Increased tear evaporation in eyes with keratoconjunctivitis sicca

Area of Science:

• Ophthalmology
• Ocular Surface Disease
• Tear Film Dynamics

Background:

• Dry eye and keratoconjunctivitis sicca (KCS) are often characterized by reduced tear film, but this is not always clinically evident.
• Existing KCS definitions may not fully capture the underlying pathophysiology in all patients.

Purpose of the Study:

• To investigate tear film evaporation rates in patients with KCS symptoms.
• To propose a new classification for KCS based on tear evaporation.
• To better describe the pathogenesis of ocular surface damage in KCS.

Main Methods:

• Studied 52 patients presenting with KCS symptoms.
• Assessed tear volume using Schirmer's basic secretion test.
• Measured tear film water evaporation rate in patients and compared with normal subjects.

Main Results:

• Patients with KCS symptoms showed a statistically significant increase in tear film water evaporation rate compared to normal individuals.
• This increased evaporation was observed even in patients without reduced tear volume.
• Elevated evaporation may lead to tear hypertonicity, a known factor in KCS-related ocular surface damage.

Conclusions:

• A subset of KCS patients, presenting with seemingly normal tear volume, may actually have a 'syndrome of increased tear evaporation'.
• This syndrome better explains the ocular surface damage observed in these 'paradoxically wet dry eyes'.
• Reclassifying these cases could improve understanding and management of KCS.