According to the US laws, patients are entitled to get the prescriptions of their eyes after paying for the eye examinations. With such a valid and updated prescription, eyewear customers can resort to any other resources for prescription eyeglasses. They are no longer limited to buy corrective spectacles from eye care practitioners. Without seeing an eyeglass prescription, some people may wonder what kinds of information are described. But another problem is that many people can not understand items listed in a prescription. In order to know details of personal visual condition, it is really important to learn how to read eyeglass prescriptions. In general, an eyeglass prescription is closely associated with refractive errors. In other words, different eyeglass prescriptions are used to describe respective visual problems or visual conditions of individuals. Being able to interpret eyeglass prescriptions is a useful skill.
In fact, eyeglass prescriptions written by eye doctors worldwide come in a standardized format with standard notation. There are some basic symbols and numbers on each of the eyeglass prescriptions. In most cases, there are two items in a prescription, each of which describes one of the two eyes. It is necessary to give a lesson in Latin in advance. The letters OD stands for “oculus dexter”, which means the right eye in English. And the letters OS represents “oculus sinister”, corresponding to the left eye. There is also OU which is short for “oculi uterque” and means both eyes. Now, it is time to give an example of the item for the right eye, like OD: -2.00 -0.5 X 180. The first number is actually the “sphere” part of the prescription, which indicates nearsightedness or farsightedness. Remember that a minus sign represents a negative powered lens used to correct nearsightedness. And a positive sign means the patient needs positive powered lenses to correct farsightedness. What’s more, the further away from zero this number, the worse the patient’s eyesight. For instance, -3.0 indicates a higher degree of nearsightedness than -2.0.
The second number -0.5 is used to describe the “cylinder” part of a prescription, which can also be interpreted as astigmatism. This number measures in diopters the degree of astigmatism, with a bigger number indicating a higher degree. And the last number “X 180” represents the location of the most positive meridian in an astigmatic eye. For individuals who do not have astigmatism, numbers including -0.5 X 180 are needless. These numbers are replaced by DS, which indicates the eye is totally spherical in nature without astigmatism. How to read eyeglass prescriptions sometimes also involves a third item beginning with symbols “ADD”, which represent the “added” power that is needed by old patients to view close objects.