Can Contact Lenses Make Your Vision Worse?

There are many myths surrounding the use of contact lenses. Most are unfounded but nonetheless, they can get into people's heads and prevent them from wanting to try contact lenses. One of these myths, which many parents use to tell their teenage children that they can't wear contact lenses, is that contact lenses make your vision worse. In this article, I will do my best to dispel this myth.

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Medical disclaimer: I am not a doctor. The information provided on this page is for general educational purposes only. You are not receiving medical advice or being given a diagnosis on this page. Please read Contacts Advice Terms of Use before continuing.

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Let's Clarify What We Mean by 'Vision'

In order to tackle this topic, let's first start by clarifying two things. There is a difference between our vision and our prescription for glasses/contacts.

1. Our vision, technically referred to as our visual acuity, is a measure of how well (how much detail) we can see. This is the number that is denoted as something over 20. I.e., 20/20 is perfect vision.

   There are two more concepts that are important to clarify. When it comes to our visual acuity, anyone with a prescription for glasses or contacts has two vision measurements. They are called the 'unaided visual acuity' (UVA) and the 'best corrected visual acuity' (BCVA).

   • UVA is how well one sees without any help from glasses or contacts.
   • BCVA is the best possible vision that one can achieve with glasses.

   So for example, someone with nearsightedness whose glasses prescription is −4.00D in both eyes will have poor UVA (without their glasses) but excellent BCVA (with their glasses).

2. The numbers in your prescription for glasses is not a measure of your vision, but of the strength in the lenses required to make your vision as good as possible. I.e., −2.50, +1.50/−0.75 x 180, etc.

So What About The Myth That Contacts Make Your Vision Worse?

Let's see how the claim that contact lenses make your vision worse applies to the vision principles we discussed above.

Changes in Our Prescription

When I have people tell me that they don't want contacts for their kids because it will make their vision worse, I think what they are saying is that contact lenses will cause their prescription for glasses to get stronger. This is not true. Our prescriptions for glasses get worse because of changes in the shape of the eyes. This can be changes in the overall length of the eye which creates either nearsightedness or farsightedness, or changes to the curvature of the cornea which can create astigmatism. There are two main factors that can determine the shape of the eyes, and thus our prescriptions for glasses.

1. Our genetics. If one or both parents are near-sighted, the chances that their children will be near-sighted increases.
2. Near point/accommodative strain. This is a term used to describe what happens to the eyes when they are focusing on things too closely, for too long.

In most people, these changes will take place predominantly in the pre-teen and teenage years, and tend to stabilize in the early twenties. You will notice that nowhere in this discussion did contact lenses come up. The use of soft contact lenses does not have an impact on the overall length of the eye or the curvature of the cornea, therefore does not make one's prescription worse.

UVA

Unaided visual acuity depends on your prescription for glasses. Typically, the higher the prescription is, the lower the UVA. But since contact lenses do not cause any changes in the numbers in the prescription, it follows that they do not have any effect on the UVA.

BCVA

The best corrected visual acuity is the highest potential for the eyes to see. For most people, the BCVA is 20/20, meaning that with glasses or contacts they should be able to see 20/20. The BCVA depends on the health of the eyes. In order to have a BCVA of 20/20, the eye's ocular media must be clear (i.e., the cornea, the aqueous humor, the crystalline lens, the vitreous humor), and the retina, optic nerve, optic pathways, and visual cortex must all be well developed and healthy.

Contact lenses do not affect the health of any of the structures mentioned above except the cornea. The only instance in which contact lenses can make your vision worse is if they cause the cornea to become less clear. This can happen if the contact lenses cause chronic dryness of the eyes, if the contact lenses do not fit properly, or if contact lenses lead to an infection of the cornea that leaves behind a scar. All of these things can generally be avoided with proper care of the contact lenses and routine eye exams.

Final Verdict

Although the language surrounding the myth is vague, it does not apply to most definitions of how we colloquially use the term 'vision'. It is possible for contact lenses to make your vision worse, but the main determinant for that to happen is not the contact lenses themselves per se, as the myth would imply. The vast majority of contact lens wearers do not encounter this issue. Rather, the main determinant is how responsible the wearer is with the contact lenses when it comes to wearing schedule, replacing them on time, cleaning & disinfecting the lenses, avoiding activities that are restricted for contact lens wearers, etc.

So don't believe everything you hear out there. Contact lenses are great but they are medical devices and need to be taken seriously in order to avoid any complications. I hope you found this information helpful!