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Keratometer Training
Master corneal curvature measurement
A keratometer (also called ophthalmometer) measures the curvature of the anterior corneal surface. It provides "K-readings" that are essential for:
- Contact lens base curve selection
- Detecting and quantifying corneal astigmatism
- Monitoring corneal changes (keratoconus, post-surgical)
- IOL power calculations for cataract surgery
- Fitting orthokeratology lenses
What K-Readings Tell You
K-readings express corneal curvature in diopters (D) or millimeters (mm) of radius. The typical cornea has a radius of about 7.8mm or approximately 43.00D. The keratometer measures the central 3mm zone of the cornea.
Conversion Formula:
Diopters = 337.5 / Radius (mm)
Radius (mm) = 337.5 / Diopters
Example: 7.8mm radius = 337.5 / 7.8 = 43.27D