Eye Care

Our eyesight is a precious gift and we can care for it better if we understand how vision works. The main parts of the eye which work together to give clear vision are:

  • The cornea – clear front covering of the eye, which is curved and refracts (bends) incoming light.
  • The lens – behind the iris (colored part), which further bends light, causing it to focus on the retina.
  • The retina – the inside back eye surface, which is filled with light-sensitive cells. They receive the refracted light, with its image information, and send it to the brain.
  • The optic nerve – which connects the retina to the brain’s vision center, and carries image information for the brain to interpret.

20/20 Vision
In a 20/20 eye, the cornea and lens together bend light correctly to make it focus on the retina. The first “20” refers to the distance of 20 feet. The second number varies according to how close to “normal” your vision is. If what you see at 20 feet compares in clarity to what an average person can see from 40 feet away, you have 20/40 vision. If what you see at 20 feet compares to what an average person can see from 15 feet, you have 20/15 vision, which is better than 20/20.

These numbers refer to visual clarity – but there are other important aspects to good vision too. They are:

  • Peripheral (side) vision
  • Night vision
  • Eye coordination
  • Color perception
  • Depth perception

Refractive Error
Several common vision problems arise from the way the eye bends (refracts) light. In a normal eye, the light is refracted so as to focus in a single point on the retina. This gives a clear image. When refractive error is present, the light rays are bent in ways that do not come to a single focus on the retina. Instead, they focus in front of it, or behind it, or in more than one place.

Types of Refractive Error
There are three common types of refractive error, all of which can be corrected by a LASIK procedure.

  1. Myopia (Nearsightedness)
    A myopic eye cannot see clearly in the distance, although it sees clearly at close range. The cornea is too steeply curved, so that it refracts light from distant objects too much and focuses it in front of the retina. This is a common hereditary eye condition and tends to develop at the age of eight or nine.

  2. Hyperopia (Farsightedness)
    A hyperopic eye cannot see clearly at close range, but can see distant objects well. This type of eye has a flatter cornea, too flat to refract light coming from close up objects. Instead of focusing on the retina, this light focuses behind the retina, giving blurry vision.

  3. Astigmatism
    An astigmatic eye has a misshapen cornea which refracts light at more than one angle. This focuses the light in more than one place on the retina, distorting vision at all distances.

  4. All of these refractive errors have traditionally been corrected with glasses or contact lenses, but for many people, LASIK is a permanent and better alternative.

Is Presbyopia a Refractive Condition?
No, presbyopia is not caused by the corneal curvature. It is an age-related loss of near vision which begins to be evident at about age 40. The lens becomes less able to change its curvature and cannot focus light clearly at close distances. Reading glasses become necessary, although distance vision remains clear. The aging eye may gradually lose its distance clarity also, so that bifocals become necessary.

Caring For Your Vision
As is the case in all areas of health care, early detection of any problem gives the best chances of treating it effectively. Regular eye examinations are important. They enable your ophthalmologist to give you vision correction promptly, and to monitor your eye health. Many eye diseases can be treated or managed so that vision loss is prevented.