## Corneal Topography in Keratoconus **Key Point:** The hallmark topographic finding in keratoconus is **inferior steepening** with a characteristic **'bow-tie' or 'scissor' pattern** on Scheimpflug imaging or corneal topography. ### Topographic Features | Feature | Finding in Keratoconus | | --- | --- | | **Steepest meridian** | Inferotemporal quadrant | | **Pattern** | Bow-tie or scissor-shaped asymmetry | | **Central cornea** | Irregular astigmatism with variable curvature | | **Progression** | Cone apex typically inferotemporal | | **Mire pattern** | Irregular, distorted (vs. regular in normal cornea) | **High-Yield:** The **inferior steepening** distinguishes keratoconus from other causes of astigmatism (superior steepening occurs in pellucid marginal degeneration, which is a different ectasia). The bow-tie pattern reflects the cone morphology — the apex is typically located inferotemporally, creating this characteristic asymmetric steepening. **Clinical Pearl:** Scheimpflug imaging (e.g., Pentacam) provides 3D reconstruction and is more sensitive than traditional placido-based topography for detecting early keratoconus and monitoring progression. ### Why Inferior Steepening? The cone in keratoconus is typically located in the inferotemporal cornea, causing maximal steepening in that region. This is thought to relate to biomechanical weakening of the corneal stroma, possibly linked to abnormalities in collagen cross-linking. 
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