The corneal epithelium (CE) is the outermost layer of the cornea, characterized by constant turnover, relative stability, and remarkable plasticity. The advent of quantitative imaging modalities, such as very high-frequency ultrasound (VHF-US) and spectral-domain optical coherence tomography (SD-OCT), has enabled the characterization of different patterns of epithelial remodeling. This comprehensive review aims to gather and synthesize all available data on epithelial thickness mapping (ETM) using various imaging methods in normal individuals and in corneal/systemic diseases. The review covers the reproducibility of ETM studies using VHF-US and SD-OCT technologies, comparing their performance in different conditions. It discusses the differences between male and female CET, the effects of aging, ocular biometric parameters, and refractive errors on CET. The review also explores the impact of intraocular pressure, diurnal changes, and pediatric age groups on CET. In the context of corneal diseases, the review examines ETM changes in keratoconus (KCN), corneal dystrophies, limbal stem cell deficiency, and other miscellaneous corneal disorders. It highlights the diagnostic value of ETM in differentiating KCN from normal eyes, subclinical KCN, and other conditions. The review also discusses the role of ETM in planning refractive surgeries, including laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK), and assessing postoperative changes. Overall, the review provides a comprehensive overview of ETM techniques, their applications in normal and pathological conditions, and their potential role in clinical decision-making and surgical planning.The corneal epithelium (CE) is the outermost layer of the cornea, characterized by constant turnover, relative stability, and remarkable plasticity. The advent of quantitative imaging modalities, such as very high-frequency ultrasound (VHF-US) and spectral-domain optical coherence tomography (SD-OCT), has enabled the characterization of different patterns of epithelial remodeling. This comprehensive review aims to gather and synthesize all available data on epithelial thickness mapping (ETM) using various imaging methods in normal individuals and in corneal/systemic diseases. The review covers the reproducibility of ETM studies using VHF-US and SD-OCT technologies, comparing their performance in different conditions. It discusses the differences between male and female CET, the effects of aging, ocular biometric parameters, and refractive errors on CET. The review also explores the impact of intraocular pressure, diurnal changes, and pediatric age groups on CET. In the context of corneal diseases, the review examines ETM changes in keratoconus (KCN), corneal dystrophies, limbal stem cell deficiency, and other miscellaneous corneal disorders. It highlights the diagnostic value of ETM in differentiating KCN from normal eyes, subclinical KCN, and other conditions. The review also discusses the role of ETM in planning refractive surgeries, including laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK), and assessing postoperative changes. Overall, the review provides a comprehensive overview of ETM techniques, their applications in normal and pathological conditions, and their potential role in clinical decision-making and surgical planning.