Can I have Reactolite lenses for driving?
Reactolite is a trade name for an obsolete brand of Photochromic lenses. These are lenses that change with the light.
Most Photochromic lenses do not react behind the windscreen of a car so they are not good as driving sunglasses. They are activated by UV light, which is blocked by glass windscreens. They are very good for outdoor activities and for people who work outside.
A new photochromic lens was launched in late 2006. The Nupolar Drivewear lens. This does change behind a windscreen but has a permanent tint so is not suitable as a general purpose lens. It is not legal for night driving.
Why can’t I see TV in my reading glasses?
For the same reason that you can’t read in TV specs. The laws of physics mean that a lens has a limited range of focus. Reading glasses are focussed for close work and usually have a range that is within 50cm of your nose.
If you have specific reading spectacles it means that your eyes can no longer change focus from distance to near and you need an increase in positive lens power to allow you to read clearly and comfortably. This is called presbyopia.
If you want to be able to see to watch TV and read without changing your spectacles you need either a bifocal or a varifocal. If you do not need spectacles for distance you can have half-eye spectacles which you wear down your nose slightly so that you can look over the top of them for TV.
Why can’t I read in my normal everyday glasses?
For the same reason that you can’t see TV in your reading glasses. The laws of physics mean that a lens has a limited range of focus. Your everyday glasses are focussed for long distance. Driving, TV, cinema, theatre etc.
If you can’t read in your everyday glasses it means that your eyes can no longer change focus from distance to near and you need an increase in positive lens power to allow you to read clearly and comfortably. This is called presbyopia.
If you want to be able to see in the distance and read without changing your spectacles you need either a bifocal or a varifocal.
What are varifocal lenses?
Varifocal is another word for multifocal lenses.
These are more properly called progressive addition lenses. These lenses allow people with presbyopia to see clearly at all distances without the need to swap glasses.
They are often described as “the bifocal without the line”. This is not quite accurate as they cover a far greater range than a bifocal and can be used for most purposes. They are excellent lenses for general use but are not ideal for some sports or hobbies.
Some people find that it takes a few days to learn how to use their varifocal lenses properly. It is just like learning to use any new tool; some people will pick it up straight away, others will take a while to get the hang of it and a very small number of people will never quite manage it.
All varifocal lenses have an area of distortion at the edges. More modern designs have reduced this distortion quite considerably and there are many different manufacturers and designs available. You need to discuss your precise vision requirements with your practitioner to make sure that you get the best lens to suit your lifestyle.
In general, a cheaper lens will often have more peripheral distortion and may be more difficult to get used to. At the other end of the scale are lenses that are computer designed for the individual client from a series of measurements taken by the practitioner. There are a lot of lenses that fall somewhere between these two extremes and there should be one to suit you.
Frame choice and fitting are crucial to the success of varifocal wear. If your frame is bent or badly fitting then you will find that you get a narrow corridor of vision and your lenses are difficult to tolerate. If you have to move your head around to see clearly at specific distances then you need to have them adjusted. A minor adjustment to the fitting can make the difference between a lens that works for you and a lens that you cannot stand.
What are bifocal lenses?
Bifocal lenses are lenses that have two distinct areas that are focussed at different distances. In most cases the top part of the lens is focussed for distance vision and the bottom part for close work.
The reading segment can be curved on the top (round segment) or flat on top (“D” segment). The shape of the reading area will be determined by your optometrist or dispenser.
We can create non standard bifocals that are for intermediate/near tasks or distance/intermediate tasks.
Intermediate / near bifocals are often used by office workers who need to see their computer screen at arms length but need a bit more strength in the lens to see small print on documents. They are no good for walking around or driving and are only really suitable if distance spectacles are not needed indoors.
Distance / Intermediate bifocals are great for LGV drivers or car drivers who need to see long distance to drive but need the mid range for dash instruments or satellite navigation systems. They are not much good for reading the A-Z.
If you need to see long distance, intermediate and close up without removing your glasses then you need to consider a varifocal lens.
Why do I need reading glasses but not distance glasses?
This is a condition called presbyopia.
It happens to most people at around 40 years of age. It is caused by normal changes in the lens inside the eye and not, as is commonly thought, due to weakening muscles in the eye.
The lens inside the eye loses it’s flexibility with age and cannot change shape as easily as it did. This shape change is needed to change focus from long distance to close up. It is a gradual change and continues throughout life.
You may need to update your reading glasses quite regularly.
Your eyes will not get weaker because you start wearing reading glasses. The changes continue to occur as they did before you got the glasses.
Not wearing reading glasses when you need to will cause headaches, eyestrain and wrinkles but "putting it off" and "doing without them for as long as possible" will not prevent your presbyopia from increasing.
Can I wear ready made reading glasses from the local shop?
If you have regular eye examinations to ensure that your eyes are healthy and your optometrist has said that your prescription is roughly equal in both eyes then, yes, you can safely wear “ready readers”.
You should NOT just use these spectacles in lieu of regular eye care. The eye examination is much more than just a test for spectacles, it is a health check as well. We have seen too many people who have put off having an eye exam until the ready readers didn’t work anymore, only to find that they have permanently lost their sight through a disease which would have been detected at a regular examination.
Some prescriptions are not adequately corrected by these "ready readers". If you are moderately short sighted or have astigmatism then they will not work properly. They are also unlikely to be suitable if you are very long sighted.
They must not be worn for driving. If you find that your distance vision (driving or TV) is improved whilst wearing them then you probably need proper corrective lenses and should see an optometrist for a full eye examination.
Why can’t I see the computer screen with my reading glasses?
For the same reason that you can’t read in TV specs or see TV in reading specs. The laws of physics mean that a lens has a limited range of focus. Reading glasses are focussed for close work and usually have a range that is within 50cm of your nose. Your computer screen will be beyond the range of your reading glasses. We call this the intermediate range.
The most appropriate correction to enable you to see your screen clearly and comfortably will depend on a combination of factors including the layout of your desk and workspace and the amount of time you spend using the computer.
You may need specific computer glasses, or you might be recommended a pair of bifocals or varifocals.