Refractive Errors of Eye: Types and Treatment

The eye is like a camera in which the light passes through a lens system back onto the film. The cornea and lens are at the front of the eye (anterior chamber) and are similar to a camera's lens system. The retina is located at the back of the eye (posterior chamber) and is similar to the camera's film. In the normal eye, light rays of an image pass through the cornea and the lens and are focussed directly on the retina to produce a clear image.

A refractive error, is an error in the focusing of light by the eye and a frequent reason for reduced visual acuity (VA). Visual Acuity (VA) can be defined as "acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain."

Refractive Errors of Eye can be classified as Spherical Errors and Cylindrical Errors.

Spherical Errors: These type of errors are caused when the optical power of eye is either too small or too large to focus light on retina of eye, resulting in a blurry vision. These can be further split into two cases: Nearsightedness (Myopia) and Farsightedness (Hyperopia).

In Myopia (or nearsightedness), the light rays are passed through the cornea and lens but the point at which they converge (focus) is in front of the retina, not on the retina. This configuration allows clear images of near objects but not those that are far away.

 Whereas in Hyperopia, the light rays do not converge or focus by the time they reach the retina. Hyperopic patients can focus on more distant objects, but not images that are close at hand.

Cylindrical Errors: Cylindrical errors occur when the optical power of the eye is too powerful or too weak across one meridian. It is as if the overall lens tends towards a cylindrical shape along that meridian. The angle along which the cylinder is placed is known as the axis of the cylinder, while 90 degrees away from the axis is known as the meridian of the cylinder.

People with a simple astigmatic refractive error see contours of a particular orientation as blurred, but see contours with orientations at right angles as clear. A person with cylindrical error is said to have Astigmatism.

The other type of Refractive Error is Presbyopia. Presbyopia describes the condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Although exact mechanisms are not known with certainty, however, the research evidence most strongly supports a loss of elasticity of the crystalline lens, although changes in the lens's curvature from continual growth and loss of power of the ciliary muscles (the muscles that bend and straighten the lens) have also been postulated as its cause.

Treatment of Refractive Errors:

How refractive errors are treated or managed depends upon the amount and severity of the condition. Those who possess mild amounts of refractive error may elect to leave the condition uncorrected, particular if the patient is asymptomatic. For those who are symptomatic, glasses, contact lenses, refractive surgery, or a combination of the three are typically used. For more information, visit accuratesight.com

Surgical treatment options include clear lens extraction, LASIK eye surgery, phakic IOL and Radial Keratotomy.

As Presobyia,is a natural part of the human aging process, presbyopia is not routinely curable.Treatment for presbyopia has advanced significantly in recent years, thanks in no small part to the ready availability of inexpensive over-the-counter reading glasses with corrective lenses that cover a wide gamut of magnification levels. Contact lenses have also been used to correct the focusing loss that comes along with presbyopia. Some people choose to correct the focus problems with bifocals, giving them a wider range of vision without having to use a second set of glasses. ew surgical procedures may also provide solutions for those who do not want to wear glasses or contacts, including the implantation of accommodative intraocular lenses (IOLs).