If your eyes are often dry and itchy, there could be many causes. Issues like dry air and dehydration are common causes of dry eyes. But chronic dry eyes could be caused by an ocular surface disease (OSD).

Ocular surface diseases are conditions that affect and damage the surface layers of the eyes. Your eyes have many parts to them, but the ones most affected by OSDs are the cornea, the conjunctiva, and the glandular network.

The cornea. The cornea is the clear, dome-shaped lens that covers the front of the eye. The cornea’s job is to focus the light coming into your eye.

The conjunctiva. The conjunctiva is a clear membrane that lines the inside of your eyelids and covers the whites of your eyes. The conjunctiva produces a layer of mucus that covers your eyes and becomes a part of your tears. It also creates a barrier that helps keep microorganisms and foreign objects out.

The glandular network. The glandular network is made of the Meibomian glands. These glands are located along the edge of your eyelids, where your eyelashes are. The Meibomian glands produce oil that makes up a part of your tears.

There are a few types of ocular surface diseases. Dry eye is the most common, but other conditions like blepharitis, neurotrophic keratitis, ocular rosacea, and Meibomian gland dysfunction are included as well.

Dry eye. Dry eye is a condition in which your eyes either don’t form enough tears or don’t form functional tears. This can lead to eye infections and damage to the surface of your eyes, which can harm your quality of life.

Blepharitis. Blepharitis is when your eyelids become inflamed, usually as a result of clogged oil ducts near the base of your eyelashes. Although blepharitis itself usually doesn’t cause any issues with your vision, it’s uncomfortable and it can lead to issues like eyelash or eyelid skin problems, dry eyes, styes, chronic pinkeye, corneal injury, or a chalazion. A chalazion is a blockage that can cause swelling and a hard lump in your eyelid.

Neurotrophic keratitis. Neurotrophic keratitis is a degenerative condition caused by nerve impairment. This impairment leads to reduced sensitivity of your cornea. As a result, your eyes don’t instinctively close when they need to, which can result in dry eyes or damage to your cornea.

Ocular rosacea. Ocular rosacea is a type of rosacea that affects your eyes, causing itching, burning, and redness. It can lead to dry eye, blepharitis, and corneal complications that may lead to vision loss.

Meibomian gland dysfunction. Meibomian gland dysfunction is a common condition in which your Meibomian glands aren’t producing sufficient oil. It can cause dry eyes and eyelid inflammation.

Each type of OSD has its own symptoms, although many of them include dry eyes.

Symptoms of dry eyes may include: 

Symptoms of neurotrophic keratitis may include:

Symptoms of ocular rosacea include:

Symptoms of Meibomian gland dysfunction include: 

Because many of these conditions have similar symptoms, it’s important to talk with your doctor to get a proper diagnosis. The diagnostic tests that your doctor performs will depend on which symptoms you're having and what the doctor suspects your diagnosis may be. Diagnostic tests may include:

Testing for neurotrophic keratitis may include:

The causes of OSDs differ between the types.

There are many causes of dry eyes, and many other OSDs can cause dry eyes. Other potential causes include:

Scientists aren’t exactly sure what causes blepharitis, but leading theories suggest that it may be associated with:

Neurotrophic keratitis can be a result of any condition that affects the corneal nerves. This may include one of the herpes viruses, topical medications, or surgery near the eye area.

As with rosacea of the skin, scientists don’t yet know the cause of ocular rosacea. Possible causes include:

Some factors that can aggravate ocular rosacea are:

Meibomian gland dysfunction is often due to age or hormonal changes. Other causes include:

Each type of OSD has its own treatment plan. Your doctor will start by trying to find the cause of your OSD. That cause will then determine your treatment, which may include eye drops, ointments, eyelid scrubs, warm compresses, or artificial tears. 

If you suspect that your dry eyes are caused by an OSD and not dry weather or dehydration, call your doctor or ophthalmologist right away.

American Academy of Ophthalmology: “Cornea,” "Corneal Esthesiometry," “Eye Anatomy: Parts of the Eye and How We See,” “Meibomian Gland Dysfunction.”

American Association for Pediatric Ophthalmology and Strabismus: “Meibomian Gland Dysfunction and Treatment.”

Mayo Clinic: “Blepharitis,” “Dry eyes,” “Ocular rosacea.”

Merck Manual: “Overview of Conjunctival and Scleral Disorders.”

National Organization for Rare Diseases: “Neurotrophic Keratitis.”

Ohio State University Wexner Medical Center: “Program of Excellence for Dry Eyes and Ocular Surface Diseases.”

Optomoetrists Network: “Meibomian Gland Dysfunction."

Wills Eye Hospital: "Ocular Surface Disease."

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