Spherical soft contact lens: corrects for near or farsightedness. They are ideal for patients that have little or no astigmatism in their prescription.

Example of a “spherical” nearsighted prescription:

John Doe

Sph            Cyl                Axis                  Add

OD            -1.00

OS            -1.50

If you also have astigmatism, you will have Cyl in your prescription. The question is should you wear a Toric lens or can you wear a spherical lens instead. The answer isn’t straight-forward but there is a general rule of thumb: If the sphere power is 3 times or greater that your cylinder power (a ratio of 3:1 or greater between sphere:cylinder) a spherical lens may give you clear enough vision but may not be “20/20” but very close to it. Currently, Toric contact lenses only correct for -0.75 Cyl or higher & therefore Cyl amounts of -0.50 & -0.25 will need to be corrected by a spherical lens. So how do you pick the correct sphere power if you have a little astigmatism in your prescription ? The answer is you take ½ of the amount of the Cyl & add it to your sphere power.

Example of a “spherocylinder” prescription:

Jane Doe

Sph               Cyl            Axis             Add

OD              -1.00.         -0.50.             180

OS              -1.50.         -0.50.             170

Calculation of contact lens sphere power:

OD  -1.00 (sphere) + ½ -0.50 (Cyl) = -1.25 Sphere

OS  -1.50 (sphere) + ½ -0.50 (Cyl) = -1.75 Sphere

Do not worry about the “axis” numbers, they are not needed for spherical lenses

Toric soft contact lens: corrects for astigmatism prescriptions of -0.75 or higher. Astigmatism is like having two different curves or prescriptions in one eye & require a more specialized fit by an eye care professional than spherical lenses due to the importance of lens rotation & stability. A poorly fitted Toric lens may rotate too much & create intermittent blurred vision.

Example of a “spherocylinder” prescription requiring a Toric contact lens:

John Doe

Sph            Cyl            Axis               Add

OD             -1.00         -1.25               180

OS             -1.50         -1.75               170

Bifocal soft contact lens: (also known as progressive or multifocal) corrects for an age related vision change called presbyopia, allowing for improved near & distance vision. If you have an “Add” power in your prescription, you are likely above the age of 40 & may benefit from a multifocal or bifocal contact lens design. These lenses are also more challenging to fit than spherical lenses & may require a specialized fit from you eye care professional.

Example of a multifocal prescription:

Jane Doe

Sph            Cyl                Axis                  Add

OD            -1.00.                                     +1.75

OS            -1.50.                                     +1.75

RGP (Rigid Gas Permeable) also known as a “hard” contact lens is an older technology that requires a specialized fitting by an eye care professional. With a correct prescription & fit, these lenses provide excellent vision & are very breathable. However, they tend to be more challenging to wear due to comfort issues, especially for individuals that are use to wearing soft contact lenses.Today RGP’s are typically worn by people that have “irregular” prescriptions that can’t see as clear with soft lenses or glasses due to corneal diseases such as keratoconus. Most eye doctors will recommend soft contact lenses for patients who are looking to be less dependent on eye glasses & who have normal ocular surface health. RGP lenses are not available for purchase at BC Contact Lenses.