Refractive and LASIK
Blurred vision and headache are the most common reasons we visit Ophthalmologist for and come to know that we have a refractive error, wondering how it occurred and how do our eyes see the world.
Refractive error is an inability of the eye to focus light properly, causing blurring of objects we see. Refractive error is a leading cause of vision loss along with cataract and vitamin A deficiency. They usually can be corrected by wearing eyeglasses or contact lenses or can be permanently treated with LASIK.
How do eyes see the world?
A normal eye, also called emmetropic eye can focus parallel rays of light on the retina, without using any accommodation. Rays of light being focused on retina lead to sharp and clear image perception by our brain. If rays of lights get focused in front or behind the retina, it leads to blurring of vision. It happens because of the improper ability of the lens to focus rays of lights, irregular shape of the cornea, elongated or short eyeball. Such an eye is called ametropic or having a refractive error.
Types of Refractive errors
Common types of refractive errors are near-sightedness, far-sightedness, presbyopia, and astigmatism.
Near-sightedness or myopia means the person is able to clearly see near objects but far objects appear blurry, due to rays of light getting focused in front of the retina. Myopia can be corrected with a concave lens which diverges the light rays to get it focused on the retina.
Far-sightedness or hyperopia means a person can see far objects clearly, but near objects appear blurry, due to rays of light getting focussed behind the retina. Far-sightedness can be corrected with a convex lens which converges light rays to get it focussed on the retina.
Presbyopia means the inability of the lens to focus on near objects due to aging changes in the lens. The affected person, usually above 35 years of age would experience difficulty in reading a book or newspaper, relieved by reading glasses, bifocal, or progressive lenses.
Astigmatism objects appear stretched out or blurry due to the irregular shape of the cornea. It can be corrected by refracting light more in one meridian than the other by using cylindrical lenses.
Blurred vision, double vision, headache, and eye strain are typical symptoms of refractive error. Diagnosis is done by Ophthalmologist by eye examination and test for Visual Acuity, wherein a patient is asked to read alphabets from a distance of 6 meters. Different powers of lenses are used to identify optimum corrective lens. Pupils may also need to be dilated with eye drops to visualize retina by retinoscope. Retinoscopy helps rule out defects of the retina and objectively estimate optimum lens power needed to correct refractive error. Alternatively, an automated refractor is used to objectively estimate the lens of correct optical power to rectify the refractive error.
Refractive errors are corrected with eyeglasses, contact lenses, or surgery. Eyeglasses are the easiest and safest method of correction. Contact lenses can provide a wider field of vision, however, are associated with a risk of infection. Eyeglass lenses and contact lenses with correct optical powers refract light to the degree necessary to compensate for refractive errors leading to sharp focus of light rays on the retina.
LASIK stands for Laser-Assisted in Situ Keratomileusis, also referred to as laser eye surgery or laser vision correction. LASIK is a vision correction surgery wherein an Ophthalmologist uses a laser or microkeratome to reshape eye’s cornea, with an aim to make light rays focus sharply on the retina. LASIK is a delicate procedure, success of which depends on equipment, skill, and experience of an Ophthalmologist. LASIK in the hands of a renowned Ophthalmologist can help you kiss goodbye to your glasses.