In people with normal vision parallel light rays enter the eye and are bent by the cornea and the crystalline lens allowing for a crisp and clear image. For perfectly clear vision, incoming light is focused on one precise part of the retina rather than in front or behind it. It is similar to a camera that has to be focused properly in order to take a clear picture.

Visual stimulation either fails to transmit or is poorly through the optic nerve transmitted to the brain for an extended period of time. Amblyopia (referred to as lazy eye), results from abnormal development of vision in early childhood. In amblyopia one eye develops proper vision while the other eye (the amblyopic eye) fails to develop normal vision. There are three major causes of amblyopia. Strabismus is a misalignment of the eyes. The two eyes are looking in two different directions at the same time.Images from the misaligned or crossed eye are turned off to avoid double vision. The stronger eye develops normal vision while the wandering eye becomes amblyopic. The brain ignores the unfocused eye and the stronger eye develops normally while the weaker eye becomes amblyopic. The brain prefers the clearer image making the other eye amblyopic. A drooping eyelid does not allow light to enter and this eye is essentially not being used which can lead to amblyopia. Nutrition deficiencies or chemical toxicity may cause amblyopia. Amblyopia can be inherited. In people with normal vision parallel light rays enter the eye and are bent by the cornea and the crystalline lens allowing for a crisp and clear image. For perfectly clear vision, incoming light is focused on one precise part of the retina rather than in front or behind it. It is similiar to a camera that has to be focused properly in order to take a clear picture.

This is the inability of the eye to focus a point object into a sharp image on the retina. A normal eye is in the shape of a sphere. The astigmatic eye is shaped more like a football or the back of a spoon. When light enters the eye it is refracted in more than one direction so only part of the object can be focused on at one time. It is a focusing problem causing asymmetrical blurring. Some directions of an image are more out of focus than others. In other words, objects are not uniformly blurred. Objects at any distance can be blurred, wavy, or distorted.

Color vision is found on the central part of the retina known as the macula. Therefore, any disorder affecting the macula may cause a problem with color vision. Although, most often these defects are a genetically inherited trait. Studies have shown it is more prominent in males than females. There are exceptions as to the causes of this condition, and in some instances, it can be acquired as a result of diseases or injuries. Reds, browns, olives and gold can be confused, and purples appear as blue. Colors like pastel pinks, oranges, yellows, and greens cannot be distinguished.

Convergence insufficiently is a common near vision problem. In order to see clearly and without confusion at close distances, both eyes must be aimed precisely at the object the person is trying to see. Unfortunately, not everyone develops this ability in childhood. Convergence insufficiency is a condition in which the eyes have a tendency to aim further away from the object they are supposedly viewing. It interferes with a person's ability to read, perform computer work, desk work and any type of activity at near distances. Prolong periods of close work can cause discomfort. This inaccuracy of the alignment of the eyes can result in eyestrain, blurred or doubled vision, poor judgment of depth, eye ache, headache, mental fatigue, short attention span, inability to concentrate, squinting, rubbing, closing or cover an eye, and trouble remembering what was read. Those with this condition may experience incoordination in their ability to catch a ball, stumbling on uneven surfaces like stairs, bumping into things, knocking over things, and poor posture when attempting to do things at close distances. The good news is that this condition responds well to treatment. Unfortunately, it seems that many people are not getting the help they need for this condition because of the lack of testing.

Farsightedness or hyperopia, the medical term to describe it, a condition in which distant images are usually seen clearly whereas close objects do not come into proper focus. The lens of the eye and cornea focus light into an image on the retina similar to that of the lens of a camera, which focuses light onto a film. In a hyperopic the light is focused behind the retina making the image appear blurred. With hyperopia people may experience symptoms like headaches after close work, eye strain, fatigue, or burning eyes.

Eye coordination is the ability of the eyes to work together as a team. Difficulties occur with eye muscle coordination when the eyes do not align or focus together as a team. This improper control of the eye muscles can result in symptoms such as crossed-eyes, poor focusing ability, double vision, fatigue, irritability, dizziness, difficulty in reading and concentrating or simply discomfort and headache from the extra effort required. Good eye coordination keeps the eyes in proper alignment. Eye coordination is a skill that must be developed. Eyes that are able to fixate, track, and jump from object to object efficiently are characteristics of good eye movement skills. In the classroom, normal eye movements allow rapid and accurate shifting of the eyes along a line of print while reading or from book to desk to blackboard. Individuals with poor eye movement skills tend to be poor readers. In sports, efficient eye movements contribute to eye-hand coordination, visual reaction time, and accurate tracking.

The success rate with treatment for achieving proper eye coordination is quite high. Treatments used for this condition include vision training, prisms, therapeutic spectacles, and multifocal lenses.

Myopia is the term used to describe shortsightedness. People with this condition have difficulty seeing objects that are in the distant clearly. Things that are far away appear fuzzy. They are unable to recognize people in the distance and read road signs. The lens of the eye and the cornea normally focus light on the retina, but in the case of the myopic eye light rays are bent. The light is focused in front of the retina, thus making the image blurred. Those with myopia have options for treatment which include eyeglasses, contact lenses, and for those that meet the criteria, refractive surgery.

There are age related changes of the eye which make it difficult to see small objects and perform up close tasks particular under poor lighting conditions. People find they need to hold reading materials at a farther distance to focus properly. Others find whether the page is moved close to the eyes or held at arm's length, the print is blurred and attempting to read is difficult causing frustration. When performing near tasks work such as sewing or computer work they may develop headaches from straining their eyes. This loss of near vision happens to all of us and is quite normal. It begins for most of us in the early forties and this is called presbyopia. It is a common eye condition when the lens loses the ability to focus over time. With age the lens gradually thickens making it lose its flexibility and the ability to change its shape. This loss of flexibility is the reason that focusing becomes more difficult. Over time the lens becomes harder and has less elasticity. There is no prevention for this condition. Fortunately, there is a solution to this problem, wearing corrective spectacle lenses brings the sharpness again to fine print.

When the peripheral vision, or side vision, is lost, but the central vision is not affected, it is referred to as "tunnel vision." Thus, the vision is like looking through a tunnel, or through a paper towel roll. Glaucoma and stroke can cause this disorder.

Each year over three million go blind from ultraviolet (UV) exposure to their eyes. The UV radiation present in sunlight is not useful for vision. From this statistic it is obvious that our eyes are susceptible to damage from this UV light.

There are three types of UV radiation: UVA, UVB and UVC. UVC rays do not pose any threat, as they are absorbed by the ozone layer. However, exposure to UVA and UVB rays can have adverse effects on your eyes and vision. Short- and long-term exposure to these dangerous rays can cause significant damage. UV radiation can also be given off by artificial sources like welding machines, tanning beds and lasers. Scientific research has also definitely linked several eye diseases from the damage of the UV light. These diseases include cataract, macular degeneration, snow-blindness, pterygium and skin cancer, to name a few. More than ninety- nine percent of UV radiation is absorbed by the anterior structures of the eye although some of it does reach the light-sensitive retina. Quality sunglasses act like a sunscreen for our eyes. They have ultraviolet coatings to block UV light from reaching the eyes and surrounding skin.

Recently one of the most significant changes to the modern office has been the increased use of computers in the workplace. As a result we spend a lot more time using a computer screen or computer monitor. As with many success stories, there have been some unexpected problems. Eye strain or near visional stress problems are among the most frequent complaints while using a computer monitor. In order to alleviate some of these problems, it is usually desirable for the computer screen brightness to be three to four times greater than ambient office lighting. Whenever possible a lower level of general room lighting should be maintained where computers are used. The use of well-designed furniture and proper positioning of the hard copy can help prevent or reduce computer operator discomfort induced by computer use. Remember that rest breaks are important because computer operation often requires intense concentration.

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