1975; the first commercial system was created by Tachisto in 1979. Research into ophthalmology usage was noted by Taboada, Mikesell and Reed in 1981 who performed procedures on the anterior corneal surface. In 1983 Stephen Trokel presented a paper describing the potential of the excimer laser for performing photorefractive keratectomy (PRK) on humans. The first experiments were soon after performed by Trokel and R. Srinivasan. Shortly afterwards in 1985 and 1986 were formed two companies, VISX and Summit Technology, Inc., which introduced the excimer laser to the ophthalmology community of the United States.
The Excimer Laser
This revolutionary laser was originally used to work with the making of computer chips. The excimer laser is a specific type of "cool" laser that generates its power from light in the ultraviolet range. It cannot be visualized by the human eye. Because the laser does not generate any heat, there is no tissue damage as the result of the laser light. The energy of the laser simply causes miniscule amounts of corneal tissue to dissociate a microscopic level. As the treatment with the laser proceeds, microscopic layers of tissue, approximately 1/10th the width of a human hair are removed. The laser is programmed to remove precisely the amount of tissue needed to achieve the desired result.
- After a series of clinical studies, the United States FDA finally approved the use of the Summit laser for PRK correction of myopia in 1995; approval for the VISX laser was granted later in 1996. A year later, the FDA approved the use of the VISX laser for the correction of myopic astigmatism.The Food and Drug Administration of the United States approved the excimer laser for Photorefractive Keratectomy (PRK) in October, 1995, for the purpose of correcting nearsightedness. The procedure of PRK reshapes the human cornea by application of laser energy to its front surface, producing a flattening effect. Approval was based on clinical trials of more than 1600 eyes followed for three years. Additional consideration was given to studies from Canada and Europe, where the procedure has been performed since 1987
The Advent of LASIK (Laser Assisted In Situ Keratomileusis)
With the development of precise surgical cutting instruments, the use of the excimer laser could be combined with an incision to produce a particular surgical result. It has become, by far, the most commonly performed refractive surgery procedure used today. During LASIK the surgeon first creates a thin corneal flap using a device called a microkeratome. The corneal flap is lifted up, and the excimer laser beam is applied to the exposed interior surface of the cornea to reshape the tissue. The flap is then replaced over the treated area. This corneal flap serves a natural bandage, which eliminates the discomfort associated with other types of refractive surgery, and expedites the healing process. Because of the extraordinary bonding properties of the corneal tissue, stiches are not needed to keep the flap in place after LASIK surgery.
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Wavefront Technology – Custom LASIK
Wavefront Technology is the scientific base for Customized LASIK laser vision correction currently being performed today. Wavefront Technology has improved the visual outcomes of patients and provided significant advantages over conventional LASIK.
What is wavefront technology?
Just like a fingerprint no two corneal maps are the same. In the system's diagnostic phase, a device called the WaveScan makes a WavePrint Map, a detailed map of the patient's vision. In the treatment phase, the doctor uses the information from the WavePrint Map to perform the vision correction using the excimer laser.
Wavefront technology was first developed in 1978 by Josef Bille, Ph.D., director of the Institute for Applied Physics at the University of Heidelberg, to measure wavefront distortions that occurred when light traveling through the atmosphere entered a telescopic lens. This technology removed any visual distortion or aberrations from the atmosphere allowing astrophysicists to more accurately view images of the stars and planets.
It is now possible to utilize this technology to record detailed information about the visual characteristics of the eye. Unlike standard measuring devices such as corneal topography, which measure the front surface of the eye called the cornea, the wavefront scans the way the entire optical system processes light.
“Fingerprint” of the Eye (just like snowflakes are unique)
Wavefront analysis works by measuring the distortion or irregularities of the eye, known as higher-order aberrations. When a ray of light first enters the eye, it passes through the cornea to the lens and vitreous, ultimately reaching the retina. As it bounces off the retina and returns back through the cornea, the wavefront analysis detects and documents these distortions, which are unique to each individual. Because each patient has a unique visual optical system, the wavefront data has been likened to a fingerprint.
Once the wavefront data has been documented for an individual patient, the next step is to use this information to utilize the excimer laser to correct the higher-order visual aberrations. The surgeon can then determine what adjustments must be made to the corneal surface to produce a clear, crisp image for the unique individual needs of each patient. The use of wavefront technology to provide a more precise laser vision correction is known as, "Custom LASIK" or "Wavefront-Driven LASIK". Early data suggests that the 5-10 percent of patients who demonstrate higher-order aberrations are the patients that will significantly benefit from Custom LASIK treatments. Other patients may benefit from Custom LASIK to a smaller degree.
Clinical Study Results
VISX's FDA clinical study results were remarkable. Among other things:
- At one year after the VISX CustomVue procedure;
100% of the clinical study participants could pass a driving test without glasses or contacts
98% of the clinical study participants could see 20/20 or better without glasses or contacts
70% of the clinical study participants could see 20/16 or better without glasses or contacts
- Four times as many clinical study participants were very satisfied with their night vision after the VISX CustomVue procedure, compared to their night vision before with glasses or contacts.
Epi-LASIK eye surgery
Epi-LASIK involves cutting a super thin flap from tissue known as epithelium that covers the very front of the eye's surface or cornea. Epi-LASIK does differ from LASIK primarily based around the type of flap created. The flap cut is so thin that it does not penetrate the actual cornea, whereas LASIK actually penetrates into the cornea. With Epi-LASIK the ophthalmologist uses epithelial separator to separate the sheet from the eye. After the epithelial separator has created this ultra thin flap the flap is lifted and carefully folded back. The next step involves using an excimer laser just like with conventional LASIK. The laser treatment then occurs, thus reshaping the surface of the eye. The epithelial flap is then gently repositioned back on the eye. A contact lens bandage may be required after the surgery to assist with the healing process. After Epi-LASIK, like regular lasik eye surgery a patient typically enters the post-operative period where close attention is needed. Most epi-LASIK patients are not as comfortable in this initial post-operative period as they are with LASIK. Traditional LASIK still offers better initial improvement and a WOW factor! In about 2 weeks the vision after Epi-LASIK is comparable to that of LASIK.
Refractive Surgery or Clear Lens Exchange for Candidates without Cataracts
Patients without cataracts may also choose a multifocal lens to correct for far sightedness, near sightedness, and presbyopia to give them a quality range of vision like they had when they were younger. Presbyopia is a condition that usually starts to affect people in their early to mid forties when they can no longer see well up close. As a result, presbyopic patients have difficulty with activities such as reading, sewing, and using the computer. A procedure called a clear lensectomy, which is similar to cataract surgery, is performed to remove the natural lens and replace it with the multifocal lens. Refractive surgeries are elective procedures and therefore the patient is responsible for all costs.
While mulitfocal lenses are designed with the goal of providing independence from glasses and contacts for most activities, they do not guarantee that you will be completely free from needing some correction for certain tasks. Additional refractive adjustments, such as LASIK, may be needed to correct patients to their desired distance results.