| Laser Eye Correction |
| Written by James Black | |
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Laser eye correction is performed by ophthalmologists on patients who suffer from long sight, short sight or astigmatism. This refractive laser eye surgery is given more preference to Advanced Surface Ablation as the former enables the patient to recover faster and he/she feels reduced pain due to this laser eye surgery. There are advantages as well as disadvantages of laser eye correction. Some people do not like to wear vision corrective eyeglasses or contact lenses for loss of personality. They volunteer to get their vision corrected by refractive laser eye surgery. Let us know how the eye surgeon performs the surgery. Change in the corneal curvature of the eye is the reason for myopia, hyperopia and astigmatism. Astigmatism brings blurred vision because of the inability of the eye to focus a sharp image on the retina. It is caused by a corneal scar which results in light scattering in the lens. Laser eye correction is the technique of modifying corneal curvature by cutting a flap in the cornea and folded to expose the corneal bed. The exposed surface is brought to the correct shape by ablation with an Excimer laser, followed by closing the flap back to its original position. Recently, FEMTEC laser has been successfully used for incision-less ablation of the corneal surface on patients suffering from presbyopia. Research on patients with myopia and astigmatism is still going on. Before laser eye correction surgery is done, the ophthalmologist advises the patient some preoperative precautions to be adhered to. Patients already using soft contact lenses are refrained from using them a fortnight before the operation. Hard contact lenses have to be avoided from 6 weeks before the laser eye surgery. The surgeon measures the thickness of the cornea with a pachymeter and their surface contour using a topographer which gives a topographic map of the cornea. Defects of astigmatism are also detected by this instrument. The patient is advised to swallow antibiotic pills to overcome infection during and after surgery. What happens in the operation theatre? The patient is allowed to be awake and mobile. He is administered with a light sedative like valium and anesthetic eye drops wet the eye which is to be operated. The laser eye correction surgery is performed by the ophthalmologist in three stages. The top layer of the corneal tissue is cut into the shape of a flap and folded. The corneal stroma under the flap is remodeled using laser to the required curvature and the flap is covered to heal on its own. The eye is held in position using a corneal suction ring. Slight carelessness can injure the small blood vessels in the white part of the eye to burst. This is called subconjunctival hemorrhage which might get cured during recovery. If the suction ring exerts more pressure on the eye ball, the vision may become dimmed. A femtosecond laser microkeratome is artistically used by the surgeon to create closely packed tiny bubbles within the cornea. The top layer opens like a flap with a hinge on the side. It is folded to get access to the corneal stroma which is the middle section of the cornea. The surgeon with an Excimer laser remodels the corneal stroma by vaporization of the tissue. The removed tissue is only few micrometers thick. The patient experiences better visual recovery if the deeper corneal stroma is ablated. On folding of the flap, the patient’s vision blurs and sees only white light bordered by the laser orange light. Latest excimer lasers use eye tracking systems that monitor the patient’s eye to the tune of 4000 times per second. The tracking redirects laser pulses for meticulous placement in the treated zone. Following the reshaping of the layer of the corneal stroma, the flap is repositioned on the corrected stromal area and checked perfectly for absence of dirt and air bubbles. The surgeon takes utmost care in properly fitting the flap back to its original position. Patient’s eye is treated with antibiotic and anti-inflammatory eye drops for weeks after the laser eye surgery. They should sleep for more hours and wear dark glasses to avoid light glare. The eye should be moisturized with pure tears. Laser eye correction surgery has high tendency to create high-order aberrations. This is a disadvantage due to this surgery. The patient might experience significant vision impairment. Ghosting, double vision, starbursts and halos are some of the post operative problems. The aberration results due to correlation between the normal part of the cornea and the reshaped part. At nights, when the pupil enlarges beyond the flap, light sneaks through the edge of the flap into the pupil to create halos surrounding light sources. Some patients suffer loss of contrast recognition in dark places. About 95% of patients who were operated for laser eye correction have shown sense of satisfaction. The remaining of the patients reported significant reduction in the quality of their life due to visual problems after operation. |
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