With Halloween just around the corner, thousands will be shopping for fancy dress contact lenses to go with their costume.

The appeal is clear, as their endless colours and shapes allow you to radically change how you look – who wasn’t scared by the white and yellow eyes of the girl in The Exorcist?

However, we also have to be careful. These lenses can cause serious harm – and even blindness – if we fail to take the necessary precautions.

The complications associated with these accessories range from mild symptoms such as dryness, itching and irritation to more serious ones like infections, scarring and loss of vision.

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So why are they dangerous? And what can we do to minimise the risks?

Materials matter

Around Halloween, fancy dress contact lenses can be found everywhere. This makes it easy for anyone to purchase them without a second thought as to where they came from.

However, for an optician or optometrist, few things are more frightening than the sight of a patient who decided to complement their costume with novelty contact lenses.

The quality of the materials is an especially important factor here. Studies have found unauthorised dyes and other substances such as chlorine or iron in cosmetic contact lenses, which can cause irritation, burning, and even trigger allergic reactions when they come into contact with the eyes.

Furthermore, many of the pigments used in these contact lenses increase microbial adhesion. This increases the risk of infection.

To minimise these risks, anyone who decides to purchase these contact lenses should do so at a recognised establishment, and always follow the instructions of their optician or optometrist.

It should be noted that contact lenses are regulated medical devices that must meet strict safety and quality criteria in terms of their manufacture, marketing and use. These criteria are established by national bodies, such as the AEMPS (Spanish Agency of Medicines and Medical Devices).

For an optician or optometrist, few things are more frightening than the sight of a patient who decided to complement their costume with novelty contact lenses. (pixelshot/Canva)

Injury, infection, ulcers

If contact lenses are not properly fitted to the patient’s eye, or if the materials are not suitable, it can cause injuries. These facilitate the entry of bacteria, viruses and fungi, which can cause serious and painful eye infections such as keratitis. If an injury is very serious, it can lead to a corneal ulcer and cause the patient to lose their vision.

Additionally, most people who buy cosmetic contact lenses have never used them before and may never use them again. This multiplies the chances of them being used incorrectly.

One of the most common mistakes is cleaning or storing contact lenses in water instead of using a specially designed solution. Water may contain dangerous microorganisms such as Acanthamoeba, which can cause serious infections when they come into contact with the eyes.

Similarly, the case or lens holder should not be cleaned with water, but always with a specific solution for contact lenses, which ensures greater protection. In addition, contact lenses cannot be stored in maintenance solution for long periods of time, as it can lead to microbial growth.

If you do have any doubts, it is best not to consult artificial intelligence (AI). AI can offer recommendations based on data, but it cannot adapt to the particularities of each user as an eye care professional would.

This is because it cannot perform a physical examination, nor is it capable of interpreting nuances and symptoms.

Furthermore, AI models depend on the information with which they have been trained and the updates they receive.

They should be used as nothing more than a complementary tool, and certainly not as a substitute for a consultation with an eye care professional.

How to use contact lenses safely

1. Do not use fancy dress lenses without the supervision of an eye care professional
2. Ask your optician or optometrist if they would be suitable for you, and ask about what options are currently available to buy.
3. Buy high quality lenses in a recognised establishment, and double check that the product you get is safe.
4. Ensure proper hand hygiene before handling the lenses. Always use a specific solution for contact lenses, never water or saliva.
5. If you feel irritation, take them out immediately. If the irritation continues, pay an eye care professional or doctor a visit promptly.
6. Never share lenses. This can greatly increase the risk of infection.
7. Always put lenses in before you apply makeup.
8. Limit how long you use them for. The recommended time should be provided by the manufacturer.
9. Always remove them before going to sleep.

Contact lenses can be the perfect way to achieve a truly terrifying look this Halloween.

If you protect your eyes properly, the night won’t end with the wrong kind of fright.

Sofía Rendo González, Investigadora predoctoral Xunta de Galicia, Universidade de Santiago de Compostela; Justo Arines, Catedrático de Universidad , área de especialización de Óptica y Optometría, Universidade de Santiago de Compostela, and Nery García Porta, Profesora de optometría, Universidade de Santiago de Compostela

This article is republished from The Conversation under a Creative Commons license. Read the original article.