Forme Fruste Keratoconus Imaging and Validation via Novel Multi-Spot Reflection Topography

Abstract

Background/aims: This case report aims to evaluate safety, efficacy and applicability of anterior surface imaging in a patient with forme fruste keratoconus (FFKC) based on a novel multi-spot, multicolor light-emitting-diode (LED) tear film-reflection imaging technology.

Case description: A 45-year-old male patient, clinically diagnosed with FFKC, with highly asymmetric manifestation between his eyes, was subjected to the multicolor-spot reflection topography. We investigated elevation and sagittal curvature maps comparatively with the multicolor-spot reflection topographer, a Placido topographer and a Scheimpflug imaging system. For the right eye, steep and flat keratometry values were 41.92 and 41.05 D with the multicolor spot-reflection topographer, 42.30 and 42.08 D with the Placido, and 41.95 and 41.19 D with the Scheimpflug system. For the left eye, steep and flat keratometry values were 41.86 and 41.19 D with the multicolor spot-reflection topographer, 42.06 and 41.66 D with the Placido topographer, and 41.96 and 41.66 D with the Scheimpflug camera. Average repeatability of the keratometry measurements was ±0.35 D for the multicolor spot-reflection topographer, ±0.30 D for the Placido, and ±0.25 D for the Scheimpflug camera. Very good agreement between the instruments was demonstrated on the elevation and curvature maps.

Conclusion: The ease of use and the comparable results offered by the multicolor spot-reflection topographer, in comparison to established Placido and Scheimpflug imaging, as well as the increased predictability that may be offered by the multicolor spot-reflection topographer, may hold promise for wider clinical application, such as screening of young adults for early keratoconus and, in a much wider perspective, potential candidates for laser corneal refractive surgery.

Keywords: Color-point topography; Diagnosis of keratoconus; Differential topography; Forme fruste keratoconus; Index of Height Decentration; Index of Surface Variance; Light-emitting diode Cassini; Light-emitting diode topography; Pentacam HR; Placido topography; Point-source topography; Surface Asymmetry Index; Surface Regularity Index.

Fig. 1

a Top panel: anterior surface elevation map of the OD obtained by the Cassini. Bottom panel: anterior surface elevation map of the OD obtained by the Pentacam. b Top panel: anterior surface elevation map of the OS obtained by the Cassini. Bottom panel: anterior surface elevation map of the OS obtained by the Pentacam.

Fig. 2

a Top panel: anterior surface tangential curvature map of the OD obtained by the Cassini. Bottom panel: anterior surface tangential curvature map of the OD obtained by the Pentacam. b Top panel: anterior surface tangential curvature map of the OS obtained by the Cassini. Bottom panel: anterior surface tangential curvature map of the OS obtained by the Pentacam.

Fig. 3

Placido topography imaging of the OD (top) and OS (bottom).