When it comes to glasses, there are several terminologies that can be confusing, one of them is ‘SPH’. Standing for ‘Sphere’, SPH is a term used to indicate the power of the lens needed to correct your vision. Generally, it is stated on your glasses prescription and the understanding of what it means can be critical for your vision correction.
Understanding the Sphere (SPH)
The Sphere (SPH) is a term used to represent the amount of lens power, measured in diopters (D), prescribed to correct nearsightedness or farsightedness. If the number appearing under this column on your prescription is followed by a minus sign (-), it means you are shortsighted (myopia), whereas a plus sign (+) indicates longsightedness (hypermetropia).
Generally, the farther away the number is from zero, the more vision correction you need. For example, a person with an SPH of -2.00D would require a less powerful lens than a person with an SPH of -5.00D because a higher dioptre (either positive or negative) represents a significant refractive error.
Importance of SPH in Glasses Manufacturing
SPH notations are essential cues in the manufacturing process of corrective glasses. They guide the lens maker on the correct curvature to grind each lens to ensure it functions optimally. For someone with myopia, or nearsightedness, the lens needs to be made thinner at the centre than at the edges, while the opposite is true for a person with hypermetropia, or farsightedness, where the lens needs to be thicker in the middle than at the edges.
Frequently Asked Questions About SPH
Does a higher SPH mean worse vision?
In short, yes. A higher SPH (either positive or negative) means your eyesight is weaker and you need a stronger prescription, be it for near or far sightedness.
Can SPH be zero?
Yes. If the SPH on your prescription is recorded as ‘PL’ or ‘Plano’, it means that you have no refractive error in the spherical part and therefore need no correction.
What does “DS” mean in the cylinder column?
DS, standing for Diopters Sphere, is usually written in the cylinder column of your glasses prescription if you have Sphere-only prescription and no astigmatism.
Understanding your glasses prescription, including the meaning of SPH, is crucial. It is this knowledge that allows you to decipher the exact specifications of your vision correction and ensures you get the right glasses for optimal visual performance. If you are unsure about any aspect of your prescription, it is always a good idea to consult with your eye care professional.