What does the numbers mean on contact lenses?
DIA: Diameter – the distance across the surface of the contact lens, measured in millimeters. This number is usually between 13 and 15 and determines where on your eye the contact lens will sit.
How do you know what strength contact lenses you need?
You’ll find that the cylinder number on a contact lens prescription is always a minus number. This indicates the extra power you need for astigmatism correction. A higher number denotes a more severe level of astigmatism. The cylinder value for a glasses prescription on the other hand can be a plus or minus.
What does 1.50 mean on contacts?
The second number -1.50 identifies your degree of astigmatism. The number can be written either with a (+ sign) or a (- sign). The third number 180 identifies the axis, which indicates the direction of your astigmatism.
What does 8.4 mean on contacts?
A BC of 8.4 mm of radius is more curved, and therefore a tighter fit, than 8.8 mm base curve. People who have steeper corneas require tighter fitting contacts. If a contact is too loose, it may be uncomfortable, fold, or come right out.
What is the difference between 14.0 and 14.2 diameter contacts?
14.0mm and 14.2mm contacts
In fact, there is not much difference between these two. Some manufacturers only make 14.2mm diameter contacts, and some others produce 14.0mm diameter contacts. … Many 14.0mm contacts users use 14.5mm or 14.8mm contacts to demonstrate dolly effects on their eyes.
What does D mean on contacts?
Sphere (SPH): The amount of lens power, measured in diopters (D), which corrects nearsightedness or farsightedness. If the number under this heading features a minus sign (–), this means you’re nearsighted; if it has a plus sign (+), this means you’re farsighted.