Questions and Answers About Lasik Surgery

Chapter Twelve:
Questions and Answers About Lasik Surgery

What Is the Difference Between PRK and LASIK?

Both procedures use the excimer laser to reshape the cornea and correct nearsightedness, farsightedness, and astigmatism. The difference is that with PRK the laser is used on the surface of the eye, while in LASIK the laser work is performed under a thin, protective, corneal flap. The long-term results of both procedures are similar. Additionally, visual recovery with LASIK is usually faster, with less discomfort and less possibility of scarring.

With PRK, postoperative drops are needed for up to three months, whereas with LASIK, medicated drops are only needed for five to seven days. Since its advent, LASIK has become the procedure of choice over PRK.

Does LASIK Hurt?

Before the LASIK procedure begins, your eye is made numb by drops. While you may feel a pressure sensation as the corneal flap is being made, actual pain is rare. Any discomfort you may feel subsequent to the LASIK procedure will last only a few hours. Sleep and lubrication, as well as Tylenol® or ibuprofen, are usually enough to counteract any discomfort.

Can You Guarantee 20/20 Vision?

As with any surgical procedure, there are no guarantees. Although the results are extremely good (ninety-five percent of patients in national studies no longer need glasses for driving), the results of the procedure depend on your initial refraction, your own healing characteristics, and other factors. It is good to look at LASIK vision correction surgery as a way of achieving an extreme decrease in your dependence on glasses or contact lenses. If 20/20 vision is not obtained after the primary LASIK procedure, enhancements may be effective to further improve vision. 20/20 can only be achieved in patients who have the potential to obtain 20/20 vision. For example, LASIK performed on a patient with a lazy eye that can only see 20/40 will only achieve 20/40 best-corrected vision.

Has Anyone Ever Gone Completely Blind from Their LASIK Procedure?

No. In over 8 million cases done worldwide, no one has ever gone completely blind from a LASIK or PRK procedure, although you can lose a significant amount of vision if the procedure is not performed correctly or if you develop an extremely rare complication, such as an infection.

Can Both Eyes Be Done at Once?

LASIK is often done on both eyes at the same sitting. The results are so predictable and the procedure safe enough that most people undergoing LASIK surgery prefer to have both eyes done on the same day. The advantage of bilateral surgery is the convenience of having both eyes done at once. It also restores your balanced vision as quickly as possible, especially if you are unable to wear a contact lens in the unoperated eye.

If you undergo PRK, however, you may want to have your eyes done on consecutive weeks as it may take a few days for functional vision to return. By doing one eye at a time, you can rely on the other while the postoperative eye is healing. Additionally, surgeons may elect to do one eye at a time in patients with extreme myopia, as these patients can be less predictable in terms of their response to the laser.

One theoretical advantage of unilateral surgery is that if one eye should become infected, the second eye would have an increased risk for this complication if it were treated concurrently. Infection turns out to be a very rare occurrence, so this advantage becomes more of a theoretical benefit than a real one. Another theoretical advantage quoted by proponents of unilateral surgery is that the results of the first eye can be used to fine tune the results of the second. Again, in practice this turns out not to be clinically significant in most cases.

What Are the Results of LASIK Surgery?

Results may vary from surgeon to surgeon and from center to center. Results also vary depending on your initial refractive error. With higher amounts of myopia, hyperopia, and astigmatism, results are less predictable and retreatments are more common. It is important to ask your surgeon about his or her experience and results.

How Long Will the Correction Last?

Once your eye has stabilized (which is about three months with LASIK and six months with PRK), your correction is permanent. Any additional need for glasses after that will be the result of normal aging processes that befall everyone and not due to any instability of the refractive procedure.

What about Enhancement Surgery?

In the event that you are undercorrected or overcorrected, it is possible to perform an additional treatment. But first your eye must stabilize. Typically, retreatment with LASIK usually takes place two to three months after the original procedure. With PRK this can occur after about six months to one year. In PRK, the front surface of the cornea is treated again, and the recovery time is a week to a month.

With LASIK, the corneal flap may not need to be recreated. Using specialized instruments, the surgeon can gently lift the preexisting flap and perform additional laser work. Recovery time is similar to the original procedure. Such enhancement surgery is usually not an additional charge but is considered part of the original fee if performed within a specified time after the original surgery.

I Have Dry Eyes. Will This Affect My LASIK Surgery?

Many patients seeking refractive surgery do so because they have dry eyes and are unable to wear contact lenses anymore. It is important that your dry eyes be treated. This usually involves the use of tear supplements and punctal plugs (tiny silicone plugs placed in the tear drainage openings of your eyelid) that delay the drainage of your own tears so your eyes will stay moist.

After the procedure, your operated eye may feel temporarily drier because the corneal nerves are severed during LASIK surgery, causing the eye to make fewer tears. This condition is temporary and typically lasts three to six months.

Dry eye symptoms can be particularly noticeable if you use the computer frequently, read for long periods of time, or drive extended distances. These types of activities exacerbate dry eyes because they cause you to stare and not blink as often. It is important to use ample lubrication, especially during the first few months after surgery.

If I Need to, Can I Wear Contact Lenses after Surgery?

If you have a residual refractive error and you choose not to have an enhancement procedure, you may elect to wear contact lenses. With PRK you may need to wait up to three months; with LASIK you may wear contact lenses within a few weeks. If you were a good contact lens wearer before LASIK, it is unlikely you will have problems afterward.

What Is Monovision?

In patients in their mid-forties who are already experiencing difficulty with reading in their distance correction, it is possible to treat one eye for near vision and the other for distance vision, thus decreasing the necessity for both near and distance glasses.

If you are considering monovision, it is advisable to try it out with contact lenses before proceeding directly to LASIK surgery. If you have already been successful with monovision in contact lenses, you will most likely enjoy this type of correction following PRK or LASIK. If you are over forty and hope to avoid glasses altogether in your life, this is presently the only way to accomplish this.

Can There Be a Problem with My Eyes Twenty Years from Now Because I Had LASIK?

This is very unlikely. LASIK is a form of lamellar refractive surgery, and lamellar refractive surgery (myopic keratomileusis) has been performed since 1949. Patients who have undergone these related but less accurate and more invasive procedures fifty years ago have not developed any unusual problems.

Can I Have Cataract Surgery If I Need It in the Future?

Yes. The surgical technique used will not change. However, your lens implant will be calculated using a different formula.

No. LASIK does not prevent cataracts, glaucoma, retinal detachment, macular degeneration, or any other eye disease. Ophthalmologists term LASIK as disease neutral: It doesn’t cause disease, it doesn’t prevent disease, and it doesn’t prevent diseases encountered in the future from being treated.

A Note on Retinal Detachment: Severely nearsighted people are at greater risk for retinal detachment. Generally, the more nearsighted one is, the greater the risk. It is important to understand that after LASIK or PRK, the eye is still anatomically myopic (structurally too long) and subject to the same retinal detachment risk as before the procedure.

Is LASIK Approved by the Food and Drug Administration?

In 1995 the FDA approved the use of the excimer laser for the treatment of myopia using PRK. In recent years LASIK has gained popularity in many practices and has become the procedure of choice worldwide. Since 1999, the Food and Drug Administration approved LASIK when performed with a number of laser systems including the VISX Star S2, S3 and S4 and the Alcon Ladarvision® Excimer Laser System.

What Does Laser Vision Correction Surgery Cost?

PRK costs from $1,500 to $3,000 per eye, depending on your area of the country, the laser used, the experience of your surgeon, and the services covered. LASIK, because of higher material costs, may cost a little more. This fee usually includes the surgery, a post-op kit containing medication and sunglasses, follow-up care, and any enhancement procedures during the first year. It typically does not include the cost of temporary glasses or contact lenses, if needed. Affordable payment plans are usually available to qualified candidates. Please ask about payment options available and services that are covered.

One way to save substantially is to use flexible benefit or medical savings accounts to pay for the procedure using pretax dollars. Ask your employer’s benefits administrator about flexible benefits. Laser vision correction practices often have a financial counselor available to discuss payment options and covered services.

Some insurance companies will pay for the procedure, but that is the exception rather than the rule. It doesn�t hurt to ask.

Who Is a Candidate for LASIK Vision Correction?

You must be at least eighteen years old and have a stable prescription. Good candidates have myopia up to -14.00 or hyperopia up to +6.00. Your level of astigmatism may be as high as 6.00 diopters. You cannot be pregnant or nursing, have any unstable medical condition, or any uncontrolled eye diseases. It is also important that you have reasonable expectations.

Who Is Not a Good Candidate for LASIK Surgery?

Anyone whose prescription is actively changing more than one diopter per year.
Pregnant or nursing mothers with unstable refractions.
Anyone who feels that he or she must absolutely gain 20/20 vision without glasses or contact lenses. (No surgeon can guarantee 20/20 vision without correction. Think of it, instead, as achieving a vastly decreased dependency on glasses and contact lenses.)
Anyone unwilling to accept the possible risks and complications of LASIK surgery.
Anyone with an uncontrolled or untreated eye disease. Certain corneal dystrophies or a history of herpetic keratitis (a herpes infection in the eye) may be relative contraindications, as are certain arthritic syndromes and other autoimmune disorders.
Anyone on certain medications such as Acutane, etc.
When Can I Drive?

With LASIK you can usually drive within one to three days. With PRK you should probably not drive for a week. This depends on whether you have one eye done at a time or have simultaneous surgery on both eyes. The Department of Motor Vehicles typically grants unrestricted driving privileges to individuals who possess 20/40 or better vision. Over ninety percent of all patients who undergo LASIK surgery have this level of vision or better by the first day after their procedure.

When Can I Return to Work?

With PRK you should plan on taking off at least two days if you have both eyes done simultaneously, as you will experience some discomfort and your vision will be fairly blurry. With LASIK the majority of patients can return to work the next day, although it is advisable to take twenty-four hours off following surgery on both eyes. If you work in a dusty environment, you should wait forty-eight hours prior to returning to work.

While most patients can function normally at work the day after their LASIK procedure, we recommend that you not schedule any unbreakable appointments or meetings on that day. If your recovery is delayed slightly, you will still be able to accommodate the delay without any undue stress.

 

LASIK Postprocedure Care

Chapter Eight:

LASIK Postprocedure Care

Once your procedure is completed, you will sit with your eyes closed for approximately thirty minutes. Afterward, your doctor will check your eyes to ensure that the corneal cap is properly positioned; then you will be instructed to go home and take a nap. Because your vision will be somewhat blurry and you will have received a sedative, you will need to have someone drive you. Additional drops will be placed in your eyes, and you will be instructed on the use of your medications. You will also be given clear plastic shields to wear at night for as long as your doctor instructs (at least two nights, usually three days to one week). These prevent accidental trauma to the flap during the healing period should you inadvertently bump your eye.

Before you go home to rest, your surgeon may also give you something to help you sleep; this is the best way to keep your eyes closed for the first few hours. Following the LASIK surgery, you may experience some discomfort, which may last for six to eight hours. Patients describe the discomfort as a “sandy feeling” or liken it to having a dirty contact lens in their eye. With LASIK this discomfort is usually gone by the next day. Tylenol®, aspirin, ibuprofen, or similar over-the-counter pain medications are usually adequate to keep you comfortable.

You will also be given antibiotic eye drops, anti-inflammatory eye drops, and lubricant eye drops to promote healing. It is common for the eyes to feel somewhat dry, and the lubricant drops (also called “artificial tears”) may be used frequently.

Guidelines for Healing – Follow these guidelines to promote safe and rapid healing:

Rest. Sleep aids recovery.
Particularly in dry climates, apply nonpreserved lubricant eye drops very frequently. This encourages rapid recovery and enhances comfort. (Some patients may need these drops every half-hour the first few days, every couple of hours the first week, and at least four times daily for the first three months.)
Sensitivity to light is normal and will improve. Wear good ultraviolet-protecting sunglasses.
Avoid rubbing your eyes and squeezing your eyelids for one week.
Avoid swimming, surfing, and hot tubs for at least two weeks.
Showers and baths are fine, but avoid getting water and shampoo directly into your eyes for the first few days.
Avoid dusty or smoky environments for several days.
Avoid eye makeup for one to two weeks.
It is a good idea to plan on not driving until you feel your vision has improved. You may drive as soon as you are visually comfortable and your doctor approves. This may be the next day or take a few days.
Postoperative Follow-up Schedule

When you leave the laser center, you will be given complete instructions to follow, including a postoperative appointment schedule.

Here is a typical postoperative appointment schedule:

Purpose of Appointment
Time Frame Following LASIK Procedure

To ensure that there is no evidence of infection, that the flap is healing properly, and to remove the bandage contact lens (if one was used)
1 day
To ensure that your eye is healing properly
1 week,
1 month
To measure your visual progress and to consider enhancement treatment (if necessary)
3-6 months
To measure the stability of your result, check your eye pressure, and assess your general eye health
12 months/annual exam
The LASIK Recovery Cycle

Your vision improves quickly after LASIK, and many patients feel comfortable enough to drive in one to two days. The corneal flap is relatively adhered in one week, but it is advisable not to rub your eyes vigorously for one month.

The return of visual stability after LASIK varies for each patient. For some, stability can be achieved in as few as two weeks; for others, stability may take from three to six months. As a rule, vision will improve in three hours, more in three days, three weeks, and even in three months. Generally, during the course of the first month, there is gradual improvement in the already good vision following LASIK. You can also expect a small reduction in nighttime halos and some return of near vision in patients over forty.

For the first five to seven days after your operation, you will be using medicated eye drops. It is generally advisable to continue using lubricant drops for the better part of the first month after your procedure. Well lubricated eyes heal better, maintain better visual stability, and are more comfortable. These drops are available over the counter.

It is important that you keep your postoperative appointments as your eye drop regimen may be altered. Also, the doctor may need to monitor your eye pressure if you are on postoperative steroids for any length of time. Be sure to keep your follow-up appointments.

Most patients enjoy good functional vision during the first month. Fluctuations in your vision are common during the first two to three weeks, especially for higher visual corrections. Patients undergoing hyperopic LASIK (farsightedness treatment) may notice that their near vision is better than their distance vision. This is quite common, and the distance vision will continue to improve during the first month.

Some patients may feel more comfortable with a thin pair of glasses to assist them with more critical distance vision activities, such as night driving or attending a play and trying to see the expressions on the actors’ faces. Patients over forty years of age may require a thin pair of reading glasses.

While many patients notice halos around lights or ghosting of images at night, these symptoms tend to diminish substantially within six months.

Patients with drier eyes or who use the computer, who read for long hours, drive long distances, or live in low-humidity climates may notice some minor discomfort and blurring of their vision, particularly toward the end of the day. This is usually related to dryness of the surface of the eye. The frequent use of lubricant drops will help significantly.

With LASIK, your vision usually becomes stable within three to six months. Once your vision is stable, your treatment is permanent. You now have less dependence on, and maybe complete freedom from, glasses and contact lenses.

 

 

Lasik Preprocedure Consultation crucial first step in the surgery process!

Chapter Six:

The Preprocedure Consultation

If you decide to proceed with LASIK eye surgery, there will be three distinct parts to your experience: Lasik Preprocedure Consultation is the first of your lasik experience.

The preprocedure consultation with the LASIK surgeon and his/her staff
The LASIK procedure
LASIK postprocedural care
This and the next two chapters review in detail each part of the experience.

Lasik Preprocedure Consultation

Before you proceed with LASIK vision correction, you need a preprocedure consultation with the surgeon and his or her staff. This consultation is important for several reasons. First, it must be determined whether you are a candidate. It is also vital for you to learn as much as you can about your options and have as many of your questions answered as possible. With few exceptions, you must meet the following criteria to be considered a good candidate:

Be over eighteen years of age for treatment of myopia up to -14.00 diopters or hyperopia up to +6.00 diopters, with or without astigmatism (up to 6.00 diopters).
Have vision that has been stable for at least a year.
Be free from certain diseases of the cornea, lens, and retina.
Not be pregnant or nursing.
Be in good general health.
Fear of the Unknown
Of all the concerns that face people considering refractive surgery, fear of the unknown is perhaps the greatest. Este’s story is the norm for people about to undergo LASIK:

“Talk about high anxiety. I almost didn’t go through with it because of fear of the unknown. I completely freaked out and was a basket case. After the procedure, I could tell that I could see better, but there was a bit of a haze. By the evening, I was reading the stock exchange numbers that scroll across the bottom of the TV on CNN. By the morning, I could see perfectly. It was amazing. I just can’t believe that one day I’m wearing glasses and a day later I’m not. I absolutely encourage anyone who needs or wants this surgery to do it. It is probably one of the best decisions you will ever make.”–Este W.

Wesley’s story is a bit different, and notwithstanding all the study and preparation he did prior to choosing LASIK, he still experienced that very normal nervousness and trepidation of having someone work on your eyes. This is what he went through:

“I must admit that I was incredibly nervous undergoing the LASIK procedure on my eyes. I had read numerous articles, discussed the procedure with numerous professionals, and researched various centers and doctors before deciding to have the surgeon I chose perform my LASIK procedure. In retrospect, the worst part of the experience was the anticipation of having someone operating on my eyes.

The surgery was completely painless and was completed within fifteen minutes on both eyes. I couldn’t believe that it would be so easy. I was totally comfortable during the surgery and was engaged in a relaxing conversation with the surgeon and his staff. Immediately after the procedure I stood up and couldn’t believe how well I could already see. It was incredible!

On the way home, I could already see license plates and road signs. In the morning, my vision was better than perfect. I went from 20/200 vision to 20/15 vision in less than twenty-four hours. It’s a true miracle. I was able to return to my duties as a police officer the following day. The freedom experienced by being contact lens and glasses free is exhilarating. I would encourage anyone contemplating the surgery to have it done. The LASIK procedure has changed my life and is one of the best decisions I have ever made.” –Wesley L.

These are but a few of many testimonials from thousands of thrilled patients who have undergone LASIK. In a matter of minutes, they have been transformed from a lifetime of visual bondage to freedom, no longer dependent on cumbersome eyeglasses or irritating contacts.

What to Expect

Medical and Ocular History

At your preprocedure evaluation, a thorough eye exam will be performed. This will include collecting a careful medical and ocular history. It is important for your doctor to know everything about your medical history as certain systemic diseases such as rheumatoid arthritis, lupus, certain healing disorders, diabetes, and a current or planned pregnancy may need special consideration. The ocular history will include questions about previous contact lens wear and eye disease. One specific eye disease that the doctor must know about is herpes simplex on the eye. He will explain that diseases such as glaucoma or diabetes will not preclude you from having the procedure, but they must be identified and controlled. It is important for you to notify the doctor of any ongoing changes or problems with your vision during the consultation. If you have a significant cataract and are experiencing glare, changing vision, or decreased sight compared to what you normally see, you should not undergo LASIK eye surgery.

LASIK Measurements

The examination will include a measurement of your refractive error and a complete exam of your eye, including a sophisticated digital mapping of your cornea with a device known as a corneal topographer. The thickness of your cornea and your intraocular pressure will be measured. Also, your dominant eye will be determined and your pupil size measured.

Contact lenses, particularly hard or rigid gas-permeable lenses, have been known to warp the cornea and interfere with some of these measurements. If you wear contact lenses, they must be removed prior to the final LASIK measurements in order to allow the cornea to return to its natural shape–three to seven days for soft lenses, two to three weeks for toric or gas-permeable lenses, and possibly longer for hard lenses.

After the LASIK measurements, if you are unable to tolerate glasses for the length of time necessary for unwarping to occur, some hard-lens wearers may be able to switch to soft lenses until two weeks before the surgery. It is important that your refraction and corneal topography readings be stable before you proceed with surgery.

Pupillary Dilation

To get an accurate check of your refraction, drops will be instilled to temporarily relax your eye’s focusing muscles. This pupillary dilation also allows the doctor to examine the back of your eye, including the retina and the optic nerve. These dilating drops will make you sensitive to light and may affect your near vision for up to thirty-six hours, so you should plan accordingly. You may want to have someone drive you home. Also, there are eye drops that will reverse dilation sooner.

Monovision

If you are in your late thirties or older, the option of monovision (or blended vision) should be discussed at your preoperative consultation. Monovision allows some patients to see near objects without the use of reading glasses. As mentioned in Chapter Two, patients in their late thirties to mid-forties begin to develop presbyopia, or difficulty with their fine focusing. The laser cannot correct this problem. Thus, a patient who has presbyopia in addition to nearsightedness or farsightedness will still need reading glasses if both eyes are corrected perfectly for distance.

Monovision refers to the “undercorrection” of one eye in a nearsighted patient or the “overcorrection” of one eye in a farsighted patient. The technique involves correcting the dominant eye for distance and the nondominant eye for near vision, thereby reducing the need for reading glasses. When both eyes are functioning together, the brain naturally “looks” through the eye that is clearer. So, for distance vision the brain sees mostly with the dominant eye, and for near vision it sees mostly with the nondominant eye. Having eyes for different purposes might sound unsettling, but some patients do quite well with some degree of monovision.

The best way to decide if this is something you want is to discuss it with your doctor. He or she may be able to show you with contact lenses what it will feel like before you have your surgery. Additionally, in the event you do try monovision and do not like it, additional laser correction can be added to make both eyes equal, although ideally this is determined in advance to avoid the risk of unnecessary surgery.

Education

In addition to obtaining the medical information necessary for your laser eye surgery, an equally important objective of the consultation is to educate you regarding all aspects of LASIK eye surgery. Learning about the procedure and discussing your options are important for making an informed decision. The initial educational process should include videos and written information to help you understand what you can reasonably expect from the procedure. Reasonable expectations are an essential ingredient for a happy postoperative patient.

If you are over forty, your ability to read normal size (twelve-point) text should be discussed, including the option of correcting your nondominant eye for reading (monovision).

You will be asked to decide whether you want both eyes done at the same time or whether you prefer that the procedures be done on separate days. While most patients prefer to have both eyes done at the same time, this is optional rather than mandatory. Some surgeons only perform surgery on one eye at a time to reduce risk or increase accuracy, but studies have shown that there is no statistically significant difference in the refractive outcome between sequential and simultaneous bilateral LASIK.

While much of the education process can be done by a specially trained counselor or technician, you will still be given the opportunity during the preprocedure evaluation to have a one-on-one meeting with the surgeon for him or her to carefully evaluate your eyes and answer any questions you may have. It is most important that you feel comfortable and confident with your doctor.

LASIK requires a highly skilled surgeon to create the flap–one dedicated to obtaining precise results–in order to properly program the excimer laser. The follow-up care is relatively simple in most cases.

Previous Surgery

Patients who have previously had certain types of surgery are sometimes candidates for LASIK or PRK as a second procedure to enhance visual results. LASIK on top of a previous radial keratotomy (RK) to correct myopia and astigmatism is a technique that has been used successfully in many cases, provided that the patient’s vision is relatively stable and there is no significant corneal scarring.

Patients who have had a previous corneal transplant can have a secondary LASIK or PRK procedure to enhance the results. This is especially effective for patients who develop a high degree of astigmatism that is surgically induced. A clear corneal transplant can only allow good vision if it has a relatively smooth corneal surface. Laser vision correction is especially beneficial to corneal transplant patients with unusual refractive errors and can smooth out astigmatic curves in the cornea. These are often more difficult surgeries with less predictable results, and patients should consult with their surgeon to determine their eligibility.

Price

You will decide with your surgeon which procedure is best for you, and that procedure will be discussed with you in detail. You may also view a video that further demonstrates the procedure. Time will then be taken with you to answer any questions that you may have. After you decide to undergo LASIK vision correction, the only other preliminary step remaining is to have you sign an informed consent form and arrange for payment of the procedure.

The cost of LASIK and PRK varies from $1,500 to $3,000 per eye, depending on the procedure, your area of the country, the type of equipment used, the experience of your surgeon, and whether follow-up care and enhancement (retreatment) procedures are included. You should always feel comfortable about asking questions of your surgeon, both prior to and following the procedure.

This should cover most aspects of your Lasik Preprocedure Consultation. You want to know how to select a LASIK surgeon visit here.

 

How the Eye Works

Chapter Two:

How the Eye Works

In order for you to fully understand how refractive surgery works, you need to understand how your eye works. This basic knowledge will help you determine if LASIK surgery is right for you. The primary purpose of your eye is to focus light. When the rays of light are not focused properly, you need glasses or contact lenses.

Your eye works very much like a camera. Light enters the eye through the cornea, the clear front surface or “window” of the eye. As the light passes through the cornea, it is bent or refracted. This bent light then travels through the pupil (the opening in the colored iris) and into the natural “crystalline” lens. The lens acts to fine tune the focus of light onto the retina. The retina turns the light energy into electrical impulses that travel along the optic (eye) nerve from the eye to the brain, where the image is interpreted. (You actually see with your brain, not with your eyes.)

On the following pages is a series of pictures and short descriptions of the various parts of the eye that will help you understand the vision process, why vision is sometimes blurry, and how these vision disorders can be corrected.

Diagram of the anatomy of the eye

Diagram of the anatomy of the eye

Normal eyesight is present when light rays are in focus on the retina, causing a clear image to form

 

Iris

The iris is the colored part of the eye. The muscles of the iris act to control the size of the pupil.

Pupil

The pupil is the opening that appears as a black spot in the center of the iris. The pupil acts to regulate the amount of light that enters the eye. In bright sunlight it becomes small to let in less light. In a dark environment the pupil expands to allow more light to reach the retina.

Lens

The crystalline lens is a normally clear structure located behind the pupil. It acts to fine tune the focusing. By changing shape, the lens allows us to focus near and far. This ability to focus near (accommodation) gradually worsens with age as the lens gets harder and less supple. Most people notice this in their early forties, at which time they begin to need reading glasses or bifocals. In people over sixty, the lens may become cloudy. This clouding of the lens is called a cataract and may interfere with your vision.

Vitreous

This is the clear gel substance that fills the space between the lens and the retina. If there are opacities in the vitreous, you may see them as “floaters.”

Retina

The retina is the thin layer of nerve tissue that lines the inside wall of the eye. It is very similar to film in a camera and functions to capture and transmit images for interpretation to the brain.

Optic Nerve

The optic nerve carries the images from the retina to the brain.

Refractive Errors

Refractive errors (vision-focusing problems) refer to disorders that are related to how your eye focuses light. The word refraction is used to describe the way light is bent by your eye. The factors that influence how your eye refracts (bends) rays of light are the curvature of your cornea, the power of your lens, and the length of your eye.

Myopia (nearsightedness)


Myopia occurs when the eye is functionally too long for the focusing power of the cornea and lens. In some eyes, the cornea is too steep. As the light rays pass through the cornea, they come to a point of focus in front of the retina. This creates a blurred image. Patients with myopia are able to see near objects well but have difficulty with their distance vision.

In myopia (nearsightedness), rays of light focus in front of the retina instead of upon it, causing distant objects to appear blurred.

 Hyperopia (farsightedness)

In hyperopia (farsightedness), rays of light focus behind the retina
Hyperopia occurs when the eye is functionally too short or (rarely) the curvature of the cornea is effectively too flat. The light rays that enter the eye are not bent sharply enough, causing them to come to a point of focus behind the retina. This produces a blurred image. Farsightedness means distant objects are seen more clearly than near objects. Although farsighted patients see distant objects more clearly than near objects, they often have difficulty with both, especially after age thirty.

In hyperopia (farsightedness), rays of light focus behind the retina

Some younger people who are mildly farsighted are able to use the focusing muscle around their lens (accommodation) to bend the light more steeply. This brings the point of focus forward toward the retina and allows them to see more clearly. However, this ability decreases with age, so that reading glasses are needed at an earlier age than normal, and glasses or contact lenses may also be needed to see at different distances.

Farsightedness is often confused with presbyopia. Presbyopia is the age-dependent need for reading glasses. Even people who have never worn glasses before find that they start needing reading glasses in their forties and fifties. This is because the up-close focusing ability of the natural lens is progressively lost with age. This occurs with everybody. At first they just need them for seeing things up close (presbyopia). Farsighted people in whom the length of the eye is too short require the natural lens to supply the additional focus for both near and distance vision. Therefore, many farsighted individuals as they age lose not only their near vision but their far vision as well, becoming totally dependent on their glasses or contact lenses. This phenomenon is called latent hyperopia.

Astigmatism

Many patients with myopia or hyperopia have some degree of astigmatism. This means that your cornea, rather than being completely spherical like a basketball, is slightly oval and shaped more like half a football. People with astigmatism experience blurred vision and sometimes distortion of images due to unequal bending of the rays of light entering their eyes. Astigmatism causes blurred vision for both distant and near objects.

Almost everyone has at least a small amount of astigmatism. For many people, their astigmatism has very little effect on their vision. Unfortunately, the word “astigmatism” is one of those magic words in the English language that almost everyone remembers and is frequently concerned about. The good news is that almost everyone with significant astigmatism can dramatically improve his or her vision using refractive surgery to reduce the amount of astigmatism.

Astigmatism

In astigmatism, light entering the eye focuses in multiple areas rather than in one location

 

 

Presbyopia

Presbyopia (literally, “old eyes”) is a normal aging process. It occurs as the protein composition of the lens changes, making it harder and less flexible. As the lens loses its ability to flex, it can no longer bend light rays as sharply, and the ability to focus on near objects is impaired. The onset of presbyopia typically occurs between age forty and fifty and continues to worsen through age sixty-five. When this occurs, people who already wear glasses may need bifocals, and those who have never worn glasses may require reading glasses.

Presbyopia is an important concept to understand. The excimer laser has no effect on your eye’s focusing muscles or on the lens, so it cannot treat pure presbyopia. Thus, if you only need glasses for reading, refractive surgery is not likely to help you unless you choose to have surgical correction for monovision (adjusting one eye for reading, mentioned below). Additionally, if you are mildly nearsighted and in your forties, you may notice that while you cannot read clearly with your glasses or contact lenses on, you can read well without them. One advantage of mild myopia is the ability to remove your glasses after presbyopia sets in and still be able to read.

If you are myopic, over forty, and obtain excellent distance vision after undergoing laser vision correction, you will typically become normal sighted. This means that you will lose the ability to read without glasses once presbyopia begins. Like other normal sighted individuals, you will begin to require reading glasses for small print, generally sometime in your forties.

One way to counteract the loss of near vision if you are nearsighted is to keep one eye slightly myopic after LASIK. If you are farsighted, your surgeon could overcorrect one eye and make it slightly nearsighted. Your brain will automatically use this eye for reading and the fully corrected eye for distance. This is called monovision or blended vision. (Remember, you see with your brain, not with your eyes.) You may want to discuss this possibility with your doctor. LASIK Eye Surgery designed for monovision should be reserved for those individuals who are already accustomed to and comfortable with monovision utilizing contact lenses.

Monovision is good for people with relaxed personalities and those who do a lot of simultaneous near-distance activity, like schoolteachers, salespeople, and busy parents. It usually does not work for people with rigorous vision needs such as professional tennis players, accountants, or architects.

Measurement of Refractive Errors

You may hear your vision referred to as 20/20 or 20/40 or even 20/400. This is a measurement of your visual acuity using a Snellen chart (vision chart with progressively smaller letters). The notation 20/40 means you can see at twenty feet what a normal sighted person sees at forty feet. These numbers measure your vision but do not quantify your refractive error. There are other variables that affect an interpretation of the chart, such as squinting, guessing at the letters, and room light.

Quantifying your refractive error is done in diopters. This is the number used to determine your refractive treatment. The more nearsighted or farsighted you are, the higher your prescription is in diopters.

Your prescription for glasses may be written in three numbers.
Let’s take the prescription -4.00 -1.50 X 90

The first number (-4.00) identifies your degree of nearsightedness or farsightedness. The sign is an indication of whether you are nearsighted (-) or farsighted (+).

The second number (-1.50) represents your degree of astigmatism. This can be written as either + or -.

The third number (90) represents where the astigmatism lies. In this person the astigmatism is at ninety degrees or vertical. When your ophthalmologist corrects your refractive disorder, he uses this prescription to determine the treatment.

Your prescription (measured in diopters) forms the basis for the number entered into the computer that controls the excimer laser. This number determines how much and in what pattern the laser removes tissue from the cornea. The amount of tissue removed depends upon the refractive error and is usually no more than ten to twenty percent of the total thickness of the cornea.

Nonsurgical Vision Correction Options

Before considering LASIK Eye Surgery, you should review the variety of different nonsurgical ways refractive disorders can be corrected. All have benefits and drawbacks.

Glasses

Glasses are time proven and have been in existence for a thousand years. They are affordable (unless you buy multiple pairs of designer frames), easy to maintain, and versatile. They may, however, restrict peripheral vision, be difficult to wear in certain weather conditions, cause minification of images, cause a number of visual aberrations (including halos around lights), and have a limited usage life. They may interfere with certain occupations and recreational activities, and some people don’t like the impact glasses have on their appearance.

Contact Lenses

Contact lenses are another common solution for the correction of refractive visual problems. Advantages include more natural vision, no change in cosmetic appearance, improved visibility, more freedom in recreational activities, and better peripheral vision. On the other hand, contacts are high maintenance, may get lost, are less comfortable for patients with dry eyes, may cause visual aberrations (including halos and fluctuating vision), and always carry an increased risk of infection and possible corneal scarring. In higher altitudes many adults become intolerant of contact lenses over time because of dry climate and decreased oxygen in the air.

There are so many types of contact lenses available today-soft, rigid, gas permeable, toric for astigmatism, disposable, etc.-that the vast majority of people can be fit comfortably, regardless of their level of nearsightedness, farsightedness, or astigmatism. For people who are presbyopic and over thirty-five, contact lenses can be fit asymmetrically to obtain monovision for reading. Ophthalmologists and optometrists recommend not sleeping with any contact lens in because this increases the chance of corneal infection.

Orthokeratology

This is a technique that uses a series of rigid contact lenses to flatten your cornea to treat myopia. The effects are not permanent and require continued dependence on part-time retainer lenses. The technique is expensive, high maintenance, and requires continuous follow-up visits. The long-term effects may also lead to permanently warped corneas. The risk of keratitis or infection is also considerably increased over normal contact lens wear.