Our vision depends on many different parts of the eye working together to focus light on the retina. When these parts stop working due to aging, injury or genetic conditions, Eyeglasses and contact lenses help correct these problems, but if refractive eye issues are significant, your eye doctor may recommend refractive eye surgery. Isa Sayyeed Karim Mohammed, M.D., an ophthalmologist with The Wilmer Eye Institute, Johns Hopkins Medicine, explains common types of refractive eye .

What is refractive eye surgery?

Most procedures focus on the cornea, the clear outer layer of the eye where light enters. Other procedures address issues with the lens, an inner layer of the eye behind the iris where light is focused before it reaches the retina. Your eye doctor will recommend refractive eye surgery based on many factors, including:

• The type of refractive eye error
• A desire to reduce the need for glasses or contacts
• Whether eyes are disease-free
• The potential risks and effects of eye surgery
• Age and overall health

Laser Refractive Eye Surgery Procedures

For many people with refractive eye issues, lasers allow for minimally invasive surgical corrections to the cornea. LASIK (laser-assisted in situ keratomileusis), topography-guided LASIK, photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) are laser-based refractive eye surgery procedures.

LASIK Eye Surgery

LASIK is one of the most common refractive eye procedures. It works by using lasers and other instruments to correct the shape of the cornea. LASIK treats nearsightedness, farsightedness and blurriness, and is best for healthy people over the age of 18 (preferably 21 or older) who have no significant eye problems aside from refractive eye issues and have stable vision (meaning they have not experienced any major changes to their vision in the past year).

During a LASIK procedure, the eyes are numbed with drops and held in place by both an eyelid holder and a suction ring. Once these are applied, your vision will go black. Using either a laser or a device called a microkeratome, the surgeon will make a thin flap in the cornea, which will be lifted and folded back. You will be directed to stare at a target light to further ensure that your eyes do not move. The surgeon will then reshape the cornea using a laser. After reshaping is finished, the surgeon folds the flap back down into position and smooths it out — the flap will attach on its own within three minutes and heal where it is placed.

Topography-Guided LASIK

Topography-guided LASIK is best for people with nearsightedness and blurry vision. This type of LASIK is more customized because it allows for treatment of preexisting issues on the surface of the cornea, as opposed to LASIK that just changes the shape of the cornea. Topography-guided LASIK is similar to standard LASIK, but before the procedure, the corneas are scanned in detail to create a surface map of problem sections, and these surface issues are corrected during the . As with standard LASIK, after the reshaping of the cornea, the flap is laid back into position and will reattach within three minutes to begin the healing process. 

PRK

PRK is another variation of LASIK. PRK is often recommended for people with thin corneas and dry eye. Like LASIK and topography-guided LASIK, it involves using a laser to correct corneas, but in PRK, no flap is made in the cornea surface to help with the correction. Instead, lasers either increase or decrease the curvature of the cornea as needed. After the surgery, a transparent bandage contact lens is applied to help with healing.

SMILE

SMILE is typically recommended for people with nearsightedness or astigmatism that falls within a specific range of severity. In SMILE, a minimally invasive laser is used to create a lenticule and to make a small incision into the eye to remove the lenticule. A lenticule is a disc-shaped piece of tissue carved out of the cornea. Prior to surgery, the surgeon will measure the corneas to calibrate the laser. During surgery, the patient’s eyes are numbed, and a laser is used to create the lenticule and the incision necessary to remove it from each eye. No stitches are required, and the eye should heal in one to two days. The procedure itself is very quick, taking only a couple of minutes for each eye.

Other Types of Refractive Eye Surgery

Not all refractive eye surgery targets the cornea for correction. Many refractive eye issues are caused by problems with the lens, and for people with major refractive eye complications, it may make sense to treat the lens directly with an implant or replace it with an artificial lens.

Implantable Collamer Lens (ICL)

ICL is one type of surgery that may be offered to people who have nearsightedness but are not suited for LASIK. In this procedure, no lasers are used. Instead, a small Collamer lens made from plastic and collagen (a structural protein) is implanted behind the eye. The combined material of this lens allows water and nutrients to pass through it, which makes it easier to integrate into the eye. During ICL surgery, the eyes are dilated and numbed with drops. Next, a small cut is made in the cornea, and an implantable lens is inserted behind the iris and in front of the lens. Because the cut to insert the Collamer lens is so small, stitches are usually not needed.

Refractive Lens Exchange

For people with major refractive eye issues or age-related farsightedness, a doctor may recommend replacing the existing lens altogether with a custom-fitted intraocular lens. This implant is permanent, unlike ICL, which is reversible. The procedure starts with drops to numb the eyes, and may also involve some mild, calming anesthesia. Patients are awake, with blurred vision, and the doctor uses a laser or blade to make a small cut where the sclera (the white outer coating of the eye) and cornea meet. A tool is used to remove the lens by breaking it into small pieces, then ultrasound waves are used to further break up these pieces before they are vacuumed out. The new intraocular lens is then inserted and positioned within the membrane that holds the lens. This incision is very small, so stitches are not required. Finally, a shield is taped over the eye to protect it while healing.