Keratometry

Keratometry is a diagnostic procedure used in ophthalmology to measure the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism. It is a critical measurement for determining the power of an intraocular lens (IOL) for cataract surgery and for fitting contact lenses.

History

The first keratometer, also known as an ophthalmometer, was invented by the French ophthalmologist Louis Émile Javal in 1875. The Javal-Schiotz keratometer, a later version of Javal's original design, is still in use today.

Procedure

During keratometry, a series of concentric circular rings are projected onto the cornea. The reflections of these rings are then observed through the keratometer's eyepiece. The size and shape of the reflections provide information about the cornea's curvature. The procedure is non-invasive and typically takes less than a minute to perform.

Types of Keratometers

There are two main types of keratometers: manual and automated. Manual keratometers require the operator to manually align the device with the patient's eye and interpret the reflected images. Automated keratometers, also known as auto-keratometers, use computer technology to automatically align the device and interpret the reflections.

Clinical Significance

Keratometry is an essential tool in the diagnosis and management of various ocular conditions. It is used to diagnose and monitor the progression of keratoconus, a degenerative disorder that causes a cone-like bulge on the cornea. It is also used in the preoperative assessment for refractive surgery, such as LASIK and PRK, and for the fitting of orthokeratology lenses.

Limitations

While keratometry is a valuable tool in ophthalmology, it has its limitations. It only measures the central 3-4mm of the cornea, which may not be representative of the cornea's overall shape. It also assumes that the cornea is a perfect sphere, which is not always the case, especially in conditions like astigmatism and keratoconus.

See Also

• Ophthalmology
• Cornea
• Astigmatism
• Keratoconus
• Intraocular lens
• Cataract surgery
• Contact lens
• LASIK
• Photorefractive keratectomy