• The workings of the eye
• Short-sightedness
• Long-sightedness
• Cylinder deviations
• Senile vision 
    

The workings of the eye.

The eye consists of a number of different parts, each with its own specific purpose. Together, these parts enable us to see.
Light that enters the eye first passes through the cornea. The transparent cornea refracts the rays. Via the pupil, the light then reaches the interior of the eye. Via the natural crystalline lens, which further refines the refractive effect, the light rays reach the retina.
The retina consists of photosensitive cells which convert light into “electrical signals”. These signals are sent to the brain via the optic nerve. The image is perceived.
 
An incorrect ratio between the strength of the cornea and the intra-ocular lens on the one hand and the length of the eyeball on the other hand, may result in a blurred image on the retina. This is referred to as refractive deviation. This kind of deviation can be corrected with glasses, contact lenses or refractive surgery.
  

Short-sightedness

 In short-sightedness nearby objects are in focus while distant objects are blurred. This is because light rays converge in front of the retina instead of on the retina. This results in a blurred image.



Short-sightedness can be corrected with “minus” or concave lenses. The convergence of light rays is shifted backwards until these rays actually meet on the retina. The image becomes focused once more. Short-sighted people who wish to go through life without having to wear glasses or contact lenses can have an Artisan or Artiflex lens implantation.  
  

Long-sightedness

In long-sightedness distant objects are in focus while nearby objects are more blurred. This is because light rays from nearby converge behind the retina instead of on the retina. This causes a blurred image.



Long-sightedness may be corrected with plus or convex lenses. The convergence of light rays is shifted forwards until these rays actually meet on the retina. The image becomes focused once more. Long-sighted people who wish to go through life without having to wear glasses or contact lenses can have an Artisan implantation. 
  

Cylinder deviation

In a cylinder deviation, the cornea does not refract the light in the same way in all directions. This results in a blurred image.

This is because the cornea does not have a perfectly spherical shape. It is more convex in one direction than in the other (rugby ball).
Cylinder deviations frequently occur in combination with short- or long-sightedness. Artisan and Artiflex lenses are available with a cylinder correction. 
  

Senile vision

The accommodative power of the eyes (their ability to focus) diminishes with age. The natural crystalline lens is unable to assume a sufficiently convex shape in order to focus on nearby images. Senile vision (presbyopia) can be corrected by using reading glasses. Artisan and Artiflex lenses offer no solution for presbyopic eyes. Neither does laser treatment.