Tear osmolarity asymmetry between the eyes greater than how many mOsm/L is diagnostic for dry eye disease?

Tear osmolarity asymmetry between the eyes greater than how many mOsm/L is diagnostic for dry eye disease?

• A. 6 mOsm/L
• B. 8 mOsm/L
• C. 10 mOsm/L
• D. 12 mOsm/L

Answer: (B)

Tear osmolarity reflects how concentrated the tear film is. In a healthy eye, both eyes have similar tear composition, so the osmolarity difference between eyes stays small. Dry eye disease disrupts the tear film, often making one eye more hyperosmolar than the other. When the inter-eye difference exceeds 8 mOsm/L, it indicates a meaningful imbalance consistent with dry eye, beyond normal variability. This threshold is used clinically to help diagnose dry eye, so an inter-eye difference greater than 8 mOsm/L is the indicator.

Tear osmolarity reflects how concentrated the tear film is. In a healthy eye, both eyes have similar tear composition, so the osmolarity difference between eyes stays small. Dry eye disease disrupts the tear film, often making one eye more hyperosmolar than the other. When the inter-eye difference exceeds 8 mOsm/L, it indicates a meaningful imbalance consistent with dry eye, beyond normal variability. This threshold is used clinically to help diagnose dry eye, so an inter-eye difference greater than 8 mOsm/L is the indicator.