Junior Optometry Class 12 January 2018 Introduction As of 2004 the refractive error known as Astigmatism ASM has affected a total amount of 45 million Americans which two thirds of those people also have myopia Astigmatism is when the light rays are not properly focused at one single point but instead its focused at two separate points most of the time this is due to the curvature of the cornea but it can also be due to the curvature of the lens The curvature of either the lens see image 1 or the cornea see image 1 affects the refraction Refraction is the method of light rays bending in order to properly pass through a medium such as your cornea or lens ASM is mostly present at birth but could also occur due to a combination of myopia and hyperopia Symptoms Diagnosis The signs and symptoms of ASM are squinting headaches difficulty with night vision eye strain or discomfort and blurred or distorted vision Astigmatism can be diagnosed by an eye exam that will examine the way your eye bends light The machines that help observe the way your eye is bending light are called the auto refractor phoropter and the topography machine which is also known as the keratometer What the auto refractor does is shine a light into your eye and measures how the light changes as it bounces off the back of the eye The phoropter works by manually switching through lenses in front of your eyes and being able to determine how the lens of one s glasses need to be shaped and it what areas should be curved
The topography machine aka the keratometer is a computer based diagnostic tool that creates a three dimensional map of the surface curvature of the cornea Treatment One of the methods of treatment for ASM are corrective lenses such as eyeglasses and contact lenses Eyeglasses that are specifically crafted for someone with ASM are made with spherocylindrical lens which are made up of one spherical and one cylindrical surface If one chooses contact lenses as a method of treatment there are types of contacts such as toric contact lenses gas permeable contact lenses GP or RGP and hybrid contact lenses Toric lenses are specifically created with an area with weight to prevent the lenses from rotating due to blinking Due to every eye with ASM being different it may take more than one pair of toric contact lenses to find the proper brand and and design that provides the most comfort efficiency and visual acuity Gas permeable contact lenses are rigid and are able to retain their original spherical shape which makes it beneficial GP lenses can be more difficult to become accustomed to due to the thickness of the lenses but many patients have realized that they perceive a sharper image than when wearing soft or toric contact lenses Some gas permeable lenses can be made with a toric design but they are only used in cases where someone has a relatively high amount or unusual type of astigmatism Hybrid contact lenses are a mixture of both GP lenses and toric lenses the GP lenses factor comes into play in the central zone of the contact which is rigid and the toric lens aspect goes into play in the fitting zone edges of the contact
When properly fitted the hybrid contact lenses will give the sharp vision of the GP lenses and the comfort of the toric lenses Another method of treatment are refractive surgeries the different types of refractive surgeries are laser assisted in situ keratomileusis LASIK laser assisted subepithelial keratectomy LASEK photorefractive keratectomy PRK and epi lasik More in Depth Refractive Surgeries The LASIK procedure is the most common refractive surgery the procedure is done while the eye is numbed with topical anesthetic During the LASIK procedure the eye is sustained still with an eyelid holder preventing blinking The cornea then is flattened with a suction ring then they proceed to create a flap of corneal tissue and then the flap is lifted and folded back The patient is then told to look at a pinpoint light and the surgeon then begins to use a laser to sculpt the corneal tissue The flap is placed back and the edges are then flattened Stitches are not needed for this procedure because the corneal flap will stick to the underlying corneal tissue within two to five minutes Just like any other surgery the LASIK procedure comes with its potential risks and side effects such as blurry vision dryness in the eye discomfort or pain halos around lights difficulty with night vision light sensitivity and patients may even notice small pink or red dots in the sclera the white part of the eye In certain cases when a patient has a high amount of astigmatism they need to go through retreatment in order to fully correct the ASM According to the American Academy of Ophthalmology approximately 10 5 percent of LASIK patients in the United States require a retreatment
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