The Ultimate Guide to Reading Glasses Strength

Model wearing reading glasses

This blog post from Tiger Specs explains reading glasses strength and the causes of age-related vision deterioration in detail. In this post, we provide the essential answers to the important question of “what strength reading glasses do i need?”

Having read this post you will be able to:

  • Assess the strength of your current reading glasses
  • Gauge the extent that your vision has deteriorated
  • Choose the right strength reading glasses for your condition
  • Find out how Tiger Specs will assist you with making the right choices

Read on for the Ultimate Guide to Reading Glasses Strength. Approximate read time 4 minutes.

The importance of reading glasses strength

Reading glasses compensate for the natural loss of eye focal adjustment that occurs with age. From age 25 onwards for some people, the ability to focus properly starts to reduce. By the age of around 40, a large percentage of people will start to need some sort of reading assistance. 

This diminishing capacity to focus properly is called presbyopia and it normally progresses with age. At Tiger Specs we recommend that once you have started with your first pair of reading glasses, you should reassess the reading strength needed at least every 2 years.

What are the different strengths of reading glasses?

The eye care industry classifies reading glasses lenses in diopter strengths that increase in quarter powers or 0.25 of a diopter. for example, +1.00: +1.25; +1.50; etc. starting at + 0.50 and going up to +5.00. 

A quarter-diopter reading strength increase is a more significant step up than many people realise and is a good way of gauging the strength of your next pair of reading glasses when you start to struggle.

The Lowest Strength Reading Glasses

So what’s the lowest strength reading glasses? Here at Tiger Specs, the reading glasses range starts at +0.00 (clear lens and with no reading strength) for style purposes only. The actual lowest strength reading glasses start at +0.50 and go up in quarter powers to the strongest strength of reading glasses at +5.00.

The Highest Strength Reading Glasses

We often get asked the question “what is the strongest strength of reading glasses?” High power readers go as high as +7.00. These reading glasses are for those who may have extremely low vision or need more magnification to help with a serious vision problem. 

They are not widely available or even legal to sell in the UK. The consensus is that people with vision that is impaired to the point that they need reading strengths above + 5.00 should be under the care of a specialist.

Will wearing the wrong strength glasses harm my vision?

Knowing how to choose reading glasses strength is important but there are many misconceptions out there that suggest wearing reading glasses that are either too strong or too weak might harm your eyes.

The main worry is that wearing reading glasses that are too strong will teach your eyes to adjust and make them lazy. This is not backed up by any scientific evidence and is widely acknowledged to be incorrect. 

One thing is for sure – you cannot retain strong vision by avoiding the need to wear reading glasses.

Wearing incorrect strength reading glasses can lead to symptoms that start with a vague feeling of discomfort and extend out to eye strain, headaches, balance issues and blurred vision. Reassessing the strength of your reading glasses will help to avoid these symptoms.

Is it possible to need more than one strength of reading glasses?

Yes, you might need more than one strength. For example, you could need reading glasses of one strength for working on a computer with a large screen and another pair one-quarter power stronger or more for your much smaller smartphone. It might also depend on the amount of light. Reading in bright light is always easier than in dull conditions. Experienced users of reading glasses may well have more than one pair, each with different diopter strengths.

Can eye exercises improve my vision?

Eye exercises have not been proven to correct your vision. They may help alleviate eye strain and help your eyes relax to the point where they focus better but this is by no means a permanent effect. You might not be fixing or healing your eyesight but there is certainly no harm in developing an eye exercise regime to help them relax.

How can I tell the strength of my existing reading glasses?

If you have a pair of reading glasses that you bought online or from a local store and you break them or you start finding they are not doing the job, it would be useful to know what strength they are. This gives you a reference point for what strength of reading glasses you might need to replace them with.

If you have had them for a while you may well have forgotten what strength they are. Those people who have bought reading glasses online will find it much easier to trace a record of their purchase than those that bought them from a shop. Normally you will be able to log into an account and look at your purchase history.

Often the strength of reading glasses is marked on the inner temples so it is worth checking there in the first instance.

If however you have no other way of finding out the strength of your existing reading glasses you can try this method to get an idea of what strength reading glasses to replace them with.

Measure and calculate the focal length of your reading glasses.

You need to bear in mind that this method only works with reading glasses because they have spherical lenses with positive powers. It will not work with prescription glasses that contain any kind of cylindrical corrective component. You should also understand that this method gives you nothing more than a ballpark assessment.

Method: This is a two-person job so you will need an assistant. Hold your glasses in a beam of light from the sun and have your assistant hold up a sheet of white paper. You are looking to produce a focused and sharp image of the sun on the white paper held at distance from the lenses and then measure that distance. That’s the focal length (distance) of the lenses.

When you know the focal distance you need to convert this to a reading strength measured in Diopters. Diopter strength relates to the optical power of a lens. It’s commonly applied to reading glasses strengths going up in quarter powers.

The formula to remember is D = 100 divided by F, where D is diopter strength and F is the focal length (or distance) in centimetres.

Examples: A focal length of 100cm (about 39 inches) equates to a diopter strength of 1 (+1.00); a 2 diopter (+2.00) lens has a focal length of 50cm and so on.

How to choose reading glasses strength

1. Convert your glasses prescription into a reading strength

When vision starts to deteriorate it is always recommended that you should seek a professional assessment. An optometrist will examine and diagnose your condition and then issue you with a prescription for the right glasses to assist you. You might then take this to an optician.  Opticians take care of the technical aspects of fitting glasses, contact lenses, and other vision-correcting devices.

Although some financial help is available to those that need it, a pair of prescription glasses is not going to be cheap. The life of a pair of glasses is fraught with danger, They get snagged, dropped, sat on and left behind very easily. 

Having a backup in the form of a pair of reading glasses for casual use is a great idea. Reading glasses from Tiger Specs are top quality items at a fraction of the cost of prescription glasses. You then have the option to use your prescription glasses for important work but let a cheaper pair of reading specs do the day to day more casual but still heavy lifting.

The Tiger Specs prescription converter

So let’s have a look at how to determine reading glasses strength from a prescription without leaving the Tiger Specs website.

 If you have been given a prescription you are welcome to use our tool to convert your prescription to a suitable reading strength. Simply enter the details of your prescription into the fields provided and find out the exact reading strength you need. 

**Please note that if your prescription is more than two years old we recommend that you have your eyes retested before using this converter.

View our prescription calculator

2. Your optician

Should you not have a prescription available, your optician will be able to tell you your ideal strength reading glasses either if they have your current glasses prescription on file or at the completion of an eye test.

3. Use an eye test chart

The Tiger Specs eye chart

Another alternative without a prescription is to use our eye chart which is available for you to download and print. Printing of the chart gives you varying text sizes that you work your way down until you find the line that you can see clearly without reading assistance. Coming with full instructions for use, you will be able to get a reasonably accurate idea of the strength of reading glasses you need.

Download our eye chart

4. Use the age average scale

If you don’t have a prescription or access to a printer you might find it useful to use your age as a predictor of the reading strength you need. This is the least reliable method of assessing the strength of reading specs you need but does help give you a starting point. 

As previously stated, presbyopia is a progressive weakening of vision that is unavoidable. It affects some people at different times and at different speeds than others.

If you are under 40 years old and beginning to experience vision problems, you should start out trying strengths between +0.50 and +1.25. Between ages 40 and 45, try a reading strength of +1.75. At ages 45 to 50 +2.00. After age 50, you probably need +2.25 and upwards.

While this is based on averages, you should try to narrow this down a little and find the precise lens that makes your eyes feel comfortable and without strain when reading.

5. Order different strengths of reading glasses

Tiger Specs offers a no-quibble 28 returns policy on any of our reading glasses. This allows you to order reading spectacles of different strengths to gauge what strength suits your vision best. You are then perfectly within your rights to return the unsuitable specs in original condition for a full refund within 28 days. 

You might find that the different strengths both suit you in different conditions and keep them both. In this case, you will already have taken advantage of our long-standing offer of a £5.00 reduction when ordering any 2 pairs of specs. A win/win situation by any standards!

What strength reading glasses after cataract surgery?

After cataract surgery your vision will start to improve in the first week, We always advise that you should wait for closer to a month before getting any new reading glasses. You can then either have your vision professionally assessed or use one of the methods described here to find out what strength reading glasses you need.

What options do i have for choosing reading glasses?

The Tiger Specs range includes reading glasses and reading sunglasses. Some are styled to suit men, some for women and also a large selection of universal specs for his and hers enthusiasts.  We offer a huge range of styles and designs from top brands and up and coming designers in a virtual cacophony of colours. Traditionalists can choose classically styled retro and vintage readers with some fantastic options always in stock.You might be interested in a previous blog post that covered choosing the perfect reading glasses in detail.

What you can expect from Tiger Specs

Tiger Specs is one of the leading online eyewear retailers in the UK. As a family business, for more than a decade we have been applying our own brand of superior customer service whilst providing great quality products at exceptional prices.

We understand that customers want vision assistance that remedies the problems of deteriorating vision, eye strain and discomfort rather than adding to it. We also understand that getting it right is not easy. This is why we offer our own no questions asked 28 day returns policy in addition to the normal guarantees.

Unusually for an online retailer, if you need to speak to a real person we are always here to help. Our telephone number is available on our contact page where you will find all of the ways to get in touch. When you deal with Tiger Specs you are joining thousands of satisfied customers that come back to us time after time. Why not take a moment to review what they have been saying about us and then use our handy filtering tools to dive into our website and find the perfect pair of reading glasses for your vision?

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