RefraCard
Can I use my glasses prescription for contact lenses?
No — and not because of red tape. A contact lens sits directly on the eye; a spectacle lens sits about 12 mm in front of it. That distance changes the power required, and the contact lens prescription contains measurements a glasses test never takes.
Vertex distance — why the power differs
Lens power depends on how far the lens is from the eye. Move the same lens closer and its effective power changes. Below about 4 dioptres the difference is small enough to ignore; above that it becomes real:
- −4.00 D in glasses ≈ −3.75 D in contacts
- −8.00 D in glasses ≈ −7.25 D in contacts
- The correction runs the other way for plus lenses — a hyperope needs more power in a contact lens, not less
So a strong prescription copied straight across will be noticeably wrong, and wrong in a direction that depends on the sign.
What a contact lens prescription has that yours does not
The curvature of the back of the lens, in millimetres (commonly 8.4–8.8). It has to match your cornea: too flat and the lens moves too much, too steep and it grips.
The lens width, typically 13.8–14.5 mm. It determines how the lens sits relative to the edge of the cornea.
Part of the prescription, not a shopping preference — BC and DIA mean different things between manufacturers, and oxygen transmission varies by material.
Toric lenses (for astigmatism) add their own cylinder and axis, which are not simply your spectacle values; multifocals add an addition expressed in the manufacturer's own low/medium/high steps.
Keep both
They are two different prescriptions describing the same eyes, they expire on different schedules, and you will be asked for whichever one you do not have to hand. Storing both against the same eye, with dates, is the point of a record rather than a drawer.