Contact Lens Glossary
To help you understand your contact lens prescription and to assist with information required for ordering contact lenses online, see our definition of contact lens terms below:
Contact lens parameters
- OD: Right eye parameters.
- OS: Left eye parameters.
- SPH: Sphere indicates the amount of lens power prescribed for short-sightedness or long-sightedness.
- CYL & AXIS: A Cylinder (CYL) and Axis is required to correct Astigmatism.
- ADD: Addition provides magnifying power for reading, progressive and bifocal lenses.
- Diameter: Usually between 13.8mm and 14.5mm. It’s the size of the contact lens.
- Base Curve (BC): Curvature or steepness of the lens usually between 8.1 and 9.0.
- Spherical lens: Corrects short-sighted vision (minus) and long-sighted vision (plus).
- Multifocal lens: Corrects distance and near vision for people generally above 43 years of age. Addition parameters are required for this lens. It’s also known as a presbyopia lens.
- Toric lens: Corrects astigmatism. Cylinder and Axis required for this lens.
- Coloured lens: Prescription and non-prescription for cosmetic use.
- Plano lens: Zero value (no prescription).
- Daily lens: Used once and discarded.
- 2 Weekly lens: Used for 14 days.
- Monthly lens: Used for 30 days.
- Extended wear lens: Can be worn over night.