Is it really keratoconus or pseudo-keratoconus? – Topographic mimicry

This case series aimed to present eyes with a topographic pseudo-keratoconus configuration resulting from corneal diseases other than keratoconus (KC). Inclusion criteria were a topographic classification of the cornea as KC by Scheimpflug imaging, considering the topographic keratoconus classification (TKC), and a typical height-data profile with irregular astigmatism and an inferior-superior asymmetry value (I-S value) > 1.4 at 6 mm of the cornea. Clinical slit-lamp examination, best-corrected visual acuity, and Scheimpflug tomography (Pentacam®, OCULUS, Wetzlar, Germany) were analyzed. Standard deviations and 95% confidence intervals were added where applicable to enhance descriptive precision. Fifty-seven eyes of 37 patients were included (mean age 49 years, range 18–78; female-to-male ratio 16:21). The mean Kmax was 50 D (42.4–57.8), mean TKC 2, and I-S value 2.87 (1.4–4.91). Mean corneal thickness at the thinnest point was 528 μm (274–709). Study eyes were divided into three groups according to the underlying cause of topographic change: (1) inferior steepening (e.g. Map-Dot-Fingerprint dystrophy); (2) superior configuration (e.g. dry-eye disease or Salzmann nodular degeneration); and (3) newly developed keratoconus-like configuration after phototherapeutic keratectomy. Different corneal pathologies can imitate a topographic KC configuration. Differentiating pseudo-keratoconus from true ectasia is clinically relevant to avoid inappropriate treatment and ensure correct patient counseling. Identifying and distinguishing these pathologies – particularly at the slit lamp – are essential for accurate diagnosis and adequate therapy.