Nearsightedness, farsightedness and astigmatism : Laser Eye Surgery
Laser eye surgery is mainly used to alter the corneal stroma to fix three visual impairments. These are nearsightedness or myopia, farsightedness or hyperopia, and astigmatism, which is blurred vision. They are all refractive defects which cause the eye to see images incorrectly when the refracted light entering the eye is not focused clearly at the retina.
Nearsightedness
With nearsightedness, objects appear clearer the closer they are to the eye. Objects that are further away appear blurred, with the exact distance depending on the severity of the impairment. This is usually due to excessive length of the eyeball or steepness of the cornea, which consequently means images are focused to the vitreous, in front of the retina near the middle of the eye, as opposed to the retina at the back. Myopia is characterized as low when between -0.50 and -3.00 diopter, medium from -3.00 to -6.00, and high when greater than -6.00 diopter. People with high myopia are likelier to suffer from further conditions like glaucoma or retinal detachment. Severe myopia can also render laser eye surgery less effective or more fraught with risks.
Farsightedness
When distant objects appear clear but objects at close range seem blurred, this is farsightedness. As the reverse of myopia, farsightedness generally arises as the result of the eyeball being too small or the cornea too flat (and therefore not curved enough). The refracted light, when entering the eye, does not focus on the retina but instead at a point behind the retina. People with farsightedness require reading glasses, and often do not initially notice the problem – they simply feel tired or pain in their eyes after reading or focusing on something close. Mild hyperopia falls between +0.50 and +2.0 diopter, with moderate hyperopia between +2.0 and +4.0, and severe farsightedness any higher than this. Again, the effectiveness of laser treatment may wane with very severe refractive errors; please speak to your surgeon for clarification.
Astigmatism
Astigmatism describes blurred vision caused by the lens, cornea or other eye structure being elliptical in parts as opposed to spherical. This means that refracted light entering the eye is bent a number of different ways, falling on multiple focal points which do not allow successful focusing. It is not a disease but an unfortunate variety in eye shape. Astigmatism is often found in conjunction with forms of near- and farsightedness, and when under +5.0 diopters it can usually be correctly using wavefront laser eye surgery. When the surgeon uses wavefront technology, this allows precise accuracy. An alternative to laser treatment is implantable lenses, and other laser-based procedures such as LASEK, Epi-LASIK and PRK can be beneficial depending on individual factors.