Deciphering Your Contact Lens Prescription
There is, more often than not, a distinct difference between an eyeglass and a contact lens prescription. Moreover, considering that a contact lens is placed directly on the eye it will most likely need to have its power adjusted accordingly. This is more evident in moderate to higher prescriptions. In addition, the actual fitting parameters need to be documented. Here is a sample contact lens prescription:
O.D. -2.00 8.6 14.0 Brand
O.S. -1.50 8.6 14.0 Brand
Letters and Numbers - The first thing we see are the initials O.D. (Ocular Dexter) for the right eye and O.S. (Ocular Sinister) for the left eye. Next we see -2.00 and -1.50 which represents the power of a lenses. Some people with slightly higher prescriptions may notice that there is a power variance between their spectacle prescription and contact prescription. This is to compensate for something called vertex distance. The closer or further a lens is moved the more the power will change. In the case of an individual with a plus or magnifying lens the closer the lens is moved toward the eye the weaker it will become. This individual may require a little more power for their contact lens prescription. In the case of a person who wears a minus or minifying lens the closer the lens is to the eye the stronger it will become so the wearer would need a little less power.
Additional Parameters - After the lens power we come to the lens base curve. With contact lenses, the base curve is the curve of the back surface of the lens within the optical zone of the lens. Contact lens base curves are designated in millimeters (e.g. 8.3mm, 8.6mm, 8.8mm). This number is the measurement of the radius of curvature in millimeters of the inside curve. The doctor tries to match the lens curvature to the patient's cornea. Furthermore, because of their flexible nature soft lenses tend to fit more corneas with a smaller number of base curves. Rigid contact lenses on the other hand need to have a more accurate fit because of their rigid nature a lens that is too steep or too flat may cause discomfort.
After the base curve we come to the lenses diameter in millimeters. Like base curves soft lenses come in a limited amount of diameters due to their rather forgiving nature when it comes to fitting. Again like base curves the doctor will be more precise in specifying the diameter of a rigid contact lens.
Contact Lens Brand(s) - Lastly we have the brand of contact lens. The doctor chooses which lens is best for you based on several factors including: tear quality and quantity, intended wearing schedule, work and hobby conditions and specific vision requirements. The lens that has been chosen by your doctor meets your particular individual requirements.
For further information or to book an appointment please call any of our three Rochester, NY Cornerstone Eye Associates locations in gates (585-328-0153), Brighton (585-244-2200) or Irondeqouit (585-266-7880).
Cornerstone Eye Associates - your VISION for LIFE