Keratoconus is a progressive eye disease that weakens and thins the cornea, the clear front surface of the eye. In its early, subclinical stage, the cornea can still appear normal on routine exams.

Alexandra Twin has 15+ years of experience as an editor and writer, covering financial news for public and private companies. Eric's career includes extensive work in both public and corporate ...

Investopedia contributors come from a range of backgrounds, and over 25 years there have been thousands of expert writers and editors who have contributed. Robert Kelly is managing director of XTS ...