What are refractive errors?

In a normal eye, light is focused onto the retina, a light-sensitive tissue lining the back of the eye, for clear vision. Refractive errors exist when the curvature of the eye is mismatched to the length of the eye and light rays cannot focus properly on the retina. Myopia (near sightedness) is the most common refractive error, and occurs when the eye is too long or the cornea is too steep. Near vision is possible but distant objects appear blurred. Patients with hyperopia are farsighted; they can focus on more distant objects, but close-up objects appear blurry. This occurs when the eye is shorter than normal or the cornea is too flat. In astigmatism the curve of the cornea, and sometimes the lens, is uneven – steeper in one direction than the other – like a football or the back of a spoon. Presbyopia is the age-related loss of close-up focusing ability.

Who can get refractive errors?

Refractive errors can occur as part of the development of the eye in children, when they are usually of a mild to moderate degree, or they can be inherited from the parents, when they are moderate to severe in degree. In adult life, refractive errors can become manifest as the muscles in the eye weaken – this is usually seen with hyperopia. Refractive errors can also occur at any age due to pathological changes in the structures of the eye.

How can they be treated?

Light rays can be made to focus properly on the retina by using glasses, contact lenses, or by a variety of surgical methods – the most common and popular is the excimer laser. Other surgical procedures require the use of heat to shrink the cornea selectively (conductive keratoplasty), or implant material in the cornea to change its shape (intrastromal corneal ring segments), or the implantation of a lens inside the eye (phakic intraocular lens) or replacement of the natural lens with an intraocular lens (clear lens extraction).

Am I a good candidate for vision correction surgery?

To be a good candidate for vision correction surgery, you must be at least 18 years of age and have healthy eyes, a stable glass prescription, and an error within the correctable range of the procedure. You may not be suitable if you have a history of autoimmune diseases, are pregnant or nursing, have eye diseases or previous eye injury, or take medications that may affect corneal healing or vision. You should fully understand the procedure and be aware of the risks and possible side effects. However, a consultation with a refractive surgeon is necessary to determine whether you are truly a candidate.

Which treatment is best for me?

Most patients can be helped with glasses. In some patients with irregular corneas, a contact lens may provide better quality of vision. Contact lenses are also helpful in very high refractive errors and when improved cosmesis is desired. Excimer surgery can be performed in a variety of ways – photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and laser epithelial keratomileusis (LASEK). The efficacy of surgery may be enhanced in some instances by the use of adjuncts like mitomycin C. Other procedures include other types of corneal and lens surgeries. It is best to have a detailed discussion with your doctor about the procedure most suited for you.

How does the doctor decide if I can have vision correction surgery?

Your doctor will first perform a thorough eye examination to determine your refractive error, the status of tear function, lids, cornea, lens, eye pressure and retina, and your pupil size. He will then proceed to do special investigations that help determine corneal shape, thickness and endothelial cell count to determine if corneal surgery is possible. If these are normal, he will discuss with you your motivation and understanding of procedural benefits and risks, your health status, and the options available, to help you decide.

General information

Refractive procedures have helped millions of people become less dependent on eyeglasses or contacts. A large part of the success of any procedure depends on your understanding of the procedure and your expectations. With the help of your ophthalmologist, it’s ultimately your responsibility to weigh the risks and side effects with the benefits. If you are considering refractive surgery, consult with your ophthalmologist, read all the provided literature, and make an informed decision.