Corrective Eye Surgery Basics
In recent years there have been tremendous advances in the field of vision correcting eye surgery which is also known as refractive or laser surgery. Corrective eye surgery offers patients clear vision without the use of glasses and contact lenses. There are a number of types of refractive surgeries that are able to correct different vision problems, so if you are considering surgery here are some of the options you should know about.
LASIK (laser-assisted in situ keratomileusis) surgery is perhaps the most well-known refractive surgery today. LASIK can help patients with myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. During the procedure, the doctor makes a flap in the outer layer of the corner to reach the underlying tissue and then uses a laser to reshape the tissue which allows the cornea to then focus light properly. The procedure is usually painless and vision is usually clear within a few hours.
Recent advances in the field have developed subcategories of LASIK surgery such as Bladeless LASIK, which uses a laser rather than a mechanical tool to make the initial flap or Wavefront (custom) LASIK which uses computer mapping to guide the reshaping of the cornea and is able to create a much more precise visual correction for very subtle optical imperfections. There is also a procedure called Epi-LASIK in which following the procedure, the doctor applies a soft contact lens to protect the surgical area, holding the flap in place while it heals.
Monovision is a technique that began with presbyopia-correcting contact lenses designed for individuals with presbyopia and nearsightedness or astigmatism. Each eye gets a different lens power – one lens is used in the dominant eye to correct for distance vision and the other for near vision. The eyes adapt to the two lens powers by learning to use the appropriate eye for the necessary distance power. Monovision LASIK surgery is based on the same principle of correcting each eye for a different refractive power and has shown just as high if not higher success rates than the contact lens technique. Usually, patients will try out monovision with contacts first to ensure that it works and that the eyes adapt properly.
PresbyLASIK is a procedure that is currently available in Canada and Europe and undergoing clinical trials in the United States. As opposed to monovision LASIK, this procedure is a multifocal alternative in which different rings of refractive power are created on the cornea, similar to multifocal lenses. This provides vision correction at all distances simultaneously.
In LASEK or laser-assisted sub-epithelial keratomileusis, the doctor creates a flap smaller but similar but to LASIK, and then uses an alcohol solution to loosen the tissue around the cornea which is pushed aside, and then a laser is used to reshape the cornea itself. In an Epi-LASEK procedure, the doctor may apply a soft contact lens to hold the flap in place to assist in reattaching to the cornea as the eye heals. Patients that undergo LASEK generally experience less discomfort and quicker vision recovery than PRK patients. LASEK may be preferred over LASIK as a safer option for patients with a thin cornea.
Cataract Surgery is a very common refractive surgery that removes the clouded natural lens of the eye and replaces it with an artificial lens called an IOL (intraocular lens). Many patients these days will receive a lens that also corrects any refractive error they have such as nearsightedness, farsightedness or presbyopia.
RLE or refractive lens exchange is a non-laser procedure the replaces the natural lens of the eye. This is the same as the surgery that is used to treat cataracts, ,yet for non-cataract patients, RLE is used to correct severe nearsightedness or farsightedness. The procedure involves the doctor making a small cut in the cornea, removing the natural lens and replacing it with usually a silicon or plastic lens. It is particularly useful for patients with minor corneal problems such as thin corneas or dry eyes.
RLE is more risky than the other procedures mentioned and can affect the patient’s ability to focus on close objects, possibly requiring reading glasses following the procedure. However, in cases of severe vision correction it is often the preferred method.
PRELEX or presbyopic lens exchange is for patients with presbyopia, the age-related condition in which you lose the flexibility of your lens and can no longer focus on close objects. Patients that prefer not to wear reading glasses or multifocals, can opt for a procedure in which the doctor removes the natural lens of your eye and replaces it with a multifocal artificial lens. This procedure is often done in conjunction with cataract surgery.
Phakic Intraocular Lens Implants
Phakic IOLs are implants that are used for individuals with very high nearsightedness who do not qualify for LASIK or PRK. The implant is attached to your iris or inserted behind your pupil, while the natural lens remains intact. Because this is a procedure that involves the inner eye, it is more risky than LASIK or PRK and is therefore also typically more expensive.
Conductive Keratoplasty (CK)
CK uses a hand-held radio wave device to shrink tissue on the cornea to reshape it. The procedure is typically used to treat mild farsightedness and presbyopia, particularly for patients who have already undergone LASIK.
Any surgical procedure has risks and may have some side effects or complications that you should research before you decide to go ahead with the surgery. Nevertheless, as technology advances these complications are being significantly reduced making refractive surgery a great option for vision correction in many patients.
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Corneal Inlays and Onlays
Corneal inlays and onlays are corneal implants that are used to correct presbyopia, a common condition for individuals over age 40 in which the eyes have difficulty focusing on near objects. Presbyopia occurs as the lens of the eye begins to age and weaken, reducing the ability to focus on close objects without the assistance of reading glasses or another visual aid.
Corneal implants, such as inlays and onlays, offer a treatment solution to correct presbyopia as an alternative to using reading glasses or multifocals to obtain clear vision at a close range. Corneal inlays and onlays are like tiny contact lenses that are inserted into the cornea which reshape it to improve the refractive power and thereby improve near vision. Unlike corrective laser surgery such as PRK or LASIK the actual corneal tissue isn’t touched, but rather the shape of the cornea is changed by the transplanted lens.
Corneal inlays are placed in the stroma, the middle layer of the cornea (thus the name “in-lays”), while onlays are implanted closer to the surface of the cornea, under the epithelium, which is the thin outer layer of the cornea. The procedures for both inlays and outlays are relatively simple and quick, with minimal recovery.
Corneal Inlay and Onlay procedures are still in the early stages of development and with a number of clinical trials in progress, the technology should only improve in coming years.
Photorefractive Keratectomy or PRK is a type of refractive laser eye surgery used to correct a patient’s vision to eliminate or reduce their dependence on glasses or contact lenses. PRK is the style of laser eye surgery that preceded LASIK, having been the former most common type of refractive surgery until LASIK came along.
PRK is effective in correcting nearsightedness (myopia), farsightedness (hyperopia) and astigmatism and has very similar rates of success and outcomes as LASIK. PRK remains a common option for laser eye surgery.
How Does PRK Differ From LASIK
PRK and LASIK both permanently reshape the cornea to improve vision by using a laser (an excimer laser to be exact) to remove part of the tissue underneath the corneal epithelium. The epithelium first needs to be removed in order to get access to the tissue and how this is done is what differentiates the two procedures. While LASIK creates and lifts a flap on the outer corneal layer, reshapes the corneal tissue underneath and then replaces the flap, PRK removes the outer layer of the cornea completely. The outer layer will regenerate usually within a few days.
Advantages of PRK
Since PRK completely removes the outer corneal layer, there is a greater area of the cornea to work with. This is ideal for patients with a thin cornea who would otherwise be at risk with LASIK. It is also usually recommended for patients with chronic dry eyes. With PRK, there is also less risk of infection or issues having to do with the flap and the related healing process. This is an advantage for individuals who lead a lifestyle in which they are at risk for eye injuries (athletes, military, law enforcement etc.) which may subject the flap to injury or complications.
So, Why Is LASIK More Popular?
The main advantages that LASIK has over PRK are two-fold and mainly have to do with comfort and recovery time. First of all, PRK patients usually experience slightly more discomfort during the first couple of days of recovery, mainly because it takes time for the outer corneal layer to heal. They will be prescribed eye drops to be taken for several months to prevent infection, increase comfort and assist the healing process. LASIK patients on the other hand, typically experience less discomfort and if they do, it subsides very quickly.
Additionally, vision recovery takes longer with PRK. While LASIK patients can typically see normally within a few hours after the surgery, with vision gradually continuing to improve within the next few months, PRK patients may experience blurred vision for up to three days and it can take up to six months until they achieve full visual clarity. While patients who undergo LASIK can usually drive and resume normal functioning within a day or two, PRK patients shouldn’t plan on returning to normal for at least several days until the outer layer of the cornea has grown back.
Whether PRK or LASIK is a better option for you depends on a number of factors, including the health and structure of your eye. This is a decision that your eye doctor or surgeon will help you make. Rest assured however, that both procedures have been shown to be incredibly successful in correcting vision, with minimal complications.
What You Need to Know About PRK
Prior to any laser correction surgery, you will meet with a surgeon for a thorough exam to assess your eye health and determine whether you are a candidate and if so, which type of surgery would be best suited to your needs. During this exam it is essential to tell the doctor any relevant medical history (injuries, hospitalizations, diseases etc.) and existing conditions you have. The surgeon will determine if you are currently eligible for surgery and if not, if you will be at a future point, and whether you require any specialized care pre or post surgery.
The surgery itself is an ambulatory procedure. It takes about 15 minutes or less for both eyes and you go home the same day. You will need someone to drive you home from the procedure.
The first step in the procedure is that your eye will be anesthetized using numbing eye drops and then a device will be inserted to prop your eyelids open so you won’t blink. Once the eye is numb, the surgeon will remove the outer epithelial layer of the cornea to expose the underlying tissue. Then the surgeon will use the laser to reshape the corneal tissue. You may feel a small amount of pressure during this step. Lastly, the surgeon will apply medicated eye drops and place a temporary contact lens that is used as a bandage to protect the eye.
Following the surgery you will be instructed to apply medicated eye drops multiple times each day to reduce the risk of infection and you may also be given prescription pain relievers to alleviate any pain or discomfort.
As with any type of surgery, it is critical to carefully follow your surgeon’s instructions after PRK. Make sure that you take your medication as prescribed, get enough rest, and call your eye doctor immediately if you experience any problems.
It is normal for it to take several days or even weeks for your vision to improve and up to 3-6 months for full recovery to clear and stable visual acuity. Usually, your doctor will require you to refrain from driving for a week and up to three weeks depending on how fast your vision recovers.
Risks and Complications of PRK
While serious complications are rare, like any surgery, there are some risks to PRK, and these happen to be very similar to any laser corrective surgery like LASIK. They include:
- Dry eyes- this condition usually goes away within a couple of months, but there is a chance that it could become chronic.
- Infection or Inflammation- the risk of infection is greatly reduced if you take proper care to follow your doctor’s instructions following the procedure.
- Vision Problems- which can include glare, seeing halos around lights poor night vision and sometimes a general haziness.
- Incomplete Vision Correction – sometimes an additional procedure might be needed to achieve optimal visual acuity.
In general, PRK is considered to be a relatively safe and effective treatment for vision correction. If you wish to live a life without depending on your glasses or contact lenses, speak to your eye doctor about whether PRK is an option for you.
The cornea refers to the clear, front surface of your eye. When a corneal transplant is done, officially termed keratoplasty (KP), the central part of the cornea is surgically removed and replaced with a “button” of clear and healthy corneal tissue donated from an eye bank.
According to the National Eye Institute, approximately 40,000 corneal transplants are performed annually in the United States. The overall success rate for keratoplasty is relatively high, yet up to 20% of patients may reject their donor corneas. Aggressive medical treatment with steroids is generally given in response to signs of rejection, and it is often effective at subduing the negative reaction and saving the cornea. At five to ten years after KP surgery, studies report an encouraging success rate of 95% to 99%.
Why are corneal transplants done?
Corneal transplants are typically done when the cornea becomes damaged or scarred in a way that uncorrectable vision problems occur. These types of vision conditions are not resolved by eyeglasses, contact lenses or refractive laser surgery (such as LASIK). Disease or injury is the usual culprit for the vision loss.
Keratoconus is a common reason for needing a corneal transplant. In this degenerative condition, the cornea thins and bulges forward in an irregular cone shape. Rigid gas permeable (GP) contact lenses can treat mild cases by flattening the cornea, yet contacts are not effective when it comes to advanced stages of keratoconus. The National Keratoconus Foundation reports that 20% to 25% of people with keratoconus will require corneal transplant surgery to restore vision. Other corneal degenerative conditions will also result in a need for keratoplasty.
Corneal ectasia is a thinning and bulging of the cornea that sometimes occurs after LASIK or other refractive vision correction procedures. In the event that this happens, a corneal transplant may be needed to restore vision.
Corneal scarring, due to chemical burns, infections and other causes, is an additional reason that a corneal transplant may be indicated. Traumatic injuries to the eye are also commonly responsible.
Corneal Transplant Procedure
Keratoplasty is generally done on an outpatient basis, with no need for overnight hospitalization. Depending upon age, health condition and patient preference, local or general anesthesia is used.
Using a laser or a trephine, this is an instrument similar to a cookie cutter, the surgeon cuts and removes a round section of damaged corneal tissue and then replaces it with the clear donor tissue.
Extremely fine sutures are used to attach the donor button to the remaining cornea. The sutures remain in place for months (sometimes years) until the eye has recuperated, healed fully and is stable.
Recovery from a Corneal Transplant
The total healing time from keratoplasty may last up to a year or longer. At first, vision will be blurred and the site of the corneal transplant may be inflamed. In comparison to the rest of the cornea, the transplanted portion may be slightly thicker. For a few months, eye drops are applied to promote healing and encourage the body to accept the new corneal graft.
A shield or eyeglasses must be worn constantly after surgery in order to protect the healing eye from any bumps. As vision improves, patients may gradually return to normal daily activities.
What happens to vision post-keratoplasty?
Some patients report noticeable improvement as soon as the day after surgery. Yet a great deal of astigmatism is common after a corneal transplant. A patient’s prescription for vision correction tends to fluctuate for a few months after the surgery, and significant vision changes may continue for up to a year.
Hard, gas permeable contact lenses generally provide the sharpest vision after a corneal transplant. This is due to a residual irregularity of the corneal surface. Even with rigid contact lenses, eyeglasses with polycarbonate lenses must be worn in order to provide adequate protection for the eye.
Once the sutures are removed and healing is complete, a laser procedure such as LASIK may be possible and advised. Refractive laser surgery can reduce astigmatism and upgrade quality of vision, sometimes to the point that no eyeglasses or contact lenses are needed.