Myopia is a condition that occurs when the eyeball is too long or the eye’s focusing mechanism is too powerful and light rays are focused in front of the retina. People with this condition can see clearly up close, but not at a distance.
Hyperopia occurs when the eyeball is too short from front to back or the eye’s focusing mechanism is too weak, causing light rays to be focused behind, rather than on the retina. People with hyperopia have difficulty seeing objects close up.
Astigmatism is characterized by an irregularly shaped cornea that causes light images to focus on two separate points in the eye, creating a distorted image.
WHAT IS THE DIFFERENCE BETWEEN SOFT AND HARD CONTACT LENSES?
Soft contact lenses are made of a soft plastic and tend to be more comfortable than hard contact lenses, because they hold more water. Soft contact lenses are usually disposable and can be thrown away after a short period of use, generally every two to four weeks or daily, depending on the contact lens. Due to freshness of a new pair of contact lenses, the chance of infection decreases. However, since soft contact lenses are more absorbent than hard contact lenses, disadvantages to wearers include the likelihood that more pollutants like lotion or soap can penetrate through the contact lens and irritate the eyes. Soft contact lenses also tear more easily.
Hard contact lenses are more rigid than soft contact lenses and therefore more durable. Hard contact lenses are made with silicone polymers, allowing oxygen to circulate to the cornea of the eye. Compared to soft contact lenses, hard contact lenses maintain their shape better and often allow clearer vision for some types of corrections. They are more durable and are easier to take care of, but are far less comfortable than soft contact lenses.