Analytical and Morphological Characterization of Lipid Deposition and Oxidation on Silicone Hydrogel Contact Lenses: A Scoping Review

This project is a scoping review that aims to systematically map the existing scientific literature on tear film lipid deposition on soft and silicone hydrogel contact lenses, with particular emphasis on lipid extraction methodologies and analytical or morphological characterization techniques used to study these deposits. Silicone hydrogel contact lenses are widely prescribed due to their high oxygen permeability and physiological compatibility; however, their hydrophobic siloxane components promote lipid accumulation from the tear film, which may compromise lens wettability, surface properties, optical performance, and wearer comfort. Although numerous studies have examined lipid deposition on contact lenses, substantial methodological heterogeneity exists in how lipids are extracted, analyzed, and visualized, making it difficult to compare findings across studies or identify best-practice approaches. The population of interest for this review is soft contact lenses, including silicone hydrogel and conventional hydrogel materials, studied under in vitro, ex vivo, or in vivo wear conditions. The central concept is tear film lipid deposition and its investigation using lipid extraction methods, analytical chemistry techniques (such as HPLC, LC–MS, GC, and spectroscopy), and morphological or imaging approaches (such as scanning electron microscopy, atomic force microscopy, confocal microscopy, and optical imaging). The context includes both laboratory-based models and clinically worn lenses, within the period from 2005 to 2025, reflecting the era of modern silicone hydrogel lens development and advanced lipid analysis technologies. This scoping review follows the Joanna Briggs Institute (JBI) methodology for scoping reviews and will be reported in accordance with the PRISMA-ScR guidelines. A comprehensive literature search has been conducted in Scopus, Web of Science, and PubMed using controlled vocabulary and Boolean operators to capture studies reporting tear film lipids, lipid deposition, extraction procedures, and analytical or imaging-based characterization on soft contact lenses. Records are screened using Rayyan AI, with duplicate removal, title and abstract screening, and full-text eligibility assessment performed according to predefined inclusion and exclusion criteria based on the Population–Concept–Context (PCC) framework. The expected outcome of this review is a structured mapping of lipid extraction strategies and analytical and imaging methodologies used to investigate lipid deposition on soft contact lenses. The review will identify trends in solvent systems, extraction protocols, and detection techniques, as well as highlight methodological gaps, inconsistencies in reporting, and under-explored lipid classes or surface analysis approaches. These findings will provide a methodological foundation for future experimental studies, support evidence-based selection of lipid analysis techniques in contact lens research, and inform the design of optimized protocols for studying lipid–lens interactions.