1	Wavefront-Guided Laser Surgery
2	How the eye works Light rays enter the eye through the clear cornea, pupil and lens. These light rays are focused directly onto the retina, the light-sensitive tissue lining the back of the eye. The retina converts light rays into impulses, sent through the optic nerve to your brain, where they are recognized as images. 70% of the eye's focusing power comes from the cornea and 30% from the lens.
3	Refractive errors Inability to see clearly is often caused by refractive error. Four types of refractive error: Myopia (nearsightedness) Hyperopia (farsightedness) Astigmatism Presbyopia
4	Refractive errors: myopia In myopia (nearsightedness), there is too much optical power in the eye The distance between the cornea and the retina may be too long or the power of the cornea and the lens may be too strong. Light rays focus in front of the retina instead of on it. Close objects will look clear, but distant objects will appear blurred.
5	Refractive errors: hyperopia In hyperopia (farsightedness), there is too little optical power. The distance between the cornea and the retina may be too short. Light rays are focused behind the retina instead of on it. In adults (but not children), distant objects will look clear, but close objects will appear blurred.
6	Refractive errors: astigmatism In astigmatism, the cornea is curved unevenly—shaped more like a football than a basketball. Light passing through the uneven cornea is focused in two or more locations. Distant and close objects may appear blurry.
7	Refractive errors: presbyopia Presbyopia is an age-related condition in which your eyes gradually lose the ability to see things up close, because the lens of the aging eye can no longer change shape. When we are young, the lens in our eyes is flexible and is able to change focus easily between near and far objects, like an autofocus on a camera. At around age 40, this flexibility begins to gradually decrease, making it more difficult to see objects up close, unless the eye has nearsightedness.
8	What is refractive surgery? A group of outpatient surgical procedures used to alter how your eye focuses light rays on the retina, thereby improving vision and reducing dependence on glasses and contact lenses. In most cases, refractive surgery affects the shape of your cornea to redirect how light is focused onto the retina. Popular procedures include LASIK, LASEK, PRK and CK.
9	What is refractive surgery? Most refractive surgery is performed on the cornea and affects only the front of your eye, while the rest of your eye will change naturally as you age. In some cases, refractive surgery procedures don’t reshape the cornea; instead, the eye’s natural lens is either replaced or enhanced by an implantable lens that helps correct vision.
10	What is Laser In Situ Keratomileusis (LASIK)? Outpatient refractive surgery used to treat nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. With LASIK, an excimer laser is used — an invisible, cold laser capable of sculpting highly accurate changes in corneal shape. Most common type of refractive surgery procedure.
11	How is LASIK performed? Your ophthalmologist (Eye M.D.) uses a microsurgical instrument (usually a microkeratome) to cut a thin, hinged flap of corneal tissue. Once the flap is lifted to one side, laser energy is applied for a few seconds to a minute or so to reshape the exposed surface of your cornea. The tissue flap from your cornea is placed back into its original position, where it adheres naturally, protecting the treated area and restoring the smooth front surface of your eye. After the procedure, the reshaped cornea focuses light more accurately on the retina.
12	What is wavefront-guided LASIK? One of the keys to a successful LASIK procedure is the measurement your ophthalmologist takes to determine your refractive error. Small imperfections in the eye cause some light to travel through the eye at different angles, causing light to strike the retina in different places; collectively, these imperfections are called optical aberrations. Wavefront can be described as a “fingerprint of your eye;” the instruments that measure it reveal tiny, subtle variations in the way light passes through your eye that are as unique as your fingerprints. Additional subtle measurements of the corneal shape itself can be done with a surface topographer.
13	What is wavefront-guided LASIK? Wavefront-guided LASIK uses a measuring device to create a “map” of how your eye focuses light, to precisely assess the unique irregularities and variations in your eye. The wavefront map is very detailed: instead of creating a general description of your eye’s focus (for example, nearsighted), it records every subtle curve and dip in the focus of your eye.
14	What happens during the wavefront measurement? Your ophthalmologist maps both of your eyes using a wavefront scanner, called an analyzer or aberrometer. The aberrometer produces a very precise, detailed map of light rays as they travel through your eye, highlighting imperfections in your vision. A targeted beam of light will be sent through your eye and focused on the retina.
15	What happens during the wavefront measurement? A wave of light rays is reflected back from the retina through the eye’s lens, pupil and cornea.
16	What happens during the wavefront measurement? Using this measurement, the wavefront computer creates an accurate, three-dimensional map of the light rays created by your eye’s optical system. This wavefront data will be used to program the excimer laser, allowing your ophthalmologist to customize the reshaping of your cornea during the LASIK procedure.
17	What are the benefits of using wavefront technology? Wavefront-guided LASIK reduces the possibility that you will have quality-of-vision complaints, such as poor night vision, difficulty driving at night, glare, halos and blurry images after surgery. Some optical aberrations can distort your vision and cannot be corrected with glasses and contacts. They can only be measured with wavefront analysis. A main difference between conventional LASIK and wavefront-guided LASIK is that wavefront-guided LASIK reduces the likelihood that aberrations will result in quality-of-vision complaints.
18	Considerations for wavefront-guided LASIK surgery Less invasive procedure than intraocular surgery, thus reducing quality-of-vision complaints. Wavefront-guided LASIK is most useful for those individuals with measurable wavefront abnormalities. Procedure and recovery is usually painless and quick, as in standard LASIK.
19	Considerations against wavefront-guided LASIK surgery More corneal tissue is removed with wavefront-guided LASIK than in conventional LASIK. Wavefront-guided LASIK is not currently approved for surface procedures, such as PRK. Wavefront-guided LASIK is not recommended for patients with thin corneas. Wavefront-guided LASIK is not recommended for patients with keratoconus (irregular protrusion of the cornea). Wavefront-guided LASIK is not recommended if myopia, hyperopia or astigmatism is beyond the parameters of the procedure. Wavefront-guided LASIK is not recommended for patients with significant systemic medical illnesses that may severely affect healing. Wavefront-guided LASIK is not recommended for patients with severe dry eye. May be restricted from certain occupations after the wavefront-guided LASIK procedure.
20	To be a candidate for wavefront-guided LASIK, you should… Be over 21 years of age. Not be pregnant or nursing. Be free of any eye disease. Have a stable eye prescription over the past year. Have a refractive error within the range of correction.
21	Risks and possible side effects of wavefront-guided LASIK surgery Over-correction or under-correction (with a possible need for a re-treatment. Reduced contrast vision (sharpness). Poor night vision. Glare, halos, starburst, ghosting of images. Corneal infection.
22	Risks and possible side effects of wavefront-guided LASIK surgery Light sensitivity. Dry eyes. Flap complication (either during or following surgery). Loss of vision. Regression of initial surgical effect.
23	Is refractive surgery right for you? Advanced surgical procedures, including wavefront-guided laser surgery, are creating more opportunities for people who want to be less dependent on glasses or contacts. Other surgical procedures include LASEK, PRK, phakic and accommodative IOLs. Surgery may not entirely eliminate your need for corrective lenses. Glasses/contacts may still be needed for activities such as fine or detailed work, reading and perhaps night driving.
24	Is refractive surgery right for you? A large part of the success of any refractive surgery depends on your understanding of the procedure and your expectations. Since refractive surgery is an elective procedure, you have the opportunity and responsibility to become fully informed about its risks and benefits. Your ophthalmologist will explain the specific technique, its benefits, as well as possible risks and side effects associated with your case.
25	Discuss options and questions with your ophthalmologist With the help of your ophthalmologist, it’s ultimately your responsibility to weigh the risks and side effects of a procedure with the benefits it has to offer. If you decide refractive surgery is right for you, you may join millions of people who have reduced their dependence on glasses or contacts.