Dry Eye Disease Study Now enrolling adults with ongoing dry eye symptoms.

Dry eye disease is more than simply not having enough tears. It is a multifactorial disease of the ocular surface in which the normal balance, or homeostasis, of the tear film is disrupted. Tear-film instability, increased tear osmolarity, ocular surface inflammation, and tissue damage can all contribute to the disease process.

Major Components of Dry Eye

Dry eye can have different underlying causes, and patients often have more than one contributing factor.

Aqueous-Deficient Dry Eye
The lacrimal glands do not produce enough of the aqueous component of the tear film. Reduced tear volume can leave the ocular surface less protected and contribute to tear-film instability and increased osmolarity.

Evaporative Dry Eye
Tears evaporate too quickly from the surface of the eye. A common cause is meibomian gland dysfunction (MGD), in which the meibomian glands do not produce or release healthy oils that help protect the tear film from evaporation.

Mixed Dry Eye
In many patients, both mechanisms are present. Reduced tear production and increased evaporation can occur together, making dry eye a complex and individualized condition. TFOS DEWS II recognizes aqueous-deficient and evaporative dry eye as overlapping components rather than completely separate conditions.

The Inflammatory Cycle

Regardless of where dry eye begins, disruption of the tear film can lead to tear-film instability and increased osmolarity, placing stress on the ocular surface. This can trigger an inflammatory response and damage the cells that help maintain a healthy ocular surface.

As the ocular surface becomes inflamed and damaged, the tear film can become even less stable. This increases evaporation and further increases tear osmolarity, which can promote additional inflammation and surface damage.

The result is a self-perpetuating inflammatory cycle:

Tear-film instability → increased evaporation and osmolarity → ocular surface inflammation → surface damage → further tear-film instability

Understanding this cycle is an important part of modern dry eye research and treatment. Rather than simply replacing tears, effective management may require identifying and addressing the underlying factors contributing to tear-film instability, inflammation, and ocular surface dysfunction.

References / Learn More

1. Craig JP, Nichols KK, Akpek EK, et al. TFOS DEWS II Definition and Classification Report. The Ocular Surface. 2017.
2. Bron AJ, de Paiva CS, Chauhan SK, et al. TFOS DEWS II Pathophysiology Report. The Ocular Surface. 2017.
3. Jones L, Downie LE, Korb D, et al. TFOS DEWS II Management and Therapy Report. The Ocular Surface. 2017.