Different types of laser surgery for eyes ( PRK, LASEK, LASIK)!

  

      The eye is the most vital organ in the human body. It enables us to see things and observe them. The operation of the human eye is an impressive operation. The light reflected from an object enters our eyes through the cornea. The cornea refracts the light and focuses on the lens. The lens again refracts the light and focuses the image on the retina. The image appearing on the retina will always be upside down. The fallen reversed image is then converted into electrical impulses and transmitted to the brain through the optic nerve. Our brain corrects the reversed image into a correct orientation. That’s how we see an image.

 

Credit (Human Eye Anatomy): courses.lumenlearning.com

     Due to certain conditions, our eyes get subjected to certain problems. The most common problems that occur in the eye are myopia, hyperopia, and astigmatism. Myopia also called as short-sightedness, is when the person can only see the objects that are near to them and can’t see the objects far from them. This occurs due to the elongation of the eyeball. Due to this problem, the focal point that should be pointed on the retina, points before the retina. So the retina cannot convert the image into electrical impulses correctly, which makes us to look at the image far and as blurred. Another problem that is caused in the eye is hyperopia or hypermetropia, which is also called as long-sightedness. In this situation, the person can only see the objects that are far from them and can’t see the objects that are near to them. This occurs due to the shrinking of the eyeball. Due to this problem, the focal point falls beyond the retina and makes us to look at the near image as blurred. Astigmatism is a problem, which makes the person to see the object as two and as blurred. This is due to the improper shape of the cornea and lens. Due to the improper shape, the light that enters the eye is made to fall in different places in the inner eye. So the image appears as two and as blurred. There is also another defect in the eye that is caused naturally for older people; called presbyopia. This defect is similar to hyperopia but caused during older age, due to the shrinking of the eyeball. But hyperopia is caused artificially or through a genetic disorder.

 

Difference between myopia and hyperopia

     All these defects can be cured by adding separate lenses (spectacles) to the eye. These lenses are of various types namely concave and convex. Myopia can be cured by using concave lenses which refract the light from an object, outwards. Now the cornea and the lens refract the light and make the focal point right on the retina as the light is refracted outwards. Now we can see the image clearly. Hyperopia is cured by using convex lenses which refract the light inwards so that the focal point that falls beyond the retina comes in exact contact with the surface of the retina. Astigmatism is cured by the combination of both concave and convex lenses. These concave and convex lenses are produced in the form of spectacles which can be worn by the person having problems with their eyes. Persons who get uncomfortable in wearing spectacles can also wear contact lenses which are thin, and made up of hydrophilic plastics. These plastics stick to the surface of the eye and stay moist and soft by the water present in the eye, proving ultra comfort to the user.

Cure of Myopia and Hyperopia by adding lenses

But nowadays people who have problems in wearing spectacles and contact lenses can also cure the above defects through laser surgery. It is a type of surgery in which laser light is used to cure the above problems by reshaping the cornea. The most popular eye surgeries are

·        PRK (Photorefractive keratectomy)
·        LASEK (Laser-Assisted Sub-epithelial Keratectomy)
·        LASIK (Laser-Assisted in situ keratomileusis)
 

    All these three methods can cure myopia, hyperopia, and astigmatism. PRK is the first method of the evolution of laser eye surgery. In this method, a small layer called epithelium which is in the upper layer of the cornea is removed and discarded. Then by using the laser light, the cornea is reshaped. A new layer of epithelium forms above the cornea within 7-14 days. The next evolvement is the LASEK surgery. It is more similar to PRK but unlike PRK, the thin flap removed above the cornea is not discarded. Thereby after reshaping the cornea, the epithelium is made to put back on the cornea. The old epithelium is replaced by a new one within 7-14 days. In LASIK operation, the thin flap is made to cut partially thereby the edge of the epithelium still remains in contact with the eye. After that, the reshaping of the cornea is done and the flap is made to put back. The biggest advantage of this method is that it ensures the patient to recover quickly Also it is the most recommended method by doctors. 

Doctors even suggest wearing contact lenses for older people to avoid presbyopia after surgery. For younger people, contact lenses are suggested even after surgery, who has higher refractive index error. This is how laser eye surgery works.