I/ Presbyopia is a natural change in vision with affect everyone. By about the age of 40, the crystalline lens has lost of its suppleness and does not bulge sufficiently. The eye gradually loses its ability to focus. Like a badly adjusted camera, the eye no longer focuses the image correctly. Presbyopics have difficulty seeing thing up close.
I.2 Presbyopia treatment
The optimum solution for correcting presbyopia is progressive lenses. These are designed to restore clear and accurate vision at all distances, without needing to constantly changes glasses. The upper the part of the lens makes it possible to see thing far away, the central part to see the middle distance and the low part to see close up.
II/ Myopia ( nearsightedness)
Myopia is mainly caused by the eye being too long, meaning the distance between the cornea and the retina is too great. In such cases, the image forms just in front of the retina, which means a myopia has trouble seeing thing far away, but not close up. The more the person is nearsighted, the more he/ she must approach an object to distinguish it clearly.
Nearsightedness symptoms may include:
II.2 Myopia Treatment
Nearsightedness can be corrected with glasses, contact lenses or refractive surgery. Depending on the degree of your myopia, you may need to wear your glasses or contact lenses all the time or only when you need very clear distance vision, like when driving, seeing a chalkboard or watching a movie.
III/ Hyperopia (farsightedness)
A farsighted patient often has a problem for distance and close up object . This result from light being focused behind the retina. Because the focus system for the eye is not strong for the length of the eye.
Symptoms of farsightedness may include:
III.2 Hyperopia Treatment
To correct farsightedness you must change the way the light rays bend when entering your eye. Glasses, contact lenses, or refractive surgery can all be used to correct farsightedness.
Astigmatism is an eyesight problem mainly cause by an incorrect curvature of the cornea. The cornea is slightly shaped like a rugby ball instead of being spherical like a football.
Patients with astigmatism have imprecise near and far vision and can not see contrasts clearly between horizontal and vertical or oblique line. Astigmatism may be combined with other eyesight problem such as myopia, hyperopia or presbyopia. A person with astigmatism generally sees all objects in a blur, or with distortion.
IV.2 Astigmatisms treatment
Astigmatism is corrected by mean of a toric lens ( of varying thickness at the edge). This lens is designed to compensate the curvature of the cornea according to axis of the astigmatism. The difference in thickness at the edge of the lens is therefore greater the stronger the astigmatism.