In recent years, biofluids such as aqueous humor (AH) and tear fluid have been considered as potential sources for biomarker discovery studies. Advancements in high-throughput proteomics assays have revealed vast inter-individual variation in biomarkers that can potentially predict, diagnose, and assess responses to the treatment of diseases. The presence of this variation has led to the rise of ‘personalized’ medicine, which, rather than population-level based outcomes, aims to tailor interventions to optimally treat and prevent disease in the individual [1].

Previous studies have investigated the proteome of AH in healthy subjects [2], as well as in various ocular disease states such as primary open angle glaucoma (POAG) [3], diabetic retinopathy (DR) [4], age-related macular degeneration (AMD) [5], pseudoexfoliation syndrome [6], uveal melanoma [7], and others. More recently, our lab identified the constitutive proteome of human AH with high sensitivity using the latest mass spectrometry technology and data analysis methods [8,9]. These studies have shown promise for AH as a useful tool for the diagnosis and management of ocular diseases.

While the collection of AH from the anterior chamber is invasive and requires surgical expertise, tear fluid collection is a non-invasive alternative that has also shown promise as a source of biomarkers with translational potential to clinical medicine [10]. The proteome of tear fluid has been studied in both healthy subjects [[11], [12], [13]] and in several ocular diseases including dry eye disease (DED), glaucoma, AMD, and others [[14], [15], [16], [17], [18]]. However, these studies have used various sampling methods and analytical technologies, making comparisons between studies particularly difficult. Tear collection methods can vary based on the purpose of the collection, the desired sample size, and the ease of collection. The most common tear collection methods include using Schirmer strips or microcapillary tubes. Each method has its advantages and limitations, and the choice of method depends on factors such as the research or diagnostic requirements, patient comfort, and the desired tear volume or quality for analysis [19,20]. Our lab has previously developed a method of in-strip digestion of tear fluid collected via Schirmer strips that showed a significant improvement in the number of proteins identified, without pooling samples [21].

The studies comparing AH and tear fluid are limited, and a comparison of the general proteomic profiles of AH and tear fluid has not been investigated. In this study, we conducted a comparison of the proteomes of matching human tear fluid and AH samples collected from the same individuals. Tear samples were collected immediately prior to surgery, while AH samples were collected during the surgical procedure.