Goodbye to glasses

One of the latest advances in eye treatment today is refractive surgery. This means treatment to reduce the power of the glasses a patient wears. DR. AMAR AGARWAL explains the procedure.

TO a person who has known the restless waves of the ocean, the multicoloured butterflies and flowers of various hues and other sights of Nature, loss of sight is a tragedy without parallel. Therefore, those gifted with good sight have to take constant and vigilant care of their eyes. For, the cost of preventing a disease is only a fraction of the amount spent on its treatment, and a colossal amount of money is needed for the rehabilitation of the visually handicapped.

Treatment of the eyes today has become hi-tech. The latest in the treatment is refractive surgery. This means treatment to reduce the power of the glasses the patient wears. In today's world, if a person has spectacles with a power of -20 Diopter or +10 Diopter, the power can be reduced to zero after refractive surgery.

But first, let us look at how a normal eye functions. The eye works like a camera; the lens of the camera is used to focus the object onto the film. This image recorded on film is then sent to the studio for developing. The eye works in a similar way. The eye has a lens, which focusses on the object. The image is focussed on the film of the eye - the retina - which sends the image to the brain. The image is developed there and we see the object.

The eye is a sense organ. Just as we can smell and hear, so too can we see. No efforts are made to hear and smell. Similarly, the eye does not make an effort to see (when it functions normally). Some people who are not able to see clearly have to wear glasses. The inability to see clearly without spectacles is called a refractive error. Patients suffering from refractive errors see clearly only with the help of spectacles.

The types of refractive errors are:

* Myopia, or short sightedness

* Hypermetropia, or long sightedness

* Astigmatism and

* Presbyopia

Short sightedness means an inability to see at a distance. Vision is perfect for near (short) vision, but when the person tries to see distant (long) objects he finds it difficult. People who suffer from myopia have eyes longer than normal. So, the image of the object is focussed in front of the retina. Obviously, to correct this problem one has to have glasses which has the power to diverge the rays of light more so that the image is focussed onto the retina. This is done with the help of a concave lens or a minus lens.

Long sightedness means the inability to see near objects. Such persons can see distant (long) objects clearly. They have eyes shorter than normal. So, the image of the object is focussed behind the retina. A convex lens or a plus lens helps focus the image of the retina.

If one axis of the object is focussed well onto the retina (for example, the vertical axis) and the other axis (the horizontal axis) is not focussed on the retina the condition is called astigmatism. To treat this one has to use spectacles (with cylindrical lenses) only for the axis which is defective.

When we use a camera and focus on a distant object we turn the lens so that the image is in focus. When we want to photograph a near object, the lens has to be rotated again to change focus. The same thing happens with the eye. When we see a distant object, the lens automatically focusses. Suppose we focus on something near, like the letters/words in this article, the lens automatically refocusses to have this near object the letters focussed onto the retina. So, the eye works like an auto- focussing camera. After middle age, the lens gets hard and does not autofocus. So, by the time we reach 40 years our distant vision may be allright but for reading we have to use a convex lens or plus lens. This refractive error is called presbyopia.

Today, treatment is in the form of a lasik laser, where patients are treated for myopia, hypermetropia or astigmatism. The entire procedure is painless, there is no need for hospitaisation, not even injections. The front window of the eye, - the cornea - which has basically five layers - 'A', 'B', 'C', 'D' and 'E'. Now, any treatment that has to be done should be done in layer 'C'.

The lasik laser can be used for all degrees of shortsightness, longsightness and astigmatism with the least discomfort and minimal complications to the patient. Patients need not wear glasses or contact lenses. Chiron 217 is the latest lasik laser and is manufactured in Germany (it costs about Rs. 2 crores). This is the top of the line machine with potential for increased predictability. It corrects errors from one to 30 D of myopia, hypermetropia and astigmatism.

To understand now the lasik laser works, let us look at the cornea. If divided into the layers 'A', 'B', 'C', 'D' and 'E', treatment is usually effected layer C. In other procedures like PRK excimer laser, and in radial keratotomy, or RK, layers 'A' and 'B' are cut to reshape layer 'C'.

In the lasik laser a flap of layers 'A' and 'B' is made on the cornea and then the laser is applied in layer 'C'. This is the most important advantage. In this laser, 'A' and 'B' are not damaged, there is no scar, no corneal haze and no glare. It is an outpatient procedure. The laser is completely computerised and has an auto tracking system to track the eye movements similar to that used in military defence systems, so that treatment can be performed precisely. In most cases, an improvement in vision is almost instant, and discomfort, if any, is minimal.

Another modality of refractive surgery is cataract removal. A cataract is like the lens of a camera, on which someone has smeared grease. The lens is opaque and does not allow light to pass through. The solution is to implant an artificial lens called an intraocular lens (IOL) in the eye.

Previously this was done manually where an injection was administered and the cataract removed through a 12 mm opening. This meant that half the eye was cut open and then an intraocular lens is inserted. This lens is about 6 mm and goes easily inside the eye. The incisions are sutured the patient rests for 45 days and after that glasses are prescribed.

One of the biggest breakthroughs in cataract removal is called Phakonit. In this, the one mm barrier to remove cataracts has been broken. The size of the incision through which the cataract is removed is 0.9 mm. This technique is painless and the patient does not require any injection. Since the incision is below one mm, the patient is free of injections, stitches and pads. He walks into the hospital and goes back thereafter. Treatment lasts from five to seven minutes. The only problem is that at present, foldable intracular lenses have to be maufactured which would pass through a 0.9 mm opening.

Another way of getting rid of glasses is by implanting an intraocular lens without removing the eye's lens. These are called Phakic IOL's.

Thus, various modalities exist today to enable a person to get rid of his glasses. One of the best methods involves the lasik laser.

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