Most people suffer from defects of refraction. Many people need glasses to see clearly near or remote objects.
Myopia – description | causes
Hyperopia – description | causes
Astigmatism – description | causes
Presbyopia – description
How to understand a prescription for glasses?
A prescription for glasses, exemplified on the image on the right side, consists of numeric values that may seem difficult to interpret. The term OD (Oculus Dextrum) refers to the right eye and OS (Oculus Sinistrum), to the left eye.
The Sphere indicates the degree of myopia or hyperopia. The plus sign (+) indicates hyperopia and the minus sign (-) indicates myopia.
The Cilinder is the measurable degree of astigmatism of the central cornea.
If you have astigmatism, your cornea is shaped as a baseball or like the protruding surface of a spoon. The orientation of this surface can vary from person to person.
The Axisdescribes the orientation in degrees from the horizontal axis. The coordinate system for the prescription is between 0 and 180 degrees, with 90 degrees on the vertical axis, or in the position 12 o’clock.
