|
|
| So that's why those new specs are giving you a headache... |
| | Mon, 13 Feb 2012 |
| |  |
| |
First, it was the blurry train timetables on my daily commute, then the fuzzy specials on the blackboard at a local pub. But the last episode of BBC’s Sherlock was the final straw.
Long before the closing credits were rolling, all I could concentrate on was not the clever plot, but the aching, straining sensation behind my eyes.
Almost instantly after leaving my optician, Dollond & Aitchison, three weeks before with new shiny black frames and higher prescription lenses for my short-sightedness, I’d felt something was wrong with my glasses.
I was squinting to focus at anything in the distance. Put simply, I’d spent £350 on glasses that seemed no better than my old ones.
But during a return trip to my optician (or optometrist, to give the specialists who test our eyes their proper title), I was assured my glasses were correct. They didn’t like to ‘over-prescribe’ (make the glasses too strong), I was told. And the headaches? I should just ‘move closer’ to the TV.
Confused and not-so-quietly fuming, I sought a second opinion from a rival chain, David Clulow, a few weeks later. It recommended a huge increase in my prescription, from -9.5 dioptres (the unit used to measure how much your eye sight varies from the norm, i.e, 0) to -11.
Though my eyes are far worse than average — I’m granted free NHS eye tests at the grand old age of 27 because I’m so severely short-sighted — the difference seemed huge. So who was right and who was wrong?
Well, what might come as something of a shock to the 68 per cent of Brits who wear glasses is that the answer was neither. For I was to discover when I turned to the experts that eye exams are not the objective test we might think.
To investigate, I had five eye tests in a month, and every prescription came back slightly different. Dollond & Aitchison remained the lowest and David Clulow the highest, while Specsavers, Vision Express and Boots recommended prescriptions in between the two.
What’s more, I discovered that the most ‘accurate’ prescription is not even necessarily the best.
According to research from the journal of the College of Optometrists, an estimated 2 per cent of spectacle wearers — 400,000 of us a year — return to our opticians unhappy with new lenses.
The true figure might be higher still, as it’s thought that many people simply revert to old glasses if they are unhappy with new ones.
The chances are that many of these people, like me, weren’t given the right prescription for their needs — or at least an explanation of what the optician was doing.
‘The difficulty with prescriptions is they can vary a little from one day to the next,’ says Dr Susan Blakeney, of the College of Optometrists.
‘If you had your eyes tested by the same person over several weeks, or by a number of optometrists on the same day, you’d probably get slightly different results each time. The right prescription is the one the patient is happy with.’
So, if it’s not an exact science, how does your optometrist come up with a prescription for you?
The answer lies in a combination of the eye test and a discussion about your lifestyle, work, hobbies and eyesight needs. For instance, some people — those who work in an office, for example — might not need perfect distance vision.
In fact, if you’re short-sighted, in your late 30s or 40s and working, it can often be beneficial to have slightly weaker glasses than you might ideally need — this won’t give you perfect distance vision, but will allow you to focus on things close to you more easily, such as the computer screen or a book.
This practice of deliberately giving weaker lenses than your full prescription is known as ‘underprescribing’.
As Dr Blakeney explains: ‘If your glasses are made up to your “correct” prescription to make the distance vision clear, your eyes have to focus intensely to see close up. Some people can’t tolerate this; they find it too strong and will get headaches from having to focus all the time.’
However, there is another situation where a lower prescription may be given on purpose: that is, where your vision has substantially changed to the extent that your eyes may be unable to cope with the large jump in prescription.
Instead, your optometrist may recommend a strength of lenses somewhere between your old and new ‘true’ prescription so you can get used to the change gradually.
This is known as ‘partial prescribing’ and, according to Professor David Elliott, of Bradford School of Optometry and Vision Sciences, is often a tool used by more experienced optometrists.
It may be used for people who are becoming more short or long-sighted or who have trouble focusing as they get older. ‘You have to adapt to your new lenses, and the older you are, the longer it takes,’ says Professor Elliott. ‘A big change will affect the magnification of your glasses, so things will look smaller and further away or bigger and closer.’
What this can mean in practice is that giving you your true prescription straight away can result in a higher likelihood of falls and accidents — something that optometrists are clearly keen to avoid, particularly in elderly patients.
So, why don’t optometrists simply partially prescribe for everyone who has experienced a change?
First, according to Professor Elliott, one criticism that may get levelled at an optometrist for giving a partial prescription is that they are making more money by moving up people in increments — the customer may need a new prescription sooner, meaning a second pair of glasses or at least lenses to pay for.
On top of this, it can be hard to get the balance right. Giving too low a prescription can cause blurriness and headaches due to straining to see — as I experienced — and it can even be dangerous in some situations, such as night driving.
However, in certain circumstances — for example, if you drive for work — your optometrist may recommend your full distance prescription straight away, despite problems you may have adapting in the short-term.
This might explain why the second optician I saw recommended a large jump in prescription rather than a partial one.
It was the highest prescription of the five and would give me the best distance vision, but would likely be hardest to adapt to.
The other four optometrists I visited recommended partial prescriptions to avoid this leap — though it seems the mistake that my regular optician Dollond & Aitchison made was failing to discuss a deliberately low partial prescription, which made my distance vision too poor.
More positively, Specsavers, Boots and Vision Express explained that my true prescription was up to 0.5 higher than the one they were giving, but that they wouldn’t be comfortable giving it to me as I’d likely experience headaches and spatial problems while I got used to it.
Having visited all the main High Street chains and learned about the process, I’ve opted for this middle ground. Yes, it’s frustrating to know I’ll have to pay for new lenses in another year or so, but it seems necessary for good sight.
Dr Blakeney advises finding a good optometrist — a member of the College of Optometrists — and building a relationship so they know your eyes. And always go back if you are unhappy with your vision.
A spokesman for Dollond & Aitchison says: ‘It is our policy to explain in detail what the customer is getting. We apologise if this is not what you experienced, and understand a full refund was given.’
WHAT TO ASK WHEN YOU HAVE AN EYE TESTDRIVING: Tell your optician if you will be frequently taking the car out after dark. Your distance vision needs to be very strong to make the task easier.
READING: If you’re short-sighted, not yet in varifocals and over 30, bear in mind a distance prescription might make it harder to read as your eyes have to focus more. Make sure your optician asks you to read something close up.
BIG CHANGES: If your prescription has gone up or down by more than 0.5-0.75 dioptres, talk to the optician about whether a partial prescription (somewhere in between your old and new one) might be more suitable. If you have a sudden, dramatic change of prescription, it could be a sign of diabetes so seek your GP’s advice.
SPECS POSITION: Ever noticed if you push your glasses closer to your face or further down your nose, your sight gets better or worse? This relates to the distance your lens is from your face, or ‘vertex distance’. Your optician should always measure the distance the eye testing equipment is from your face, and adapt your prescription to your frames accordingly.
REFUNDS: Check the policy. Legally, mistakes have to be corrected; however, if your prescription is within the right ‘range’, you might struggle to get a refund unless there’s a no-quibble money-back policy.
|
|