The most common refractive surgical procedures are as follows:
Radial keratotomy (RK): RK was the first widely-accepted refractive surgery procedure, and was widely used from the mid-1980s to the mid-1990s. With RK surgery, 4 to 16 incisions were made in the cornea with a diamond blade to change the curvature of the cornea. RK required an exceptional amount of surgical deftness and experience, so outcomes varied widely by surgeon. Night-time ‘halos’ and gradual overcorrection were reported by up to 10% of patients, but in general the surgery was a great success. RK is no longer considered a state-of-the-art refractive surgical procedure.
Wavelight photorefractive keratectomy (PRK): PRK was first introduced in the mid-1990’s with the widespread introduction of the excimer laser, a laser first tested in clinical trials by Midwest Eye Care doctors in the early 1990’s. Rather than using blades to change the shape the cornea, surgeons utilized the excimer laser to remove very fine layers of tissue on the outside layers of the cornea. Vision with PRK typically takes a few weeks to stabilize but may offer the most predictable outcomes of any refractive surgery.
Laser-assisted in situ keratomileusis (LASIK): LASIK was first introduced as an off-label use of the excimer laser and, by the time the procedure was officially approved by the FDA in the late 1990’s, millions of Americans were having the procedure each year. LASIK uses the same laser as PRK, but also employs a piece of equipment called a microkeratome to create a small flap on the cornea. The flap is folded back, and then the excimer laser is used to treat the corneal tissue underneath the flap. Once the tissue is removed, the flap is put back into place, and the eye begins the healing process. Vision with LASIK tends to stabilize in a few days, and patients report that there is virtually no pain associated with the recovery.
IntraLase LASIK: Intra-LASIK is a branded name for the LASIK procedure when the IntraLase laser is used to create the flap instead of a microkeratome. Any type of excimer can be used with the IntraLase laser, and our practice uses the Allegretto Optimize Wavelight Laser. With IntraLase, the surgeon creates the flap with the femtosecond laser. IntraLase technology gives the doctor the capability to precisely design the patient’s intracorneal architecture in terms of diameter, depth, edge angle and morphology – creating the optimal stromal bed for the refractive procedure. IntraLase technology delivers many of the essential componets of the ideal Lasik flap and offers enhanced safety.
Conductive keratoplasty (CK): CK is a procedure that uses radio waves to reshape the cornea to correct the vision of patients with small degrees of hyperopia or presbyopia. When effective, CK is a temporary solution for hyperopia and presbyopia. The other refractive surgery procedures discussed here are considered by the FDA to have permanent effects.
Several lens manufacturers offer a toric IOL to correct for astigmatism, which is an irregular shape of the cornea. Approximately 20% of Americans have some level of astigmatism, and the condition will cause blurry vision as it becomes more pronounced. A toric IOL can be used to correct a patient’s astigmatism and provider very good distance vision. When you look at your eyeglass prescription – for example, a prescription of –1.25 x +1.50 x 105 – the middle number represents the amount of astigmatism in your eye. In this example, the patient has 1.5 diopters of astigmatism. Patients do not always have the same amount of astigmatism in both eyes, but they are generally within one diopter. The insertion of a toric IOL is no more difficult than regular cataract surgery.
Symfony multi-focal IOL by Tecnis
As noted above, ‘accommodation’ is the term used to describe the flexing of the lens within the eye to change focus between near and far objects, and only a patient’s natural lens is typically able to accommodate. The Symfony lens, approved by the FDA in March 2016, utilizes an IOL design that incorporates different strengths of vision correction throughout the lens. Because the Symfony lens is not attached to the muscles within the eye, cataract surgery with the Symfony lens is virtually identical to traditional cataract surgery in terms of technical difficulty.
This type of lens, featuring different corrections, is called a multi-focal lens. Tecnis also has developed a Symfony toric lens for patients with natural astigmatism, so after surgery patients will often able to see well in the distance without the aid of eyeglasses.