Enterprise AI Analysis

Keratoconus (KC) is a bilateral, quasi-inflammatory progressive ectatic corneal disease with paracentral thinning. Its cause is not fully understood, but genetic predispositions and exogenous factors like eye rubbing play a role. KC can lead to progressive irregular astigmatism, scarring, and visual impairment. Therapeutic options range from contact lenses to surgical interventions. Early diagnosis is crucial but challenging with slit-lamp alone, requiring computer-based tomography and biomechanical analysis. Differentiating pseudo-keratoconus from true ectasia is critical to avoid unnecessary treatments and ensure proper patient counseling. This study aims to present cases with topographic KC configuration but no actual KC, leading to a 'pseudo-keratoconus' diagnosis.

The study was conducted at the Homburg Keratoconus Center, which tracks over 3,400 KC patients. KC diagnosis requires abnormal posterior elevation, corneal thickness distribution, non-inflammatory thinning, and tomography (Scheimpflug or OCT), with Kmax > 47.0 dpt as a helpful parameter. Inclusion criteria for this study included corneas classified as KC by Scheimpflug imaging (TKC) and a typical elevation data profile with irregular astigmatism and inferior-superior asymmetry (I-S value > 1.4 at 6 mm). Differentiation relied on patient history, slit-lamp findings, and corneal thickness. Scheimpflug tomography (Pentacam®) and corneal biomechanics (Corvis® ST, measuring CBI, TBI, E-staging) were analyzed. Biomechanics were not universally performed but supported morphological interpretation qualitatively. Data were reported as mean±standard deviation or median [range], and categorical data as n/N (%).

Fifty-seven eyes from 37 patients (mean age 49, 16 female:21 male) were included. Mean BCVA was 20/40. Key corneal parameters included mean Kmax 50 D, mean TKC 2, mean I-S value 2.87, and mean thinnest corneal thickness 528 µm. Study eyes were categorized into three groups based on the cause of topographic changes: (1) inferior steepening (35 eyes, e.g., corneal scar (17), Map-Dot-Fingerprint dystrophy (10), FECD (5)); (2) superior steepening (19 eyes, e.g., Map-Dot-Fingerprint dystrophy (7), irregular astigmatism (4), DED (4)); and (3) post-phototherapeutic keratectomy (3 eyes). Corneal biomechanics, when available (11/57 eyes), showed deformation amplitudes (1.05 to 1.27 mm) consistent with stiffened corneas rather than true ectasia.

KC diagnosis relies on Scheimpflug tomography and corneal biomechanics, but a thorough patient history and slit-lamp examination are essential. Pseudokeratoconus must be considered if no obvious KC signs are present on slit lamp despite a KC topographic configuration. This study, with 57 eyes, identified various pathologies mimicking KC: corneal scar (19 eyes), Map-Dot-Fingerprint dystrophy (17), FECD (5), irregular astigmatism (4), DED (4), Salzmann nodular degeneration (3), post-PTK (3), and vortex keratopathy (2). Corneal scarring from infections or trauma, epithelial basement membrane dystrophy (e.g., Map-Dot-Fingerprint), Fuchs endothelial corneal dystrophy with edema, and Salzmann nodular degeneration can all cause KC-like topography. Post-PTK changes, DED, and vortex keratopathy can also mimic KC. Proper alignment during imaging is crucial to avoid artifacts. AS-OCT and AI are emerging tools to refine differential diagnosis. Recommendations include careful slit-lamp inspection, repeat imaging, using epithelial mapping/AS-OCT, and deferring KC-specific interventions until true ectasia is verified.