Myths

A big question markThere are so many myths involving eyes and spectacles, and despite explaining why these thoughts are incorrect to people, understandably many choose to believe what they believe.

 

 

 

 

  • “I don’t need my eyes tested- I don’t need glasses”.

You are probably correct, but do you only go to the dentist when you know you have a problem?

Many eye examinations result in onward referrals for further investigation and treatment- many of them did not know they had a problem!  As can be seen in this Post, routine eye testing should be a regular part of everyone’s healthcare routine- and parents, that also includes the children!
We have also seen many people who know they require reading spectacles but claim that they could see a “Midge on a mountain”, who would not be up to legal requirements for driving (That midge may have been a cow, or perhaps a house?)- vision can change so slowly that until you get your’s checked you wouldn’t know!

 

  • Spectacles make your eyes worse.

There is some truth to this, but only in children.

There are too many people who do not require glasses for this to be random luck, which gives rise to the Theory of Emmetropisation. This theory postulates that by unknown means the eyes have a way of sorting themselves out while growing. Perhaps a more long sighted eye somehow knows to grow faster, thus reducing the hyperopia. For this reason Optometrists will not usually prescribe spectacles to hyperopic children, unless they have difficulties. If the child has a squint, and they are longsighted, they require spectacles. If a child is myopic (shortsighted), also they require spectacles, likewise if they have a significant degree of astigmatism. In these cases Emmetropisation has already failed– it did not work for this individual.

Many people who start wearing spectacles do feel that their eyes get worse when they start wearing a correction- many 13 to 14 year olds attend for a test complaining that they can’t see the board at school, and we find them to be a little shortsighted. We would prescribe spectacles, as they “cannot see the board”, but would not make any suggestion as to when they should wear them, except for in class (because that is where they are complaining). Very often this individual will be recalled after a year for their first check, when they often complain that their vision is much worse, as the T.V. is blurred without the spectacles, as are trees down the road, and faces across the street. The question “What is it like with the glasses on?” often gets the response “It’s OK”. Usually we find that the eyes have not changed very much (which makes sense if they can still see fine with the spectacles on), but they become more aware of the fact that their vision isn’t as good as it might be for all far away things, not just the blackboard.

 

  • Giving in to reading spectacles weakens your eyes.

This is pretty much the same as above, but often involves those in their 40s who are beginning to struggle to read.

The ability to focus the eyes for close up objects begins to deteriorate at approximately 12 years of age. This happens because the lens in the eye never stops growing, and as it grows it becomes more difficult to get it to adjust to a near focused shape. To be more accurate, as the lens grows, it grows towards the muscle, releasing the tension which keeps the lens in a far focus- so the lens actually gradually takes up its near focused shape, but the flattening of the its surfaces as it gets thicker means that the distance refraction remains similar, but the near adjustment wanes. This growth of the lens happens at a steady rate throughout life, and no-one would argue that putting two pieces of plastic in front of their eyes would make the lens grow faster. So why do they argue that the glasses make their eyes worse? Most people have been struggling with reading for a while before they come for their eye test and get glasses, and they are not aware just how much of an effort reading is, and how not sharp it is, until they get their glasses. In a couple of weeks, they are used to the sharpness and ease of reading, and then they misplace their new spectacles- only then do they realise how bad their vision was! (But they feel it got worse because of the glasses).

 

  •  Eyestrain damages your eyes.

Eyestrain is caused by overworking of the muscle which controls the focus in the eye. In much the same way as “struggling on” without reading glasses will not preserve focusing ability, equally straining the eyes will not cause them actual harm or damage, though if the person continues, they will eventually either lose the enjoyment of reading or later will not be able to read. A keen reader will probably present sooner, but if someone begins to make errors particularly at work, eventually they will need to give in. There will be no harm done either way however.

 

  • Detailed or Complex work wears out/harms the eyes.

In the retina at the back of the eye are millions of photoreceptors, which convert light into a neural signal and send it off to the brain. Each individual receptor either fires or it doesn’t fire (or more accurately fire more of less frequently) in response to stimulation by light, but each receptor has no idea of the sharpness or complexity of the image landing on the entirety of the retina. For this reason there is no more difficulty/effort or wear and tear on the retina of an engineer studying the most complex technical schematics than there is a child playing with Lego.

This is an important fact, as many times we would see elderly patients who perhaps have some age changes at the back of the eyes, who have given up on their knitting or crochet in an effort to preserve their eyes for things they really need to see. It doesn’t work like that, and we would always advise them to keep doing what they enjoy doing for as long as they can.

The most difficult time for the retina is actually in the dark (Unless it is being cooked by staring at the sun- obviously a very bad idea), the retina requires much more energy when it is dark adapted than when in brighter conditions. This is not particularly significant for healthy individuals, though even their retinae could be borderline hypoxic (lacking oxygen) when in the dark and or asleep. There have been suggestions that people who could have compromised retinal circulations such as diabetics, especially those who have diabetic retinopathy, should perhaps consider sleeping with a light on, to keep the retina slightly less dark adapted when asleep.

  • A tint will help with night driving.

This is a very common request, and may seem outwardly sensible to reduce the glare from oncoming headlights. Some people insist on a tint, as they feel it is a benefit, and will not be swayed- there is little point to argue with them.

Tints will not help with night driving, because it is not the brightness of the oncoming headlights that is the problem, it is the difference in brightness between the headlights and your eyes adaption level (how dark adapted the eyes are). Those headlights cause you no problems during the day , when your eyes are light adapted, even if they are on full beam, it may be uncomfortable to look at them, but you can still see the side of the road and past the car without issues.

A tint suitable for night driving must very very slight – let’s say it absorbs 15% of the light. It makes the oncoming headlights 15% less bright, but it makes your headlights 15% less bright also, so the difference remains the same, but now you eyes wish your headlights were brighter!

More information about night driving, and what we can suggest might help can be read here.

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