The keratometer measures which portion of the cornea?

The keratometer, also known as a corneal topographer, is specifically designed to measure the curvature of the central portion of the cornea, which is critical for determining proper lens fitting and assessing corneal health. The correct measurement range for the keratometer is generally around 3-4 mm of the corneal apex. This area is significant as it directly relates to the optical power of the cornea, influencing how light is focused on the retina.

The 3-4 mm measurement allows for accurate assessment of corneal curvature, which is essential for various applications, including contact lens fitting and pre-operative evaluations for refractive surgeries. By focusing on this specific range, eye care professionals can gather reliable data to ensure that corrective lenses, if needed, properly align with the individual's unique corneal shape.