Keratometer

The keratometer, also known as an ophthalmometer, is a diagnostic instrument used by ophthalmologists and optometrists for measuring the curvature of the anterior surface of the cornea, the outer structure of the eye. This measurement is particularly critical in determining the correct fit for contact lenses and for diagnosing and monitoring corneal diseases such as keratoconus.

History

The keratometer was invented in the 19th century by the German physicist Hermann von Helmholtz. The original design has been refined over the years, but the basic principle remains the same.

Principle

The keratometer operates on the principle of reflection and refraction. It projects a series of illuminated concentric rings onto the cornea. The reflected image of these rings is then analyzed to determine the curvature of the cornea.

Types of Keratometers

There are two main types of keratometers: manual and automated. Manual keratometers require the operator to manually align the instrument with the patient's eye, while automated keratometers use computer technology to automatically align and take measurements.

Clinical Applications

Keratometry is used in a variety of clinical applications, including:

• Determining the fit of contact lenses
• Diagnosing and monitoring corneal diseases such as keratoconus
• Pre-operative assessment for refractive surgery
• Post-operative assessment following corneal transplantation or refractive surgery

See Also

• Ophthalmology
• Optometry
• Cornea
• Contact lenses
• Refractive surgery

References

• Eye doctor examining Nigerian patient with keratometer
  Eye doctor examining Nigerian patient with keratometer
• The commoner diseases of the eye - how to detect and how to treat them (1904)
  The commoner diseases of the eye - how to detect and how to treat them (1904)
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  Shin Nippon Nvision K-5001 Refkeratometer
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  The optics inside a Shin Nippon Nvision K-5001 Refkeratometer