A refractive error is an optical defect of the eye that results in light not being focused clearly on the viagra 10mg retina. If an image comes into focus in front of the retina, this is called myopia, and the person is nearsighted – able to where to find levitra click now see more clearly at near distance than at far distance. If the image comes into focus behind the retina, a condition called hyperopia, then the person is farsighted and able to see better at far distance than at near distance. Other types of refractive errors include astigmatism and presbyopia. Astigmatism represents "uneven" focusing in different planes of the eye. Presbyopia refers to the difficulty focusing up close and occurs with aging, resulting in the need for reading glasses in many people over the age of 40. The cause of refractive errors is unknown.
To permit clear vision, myopia, hyperopia, and astigmatism must be corrected, usually with eyeglasses. Uncorrected refractive error can result in visual impairment ranging from mild blurring to legal blindness, depending on the magnitude of http://www.nciaai.com/effect-of-cialis-on-women the refractive error. If the refractive error of the two eyes is very different and this is not corrected in childhood, then permanent loss of vision, called amblyopia, can result.
It has been estimated that more than a half of vision impairment, and about a quarter of legal blindness, is due to refractive error correctable with glasses. The number of people with poor vision due to uncorrected (or undercorrected) refractive error increases greatly in older age groups. In Australia this affects more than a third of the elderly folks who undergo an aged-care assessment. Particularly in older people, poor eyesight can lead to accidents, social withdrawal, and loss of independence.
If you notice a change in your vision, contact an eye care professional for an eye exam.