Different Refractive Errors
What is nearsightedness?
Over 60 million Americans suffer from nearsightedness, or myopia. A person is considered nearsighted when the eye has too much focusing power. This occurs when the eyeball is either too long or the cornea (the clear front cover of the eye) is too steep to allow light to focus directly on the retina (the “film” at the back of the eye). Instead, light focuses in front of the retina, causing distant images to appear blurry. A minus power lens in the form of eyeglasses or contact lenses is needed to subtract focusing power from the eye.
What is hyperopia?
Hyperopia is a condition where light rays entering the eye are focused behind the retina instead of directly on it, as in the normal eye. It may be present in childhood but does not usually become apparent until people are in their late 20s or 30s when they can no longer see up close. When these patients reach their 40s or 50s, they may start having difficulty seeing distant objects as well.
What is astigmatism?
Astigmatism is a condition that occurs when the cornea or lens is steeper on one axis than another, similar to a football or the back of a spoon, instead of being completely spherical or round like a basketball. Light entering the cornea focuses on more than one point within the eye, resulting in blurred vision. Astigmatism is either regular when steep and flat axes are 90 degrees apart, or irregular when they are not separated by 90 degrees.
What is presbyopia?
Literally “old vision,” presbyopia is part of the natural aging process of the eye, affecting most people by age 40. Normally, when a close object is viewed, the lens will change shape or “accommodate” to focus light on the retina. With presbyopia, the lens cannot sufficiently reshape and glasses are required for close viewing. When someone has laser vision correction for nearsightedness and he or she is already presbyopic (40+ years of age), correction for reading will still be needed, which typically means wearing the store-bought magnifying glasses.
What is a diopter?
A diopter is the unit of measure used in optics which determines the refractive power of a lens. A minus sign in front of the number indicates nearsightedness and a plus sign indicates farsightedness.
How can these visual problems be corrected?
They can be corrected with glasses, contact lenses or surgery.
Are there other non-surgical means of improving vision?
A procedure called orthokeratology has been available for many years, where a series of progressively flatter gas permeable hard contact lenses are used to gently and gradually re-shape the surface of the cornea. When the cornea has reached its desired correction, a retainer contact must be worn for several hours per day (normally at night, while sleeping) to prevent the cornea from returning to its original shape. Orthokeratology doesn’t make permanent changes to the eye; if the patient stops wearing the lens, the eyes will revert to their former state within 1 to 4 weeks.
History of Refractive Surgery
What is refractive surgery?
These are a group of surgical procedures designed to permanently reduce or eliminate the need for corrective eyewear to see distant objects. They include laser assisted in-situ keratomileusis (LASIK), photorefractive keratectomy (PRK), radial keratotomy and astigmatic keratotomy (RK/AK), laser thermal keratoplasty ( LTK), and conductive keratoplasty (CK). While these procedures can be very effective, they can only improve vision problems that are correctable with glasses or contact lenses.
What is laser vision correction (LVC)?
These are refractive procedures performed with an excimer laser. The excimer generates ultraviolet light of a specific wavelength (193 nanometers) by sending high-voltage electrical energy through a cavity containing argon fluoride gas. The beam that is emitted has enough energy to break the bonds between the molecules that make up the tissue on your eye’s surface (the cornea). Because it is a photochemical and not a heating process, the surgeon is able to sculpt very precise amounts of corneal tissue without any damage to neighboring tissue.
What is the history of the excimer laser?
The excimer laser was developed at IBM to etch computer microchips. Its extreme precision with negligible damage to adjacent tissue made it a very attractive tool for other applications. In 1983, ophthalmologist Stephen L. Trokel, M.D., in cooperation with physicist R. Srinivasan, applied it to corneal tissue in a New York laboratory. The first sighted eye was treated with the excimer laser on January 14, 1987.
What procedures are performed with the excimer laser?
LASIK (laser in-situ keratomileusis) and PRK (Photorefractive Keratectomy)
Refractive Surgical Procedures and How Do They Work
How do LASIK and PRK work?
In both procedures, a specially-trained ophthalmologist uses the computer-guided excimer laser to gently remove a thin layer of tissue from the cornea to achieve a desired correction. Prior to the procedures, drops are placed in the eye to numb it (similar to what an eye doctor uses to check eye pressure for a glaucoma test) and an instrument called a speculum is placed in the eye to prevent the patient from blinking. In PRK, the surgeon first removes the surface cells of the cornea using the laser before sculpting the underlying tissue, and then surface cells regenerate over the next 48 to 72 hours under a bandage contact lens. No needles are used, and the patient does not normally experiences any pain. In LASIK, a femtosecond laser is used to separate a thin layer of the corneal tissue, which is left attached on a hinge. The excimer laser is then used to sculpt tissue from the corneal bed and the flap is floated back into place, reattaching without the need for sutures.
How long do these procedures actually take?
Most patients are in the laser suite for no longer than 10 minutes. The actual laser treatment time takes just 15 to 90 seconds, depending on the degree of correction required. Total time at the center on the day of the procedure will be about an hour.
Why has LASIK become the procedure of choice for so many patients and surgeons?
Because the healing occurs in the interior of the cornea, no regrowth of surface cells is necessary. The corneal flap protects the treated area and there is usually little, if any, post-op discomfort. Visual rehabilitation is much quicker than other refractive surgical procedures, and regulation of the healing process with long term post-op drops is unnecessary since the center of the cornea tends to have much less of a healing reaction than the surface.
How is astigmatism corrected?
The laser is used to reshape the regions where the cornea is high or elevated. Here’s a simple illustation to explain what’s done: With astigmatism, the cornea is shaped like a football. The laser sculpts the surface of the cornea into the shape of a baseball or basketball to correct for the astigmatism.
What other surgical alternatives are there to PRK and LASIK?
Radial Keratotomy (RK) is a surgical procedure that can also correct nearsightedness by changing the shape of the cornea. Microscopic incisions of 90 percent depth, placed in a radial pattern like the spokes of a wagon wheel, reshape and flatten the central cornea, allowing light to focus more precisely on the retina. The length and number of incisions determine the effect of the surgery. Patients with less than three diopters of nearsightedness and stable prescriptions are the best candidates.
Another alternative to LASIK and PRK eye surgery that has recently been approved by the FDA are implantable lenses known as refractive intraocular lens implants (RIOLs). Usually reserved for patients with extreme myopia, RIOLs are surgically placed either between the cornea and the iris or just behind the iris, to enable light to focus properly on the retina for clearer vision.
Are there other alternatives for astigmatic correction?
A variation of RK, known as astigmatic keratotomy (AK), is an effective means of reducing astigmatism. It involves making incisions in an arc-like or segmental fashion parallel to the white of the eye (where the cornea is steep) to reshape the cornea from an oval shape into a spherical shape.
What procedures are recommended for farsightedness?
In the past, automated lamellar keratectomy (ALK) was used in which a thick layer of the cornea was folded back with a microkeratome. Pressure inside the eye causes the corneal bed to steepen, the opposite of what occurs in LVC. The cap was placed back into position without the removal of additional tissue. Although it has been shown to effectively reduce or eliminate farsightedness in the +1.00 to +5.00 range, enough cases of corneal instability have been reported nationwide that this procedure has fallen out of favor. Now, LASIK for hyperopia is considered by most to be the best option. Conductive Keratoplasty (CK) uses a needle-like probe to deliver radio-frequency energy to the corneal collagen in a ring of individually placed spots to steepen the cornea. Farsighted patients with a prescription between +0.75 to +3.25 and no more than 0.75 diopters of astigmatism are the best candidates for this procedure. Because of mild regression and a lack of long-term results, the procedure has been labeled as temporary.
How does laser vision correction for hyperopia work?
Both PRK and LASIK are effectively being used to treat hyperopia. The procedure is identical to the myopic (nearsighted) procedure. However, by blocking the laser from treating centrally and allowing it to remove more tissue in the periphery of the cornea, a steepening rather than a flattening of the cornea is produced.
What are the results of laser vision correction?
The results are quite remarkable. In the U.S. clinical trials for the Wavelight Allegretto for nearsightedness, 100 percent of the patients experienced improved, uncorrected vision six months after the treatment; 98 percent were returned to 20/40 sight or better (the “driving standard” in most states) and were able to perform most activities without glasses or contacts; 88 percent saw at least 20/20; and an amazing 60 percent saw better than 20/20.
Are these procedures FDA approved?
Yes, both the PRK and LASIK procedure have been FDA-approved to be safe and effective. After extensive testing, the U.S. Army has also approved laser vision correction for American soldiers.
Who is a good candidate for laser vision correction?
The majority of all nearsighted Americans are potential candidates for the laser treatment. Patients must be at least 18 years of age, have mild to moderate nearsightedness with a stable prescription, and have no ocular or health issues. The best candidates tend to be people who are dissatisfied with their glasses or contact lenses and are motivated to make a change, either for occupational or lifestyle reasons. Although a patient’s prescription may make him or her a suitable candidate for laser vision correction procedure, it is very important that the patient have the appropriate level of expectations regarding the outcome of the procedure. Although uncorrected post-op vision (after healing) is usually excellent, no one can guarantee a 20/20 vision.
The best candidates for laser vision correction can identify with the following statements:
- I dislike being dependent on glasses for clear vision.
- I was never a good contact lens candidate/wearer.
- Wearing corrective lenses restricts my participation in sports and other activities.
- My overall appearance is improved without glasses.
- I worry about losing my corrective lenses (or breaking my glasses). Without them, I fear I would be totally disabled.
- Having good vision without corrective lenses is more important than having great vision with corrective lenses.
- I would be happy if my vision was greatly improved, even if I still had to wear corrective lenses some of the time.
- I usually adjust well to change.
- I am a fairly easy-going person.
- Not wearing corrective lenses would open new career opportunities for me.
- I’ve often wished I didn’t have to wear corrective lenses.
A person is probably not a good candidate for laser vision correction if he or she identifies with the following statements:
- I like wearing glasses and would feel uncomfortable without them.
- I don’t mind wearing contact lenses.
- I don’t accept changes easily.
- I get upset or stressed out easily when things don’t seem to happen the way I had planned or expected.
- I am a perfectionist and little irregularities bother me.
- I would be very upset if I did not end up with perfect vision after my procedure and would probably consider the entire experience a failure.
- If I needed more correction after my procedure, I would be devastated.
A person is not a good candidate for laser vision correction if he or she is under 18 years of age, unwilling to commit to follow-up care instructions, and if any of the following conditions are present:
- Progressive myopia/unstable refractive error (>0.50/yr).
- Keratoconus – a progressive disease that involves the thinning and steepening of the cornea, causing distortion of visual images.
- Cataracts – cloudy areas that form in the lens inside the eye.
- Pregnancy/breast feeding.
- Ocular herpes.
- Uncontrolled diabetes.
- Uncontrolled inflammatory diseases (e.g., tuberculosis, asthma and chronic sinusitis).
Is there a limit to the degree of nearsightedness LVC can correct?
The corneal thickness measurement is a very important test and can be the major limitation for LASIK. This measurement is a standard test at the Atlanta Vision Institute. In these situations, PRK is an alternative to LASIK.
Can refractive surgery be done after a corneal injury?
The only way to determine if someone is a good candidate is with a full eye exam. A corneal injury may or may not preclude someone from the surgery. It all depends on the size and type of injury.
What to Expect During the Procedure
Is the procedure painful?
There is very mild discomfort during the PRK procedure. Afterwards, some patients experience a gritty sensation, burning, tearing or light sensitivity for the first 2 to 3 days. During the LASIK procedure, there is mild discomfort and no pain. Following the procedure, patients may experience some scratchiness, burning and tearing for 2 to 3 hours.
Can both eyes be done at the same time?
Most patients undergoing LASIK and PRK prefer to have both eyes treated on the same day since it is more convenient for them. However, this is a decision made entirely by the patient and the doctor.
Are patients awake during the procedure?
Yes. Dr. Ashraf asks patients to fixate on the red blinking light in the microscope during the procedure. Keep in mind the whole treatment happens rather quickly. With Dr. Ashraf’s experience and the speed of the Wavelight Allegretto laser, the entire LASIK procedure is completed in less than 10 minutes.
What happens if the eye moves during the procedure?
The Wavelight Allegretto laser has a tracking device, which detects and compensates for small movements by keeping the laser beam precisely centered over the treatment area. This ensures patients the highest level of precision, comfort and safety.
When can I go back to work?
Most people can return to their normal activities the day after the LASIK procedure, and that includes driving and going to work.
Will eye drops be necessary after surgery?
In PRK, because the laser removes tissue from the surface of the eye, the body will attempt to fill in the defect much like it would for a cut on the hand. Since corneal tissue has different healing properties, the process can normally be regulated with the use of topical steroid drops, which patients may be required to use over a one-month period. In LASIK, these drops are only used for a week. These drops rarely cause any problems. However, the eyes should still be monitored on a monthly basis to fine-tune the drop dosage and check for any unwanted side effects, such as delayed or rapid healing and elevation in eye pressure (glaucoma). Antibiotic drops are also used for about a week with both procedures. Please see our post operative instructions.
How many follow-up visits will be necessary following surgery?
Plan on about three short visits in the first three months after surgery. Even if the patient is seeing well, there are things that must be monitored during the first few months in order to ensure the best possible vision outcome.
How long do I have to wait before I can take a bath or shower after surgery?
Showering or bathing in a standard shower or bathtub is okay as soon as one day after the procedure. Still, patients should avoid getting soap or water in their eyes for at least a week following eye surgery. Other types of water activities - namely immersing in a pool, a jacuzzi or ocean water - should also be avoided for at least a week.
When can I wear eye makeup after surgery?
We recommend buying new mascara after surgery to avoid infection and to wait 1 to 2 weeks before using eye makeup.
How soon after surgery can I drive again?
Patients may resume driving when they feel comfortable with their vision. The majority of patients are able to drive on their own on the day following LASIK. With PRK, it usually takes about 4 to 5 days to feel comfortable.
When can I exercise after surgery?
Exercising can resume when the patient is ready. However, it is important not to get sweat in the eyes, to keep the hands clean and away from the eyes, and to avoid rubbing the eyes for the first few weeks after surgery. Swimming should also be avoided for at least two weeks.
What to Expect After Surgery
If I have PRK, what kind of vision can be expected the following day?
Vision is greatly improved but typically blurry immediately after the procedure (20/80-20/200). It generally starts to get better once the surface layer of the cornea (epithelium) has grown back, which in most cases takes 3 to 4 days (approximately 20/40). Vision typically starts to become good within 7 to 10 days (usually 75-85 percent improvement), and typically continues to improve for the next several weeks. The healing process varies for each patient, and it is difficult to precisely predict when particular people will achieve their best visual acuity. However, most patients who have both eyes treated at the same time report they are able to drive a car safely and resume their normal activities with 3 to 5 days following PRK.
If I have LASIK, what kind of vision can be expected the following day?
Most patients experience a large improvement in their vision the first day after LASIK, usually 20/40 or better. Results depend to a large extent on the patient’s preoperative prescription. In general, patients can expect to regain approximately 90 to 95 percent of their vision in the first two to three days after LASIK. The remainder of their vision will improve gradually over several weeks. Patients with significant astigmatism or who are very nearsighted or farsighted may experience slower sight recovery and stabilization.
Will I need glasses or contacts after surgery?
If the patient opts to have only one eye treated at a time, a contact lens maybe needed for the untreated eye until the second eye undergoes the procedure. Most patients can do this, even if they have not been able to tolerate contacts in the past. Keep in mind the optics of removing the glass in front of the treated eye in the spectacles, while giving clearer vision to each eye individually, will often cause disorientation and headaches due to image size discrepancy--unless the original prescription was less than -3.00.
Will I need reading glasses after surgery?
As people enter their 40s, they start to develop presbyopia, which is a gradual worsening of close-up vision (see #4). This is part of the natural aging process of the eyes, regardless of whether a person has had laser vision correction. For people with presbyopia, Dr. Ashraf can create an effect known as monovision. This means that one eye will be left slightly nearsighted, thus enabling the eye to focus on print such as labels and menus without reading glasses. This often allows to read small print without reading glasses, well into their 50s. However, as the patient gets older, it will be necessary to wear reading glasses. For people over age 40 who are used to removing their glasses to read, they must realize this will no longer be an option following a full correction of their nearsightedness with this surgery. Shortly after the procedure, it’s possible that a temporary pair of reading glasses may be necessary if the patient is approaching 40, as the laser, by design, causes an early over-correction that normally goes away with time.
Can I wear contact lenses after laser surgery?
Patients who were able to wear contacts prior to surgery should be able to wear them afterwards.
Will the effects of the treatment be permanent?
Given the results of the U.S. clinical trials and international reports, the treatment appears to be permanent. However LVC will not prevent age-related conditions such as cataracts, glaucoma, macular degeneration and presbyopia.
Safety and LVC
What are the side effects of this surgery?
The vast majority of patients have no serious side effects. The most common complaint after laser vision correction is dry eyes. Patients at particular risk are those who have dry eyes prior to vision correction. Dr. Ashraf will perform a complete eye exam prior to laser surgery and if called for, he may initiate dry eye treatments prior to the procedure for some patients. The majority of dry eye cases usually resolve within a few weeks following surgery. Another complaint after surgery is the “halo” effect and some glare at night around lights. However, these problems are no worse than what most contact lens and eyeglass wearers often experience and the majority of patients function without any visual impairment at night. Using the Wavelight Allegretto laser, we can expand the treatment areas, thereby reducing the risk of side effects in patients with larger pupils.
Is it possible to become blind with the surgery?
As with any surgery, complications could potentially occur. The good news is that after over 3 million laser vision correction procedures have been performed in the United States, no cases of blindness have been reported as a result.
What are the drawbacks of LASIK?
While more comfortable and yielding quicker rehabilitation of vision, LASIK is technically more difficult to perform than PRK. There is an extra step involved: the creation of the corneal flap. This is rarely associated with any considerable or permanent vision loss. However, there are occasional circumstances which could cause flap complications. Fortunately, most of these can be corrected with additional procedures.
How safe is LVC?
Since being approved by the FDA in 1998, nearly 700,000 people undergo LASIK each year. Surgeons have been performing the procedure for over 15 years and over 30 million procedures have been performed worldwide. To date, very few sight-threatening complications have occurred. LASIK is generally a very safe and effective vision correction option for those who qualify.