It can be really tricky trying to work out which lens type you need to order. These terms are no doubt foreign to most of you but hopefully this article will help.
You can get some clues looking at your prescription. Does it have an ADD? If so then you have a reading prescription and it may be that you have some numbers in the sphere and cylinder comments before the add. In which case you have both a distance and reading prescription and they are not the same.
This is an indicator that you require bifocal or progressive lenses to be able to see both in the distance and reading through the same lenses without having to remove your glasses. It could be that you are happy just to have one of these prescriptions in glasses but please bear in mind that you will not be able to walk around in reading glasses without dropping them down your nose or taking them off. Equally just having your distance prescription means that everything over 3 meters away will be clear but closer may not be – so you may need to change glasses to read.
Another indicator maybe difficulties with reading and annoyance with having to take your reading glasses on and off, your distance vision may be fine. With this situation progressive or bifocal lenses could be helpful. Especially with safety as that way you can leave the safety glasses on your head for protection all of the time.
Occupational progressive lenses are also available with prescription safety glasses. Therefore if you have to wear your safety glasses to work on the computer all day and need a little more strength for reading, this could be the answer. If you are ordering occupation progressive lenses – they are clear for an arms length which is generally computer distance and clear for reading down the bottom of the lens.
I should explained the difference between progressive and bifocal lenses. Progressive/multifocal/varifocal lenses are all the same thing – which is a lens that doesn’t have any lines on the surface and the vision is clear for the distance at the top and gradually changes to be clear for reading at the bottom and has corridors of clear vision. With off to the side being blurry.
Alternatively bifocal lenses have the distance prescription at the top and then a line around the reading segment at the bottom. There is no area in these lenses that is clear for vision between 3meters and your reading prescription. So intermediate distance 1meter or so is a problem then it is probably worth investing in progressive lenses.