Healthy Eye Guide
Because of contact lenses, people with vision defects that do not see clearly objects from near, afar and the middle distance are not condemned to the use of one or more pairs of glasses. Vision defects can occur to all kind of people: young students, old pensioners, active professionals, sportsmen can have problems with their vision regardless of aging and lifestyle.
Vision defects occur when the eyes do not capture the light within the retina correctly, leading to an unclear vision in so doing. The most grave vision defects are Nearsightedness, Farsightedness, Astigmatism and Presbyopia. To all the defects mentioned above, which can occur even simultaneously, contact lenses are the best solution, as they intervene between the eyes and the external space to restore the proper qualities of eyes with refractive errors.
The articles at Healthy Eye Guide of Optic Shine:
The parameters of contact lenses
Contact lenses differ because of period of use, expiration date, color and other parameters that only oculists can determine. In fact, it is important to select contacts with proper diopters that properly suit the users’ eyes and provide users with keen vision and high degree of comfort. Spherical power, curvature, diameter, cylindrical axis, hydration degree and gas permeability are the most important parameters users must consider prior to purchase any pair of contact lenses.
The spherical power, also known as optical power, differs from the power of glasses. It is tied to the distance from eyes. Therefore, the spherical power of contacts for farsighted users must be higher than the one of glasses. Otherwise, the spherical power of contacts for nearsighted users must be definitively lower.
Curvature is the convexity angle of contacts. It is tied to the adaptation of the contacts with eyeball, as too adherent to eyes contacts block the flow of natural tears and lead users to feel discomfort in so doing. A checkup by an oculist is necessary to measure the curvature through test lenses.
Contacts must entirely cover the cornea of users with no deformations.
They are determined for users with astigmatism in order to correct their vision defects in a proper and efficient way.
It is tied to the quantity of water within the material the contacts are made of. Though a proper hydration degree amounts 38-74%, the higher the hydration degree is, the better is in order to provide users with comfort and keen vision.
Eyeballs need natural oxygen to function properly. Oxygen permeability – Dk – is tied to both hydration and the thickness of contacts. In order to provide users with proper oxygen permeability, contacts must be neither too thick, nor too thin. Moreover, contacts must combine proper hydration degree with proper thickness.