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What’s the difference between LASIK and PRK?

If you are tired of your glasses and contact lenses and just want to be able to wake up and see, you are likely aware of the very popular LASIK procedure, but what about its “cousin” procedure, PRK?

One of the more common questions that patients have for the laser vision correction specialist doctors at 20/20 Institute is about the differences between LASIK and PRK.  Our doctors routinely perform both procedures with excellent results and understand that what each patient really wants to know is which procedure would be the best for them.

So, we will use this blog post to discuss the two procedures so that when you visit 20/20 Institute for your complimentary consultation, you’ll have a great background of understanding to help the discussion with our doctors about what is best for you!

Why Would a Doctor Recommend PRK Instead of LASIK?

Most patients looking into laser vision correction know someone that has had LASIK. However, finding a friend or family member that has had PRK is usually not so easy.

When patients go to their LASIK consultation, they are hoping to find out if they are or are not a candidate for LASIK. Sometimes the doctor throws a curveball in the consultation process by telling the patient that he or she is best suited for PRK instead of LASIK.

Different anatomical attributes of a patient’s corneas may make them better suited for PRK over LASIK. Things like corneal thickness (or thinness), corneal curvature, and corneal scarring all may play a role in the recommendation of PRK over LASIK.

What is a patient to do next if the doctor recommends PRK? For all patients, it’s always best to be an informed patient. So, this blog post will hopefully provide you with the information that you need to make an informed decision about your laser vision correction procedure.

How Are LASIK and PRK Similar?

Most eye care professionals agree that LASIK and PRK are both considered safe and effective laser vision correction procedures provided, of course, that the patient is a good candidate.

Both procedures use an excimer laser to correct vision, and because they have a similar method of achieving improved vision without glasses or contacts, the final visual result for patients tends to be very similar.

In the majority of cases, the excimer laser technology that your surgeon chooses to use for your procedure has the greatest impact on your probability of achieving 20/20 vision and the quality of that visual result than whether the correction is done with the PRK procedure versus the LASIK procedure.

LASIK and PRK tend to have similar visual outcomes because they both treat a patient’s blurry vision by reshaping the cornea using the cool energy of an excimer laser.  The cornea is the structure in front of the iris that is responsible for most of the focusing ability of the eye (it’s the part of the eye where a contact lens is placed).

For the purposes of this article, we will simplify things a bit to say that a person wears glasses or contact lenses due to a mismatch between the length of the eye and the shape of the lenses of the eye, primarily the cornea.

If the cornea is the wrong shape for the patient’s visual system, the patient has blurry vision.  The excimer laser essentially vaporizes microscopic amounts of tissue in a precise, customized pattern to sculpt the cornea and change its shape to improve the patient’s vision.

A basic understanding of the makeup of the cornea will be helpful to understand more about how LASIK and PRK work.  First, the cornea has five layers.  The main layer, called the stroma, is the middle layer of the cornea, comprises 90 percent of the cornea’s thickness, and is made of collagen tissue fibers arranged in a way that makes the cornea translucent and a high refractive index – both important characteristics of a focusing lens.  The outermost layer of the cornea is a layer of translucent epithelium tissue (skin) to protect the cornea from the environment.

Just like the skin tissue on other parts of the body, the epithelial layer of the cornea grows back if it is damaged or removed; however, the collagen tissue that makes up the stroma does not.

In both the LASIK and PRK procedures, the excimer laser sculpts the stroma layer of the cornea, resulting in a permanent change to the shape of the cornea.  When the shape of the cornea is changed properly, the light that enters the patient’s eye is focused more properly for improved vision and without glasses or contact lenses.

How Do LASIK and PRK Differ?

While LASIK and PRK tend to have comparable final visual outcomes, they are performed differently, which gives each procedure its own set of advantages and disadvantages in comparison to the other.

In certain cases, a patient may be only a candidate for LASIK or only a candidate for PRK.  In other situations, the patient can be a candidate for both procedures and may choose which procedure they would prefer.

The difference between the procedures is the way that the laser vision correction surgeon accesses the cornea to reshape it with the excimer laser.  The epithelium (skin) tissue that covers the cornea must be removed or temporarily moved out of the way before the excimer laser’s energy is applied to the cornea so that the excimer laser sculpts the layer of the cornea that does not grow back.  The method that removes this skin tissue in the first step is called PRK, and the method that temporarily moves it out of the way is called LASIK.

LASIK Procedure Explained

In the LASIK procedure, the surgeon fashions what is known as a LASIK “flap” or “cap” using a specialized surgical instrument to temporarily move the epithelial layer out of the way.  The LASIK flap contains the epithelial layer and a thin portion of the stromal layer, and the flap remains attached to the rest of the cornea.

The surgeon lifts this flap and folds it out of the way to expose the lower layer of the cornea to be sculpted with the excimer laser.  After the reshaping is complete, the surgeon repositions the flap in its original position and the healing process begins.

Modern LASIK uses a femtosecond laser to separate tissue for the flap creation while early methods of LASIK used a mechanical device that contained a blade to cut the cornea to create the flap.

The bladeless (laser) method eliminates all of the possible side-effects and complications that are associated with creating the flap with a bladed surgical instrument. All LASIK procedures performed at 20/20 Institute are performed the modern way (with a laser) to create the flap.

During the flap creation step of the LASIK procedure, the patient experiences pressure on the eye (numbed with anesthetizing eye drops) and dim or dull vision for about 45 seconds.  This is usually the most uncomfortable part of the five-minute-per-eye LASIK procedure.

When the procedure is complete, the patient can see, although, most patients say it looks as though they have their eyes open underwater – it is a rather foggy view of the world, but often dramatically better than the blurry world the patient had without glasses before.

Visual recovery is, generally, very rapid, and most patients experience little to no discomfort during the initial healing time.  Most patients have 20/20 or better vision without glasses or contacts by the morning after their procedure.

Usually, the worst part of post-op LASIK recovery is approximately three hours of intense irritation or burning – like it feels if you have your eyes open in a chlorine pool too long.  Most patients fall asleep shortly after departing our office or arriving home, thanks to a little sedative pill given prior to the procedure. Most patients sleep right through any irritation and wake up feeling pretty comfortable.

For most patients, irritations that feel similar to having an eyelash in the eye are the only sensations felt after sleep. Artificial tears are all that is needed to make those sensations go away, and they are typically resolved on their own within three or four days after LASIK.

PRK Procedure Explained

With the PRK procedure, no flap is created.  Instead, the surgeon gently removes the epithelial tissue layer of the cornea and then applies the excimer laser to the exposed cornea for the reshaping step.  When reshaping with the excimer laser is complete, a contact lens “bandage” (a contact lens with essentially no prescription power) is placed over the cornea to allow the skin to grow back underneath.

During the PRK procedure, the removal of the epithelial layer is rather quick, taking less than 30 seconds typically.  Surgeons vary in technique on removal, but regardless of the technique used, the patient may experience a small amount of pressure on the eye and dim vision when the surgeon gets in the way of their vision.

The reshaping step is next and usually takes less than 30 seconds as well.  When the reshaping is complete, the patient receives the contact lens bandage and a few eye drops.  After the procedure is completed, the patient can see fairly well, often dramatically better than before the procedure without glasses.  That vision is short-lived, however, as vision tends to get worse before it improves following the PRK procedure.

Healing and visual recovery after PRK takes longer than LASIK because the epithelial tissue has to heal and become as regular and smooth as it was before removal.  Full visual recovery typically takes about thirty days and has three general stages: initial healing, bandage contact lens removal, and full healing.

The patient wears the contact lens bandage for approximately four to five days as the epithelial tissue undergoes the initial healing phase and seals the surface from where it was removed.

During this time, the patient’s vision is often fairly blurry and relatively high amounts of discomfort and light sensitivity are common.  20/20 Institute doctors will prescribe a few medicines that significantly help with discomfort, which usually lasts about three or four days, improving slightly day after day.  Most patients are not comfortable driving a car during this time, so planning for work and life is an important part of PRK recovery.

When the epithelial tissue has healed, the doctor removes the contact lens at a follow-up appointment about four or five days after the procedure.  When the contact lens is removed, the patient is typical through the worst part of the recovery period.

Each patient is different, but vision typically improves noticeably with the removal of the contact lens, and the patient’s vision tends to be rather functional at this stage.

In the last phase of recovery, the patient experiences gradual vision improvement day after day.  Patients continue to use a medicated drop during this time. A few more follow up visits with our doctors are also required to monitor the healing process.

At follow-up visits, the doctor will adjust the dosage of the medicated drop to control the healing of the epithelial tissue and to help ensure that it heals properly.  Since the epithelial tissue of the cornea regenerates itself naturally every thirty days, it is typically around the 30-day mark after PRK that the patient has achieved the majority of their final visual result.

Pros and Cons

As you have likely gathered so far, the advantages of LASIK over PRK include a significantly faster visual recovery and, comparatively, little or no discomfort during the healing phase.

These advantages are directly tied to the LASIK flap that allows the epithelium to be temporarily moved out of the way and replaced, so the patient essentially uses their own tissue as a natural bandage over the treated area.

Most patients have busy lives and appreciate getting back to life much sooner, so LASIK tends to be the more popular procedure of the two.

While LASIK’s advantages are the result of the LASIK flap, PRK’s advantages are actually the result of not having a flap.  In spite of the longer, more challenging visual recovery after PRK, for certain patients, PRK is the patient’s preference, and in other cases, PRK is the better procedure from a medical perspective to treat their vision.

While complications with the LASIK flap are very rare, especially when using modern bladeless technology, they are eliminated completely with PRK, so some patients choose to have PRK.

For patients such as MMA fighters who accept a high risk of direct trauma to their eyes due to their profession, PRK is recommended.

Also, because the PRK procedure does not involve a flap, PRK patients tend to have less dry eye after their procedure than LASIK patients.  Most commonly though, patients have PRK instead of LASIK because the PRK procedure requires less corneal tissue thickness compared to LASIK, which is of significant consideration for patients with naturally thinner corneas, higher amounts of nearsightedness, or both.

Which Procedure Is Best for You?

The first and most important step of exploring the possibility of getting rid of your glasses and contacts is to visit one of our two Denver-area locations for a free consultation. Our LASIK specialist doctors will evaluate your eyes to see if you are a good candidate for one or both procedures.

You may be a candidate for only one or the other, and if that is the case, our doctors will make sure to carefully explain their recommendation.  Most people who are candidates for vision correction are usually able to choose which procedure they would prefer. Most people’s choice, including most laser vision correction surgeons, is LASIK.

So, now, with this overview of LASIK and PRK fresh in your mind, give us a call at 303-202-0669 or contact us online. We will help find a convenient time for you to come to visit our office at no cost.

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