Refractive eye defects are caused by the inability of the eye to focus the rays of light coming from the object on the retina and are usually the result of an imperfectly shaped cornea. The problem can affect anybody irrespective of their age. Refractive eye defects are of four different types myopia, hypermetropia, astigmatism and presbyopia.
• Myopia - also known as nearsightedness, the defect is marked by the inability of a person to see the objects lying far off. Distant objects appear blurred as the image of the object is formed in front of the retina instead of forming on it.
• Hypermetropia - also known as Hyperopia or farsightedness, the defect is marked by the inability of the person to see the objects lying nearby. This happens when the cornea is too flat. The image is formed behind the retina instead of forming on it.
• Astigmatism - the defect is marked by the blurring of normal vision and the person experiences difficulty in seeing the objects lying nearby as well as far off.
• Presbyopia - also known as ageing eye, the problem is caused by the inability of the eye to change its focus. It is very common with old age and it cannot be treated completely.
The advent of laser technology in the field of ophthalmology has given rise to a number of procedures that can help to get rid of various types of refractive defects. These include LASIK (laser in-situ keratomileusis), Photorefractive keratectomy (PRK), Radial keratotomy (RK), Astigmatic keratotomy (AK), Automated lamellar keratoplasty (ALK), Laser thermal keratoplasty (LTK), Conductive keratoplasty (CK) and Intraco
eal ring (Intacs).
LASIK - laser assisted in situ keratomileuses is a technique used for patients suffering from myopia, hypermetropia and astigmatism. The procedure aims at reshaping the cornea with the help of a special laser known as an excimer laser. It is carried out by making cutting out a corneal flap with the help of a microkeratome or a femtosecond laser. Stitches are not required in this procedure. Wavefront-guided LASIK is a highly advanced method that helps to determine the extent of distortion on the eye. It is used to examine the eye before the surgery to decide the proper medical protocol to be undertaken. This helps to give higher precision and accuracy, thereby making the procedure safe and more effective.
The patients may experience mild pain after the procedure which can be taken care of with the help of certain painkillers prescribed by your doctor. Possible side effects include dry eyes, mild discomfort, uncorrected vision, Haze, glare, light sensitivity, scarring, infection and blurry vision.
Photorefractive keratectomy (PRK) - the surgery is somewhat similar to
Lasik surgery owing to the fact that it too involves the use of excimer laser for reshaping the cornea to correct vision. It is very effective in case of moderate nearsightedness (myopia). In this technique, a small amount of tissue is removed from the outer surface of the cornea. The procedure involves the use of highly advanced technology to determine and calculate how much tissue needs to be removed. Normal activities can be resumed within a week or two after the surgery. Possible side effects include eye pain that lasts for a long time, corneal Haze and glare.
Radial keratotomy (RK) - this procedure is very effective for treating myopia. It involves the use of a diamond scalpel to make minute incisions in the cornea which in turn helps to flatten the cornea thereby reducing its curve. It may take about a week or two to heal completely. Possible complications associated with it include changing vision, infection, pain, discomfort, glare, difficulty in wearing lenses and weakened cornea. Clouding of vision and partial or total vision loss is also possible though the chances are quite rare.
Astigmatic keratotomy (AK) - the surgery is used for treating patients suffering from astigmatism and involves the cutting of the cornea in a curved pattern.
Automated lamellar keratoplasty (ALK) - the surgery is used to treat patients suffering from chronic myopia and hypermetropia. The technique used for the treatment varies depending upon whether the patient has the former or the later. Possible side effects include astigmatism, over or under corrected vision, scarring infection etc.