To produce your prescription glasses accurately we need some information from your prescription. Here is a simple guide to your prescription with some explanations of what everything means. We have also included some copies of common prescriptions for glasses to show what they look like. If you have any concerns when entering your prescription information please call us. You can always email, fax or post a copy when ordering your glasses.
SPH (sphere) – spherical power, the back of the eye is shaped like a football only requiring 1 power for correction. Long-sighted plus (+) sign or short-sighted minus (-) sign.
CYL (cylinder) – cylindrical power, the back of the eye is shaped like a rugby ball, light hits the back of the eye on 2 curvatures giving a sphere and cylinder power (this requires an axis). It measures the astigmatism. If no CYL required it mat say DS which means SPH power only.
AXIS – only given if a cylinder is required (between 0 & 180 degrees) enables us the set the CYL correctly (will only have an axis is there is a Cyl value).
ADD – addition, a power added to the sphere to give extra magnification for close up work, can be Inter (intermediate) or Near (reading).
PRISM – this corrects a muscle imbalance (squint).
BASE – the prism direction either up, down, in or out.
PD (pupillary distance) – this is the measurement between the pupil centres, also known as OC – optical centres, it is measured in mm. Average for male is 63mm and female is 61mm.
DIOPTRE – the is the unit of lens powers, they are in .25 (1/4) * .25, .50, .75, 1.00 etc.
MYOPIC – myopia, short-sighted, can see more clearly close up need help with distance.
HYPEROPIC – hyperopia, long-sighted, can see more clearly far away need help with close up.
PRESBYOPIC – presbyopia, the eye looses the ability to focus close up (age related, around mid 40’s onwards), requires a reading prescription.
ASTIGMATIC – astigmatism, requires a Cylinder to correct curvature at the back of the eye (see CYL).
INDEX – the higher the index the thinner the lens of the same power.
· CR39 - 1.498, std plastic
· Polycarbonate – 1.59, 30% lighter, 20% thinner & 12x stronger than std plastic lenses, 100% UVA & UVB protection
· 1.67 – 40% thinner than std plastic, 100% UVA & UVB protection
· 1.74 – 50% thinner than std plastic (thinnest possible plastic lens), 100% UVA & UVB protection
Scratch resistant coating – hard coating on lenses, helps resist scratching, doesn’t stop it all together, anything abrasive across the surface of the lens will cause scratching.
MAR – multi anti-reflection coating, a coating applied to lenses to reduce glare from artificial lighting i.e. computer screens, overhead lighting & night-driving car headlights and street-lights. They are automatically hard coated too.
TRANSITION – new generation is the Transition VI, 100% UVA & UVB protection. Virtually clear indoors, faster fade back, suitable for night-driving. Performance is severely reduced in cars as UV changes the crystals in the lens and car windscreens stop UV passing through.
POLARISED - special order lenses, please contact us for prices
SV – single vision, a single powered lens either for distance, intermediate or reading.
Bif – bifocal - 2 powered lens, usually distance at the top and reading at the bottom but can also be distance at the top & intermediate at the bottom OR intermediate at the top and reading at the bottom.
Vari – varifocal (multifocal), top of the lens is distance then power gradually increases towards the bottom of the lens. No visible line like the bifocal, cosmetically more appeasing – younger looking as looks like a single vision lens, gives full focal range. THESE CAN ONLY BE ORDERED BY PHONE as there are different gradients of peripheral vision available
Prescription Glasses at a fraction of the High Street cost
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