Your prescription and ordering prescription glasses online
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.
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.
Some more typical glasses prescriptions:
Here are some other terms often used by opticians:
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.
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.
