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Comparing your prescription with the following examples and notes should enable you to complete your on-line order. Please note that prescription forms are not standardised and the layout of your prescription may vary from these examples.
Should I choose 'Distance' or 'Reading'?
If you normally use one pair of single vision specs to see at all distances (for example driving, reading etc) please specify lenses for 'Distance' vision. If you require glasses made solely to your reading prescription please choose 'Reading'. Note that reading glasses are designed purely for close work and will not give clear vision when looking into the distance. Please complete all prescription details when placing your order.
What are 'SPH', 'CYL' and 'AXIS'?
The lens power for each eye is specified by up to three figures; the sphere power (SPH), the cylinder power(CYL) and the axis. The cylinder and axis values are always supplied as a pair – if a cylinder is specified it must also have an axis.
Simple prescriptions may consist of just the sphere power (for example +1.25) or the sphere, cylinder and axis combined (for example SPH -1.25 CYL +0.50 AXIS 55). All lens powers are specified in quarter (0.25) steps, i.e. the value written after the decimal point will be .00, .25, .50 or .75. Other values should not appear in your prescription; for example, you would not find a lens power specified as +2.63.
The axis value represents an angle in the range 1 to 180 degrees, for example 45, 90, 37, 135, 170 etc. If a CYL value appears on your prescription there must be an accompanying figure in the axis box. If the axis includes a fraction choose an adjacent whole number, for example, where the axis is written as 137½ choose 137.
There's an 'Add' on my prescription, what does it mean?
If you require reading glasses your prescription may include a reading addition (or 'Add') – this usually appears on the prescription in one of the following forms...
'Add +2.00'
'Add +1.50 EE' (each eye)
'Add +1.75DS' (dioptres spherical)
'Add +1.25 R&L' (right and left)
The actual number will usually be between +0.50 and +4.00 and in almost all cases will be the same for each eye. If you require reading glasses and there is a reading addition on your prescription it is essential that you supply this when placing your order.
Sometimes the distance and reading prescriptions will be written out in full rather than as a distance prescription with a 'reading add' (see the fourth example above). If this is the case and you are ordering reading glasses, simply fill in your reading prescription and choose 'No Add' when placing your order.
There's something else on my prescription, what should I do?
If the word 'PLANO' or this symbol '∞' appears on your prescription this represents a lens of zero power, therefore please choose 0.00 for the SPH in that lens.
If you are unsure about any aspect of your prescription please refer to the original prescriber before placing your order as we cannot be held liable where incorrect information has been supplied.
We recommend that you have your eyes tested by a qualified professional at least once every two years or annually if aged over 65.
What is 'PD'?
Your PD or 'pupillary distance' is simply the distance between the centre of your pupils (the black central area of each eye). It needs to be carefully measured and specified in millimetres. As a general guide, most adult PD measurements fall between 55 and 68mm.
Where possible this should be supplied by your optician but you can take this measurement yourself. The easiest way to do so is by having a friend stand facing you at a distance of about 18 inches and, as you look at their nose, have them measure the distance between your pupils. Since your eyes converge when looking at near objects, you will need to modify the measurement by adding 3mm to obtain the correct 'distance vision' PD. For example, if your friend measures your PD as 58mm you will need to specify a PD of 61mm (58 + 3) on any order for 'distance' specs or 58mm for reading glasses.
Your optician may have specified 'monocular PD's' for your right and left eye individually. Simply add the two together to obtain your overall PD. For example, with these monocular PD's, R 31mm and Left 32mm, you would specify 63mm on your order.
We can only supply glasses when a PD measurement has been provided.
Please note that our Internet-only selection is limited to single vision lenses with powers within the range -6.00 to +4.00 sphere and/or -2.00 to +2.00 cylinder. We cannot supply lenses that require a prism. For prescriptions outside this range or for other lens types please visit one of our retail outlets.
Frame Sizes
As well as a general 'Guide Size' we provide various frame measurements to help you choose a suitable frame...
- Lens width is the horizontal width of one lens
- Lens depth is the vertical size of the frame (including rims)
- Bridge width is the distance between the two lenses
- Side length is the total length of the sides
Frame Materials
Each of our frames has a material description – usually 'metal' or 'acetate' – to indicate the make up of the main frame components. Acetate is a form of plastic that has been used for many years and is considered safe and inert for use in spectacle frames.
Frames that are described as 'metal' have one or more major components made of metal alloys that may contain substances to which some individuals are allergic (notably nickel). If you have, or suspect you have, an allergy to metal we recommend taking professional advice and buying only non-allergenic frames. |
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