Healthnotes Newswire (May 24, 2001)—Supplementation with vitamins A and E improves the outcome of laser eye surgery to correct nearsightedness, according to a study published in the current issue of the British Journal of Ophthalmology.1
In this double-blind trial, supplementation with the two vitamins led to faster healing and fewer side effects in people who underwent photoreactive keratectomy (PRK), a laser surgical procedure to correct nearsightedness (also known as myopia). After the procedure, participants took either the vitamin combination or a matching placebo for up to a year. Eye examinations were conducted daily until clear signs of healing occurred, and then follow-ups were done at one week, one month, three months, and six months after the procedure.
I Can See Clearly Now
Healing of the tissues of the cornea (the transparent covering on the front of the eye) was significantly faster among those who took the vitamin combination, compared to those who took placebo. The appearance of a haze on the cornea, a common side effect of PRK, was also significantly reduced among the vitamin takers. Participants who took the vitamins also had better visual acuity (sharpness) after PRK compared to placebo; this effect was most dramatic among those whose myopia was the most severe prior to PRK.
Amounts of vitamins used in the study were 25,000 IU per day of vitamin A (in the form of retinol palmitate) and 230 mg per day of vitamin E (in the form of tocopheryl nicotinate).
The Laser and the Damage Done
Although PRK does far less harm than does a conventional laser, it is not completely without adverse effects. Apart from physically disrupting tissues adjacent to those removed, the procedure can also damage healthy tissue by generating free radicals (highly reactive molecules that contain unpaired electrons). Free radicals damage healthy tissue by creating chain reactions that deprive tissue of oxygen.
Vitamins A and E are antioxidants; their ability to protect against damage by free radicals may partially explain why they reduced adverse effects of the procedure. Vitamin A is also needed for visual function and for the growth and repair of epithelial tissue (cells that form the outer surfaces of the body, including the cornea and conjunctiva of the eye). People who plan to have laser surgery and who wish to supplement with these vitamins should first consult with their ophthalmologist.
PRK, LASIK, and the Excimer Laser
PRK is one of two increasingly popular, FDA-approved laser-surgical alternatives to wearing corrective lenses (the other procedure is called LASIK, which stands for Laser-Assisted In Situ. Keratomileusis) In each procedure, an ophthalmologist (medical doctors specializing in conditions of the eye) corrects the myopia by reshaping the cornea using a computer-controlled laser. A cornea that is too “steep” causes images entering the eye to focus in front of, rather than on, the retina. (The retina is the innermost layer of the eye, which receives images transmitted through the lens and contains the receptors for vision, the rods and cones.)
The lasers used in PRK and LASIK are called excimer lasers, and they work somewhat differently than other lasers. Conventional lasers use high amounts of energy to remove tissue; however, they generate so much heat in the process that they often harm surrounding healthy tissue. In contrast, excimer laser beams do not generate heat, but rather convert tissue directly into gas by breaking chemical bonds.References