How Your Eye Works

//How Your Eye Works
How Your Eye Works2017-11-09T11:15:12+00:00

Vision begins when light rays are reflected off an object and enter the eyes through the cornea, the transparent outer covering of the eye. The cornea bends or refracts the rays that pass through a round hole called the pupil. The iris, or coloured portion of the eye that surrounds the pupil, opens and closes (making the pupil bigger or smaller) to regulate the amount of light passing through. The light rays then pass through the lens, which actually changes shape so it can further bend the rays and focus them on the retina at the back of the eye.

The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their distinct shapes. Cones are concentrated in the centre of the retina, in an area called the macula.  In bright light conditions, cones provide clear, sharp central vision and detect colours and fine details.

Rods are located outside the macula and extend all the way to the outer edge of the retina.  They provide peripheral or side vision.  Rods also allow the eyes to detect motion and help us see in dim light and at night.  These cells in the retina convert the light into electrical impulses.  The optic nerve sends these impulses to the brain where an image is produced

What is Myopia or Shortsightedness?

Myopia or short-sightedness is where close up objects are clear, but long distance objects become blurry.  This occurs when the eye is too long in relation to the curvature of the cornea.  Light rays do not focus on the retina but instead in front of the retina. Common symptoms of myopia: squinting the eye lids together when trying to make distance objects look clearer, such as details on the blackboard, signs or score boards.

  • Myopia tends to first develop during adolescence as they eye grows to full size.
  • Myopia occurs due to hereditary factors or due to environmental factors
  • Myopia affects over a third of our population.
  • Myopia can be corrected with contact lenses, glasses or refractive surgery.

What is Hyperopia or Longsightedness?

Hyperopia or long-sightedness is when you can see things in the distance but have trouble up close.  This occurs when the eye is too short in relation to the curvature of the cornea.  Light rays do not focus on the retina, but instead focus behind the retina.

Common symptoms of hyperopia: the extra effort required to bring the image clear at all distances results in eye strain and fatigue. This may manifest itself as headaches, tired or aching eyes.

Hyperopia can be corrected with contact lenses, glasses or refractive surgery.

What is Astigmatism?

Astigmatism is an eye focusing problem and occurs where the cornea is irregular in shape.  A person with astigmatism generally sees all objects, near or far, in a blur or with distortion.  This creates a distorted or uneven image because of the unequal bending of light rays entering the eye.

Astigmatism can accompany long-sightedness or short-sightedness. Astigmatism affects over a third of our population.

Common symptoms of uncorrected astigmatism can include tired eyes, eye strain, headaches and distorted or blurred vision; particularly after reading for some time.

Astigmatism can be corrected with contact lenses, glasses or refractive surgery

What is Amblyopia or ‘Lazy Eye’?

Amblyopia  also known as “lazy eye” generally occurs in only one eye. Amblyopia usually results from poor eye co-ordination, a turned eye, or one eye requiring a far greater vision correction than the other.

If untreated, reduced vision occurs, even with prescription glasses or contact lenses because one eye is being used less than the other.

If detected early enough in life, this problem can usually be successfully treated using a variety of methods, if left untreated the eye can end up severely visually disabled.

What is Presbyopia?

Presbyopia is a gradual loss of the eyes near focusing ability. It is part of the normal ageing process we all experience.

Presbyopia is caused by a natural hardening of the lens inside the eye. By early to mid forties the eye strains to focus on near tasks. Common symptoms include difficulty reading small print, particularly in poor light. Holding reading material further away (arms not long enough).  Other symptoms include tired aching eyes and possibly increased headaches.

Presbyopia can be corrected with contact lenses, glasses, laser or refractive surgery.

Visit, call or make an appointment on-line with one of our centres if you are concerned about the health of your eyes or would like to book an appointment for an eye examination.