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Eyes and Vision

How the Eye Works

Light entering the eye first comes into contact with the tear film, which protects and bathes the corneal surface. The cornea is a transparent structure at the very front of the eye that bends incoming light. It provides most of the eye’s optical power or light-bending ability. Beyond the cornea is the iris, a colored muscle that contracts and relaxes depending on light levels to adjust pupil size. Aqueous humor fills the space between the iris and cornea, providing nourishment. Aqueous fluid is also responsible for the pressure within the eye.

Once light is focused through the pupil by the cornea it is finely focused by the crystalline lens, which changes shape allowing focal adjustment of light on to the retina. This adjustment is known as accommodation and begins to diminish in our fourth decade of life. This process is known as presbyopia.

After light is finely refracted by the crystalline lens it enters the vitreous humor before striking the light sensitive layer of cells known as the retina. Embedded within the retina are millions of light sensitive cells, including rods and cones. These receptors do not sense pain but rather light. Rod photoreceptors are used in poor light conditions and are found in the peripheral retina. Cone photoreceptors are densely packed within the macular region, which is responsible for fine detail, central vision. Cone receptors sense blues, reds and greens separately and are sensitive in bright environments.

Most vision problems are due to an error in how our eyes refract light. In myopia, or nearsightedness, light rays come to a focus in front of the retina. In hyperopia, or farsightedness, light rays focus behind the retina. The corneal curvature is irregular in astigmatism, causing light to be focused at more than one point, resulting in blurred vision at all distances. Once light is focused on the retina the image or visual stimulus needs to be processed and interpreted.

Children’s Vision

It is well known that 70-80% of what we learn passes through the eyes and visual system on its way to the brain. Therefore, when the visual system is not functioning properly, learning and participation in sports and recreational activities can suffer. There are many other factors that enable a child to not only see clearly but also process what is seen. In addition to clear distance vision, the ability to focus near objects such as books is important as is binocular coordination, eye movement skills, peripheral awareness, eye-hand coordination and color vision.

Vision screenings at school are important but they are not a substitute for a thorough eye examination and often offer a false sense of security regarding functioning of the visual system.

Be alert for symptoms that may indicate your child is having difficulty seeing. Watch for any of the following in your child:

  • Frequently loses his or her place while reading
  • Avoids near work
  • Holds reading materials closer than normal
  • Rubs their eyes
  • Complains of headaches, particularly later in the day
  • Develops a head turn or tilt
  • Closes or covers an eye while reading
  • Makes reversals while reading or writing

Reading and Vision

The demands placed on the eyes and visual system during reading can be significant. Success in school depends greatly on reading and comprehension, which in turn is dependent on the eyes and visual system. Such success is contingent on a child’s ability to see clearly as well as several other factors.

  • Tracking skills are especially important in reading as the eyes move from word-to-word following a line of print. This is called a saccade. Children with tracking problems will often lose their place, skip or transpose words, and have difficulty with comprehension.
  • Focusing, or accommodation, allows us to see images clearly at near. This visual skill is required for reading and shifting focus quickly. Difficulty focusing leads to progressive blur with near work over extended periods of time, fatigue and eye strain.
  • Visual perception is the ability to interpret what is seen and can be divided further.
  • Visual discrimination is the ability to determine characteristics and features among similar objects. In reading, this allows us to distinguish between similarly spelled words.
  • Visual memory is the ability to recall characteristics of a particular object and helps with reading comprehension.
  • Visual sequential memory is the ability to remember characteristics in correct order and is particularly important in spelling.
  • Spatial recognition is the ability to distinguish differences among similar objects and relates to problem solving and conceptual skills.
  • Visual closure is the ability to visualize a complete whole when given incomplete information. This skill allows quick reading and comprehension.
  • Figure-ground allows a reader to perceive and locate an object within a busy field without getting confused by surrounding images. Poor figure-ground leads to easy confusion when looking at a page with a lot of print, reducing concentration.
  • Visual motor integration is critical to eye-hand coordination and consists of gross motor and fine motor coordination.
  • Gross motor coordination allows the visual system to adjust to changing surroundings, allowing for balance and coordination. It is beneficial in athletics.
  • Fine motor coordination is detail-oriented and is useful in such tasks as handwriting.

Sports and Vision

Your vision is composed of many interrelated skills that can affect how well you play your sport. Exercise and practice can increase your visual fitness and accuracy just as it improves speed and strength. Because all sports have different visual demands, an optometrist with expertise in sports vision can assess your unique visual system and recommend the proper eyeglasses or contact lenses.

We work hard to excel in sports and equip ourselves and our children with the best equipment in order to get an edge over our opponent. Have you ever wondered whether or not you see as well as your opponent? When gearing up for competition, you are not physically prepared until you are visually prepared. The optometrists at Williamsburg Eye Care realize that if you are not visually fit you are at a disadvantage before competition even begins. Regardless of who the opponent is, don’t place yourself or your child at a disadvantage prior to competition; have their vision and visual system examined by professionals, giving you the edge.

Eye protection should also be a major concern to all athletes, especially in certain high-risk sports. Thousands of children and adults suffer sports-related eye injuries each year, and nearly all can be prevented by using the proper protective eyewear. Especially for sports played outdoors, appropriate sunglasses are a must, and some sport-specific designs may even help you improve your game. Ask us which type is best suited for your favorite sport.