What Is Dry Eye Disease?

By Dr. Abdalrahman Alabsi – Ophthalmologist | Last reviewed: October 2026

Definition of Dry Eye Disease

Dry eye is a common, chronic, multifactorial disease of the ocular surface caused by a disturbance in the quantity, quality or stability of the tears. This raises the salt concentration of the tears, leading to chronic inflammation of the ocular surface, bothersome symptoms and sometimes blurred vision.

Tear film instability and increased tear salt concentration (tear hyperosmolarity), together with ocular surface inflammation, cell damage and corneal neurosensory abnormalities, are the main mechanisms behind this disease. They will be explained in separate articles.

The Three Layers of the Tear Film

The normal tear film consists of 3 interconnected layers: an oily (lipid) layer that prevents evaporation, an aqueous layer that moisturizes and nourishes the eye, and a mucin layer that anchors the tears to the ocular surface. A disturbance in any of these three layers leads to dry eye.

Illustration of the three tear film layers — lipid, aqueous and mucin — over the ocular surface cells

Symptoms of Dry Eye

The most common are: a burning or hot sensation in the eye, a sandy or foreign-body sensation, redness, an urge to rub the eye (itching), intolerance to screen use, sensitivity to light, and blurred vision that fluctuates during the day and temporarily improves with blinking or lubricating drops. Symptoms usually worsen with air conditioning, screen use and dry weather.

When Should You See a Doctor?

If symptoms are bothersome and persistent, or affect your daily activities (reading, driving, screen work), a comprehensive examination is recommended to determine the exact cause and set an appropriate treatment plan.

References

1. Craig JP, Nichols KK, Akpek EK, et al. TFOS DEWS II Definition and Classification Report. Ocul Surf. 2017;15(3):276-283. doi:10.1016/j.jtos.2017.05.008

2. Willcox MDP, Argüeso P, Georgiev GA, et al. TFOS DEWS II Tear Film Report. Ocul Surf. 2017;15(3):366-403. doi:10.1016/j.jtos.2017.03.006

3. Bron AJ, de Paiva CS, Chauhan SK, et al. TFOS DEWS II pathophysiology report. Ocul Surf. 2017;15(3):438-510. doi:10.1016/j.jtos.2017.05.011

4. Stapleton F, Argüeso P, Asbell P, et al. TFOS DEWS III: Digest. Am J Ophthalmol. 2025;279:451-553. doi:10.1016/j.ajo.2025.05.040