The eye works like a camera; it has lenses, an aperture, and a film. The cornea and crystalline form the lens. Between these is the iris, the center of which is where the pupil is located, that acts as a diaphragm. The cornea and lens fix the image in sharp focus on the retina, which is the delicate section of the eye and acts as a “film” that coats the back of the eyeball.
If the light rays focus on the retina correctly, then it produces an optimal vision that is sharp and clear. If instead, the light rays focus on the front of the retina, rather than on it, myopia is developed. It is a refractive defect that manifests itself with a blurred vision of distant objects. Myopia is measured in diopters (unit of measurement indicating the distance of objects before they become blurred) and is classified into three stages:
- slight, from 0 to 3 diopters,
- moderate, from 3 to 6 diopters,
- high, greater than 6 diopters.
What Causes Myopia
Myopia is a refractive defect that causes a blurred vision of far away objects. If the cornea has an overly-pronounced curvature for the length of the eye, the light rays come into focus at the front of the retina and not on it. This can occur because of genetic, environmental factors, and under particular circumstances such as pregnancy. Traditionally, myopia is corrected with glasses or contact lenses. It is possible that the patient undergoes a safe and effective refractive surgery that can correct this visual defect, thus eliminating or reducing the need for glasses or contact lenses.
How Is Myopia Treated
Traditionally myopia is corrected by the continuous use of glasses or contact lenses.
- Refractive Surgery
This is the safe and effective intervention that can correct myopia and eliminate or reduce the need for glasses or contact lenses. Today, thanks to laser technology, mini-invasive interventions are now available to change the curvature of the cornea, decrease its refractive power and correct myopia. The PRK Technique, by using the Excimer Laser Technology, acts on the corneal surface, remodeling its curvature based on the stage of myopia. On the LASIK Technique, currently the most widely used procedure in the world, the excimer laser acts within the cornea instead. On an ultra-fast femtosecond laser, it is used to create a thin flap in the cornea. Then, an excimer laser is used to reshape the underlying corneal tissue to correct the vision. The flap is then returned to its original position.
- Intraocular Lenses
In cases where corneal surgery with the laser is not feasible, an alternative intervention is done. An insertion of a phakic intraocular lens is done without the extraction of the crystalline lens. These lenses are designed and manufactured specifically for each patient. Preparatory exams are done to obtain precise measurements, from the size of the eye, its interior space, visual defect and number of its endothelial cells that protect the cornea. The phakic lens can be placed in the anterior chamber, at the front of the pupil, posterior chamber, or behind the pupil. The implant procedure is done under topical anesthesia through a small incision that requires no sutures. Normally, the operation is done on an eye at a time and the second operation is scheduled on the next day or a few days apart. Typically, this type of intervention is characterized by high-quality optical results, even for high defect correction.