High‐resolution <scp>OCT</scp> and in vivo confocal microscopy in corneal epithelial disorders

This is the first study to employ high-resolution anterior segment optical coherence tomography (HR-AS-OCT) for the evaluation of epithelial corneal disorders. The OCT REVO HR (Optopol Technology, Zawiercie Poland) uses a super luminescent diode as its signal source, operating at a central wavelength of 870 nm. The axial resolution of the device is 3 μm, with a transversal (lateral) optical resolution ideal at 12 μm and typically at 18 μm. We conducted a study involving patients with epithelial basement membrane dystrophy, Meesmann dystrophy and Thygeson keratitis to compare corneal epithelial disorders across these conditions. Each patient was examined with a slit lamp, HR-AS-OCT and In Vivo Confocal Microscopy (IVCM). Slit-lamp findings in epithelial basement membrane dystrophy (EBMD; also known as Cogan's dystrophy) are well characterized by its alternative name: map-dot-fingerprint dystrophy. Greyish borders and well-demarcated, continent-like patterns on the otherwise clear cornea represent the ‘map’ phenotype. The ‘dots’ correspond to small, irregular microcysts, whereas the ‘fingerprints’ are formed by parallel or spiral lines (Buffault et al., 2020). Meesmann dystrophy typically presents as numerous cystic lesions in the epithelial layer, extending from the central cornea to the mid-periphery (Patel et al., 2005). Thygeson superficial punctate keratitis usually manifests as small, scaly clusters of subepithelial deposits that do not stain with fluorescein. These deposits are slightly elevated, granular in appearance and have soft, feathery edges (Choe & Kim, 2023; Figure 1). In EBMD, IVCM typically reveals highly reflective extracellular deposits located in the superficial and basal epithelial layers as well as in Bowman's membrane. These deposits may appear as intercellular strands, microcysts or needle-like structures. Such features reflect the folding of a thickened epithelial basement membrane into the epithelium (Shukla et al., 2012). In Meesmann dystrophy, cystic lesions appear as hyporeflective areas within the basal epithelial layer. Hyperreflective material within these cysts corresponds to degenerated epithelial cells. Additionally, numerous isolated hyperreflective particles—unassociated with cystic structures—are seen (Javadi et al., 2010). In Thygeson keratitis, confocal imaging reveals irregular corneal nerve fibres, often obscured by marked haze. A diffuse stromal haze is also present in the anterior stroma, accompanied by areas of increased reflectivity, microdots and reflective deposits (Priyadarshini et al., 2021; Figure 2). In EBMD, high-resolution anterior segment optical coherence tomography (HR-AS-OCT) reveals irregular thickening of the epithelial basement membrane. Characteristic waviness and elevation of the corneal epithelium, along with its protrusion into the epithelial layer, are also observed. The observed imaging findings correspond to the map-like or fingerprint patterns that are often undetectable by slit-lamp examination but were previously only apparent using IVCM. Hyperreflective dots within the mid-epithelial layer correspond to the microcysts observed clinically (Eker et al., 2023). Precise assessment of structural alterations with HR-AS-OCT highlights areas prone to reduced epithelial–basement membrane adhesion and the development of secondary epithelial defects. Unlike lower longitudinal resolution OCT devices, such as the Zeiss Cirrus HD-OCT (5 μm) (Elhardt et al., 2019), the OCT REVO HR allows for the detection of hyperreflective cystic structures with posterior shadowing in both the epithelial and Bowman's layers in Meesmann dystrophy. In Thygeson keratitis, HR-AS-OCT reveals hyperreflective epithelial and subepithelial deposits that correspond to the clinically observed lesions. These deposits are distinctly elevated above the adjacent corneal surface, further supporting their identification on imaging. Even minimally elevated deposits are readily visualized on HR-AS-OCT as hyperreflective areas with indistinct margins. This further underscores the advantage of this device over others, as it enables the detection of flat lesions that may remain undetectable on slit-lamp examination (Figure 3). The recent introduction of HR-AS-OCT offers a powerful alternative, capable of producing detailed cross-sectional images of the epithelial corneal layer and accurate lesion localization, improving diagnostic precision by enabling clear identification of hyperreflective changes. The combined use of slit-lamp examination, HR-AS-OCT and IVCM provides clinicians with a comprehensive toolkit for the accurate diagnosis, monitoring and management of epithelial corneal disorders. HR-AS-OCT is particularly valuable in distinguishing subtle epithelial abnormalities and precisely localizing structural changes. This research received no external funding. The authors declare no conflicts of interest.