How dry eye syndrome affects the cornea and tear film - A State of Sight #94

Dry eye syndrome can cause blurred vision when tears do not coat the cornea properly. This can result in irritation of the corneal surface, which must be smooth along with the tear film to see clearly.

Watch this episode of A State of Sight with Isaac Porter, MD to learn more about the surface of the cornea and how this works with the tear film to provide clear vision.

Welcome to A State of Sight, I’m Isaac Porter and this is your update in ophthalmology and eye care. Today I would like to answer a question we had on twitter by Dr. Ahsan who was asked: “How can dry eyes affect the cornea?” This is a great question, and we haven’t covered it yet.
With dry eye syndrome, there is not an adequate tear film covering up the surface of the eye. If you look back to A State of Sight # 14, I went into detail about the tear film. The tears have a watery part, oily part and a mucus part that make up the tear film.
The mucus part is the back layer of the tear film that directly rests on the cornea in the front of the eye. The cornea has very fine filaments that stick out from the surface of the eye. The mucus layer actually binds in and around these filaments to help the tears stick on to the eye and helps stabilize the other layers of the tear film, the watery and oily parts.
The most important function of the tear film is to ensure that light passes smoothly into the eye. The cornea is also responsible for letting light enter the eye clearly. If the tear film is unstable or breaks up too quickly, patients with dry eye syndrome can have inconsistent vision. The vision can be good sometimes and bad sometimes when the tear film is not smooth and stable.
When we examine patients with dry eye syndrome, there can be small spots on the surface of the cornea from dryness. By using special stains or dyes like fluorescein, rose bengal, or lissamine green in the tear film, we can see areas on the cornea where there is dryness. These small spots are called Punctate Epithelial Erosions, (PEE) or sometimes they will be called SPK (superficial punctate keratitis).
In these areas where we see these spots light up on the cornea with stain, there are cells on the surface that are dead, breaking down, or unhappy where they have been exposed from dry eye syndrome.
More severe complications on the cornea from dry eye syndrome include Salzmann’s Nodules which are uneven bumps, a little bit like scar tissue. These nodules can distort vision, especially if they are in or near the center of the cornea. Severe dry eye syndrome can also cause filaments or small extensions of cells that can be very irritating to the eye.
If you have any more questions about dry eye syndrome, please post. We will be happy to answer your questions. We hope to see you again soon, the next time on A State of Sight.