Refractive Surgery

Refractive surgical procedures include any and all procedures that reduce refractive error, i.e., reduction of myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. All of these procedures are designed to minimize dependence on eyeglasses and contact lenses, and represent exciting and extraordinary advances in the field of ophthalmology.

The best procedure for any given individual depends on many factors, including age, type of refractive error (nearsightedness, etc.), degree of refractive error, and concern for reversibility. Certain refractive procedures have been studied and utilized extensively (e.g., LASIK and radial keratotomy) while others discussed below are still being evaluated in FDA regulated trials (e.g., phakic IOLs).

The term, “refractive surgery” refers to several procedures, including LASIK, PRK, LASEK, Intacs, LTK, CK, AK, RK, and several emerging techniques. You may have heard the term, “laser vision correction”, which is often used in advertising because it doesn’t sound as threatening as “refractive surgery”. “Laser vision correction” refers to LASIK, Photorefractive Keratectomy (PRK), LASEK, Conductive Keratoplasty (CK), Astigmatic Keratotomy (AK), Radial Keratotomy (RK) and Laser Thermal Keratectomy (LTK). Today, LASIK is the most widely performed of all refractive surgery procedures. For many patients – but certainly not all – LASIK is the procedure of choice.

Refractive surgery is not a single event but a process that begins with a careful preoperative evaluation and ends with regular postoperative care. In fact, the pre- and postoperative exams are more important than the surgery for maximizing the likelihood of a success.

Laser epithelial keratomileusis (LASEK) is a modified form of photorefractive keratectomy (PRK), pioneered by Italian surgeon, Massimo Camellin, M.D. First described in ophthalmic literature in 1999, this procedure requires the surgeon to loosen the outer layer of the cornea, called the epithelium. Unlike in PRK, the epithelium is not removed in LASEK. The surgeon instead folds back the loosened epithelium so that the laser can reshape the exposed cornea. After laser application, the surgeon replaces the "flap" of epithelium over the corneal bed and placed a bandage soft contact lens on top. Visual recovery after LASEK is generally faster than in PRK but slower than in LASIK

LTK procedure was for the temporary reduction of hyperopia from +0.75 to +2.50 diopters for patients 40 years and older with up to 0.75 diopters of astigmatism and refractive stability for the previous 6 months. Unlike most refractive surgery, LTK is not performed in an operating suite but in an ordinary exam room. It involves the strategic placement of 16 laser spots onto the peripheral cornea. In LTK, the eye is numbed with anesthetic drops and held open with an eyelid holder. The tear film is allowed to dry for 3 minutes before the laser is applied. The laser application itself takes less than 3 seconds per eye. The treatment thermally contracts the tissue, causing a increase steepness in the central cornea. A bandage soft contact lens is usually placed on the eye until the following day. The eye may have some irritation for the first few days.

Conductive keratoplasty (CK) was developed by Refractec, this procedure is indicated for the temporary reduction of farsightedness (between +0.75 to +3.25 diopters) in those 40 years of age or older. Similar to LTK, CK increases steepness of the central cornea by thermal contraction of the peripheral cornea. Unlike LTK, heat is applied through a radio frequency probe instead of a laser. The procedure is performed in approximately 3 minutes per eye. Studies suggest that CK experiences less regression in refractive effect than LTK, perhaps owing to a deeper and more uniform distribution of heat.

Astigmatic Keratotomy (AK) is useful for correcting astigmatism. AK is a simple procedure where the surgeon places incisions in the cornea to change its curvature in a controlled manner. Performed by an expert surgeon, AK is effective and can achieve predictability that rivals correction with the excimer laser. It is often a useful enhancement procedure following previous LASIK or PRK. While the incisions usually go 90% of the total corneal thickness in depth, a perforation can occur if the blade cuts too deeply. In this instance, fluid inside the eye leaks outward. The surgeon may need to apply temporary stitches over the perforation to stop the leak.

AK probably reduces the strength of the globe so that any direct trauma, like a fist or air bag to the eye, may cause the globe to rupture more easily. Nevertheless, any trauma enough to cause an eye with AK to rupture is likely to even severely damage a normal eye.

Like AK, radial keratotomy (RK) involves placing incisions in the cornea. However, unlike with AK, the incisions form a pattern on the eye like the spokes of a bicycle wheel. Usually, 4 to 16 incisions are made. Although popular as recently as five years ago, this procedure has fallen out of favor with more predictable techniques like LASIK. Specific concerns with radial keratotomy include a long-term shift toward farsightedness, vision that fluctuates during the day, vision that changes with altitude, night glare and halos, and reduced globe integrity. Like with AK, there is a risk of corneal perforation during the procedure. With procedures like LASIK, PRK and Intacs, RK rarely has any role today.