Contact lenses have evolved as an alternative to glasses for correcting vision problems. They are not only comfortable to use, but also help a person to look attractive. Because contact lenses affect eye hydration and tears in many ways, there are a certain number of challenges that necessitate trying to use another alternative. This blog post explains how wearing contact lenses affects tear production or eye hydration and also gives some practical ways to face these problems.

Tear Production and Eye Hydration

Water doesn't tell the whole story of tears, though. They also contain a host of other chemicals that work together to keep the eyes clear, lubricated and healthy. The tear film has three layers, from bottom to top:

  • The lipid layer forms the outermost part of the tear film. It is a layer of oils produced by the meibomian glands in the eyelids. It prevents the tears from evaporating too rapidly.
  • The aqueous layer is in the middle of the tear film. It is the layer that consists mostly of water, but also contains proteins, electrolytes, and other chemicals important for nutrition of the eyes and for fending off infections. This is the layer that also flushes away small particles such as dust and dirt.
  • The innermost of these three is the mucin layer, which coats the tear film spread across the surface of the eye, ensuring that the fluid will spread evenly, avoiding dry spots and keeping the entire surface lubricated.

To maintain healthy and comfortable vision, all three layers of the tear film must work in concert. If any layer is disrupted, dry eye and other irritating symptoms can result.

How Contact Lenses Affect Tear Film Composition

When a contact lens is placed on the eyes, it splits the natural tear film into two parts. The part of the tear film in front of the lens is called pre-lens tear film. The part of the tear film between the lens and the eye is called post-lens tear film. If contact lens wear interferes with either one of these layers, many different problems can arise.

On the one hand, some of the tear film’s volume is absorbed by the contacts so that the total thickness of the tear film is reduced. Also, the lenses can alter the basal lamella, impeding the spreading of the lipid layer and hence allowing the tears to evaporate more quickly. Unprotected from a proper and functioning tear film, the eyes become more prone to drying and discomfort.

Contact lenses, in turn, also increase the surface irregularities and make it more difficult for the lipid layer to spread out and cover the surface. The lens itself, lying in front of the tear film, actually undermines the effective spreading of the lipid oils across the surface and, hence, compromises the tear film stability. Indeed, the tear film will evaporate too fast. The eyes will grit and feel uncomfortable.

Reduced Oxygen Flow And Its Effect On Tear Production

The other significant aspect of how we feel in response to contact lenses relates to the oxygen supply for the eyes. The front part of the eye, called the cornea, has no blood vessels. Its nourishment comes from being in contact with air. The oxygen from the air is dissolved in our tears, which moisten the surface of the cornea. Wearing contact lenses covers the cornea, acting like a barrier to the oxygen supply. This makes our eyes feel dry.

Low oxygen supply

There are many potential reasons for this, which is where the second observation comes in. Essentially, if the oxygen supply to the cornea is compromised, the cells of the cornea cannot function at their optimum level. At the same time, tear production may slow down as well. Both combined result in an alteration of the hydration of the surface of the eye.

So, let's say you wear contacts for a lengthy period of time. Once the surface of the eye becomes unstable, the tear film tends to shift more so than it normally would. And now you see where the third observation comes into play.

Decreased tear production

Another consequence of reduced oxygen levels is decreased production of tears, which delay healing when the eye is cut or scratched. This is because, when the eye is wounded, reduced oxygen prevents the repair of the damage quickly. The scratches in the surface of the eye that contact-lens wearer’s experience could take a lot longer to heal because eyes that are not well-oxygenated are unable to speed up the recovery process.

Mechanical Effects Of Contact Lens Wear

Even the physical presence of contacts on the eyes is a factor in tear secretion and hydration. With every blink, the eyelids brush against the surface of contact lenses, and if they aren't properly fitted or are worn too long without a break, this can cause friction between the contact lenses and the thin tissues of the eye.

Goblet cell reduction

This in turn leads to irritation, which reduces the number of goblet cells that produce the mucin layer of the tear film. When goblet cell density is low, the mucin layer of the tear film is thinner, leading to a tear film that breaks up more easily across the surface of the eye and forming dry spots that cause discomfort and dryness.

Mechanical abrasion

In addition, the mechanical abrasion of the lenses against the eye can, over time, affect the meibomian glands in a similar manner. Meibomian glands release the oils that make up the lipid layer of the tear film, and can become blocked or damaged, rendering the oils less effective, allowing the tears to evaporate quicker and increasing dryness.

Risk Factors For Dry Eye Related To Contact Lens Wear

There are multiple risk factors that might cause dry eye while wearing contact lenses:

Overwearing contact lenses

This occurs when a contact lens is worn longer than the recommended time, which will make the eyes tired, induce microtrauma on the cornea and also make it more difficult for the tear film to stay stable.

Poorly fitting lenses

Contact lenses, even those worn without a valid prescription, can also cause dry eyes. Lenses that don’t fit properly, or that aren't suited to an individual’s eyes, can generate extra friction against the cornea, exacerbating dry eye symptoms.

Environmental factors

Similarly, some environmental factors, like wind, air conditioning and low humidity, can all accelerate tear evaporation, and make dry eye symptoms more severe for contact lens wearers.

Poor contact lens hygiene

Wearing a lens that hasn’t been properly cleaned, stored and cared for, or using a lens when you have an existing illness, such as a cold or the flu, when your eye is more sensitive and at greater risk of becoming irritated and inflamed, is a risk factor for developing dry eye symptoms.

How to Control the Production of Tears and Hydration of Eyes under Contact Lenses?

However challenging it may be for your contact lenses to make tears and keep your eyes hydrated, there are ways to remedy that.

Use correct contacts

The best option is to opt for the correct contact lenses. Silicone hydrogel lenses, for instance, allow more oxygen into the eye, keeping eyes hydrated and moist. Also available are daily disposable lenses, which prevent overwear and retain irritants on the surface of the lenses.

Proper maintenance

Dry eye also requires good lens maintenance. Using a contact lens solution should be suited to your eyes, since some solutions may be chemically reactive and cause eye irritation and dryness. If your current solution leaves you feeling irritated, you can change it to a solution without the preservatives.

Correct lens hygiene

Healthy eyes also depend on maintaining the correct contact lens hygiene. This includes regularly changing your contact lens case to prevent bacteria growth and never wearing contact lenses if you have an eye infection or are feeling unwell.

Lifestyle changes

Optimal tear production and moisture can also be improved by lifestyle. Hydration can be kept up with plenty of water and a nutritious diet that is full of eye-friendly vitamins, including vitamin A and omega-3 fatty acids. Rest days from wearing contact lenses and artificial tears can also alleviate dry eyes.

Wearing Contacts Comfortably and Keeping Eyes Hydrated: Still Possible!

Wearing contact lenses can alter the corneal surface and disrupt the eyes’ ability to produce and maintain a sufficient amount of tears. This can lead to dry eye due to changes to the tear film, reduced oxygen flow to the eye surface, and mechanical friction caused by the contact lenses.

Thankfully, there are many ways that dry eye condition can be managed, including carefully selecting the type of contact lens, as well as simple hygiene and lifestyle changes ‒ and, yes, the contact lenses themselves can be to blame for creating dry eyes. With proper care, you can both enjoy the benefits of contact lenses and maintain your eye health by keeping your eyes hydrated and lubricated.