Normal vision is a sign of healthy eyes. Any disturbance in the structure or normal physiological function of eyes will lead to changes in the vision. The cornea, iris, lens and retina of eyes, along with a nerve running within the structure of the eye known as optic nerve together perform the function of normal vision. Any of these could sustain damage and thus affect vision.
Vision correction involves treating the symptoms and causes of the disturbance. Since the causes are various, treatment methods are also varied. Vision correction could be done medically or surgically. Choice of treatment depends on cause and intensity of the disturbance.
Indications/ symptoms of vision correction
There are many contributing factors for vision disturbances. Presence of any of these in a patient can validate the need for vision correction. The eyeball is shaped in such a way that light reflecting from lens of the eye, falls on retina (a screen like structure situated at the back of the eye). This makes it possible for a person to see clearly. If there is any change in the angle of this light, it will not project on the retina. This will lead to vision disturbances. Change in the shape of eyeball usually causes this. This can lead to the following disorders:
Also known as short sightedness, this condition is caused when the light passing through the lens falls in front of retina instead of on the retina. This can happen if the eye ball flattens in a direction from above down. Person affected by myopia can see near by objects clearly. Objects placed at a distance appear blurred. Though this condition is hereditary, a lot depends on the lifestyle of a person. People who read a lot, are exposed to computer, T.V. Or mobile phone screens constantly are more likely to develop this condition. Children and young adults are most potential candidates for myopia.
This condition is also known as far sightedness. Elongation of the eye ball in vertical direction leads to change in the angle of light falling on the retina. Light gets focused behind the retina instead of focusing on the retina. Affected person can see clearly objects which are placed far away. However, objects situated nearer seem to be blurred. This is an age related disorder. People who are above 40 years of age are most likely to be affected by this condition.
Presbyopia is an age related disorder. It is different from hypermetropia or myopia. It does not occur due to changes in the shape of eyeball. In this condition, lens of the eye is thickened and degenerated. Due to this, light which passes through lens does not fall correctly on the retina. Presbyopia occurs around the age of 40-45 years. Patients have to focus the objects at about arms length till they can see them properly. It can occur with myopia or hypermetropia. It is difficult to perform tasks which require to focus the eyes very minutely like knitting, embroidering.
In astigmatism, the shape of eyeball is such that light gets focused on multiple areas rather than a single point on the retina. Due to this, objects at a distance appear wavy. Objects are seen partly blurred. It is also known as ‘cylindrical vision’.
All of these complaints are associated with headache or fatigue. This usually occurs from over straining of the eyes. If any of the symptoms described above are felt by the patient, it is advisable to consult with an ophthalmologist.
A complete eye exam is done for diagnosing vision errors. The opthalmologist will consider the patient’s ability to focus on alphabets from a screen situated at a set distance and to identify them correctly. A history regarding the patient’s use of eyes, their age, general health are also noted. Once the condition is diagnosed the treatment part is decided. There are various treatment methods for vision correction.
Treatment for vision correction can be done by non-surgical or surgical methods. Depending on each individual case, the ophthalmologist will choose the method which they feel is most suitable for that case. Each of the treatment methods has been explained below in detail:
One of the oldest, safest and most commonly used method to eliminate vision errors is to wear spectacles (also known as glasses). The opthalmologist will determine the intensity of visual disturbance by asking patient to read out alphabets placed at a distance without any visual aid. Depending on the intensity, focal power is decided. Glasses fitted with lens of the same focal power are made for the person. After wearing them, the glasses will alter the angle of light passing into the eye in such a way that it focuses on the retina and patient can see clearly.
The principle of working of contact lenses is the same as that of glasses. Lenses are made with the focal power which will match the patient’s visual error. The light passing through the lens will then be correctly focused on retina. Contact lenses are worn in the eyes over the cornea. They have cosmetic importance, as many people are bothered by the way they appear after wearing glasses. Unlike lenses, glasses could come off, if the person wearing them falls down or moves with great force. Lens stick to the eye and hence provides more freedom of movement.
Lenses have certain disadvantages too. They have to replaced after certain period of time. Wearing and removing them may take a lot of time for a new user. They have to be kept stored in a case immersed in a special liquid. There is a chance of developing dryness of eyes after using contact lenses for a long time.
Allied treatment methods
It is believed that exercising the eye muscles adequately, helps to strengthen the eye muscles. This may help in preventing further changes in the shape of eyeball. This prevents further progression of visual errors. The exercises may not help with altering the changes that have already taken place. Hence they cannot be considered a mainstream treatment method. They may be advised in association with the treatment which is being used.
Another allied therapy is use of eye drops. They help in relaxing the eyes and provide a cool and soothing sensation to the user. They are also directly not useful in correcting the visual disturbances. However, they will help reduce the strain on eyes.
Any of the above methods may be prescribed by the opthalmologist for visual correction. These are non surgical methods and opted by most people. A very popular surgical method is being used for correcting visual disturbances. It is a more or less permanent treatment method. It has been described below.
Laser insitu keratomileusis (LASIK) is a surgical procedure for correcting errors in refraction of light which falls on the retina. It is a non-invasive procedure and can be performed as an out-patient procedure. There is no need for the patient to be hospitalized for this procedure. The complete process is described in detail below:
Prior to the surgery:
Preparation for the surgery has to be started a few weeks before the actual procedure. The patient will be asked to stop wearing contact lenses for some weeks prior to surgery. A complete eye check up is done before the surgery to ensure that the patient is a suitable candidate for the surgery. Patients who undergo this procedure must have a healthy cornea. If any eye infection is active it must be controlled before the surgery is performed. The error of refraction of light is calculated.
Procedure of surgery:
Patient is made to lie down on the back. Retractors are used to hold the eyelids apart to prevent blinking. Anesthetic eye drops are used for the process. A machine is used to cut a flap of the cornea. This flap is opened and laser beams are used to give cuts on the inner layer of cornea. The angles at which these cuts are given is calculated before hand. This alters the shape of cornea. Light passing through the eyes thus gets focused on the retina enabling the person to see properly without any visual aid. The corneal flap is replaced at its original position. The procedure takes about 20 minutes to be completed. The above procedure is a brief explanation and doctor may need a based on your condition. Find the cost and procedure of LASIK eye surgery in India here.
After the surgery:
After the surgery the patient is required to wear dark glasses for sometime. There will be swelling around the eyes with pain for a few hours after surgery. The patient may feel as if their eyes are full of sand. The vision may be hazy for a while. After the swelling subsides the patient begins to see clearly. For a few days after surgery patient is to abstain from watching T.V, exposure to screen of computers, laptops or mobile phones. Strain to the eyes has to be avoided as much as possible. Antibiotic eye drops and drops to keep the eyes moist are to be used for a few weeks after surgery. The patient will be called for follow up examination at regular information. It takes time for the corneal flap to heal completely.
This surgery is a form of permanent treatment. There is very low chance of a person developing visual errors again after LASIK procedure. There is a very slim chance that the procedure might not be successful. In this case the person can continue wearing glasses to have clear vision. A repeat LASIK procedure can also be considered.
Medical studies are advancing and coming up with newer methods for visual correction. All of these methods have some advantages and disadvantages. The best treatment method for every patient with visual disturbances will be decided by the ophthalmologist.