The Concave Nearsighted Lens

Posted in nearsighted | No Comments » January 14th, 2012

A concave nearsighted lens could create a virtual image that could help a person who is nearsighted to see objects more clearly. Concave lenses are thinner at the center than on the edges and used to correct nearsightedness or myopia.

In this lens, after rays of light have passed through it,   they appear to come from a principal focus point. This is the point unto which the collimated light moving parallel to the axis of the lens is focused. The image that is formed by a concave lens is virtual, which means that it looks farther away than it really is, and   thus smaller than the object itself. Often, curved mirrors have this effect that is why many come with a warning such as: objects in mirror are closer than they look.  The image is also upright, which means it is not inverted.

The formula of the lens that is used to work out the nature and position of the image formed by the lens could be illustrated as follows: 1/u + 1/v = 1/f. The u and v are the distances of the image and object from the lens respectively. The f is the focal length of the concave lens.

Concave Nearsighted Lens

Posted in nearsighted | No Comments » December 24th, 2011

 The lens for a nearsighted person is a concave lens. Nearsightedness happens because of the excessive light ray’s convergence by the eye lens. This could be corrected by a diverging lens or concave lens. In nearsightedness or myopia, the eyeball is  longer than it should be for  ideal vision. The errors could lead to focus of image in the wrong place, which is in the back of the retina. A concave nearsighted lens bends an incoming light so the focus hits the retina.

Concave lenses can also correct errors in systems of lenses designed to focus light on a certain location. By adding lenses to a system, engineers could change the area where the rays of light end up by bending the light outward or inward.

In the concave mirror, the light reflects off various points on the glass means that rays will bounce to the center. This means that if the image reflected is far enough, the light that comes from the top of the object is far enough and the mirror will flip the image over. You can check this out by looking on the concave side of the spoon. If you are far from the spoon, your image is upside-down but if you move closer, your image will be right-side up.

The Nearsighted Lens

Posted in nearsighted | No Comments » December 7th, 2011

 Nearsightedness or myopia is a vision problem that around one-third of the population experiences. A recent study revealed that nearsightedness is more common among Americans today than it was thirty years ago. People with a hard time reading  highway signs and seeing distant  objects but could see well up close like sewing or reading are considered as nearsighted persons.

The nearsighted lens prescription is written in minus power. A contact lens or spectacle power will have a minus sing in front of the number. This indicates the amount of prescription that is needed in the lens, which is also called a diopter. The lens power ranges from 0.00 to 20.00 diopters or higher and prescribed in .25 centimeters. A sample of a nearsighted lens power is -2.00 or -2.25. The higher the number, then the thicker the lens is.

Most nearsighted lenses are made from plastic but are also available in several materials. Glass is the heaviest and not often used for nearsighted prescriptions. An ideal material is the polycarbonate for nearsightedness since the lenses and lighter and thinner and more shatter resistant compared to glass or regular plastic. Another option is called photochromic.  It is a lens that grows darker outdoors and lighter when indoors.  These lenses are useful if one has a stronger prescription and do not like to switch glasses each time that he or she goes outside or inside.

Nearsighted Lens

Posted in nearsighted | No Comments » September 30th, 2011

 There are two kinds of lenses prescribed for improving or correcting a nearsighted vision. These include eyeglasses and contact lenses. Eyeglasses are otherwise called as spectacles. They are the most common eyewear from to correct nearsightedness. Contact lenses are directly worn on the cornea of the eye. The same as eyeglasses, contact lenses help in correcting refractive errors and perform this function through adding or subtracting the focusing power to the cornea of the eyes and the lens.

Nearsighted lens could include concave lenses. These lenses are thinnest in the center and used to correct the nearsighted problem. When it comes to contact lenses, there are more than 30 million Americans who wear contact lenses today. Eight percent wear daily ware soft contact lenses. There are four types of contact lenses. These include the rigid, gas-permeable lens, soft, water-absorbing lens, flexible, non-water absorbing lenses and other rigid lenses.

A contact lens prescription includes more information than available on prescription eyeglasses. Special measurements are needed to be taken on the eye curvature. Moreover, the physician determines if the eyes are too dry for contact lenses and finds out if there are corneal problems that could prevent one from wearing them. There are usually trial lenses tested on the eyes for a period of time to ensure proper eye fit.

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