How to read your prescription to buy VR lens inserts

Reading a prescription may seem like the darks arts, but our guide below will help you to navigate and understand your prescription information.

Below is an example prescription. Prescriptions can vary, and yours may not look exactly like this.

Spherical error (SPH or S)
REQUIRED

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.

Cylinder (CYL / ZYL ) and Axis (A /ACH AXS)
REQUIRED

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. You may see DS written in the column which stands for dioptre sphere and means you have no astigmatism.

Prismatic power (prism) and base
REQUIRED IF PRESENT ON YOUR PRESCRIPTION

If your prescription includes Prism, you will need to select the ‘Higher-Strength Prescription’ lens option when ordering on our site. 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

Back Vertex Distance
NOT REQUIRED FOR VR INSERTS

Back vertex distance (BVD) BVD stands for back vertex distance and is the distance in millimetres between the front of your eye and the back of the lens of your glasses. Changes to this distance can slightly influence the effective strength of a lens and is usually only given for very high-strength prescriptions. It is not required in VR headsets.

Near ADD (& intermediate ADD)
REQUIRED IF PRESENT ON YOUR PRESCRIPTION

If your prescription includes NEAR ADD, please enter this value in the field labelled ‘Near ADD’  This number refers to the additional correction you may need to focus at shorter distances like reading and is more common over the age of 40. 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. Not all prescriptions will have a section for the intermediate add, instead it may be written in by hand if needed. We use the value for ‘Near ADD’ (when present) to calculate any adjustments the VR lenses to give clear vision in the VR headset.

Pupillary Distance (PD / IPD)
NOT REQUIRED FOR MOST VR INSERTS

Pupillary distance (PD) measures the distance between the centres of your pupils. Most VR devices move the headset lenses to correctly align with your eyes, so a PD measurement is not required. You only need to provide PD information for specific VR devices when we clearly indicate it is required on the order entry page. If it is required, this measurement is used to determine where you look through the lens and should be as accurate as possible, as it will help your eyes align to the centre of the lens. If you would like to find out what your PD measurement is, check out our guide to measuring your PD. The most accurate way of measuring your PD would be to contact your optician to get them to measure your PD.