Corneal topography
Eye Care
≈ ¥200-400
(≈ $30-60)
15 min
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Description
Estimated cost for Corneal topography at general public hospitals in China is about ¥140-320, and at Grade 3A hospitals about ¥200-400, varying by hospital tier and region.
Main Uses
Primary clinical uses include: preoperative screening and planning for refractive surgery (LASIK, SMILE, ICL), diagnosis and staging of ectatic disorders (e.g., keratoconus), contact lens fitting (especially for rigid gas-permeable or scleral lenses), assessment of corneal irregularity post-surgery or trauma, monitoring progression of corneal disease, and evaluation of corneal transplant outcomes.
Normal Range
Corneal topography is a qualitative and quantitative imaging test; no universal 'numerical normal range' applies to all parameters. Key metrics include: Simulated Keratometry (SimK) 43.0–45.0 D (average of steepest and flattest meridians), Astigmatism < 1.0 D, Surface Asymmetry Index (SAI) < 0.28, Surface Regularity Index (SRI) < 0.16, Correlation Index (CI) > 0.98, and Central Corneal Thickness (CCT) 530–550 µm. Normal maps show symmetric, concentric, smooth curvature with minimal irregularities and no localized steepening or flattening.
Low Values - Possible Causes
Low keratometric values (e.g., SimK < 42.0 D) may result from: 1) Post-refractive surgery (e.g., LASIK/SMILE overcorrection), 2) Keratoconus in early or forme fruste stages with paradoxical central flattening, 3) Chronic corneal edema causing optical smoothing and artifactually reduced curvature, 4) Advanced Fuchs’ endothelial dystrophy with epithelial microcystic changes, 5) Prior penetrating keratoplasty with donor graft flattening.
High Values - Possible Causes
High keratometric values (e.g., SimK > 47.0 D) may result from: 1) Keratoconus (progressive anterior corneal steepening), 2) Pellucid marginal degeneration (inferior peripheral steepening), 3) Post-cataract surgery corneal warpage or incision-induced astigmatism, 4) Corneal scarring or hydrops-related ectasia, 5) Terrien’s marginal degeneration with adjacent steepening.
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