Anisometropia is a significant difference between the refractive errors of the two eyes, which is usually more than thee diopters.
In the event of anisometropia, wearing corrective eyeglasses or contact lenses often leads to the so-called aniseikonia, which is an ocular condition where there is a significant difference in the perceived size of images. In this case, the most optimal method for correcting anisometropia is a refractive surgery.
The two most common refractive surgery procedures are femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) and Small Incision Lenticule Extraction (SMILE).
In Femto-LASIK, a surgeon separates a small flap of tissue from the cornea, using a femtosecond laser. The new profile of the cornea is created with a high-precision excimer laser so that light rays will be focused exactly on the retina. After changing the cornea surface, a flap of corneal tissue, which was separated in the first stage, is turned back. The flap is replaced without suturing. Because surface epithelium is not disrupted centrally, vision returns rapidly. Most people notice a significant improvement the next day.
SMILE laser eye surgery is performed using a VisuMax femtosecond laser, which is proprietary technology of Carl Zeiss Meditec. In the SMILE procedure, the surgeon uses a femtosecond laser to create a small, lens-shaped bit of tissue (lenticule) within the cornea. Then, with the same laser, a small arc-shaped incision is made in the surface of the cornea, and the surgeon extracts the lenticule through this incision and discards it. With the tiny lenticule removed, the shape of the cornea is altered, correcting nearsightedness. The corneal incision heals within a few days without stitches, and sharper vision occurs very quickly.
In some cases, photorefractive keratectomy (PRK) is performed to correct anisometropia. In PRK, the corneal epithelium is removed and then the excimer laser is used to sculpt the anterior curvature of the corneal stromal bed. The epithelium typically takes 3 to 4 days to regenerate. PRK may be more suitable for patients with thin corneas or anterior basement membrane dystrophy.