Keratometry measures the curvature of the central cornea, providing information about its focusing power and astigmatism. It is a fundamental parameter in contact lens fitting and IOL calculations.
Method
Keratometers project mires onto the cornea and analyse their reflections to infer curvature in specific meridians. Many modern devices combine keratometry with topography or biometry.
- Outputs include corneal power in dioptres and axis of astigmatism
- Assumes a standard relationship between anterior curvature and total corneal power
- Readings are most accurate over a limited central zone
- Irregular corneas may require more advanced mapping techniques
Clinical Role
Keratometry is essential in prescribing rigid contact lenses, calculating IOL power, and detecting significant corneal astigmatism. Changes over time may indicate corneal disease or effects of surgery.
- Baseline values help identify conditions such as keratoconus
- Regular measurements monitor corneal stability in refractive surgery candidates
- Errors in keratometry contribute directly to refractive surprises after surgery
- Results should be cross-checked with refraction and corneal imaging when needed
