Refractive Errors

Refractive Errors

The function of the eye is to see clearly the objects around us. The inability of the eye to accurately focus the rays of light coming from distance on the retina is called "Refractive Error". This condition may be either because the eye is too short or long in length, or because the cornea or lens does not have the required refractive power.

Like a camera, the human eye must be properly focused to see an image clearly. If light does not bend or refract correctly and focus directly on the retina, the result is blurred vision, or a refractive error.

What are the different types of refractive errors ?

The four most common refractive errors are:

  • •Myopia, or nearsightedness: clear vision close up but blurry in the distance
  • •Hyperopia, or farsightedness: clear vision in the distance but blurry close up
  • •Presbyopia: inability to focus close up as a result of aging
  • •Astigmatism: focus problems caused by the cornea
  • It is possible to have more than one refractive error, such as having both myopia and astigmatism

How can a refractive error be corrected ?

The refractive errors may be treated by either of the following ways:

  • •Glasses: this is the simplest and most popular way of correcting refractive errors
  • •Contact lens: this option is cosmetically much better though the maintenance and cleaning of contact lenses may be cumbersome and they have to be replaced at regular intervals
  • •Refractive surgeries: these are increasingly becoming popular with the advent of more predictable laser treatments
  • What types of laser refractive surgery are available ?

    Conventional LASIK (Laser Assisted In Situ Keratomileusis) can correct short sight, long sight and astigmatism, accounting for around 95 per cent of refractive error. Wavefront LASIK tackles the remaining 5 per cent of defects and many consider that it offers better results. PRK and LASEK are alternatives - the recovery period is longer than for LASIK, but might be safer if your cornea is relatively thin.

    What is LASIK ?

    LASIK, or laser-assisted in-situ keratomileusis, combines delicate surgical procedures and laser treatment. First, we surgically create a "flap" of corneal tissue less than a third the thickness of a human hair, and lift the flap to one side. We then apply laser energy to reshape the cornea according to carefully calculated measurements. When treating nearsightedness, we use the laser to decrease the cornea's relative curvature. When treating farsightedness, we increase the cornea's relative curvature. We then reposition the corneal flap. A naturally-adhering bandage, the flap helps to improve results and speed recovery. LASIK may be used for nearsightedness, nearsightedness plus astigmatism, farsightedness, and farsightedness plus astigmatism

    What is PRK ?

    In PRK, or photorefractive keratectomy, we apply the laser directly to the cornea according to carefully calculated measurements, without creating a flap. For nearsightedness, we decrease the relative curvature; for farsightedness we increase the relative curvature. At the conclusion of the procedure we place a transparent "bandage" contact lens over the cornea to promote healing. PRK is presently used to treat nearsightedness, nearsightedness plus astigmatism, farsightedness, and farsightedness plus astigmatism.

    What is LASEK ?

    In LASEK, or laser epithelial keratomileusis, alcohol is used to separate the outermost layer of the cornea to create and move aside a sheet of cells, a third the thickness of a LASIK flap (see "The LASIK treatment"). We then apply the laser to reshape the cornea. For nearsightedness we decrease the relative curvature; for farsightedness we increase the relative curvature. At the conclusion of the procedure we replace the sheet of cells and cover the cornea with a transparent "bandage" contact lens to promote healing. LASEK is presently used to treat nearsightedness, nearsightedness plus astigmatism, farsightedness, and farsightedness plus astigmatism. LASEK is reserved for patients who have thin corneas, are at risk of occupational damage to the eye, are reluctant to have a LASIK flap, or have corneal disease that precludes the LASIK procedure.

    What are risks factors and possibility of complications ?

    Complications occur in less than 5 per cent of cases, but make sure your consultant outlines all the risks. Flap complications with LASIK arise in 0-4 per cent of cases, but can usually be corrected with little or no loss of vision. Some people have a problem with dry eyes in the months after surgery and artificial tear supplements might be needed in the long term. Many patients have experienced glare or halo effects when night driving, particularly just after treatment. This is more likely in cases of higher correction that has been made, but is rarely severe. In rare cases, excessive thinning of the eye wall can cause the shape of the eye to be unstable after treatment. Severe loss of vision is very unusual, but some patients could require corneal surgery or hard contact lenses to restore vision. Most of these complications may be prevented by a thorough pre-operative examination of the prospective patients which we religiously perform at our center.

    The specialists at Shekar Eye Hospital will test your eyes completely using the best-in-class eye equipment and suggest a treatment that suits you the best. We have performed LASIK treatment for many patients in Bangalore and other parts of India.

    What is Keratoconous ?

    Keratoconus, or "conical cornea" (from kerato- cornea and conus cone), is a degenerative non-inflammatory disorder of the eye in which the cornea thins and changes shape to become more conical than its normal parabolic curve.

    • •Keratoconus can cause the vision to become distorted quite badly, with multiple images, streaking and sensitivity to light, all often reported.
    • •Keratoconus is an unpredictable and as yet incompletely understood disease, and the course of its progression following diagnosis is uncertain.
    • •The associated deterioration in vision, if in both eyes, can affect the person's ability to, for example, legally drive a car. It does not however lead to blindness.
    • •Further progression of the disease may lead to a need for surgery. There is no known cure for keratoconus, nor can its natural progression be significantly arrested, but it can be successfully managed with little or no impairment to the quality of life.
    • • With current methods using contact lens or intra corneal ring segments, only refractive error can be corrected, but it has little effect on the progression of keratoconus

    What are the treatment options available for Keratoconous?

    At Shekar Eye Hospital, with new advances in ophthalmology, for keratoconus newer treatment modalities are provided:

    • •One is to strengthen the weakend cornea known as Corneal Collagen Cross linking.( C3R ). This procedure is a simple, one hour treatment and can reduce the progress and causes regression of the disease.
    • •Another major treatment option is the implantation of ICL, which has become a procedure of choice not only for patients, their family, but also for ophthalmologists. ICL is capable of correcting most refractive disorders. Implanting ICL is considered an out patient procedure and takes about 15 minutes. A few hours after the treatment, the patient will be able to leave the clinic and resume most of the activities.
    • Both C3R and ICL implants are done regularly at Shekar Eye Hospital by our Cornea specialists.

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