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Understanding your written optical prescription
| Author: Joanna Williams | Published: 29th August 2019 12:17 |
Prescription
Understanding your written optical prescription
Spherical error (SPH)
SPH stands for the spherical error and shows whether you have myopia (with a minus sign), or hypermetropia (with a plus sign). The number shows the strength of lens you need. A smaller number means the condition is milder. PL is short for plano and means there is no refractive error in that eye. This may also be written as 0.00 or the infinity sign.
Cylinder (CYL) and axis
CYL stands for cylinder and shows the severity of any astigmatism. Axis shows the angle that the cylindrical power in your lenses must be set at to correct it. DS stands for dioptre sphere and means you have no astigmatism.
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. The number in the prism column shows the strength of the correction, and the base column shows which direction the prism is acting in.
Near Add and Intermediate Add
This refers to the additional correction you may need to focus at short distances and is more common over the age of 40. This number is added to the spherical error part of the prescription to give the actual near prescription and may be written in full or given as the "Add" (additional power required). If you need a different powered lens for viewing a ‘mid-range' distance in focus (usually the distance to a computer screen) you may have an Intermediate or Int add as well.
Back vertex distance (BVD)
BVD stands for back vertex distance and is the distance in millimetres 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.
Your written prescription should also include the date of the eye examination, when you are next due for a test, the name and signature of the optometrist with their GOC number.
If you have any queries about your prescription you should ask your optometrist or dispensing optician.
https://observatory.co.uk/sudbury/
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