The purpose with this post is to enable contact lens users to understand prescriptions and use this knowledge to easily locate and buy the same or equivalent contact lenses online that was originally fitted by the optician.
A way to easily locate the correct type and make of contact lenses suitable to your eyes, is to use the sample lenses (trials supplied by your optician). With the original lens containers and/or packaging available, you can compare measurements such as:
- Material (e.g Etafilcon A)
- Water content (e.g. “55%”)
- Power (SPH)
- Base curve (BC)
- Diameter (DIA)
- Cylinder (CYL)
- Addition (ADD)
Use the search field on Visiondirect.co.uk and type the material name (e.g. “nelfilcon A“) to perform an effective search. If you find several products, narrow down your search by comparing the remaining parameters.
Find your contactsby reading your contact lens prescription (the paperwork supplied by your optician). Contact lens prescriptions differ from spectacles prescriptions in the following ways:
- If BC (base curve) and DIA (diameter) are missing, then you can be fairly certain that you are looking at a glasses prescription.
- If your optician failed to mention that you need corrective toric lenses forastigmatism*, but you still see the values CYL (cylinder) and AXIS (measurement in degrees) printed on your paperwork, there is a risk you are looking at a spectacles prescription. When you do need toric contact lenses, the make of lens, SPH, BC and DIA are normally supplied in addition.
- The manufacturer, make and type of your contact lenses should normally be stated on the contact lens prescription (however, since some opticians do not take the time to make a note, this is not always the case.)
- SPH or SPHERE is a measurement for the primary power or strength needed. For myopia (nearsightedness) the value is negative (-) and for hyperopia (farsightedness) the value supplied is positive (+).
- ADD is an additional power and refers to presbyopic patients; one power (SPH) to correct nearsightedness and another power (ADD) to correct farsightedness. This is normally corrected by using varifocal (bifocal or multifocal) contact lenses orspectacles.