Why does my eyesight keep changing?

Posted on

13 January 2022

Author: Kate Green

eyesight changing

What is a prescription and why do I have one?


A prescription is a measurement of how much correction your vision requires. A glasses or contact lens prescription helps to ensure that your visual aids improve your eyesight the right amount to achieve good vision. The numbers on a prescription vary from person to person, depending on whether they are short-sighted or long-sighted, and how severe these conditions are. Find out how to read your prescription here.


You will have a prescription because your eye is either too long or too short to focus light directly on the retina (the back of your eye). Eyes which are too short result in the light being focused before it reaches the retina. This leaves you short-sighted, struggling to see things clearly beyond your near vision. Eyes which are too long have a light focal point behind the retina, meaning you will struggle with your near vision but see objects in the distance more clearly. To better understand the structure of the human eye, visit our blog post all about it.


Why does eyesight change in childhood?


If you’ve worn glasses since your childhood, chances are that you noticed your vision progressively got worse throughout your teens before beginning to stabilise in your late teens and early 20s. This is because your eyes tend to stop growing between the ages of 18 and 21 and eye growth can change the way in which the eyes refract light onto the retina. At birth, your eye is 80% of its final size, meaning that from birth until early adulthood, it grows along with the rest of your body, thus impacting your vision.

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Short-sightedness typically develops in childhood from the age of six and typically worsens around the ages of 11-13 with puberty. Contrastingly, long-sightedness can be detected in children even earlier than short-sightedness and can even be something that children grow out of as their eyes “grow and learn to adjust” to it


Why does eyesight change later in life?


One of the main causes of vision changing later in life occurs as a result of the ageing process. As you grow older, the lens in your eye loses elasticity which makes it more difficult to focus. If you find yourself needing reading glasses from the age of 40 onwards, this less flexible lens is likely to be the culprit. Once the lens has stiffened, it can deter the proper light refraction due to presbyopia, which is the name given to age-related long-sightedness. This can often manifest as you requiring more light to read, or having to hold things further away from your face in order to focus on them.


You might also find that, as you get older, you suffer from eye strain or computer vision syndrome. The strain comes from the effort of focusing your eyes on digital screens, resulting in your vision appearing blurry. To help your eyes feel less strained when using screens, you can try the following tips:

  • Adjust brightness and contrast settings on your computer screen
  • Install matte screen covers to prevent glare
  • Zoom in to 120% or more when using a computer
  • Increase the font size on your phone
  • Use artificial tears to help with dry eyes
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Any blurry vision from using digital screens is temporary but, due to many of us relying on digital devices throughout the day, it can appear that the blurriness is constantly affecting our vision.


Aside from age-related changes, you might also experience hormone-related changes to your vision, typically during and after pregnancy. Women may find that their prescriptions change while they’re pregnant due to fluctuations in hormone levels in this time. These fluctuations can also continue after childbirth, especially if they are breastfeeding. This is why we recommend that women who have recently had a baby or are breastfeeding should wait three months before seeking laser eye surgery or new visual aids, as their prescription is likely to return to its pre-pregnancy level.


Why is my prescription suddenly changing?


Most changes to your prescription during adulthood will come on gradually over time. If your prescription changes suddenly, you should have your eyes checked by a professional as soon as possible. Sudden changes to your vision can be a sign of glaucoma, age-related macular degeneration or cataracts.


Diabetic patients can also experience fluctuating vision which changes in line with their blood sugar levels. This usually causes blurry vision until the blood sugar levels stabilise again. Diabetes can have numerous effects on your eyesight so, if you have diabetes, you should observe any changes to your vision very closely, and seek medical advice regarding any significant changes.


Can I have laser eye surgery if my prescription keeps changing?


At Optimax, we will only treat a patient when their prescription has been stable for at least a year. This means that their prescription is less likely to change in the future. If your prescription changes after you have had laser eye surgery, you may find that the visual result doesn’t last, so we like to reduce the likelihood of that happening by only offering treatment to patients with a stable prescription. Because of this, we also have a minimum treatment age of 18 years old.

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We advise new mothers to wait three months after giving birth or finishing breastfeeding (whichever is more recent) in order to ensure their prescription has returned to its pre-pregnancy levels. Again, this is all about giving our patients a better chance of good long-term visual results – the more stable your prescription, the more likely you are to be suitable for laser eye surgery with us. You can check your suitability on our website here, or give us a call on 0800 093 1110 if you would like to chat with a Customer Advisor.

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