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 Wilmer Eye Institute, Johns Hopkins Medicine, explains common types of refractive eye procedures.

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), photorefractive keratectomy (PRK) and keratorefractive lenticule extraction (KLEx) are laser-based refractive eye surgery procedures.

LASIK

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 astigmatism, 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 eyelids are kept open. The eye is numbed with drops and gently stabilized with a suction ring. Once this is applied, your vision may dim, which is normal. Using the laser, 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, and the laser will track your eye, compensating for any small eye movements. 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.

PRK

PRK is a variation of LASIK. It is often recommended for people with thin corneas and dry eye. Like 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, the outer layer of the cornea is gently removed and the underlying tissue is reshaped by the laser. The outer layer naturally regrows in approximately three to five days. After the surgery, a transparent bandage contact lens is applied to help with healing.

KLEx

KLEx is typically recommended for people with nearsightedness or astigmatism that falls within a specific range of severity. During a KLEx procedure, a minimally invasive laser is used to create a lenticule and to make a very small incision in the cornea 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. 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 large refractive errors, 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 lens made from plastic and collagen (a structural protein) is implanted behind the iris, the colored part of 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, calming anesthesia is provided and 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 natural lens. Because the cut to insert the Collamer lens is so small, stitches are usually not needed.

Refractive Lens Exchange (RLE)

For people with significant refractive eye issues or age-related presbyopia (inability to read small print up close), 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 but comfortable, and a small cut is made 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.