Normal tear protein profiles and age-related changes.

Area of Science:

• Ophthalmology
• Immunology
• Biochemistry

Background:

• Tear film composition is crucial for ocular surface health.
• Age-related changes in tear proteins are not fully understood.
• Understanding these changes can inform diagnosis and treatment of dry eye disease.

Purpose of the Study:

• To establish normal and age-related reference values for specific and non-specific tear proteins.
• To investigate the relationship between tear protein levels, tear volume, and age.
• To elucidate the secretion pathways of key tear proteins.

Main Methods:

• Enzyme-Linked Immunosorbent Assay (ELISA) technique was employed.
• Analysis of specific tear proteins including lysozyme, lactoferrin, Immunoglobulin A (IgA), Immunoglobulin G (IgG), and caeruloplasmin.
• Correlation of protein levels with age and tear volume.

Main Results:

• A linear decline in lysozyme and lactoferrin levels correlated with age.
• Tear volume reduction was observed with age but was unrelated to lysozyme/lactoferrin decline.
• IgA levels showed a gradual decline, while IgG and caeruloplasmin increased after the fifth decade.
• Evidence suggests IgG and caeruloplasmin are serum transudates.
• Lysozyme and lactoferrin appear to be secreted independently of tear volume.

Conclusions:

• Tear protein profiles significantly change with aging.
• Age-related alterations in tear proteins like IgG and caeruloplasmin suggest a serum origin.
• Distinct secretion mechanisms exist for different tear proteins, independent of tear volume for some.