Your glasses prescription may seem like a cryptic code but fear not! Understanding what those numbers and abbreviations mean is crucial for ensuring you get the right lenses to correct your vision. Keep reading as we break down these different elements of your prescription and help you navigate through the world of optical jargon.
Sphere (SPH): Power of the Lens
SPH stands for the spherical error and shows whether you have myopia (short-sightedness), or hypermetropia (long sightedness). The number shows the strength of lens you need, commonly, this number will be different for each eye and a smaller number means the condition is milder. PL is short for plano and means there is no refractive error in that eye. A plus value indicates that you are long-sighted which means you find it hard to see things close to you and a minus value shows that you find it hard to things that are far away without glasses.
Cylinder (CYL) and axis
If you have astigmatism, a common condition where the eye is not perfectly round, you’ll find a cylinder (CYL) value. This denotes the degree of astigmatism correction needed. Astigmatism results from having a cornea that is not perfectly spherical. The axis works in conjunction with the cylinder value and specifies the angle at which the astigmatism correction should be placed on the lens. This number shows the angle in degrees from 1 to 180. A higher number for the axis doesn’t mean that your prescription is stronger, it describes the position of the astigmatism. An empty box means there is no astigmatism and your eyes are perfectly spherical. A low number like 0.25 means your eyes are not quite round and a higher number, such as 3.00 indicates your eyes are quite oval.
Prismatic power (prism) and base
Prism is short for prismatic power and is used to correct problems with binocular vision, where both your eyes may have some difficulty working together. Prism lenses will provide the correction you need and help prevent double vision or headaches. Base simply indicates to the lab where to put the prism in your glasses.
Add: Reading Addition
If you’re over the age of 40 and experiencing presbyopia (difficulty focusing on close objects), you may see an “add” value. The intermediate add refers to the additional strength of lenses you may need to bring a ‘mid-range’ distance in focus (usually the distance to a computer screen you are viewing) and the near add is usually for close tasks such as reading. This number is added to the spherical error part of the prescription to give the actual near or intermediate prescription.
DS: Diopters Sphere
The term “DS” is occasionally used and stands for “Dioptre Sphere.” It indicates that there is no cylindrical power in the prescription, meaning the entire lens has a uniform power to correct near-sightedness or farsightedness.
BVD: Back vertex distance
BVD stands for back vertex distance and is the distance in mm between the front of your eye and the lens of your glasses. This distance can influence the effective strength of a lens and is usually only given for higher-strength prescriptions.
Once armed with this knowledge, you’ll be better equipped to discuss your vision needs with your optician and select lenses that provide optimal clarity and comfort. Don’t hesitate to ask your eye care professional for clarification if needed – they’re there to ensure you see the world clearly.
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