Abstract
Purpose: Tear film lipid layer (TFLL) plays a vital role in maintaining the tear film stability and, thus, the lipid composition of the tears could greatly affect the physiological function and biophysical integrity of the tear film. The objective of this study is to assess the tear lipid composition of the patients receiving laser-assisted in situ keratomileusis (LASIK), femtosecond LASIK (FS-LASIK), or sub-Bowman's keratomileusis (SBK) surgery preoperatively and postoperatively.Methods: Tear samples were collected from the left eye of the patient who receiving LASIK (n = 10), FS-LASIK (n = 10), or SBK (n = 10) surgery in week 0, week 1, week 4, and week 52. A rapid direct injection shotgun lipidomics workflow, MS/MSALL (<2 min/sample), was applied to examine the tear lipidome.Results: In week 52, the SBK group demonstrated a similar lipidome profile compared to week 0, while the FS-LASIK and LASIK groups shifted away from week 0. Two lipids, ganglioside (GD3) 27:4 and triacylglycerol (TAG) 59:3, were found to be associated with the lipidome changes preoperatively and postoperatively. No statistical significance was found in the overall lipid classes from the FS-LASIK group. The LASIK group showed significant alteration in the phospholipid and sphingolipid over time, while the SBK group demonstrated a significant difference in the (O-acyl)-ω-hydroxy fatty acid (OAHFA) and phospholipid.Conclusion: LASIK showed the greatest impact on the tear lipidome changes over time, while SBK demonstrated minimal impact among the three types of refractive surgeries after 1 year.
Highlights
The thin layer of the tear film covers the anterior surface of the cornea and serves the critical functions in maintaining the proper ocular function and health
There is no significant difference in age, gender, spherical, cylindrical, tear breakup time (TBUT), Schirmer test, or corneal staining results among LASIK, FS-LASIK and sub-Bowman’s keratomileusis (SBK) group prior to the refractive surgery
A significant difference in the corneal staining was noted in the FS-LASIK group over time
Summary
The thin layer of the tear film covers the anterior surface of the cornea and serves the critical functions in maintaining the proper ocular function and health. It has been proposed that the tear film is composed of three layers: an inner mucin layer, a middle aqueous layer, and an outer tear film lipid layer (TFLL). The physiological function and biophysical integrity of the tear film would be greatly affected by the lipid composition. It was a challenging task to fully evaluate the lipid profile of the tear samples considering the small amount of the materials obtained from the humans, the diversity of the lipid species, and the complexities of the qualitative and quantitative lipidomics analysis [5]. The lipid composition of the tear film has been extensively studied [6,7,8]. The high sensitivity of the mass spectrometry (MS) in analyzing the low sample volumes makes it a preferred approach in the biomedical research to decipher the fine changes of the lipid metabolism in the ocular and nonocular disorders, for example, Meibomian gland dysfunction, dry eye syndrome [9], and multiple sclerosis [10]
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