Tests and diagnosis

By Mayo Clinic Staff

To diagnose keratoconus, your eye doctor (ophthalmologist) will review your symptoms and medical history and conduct a routine eye examination. Your eye doctor may conduct other tests to determine the exact shape of your cornea. Tests to diagnose keratoconus include:

  • Eye refraction. In this standard vision test, your eye doctor uses special equipment that measures your eyes to check for astigmatism and other vision problems.

    Your eye doctor may ask you to look through a device that contains wheels of different lenses, to help determine which combination of lenses give you the sharpest vision. Doctors may use a hand-held instrument (retinoscope) to evaluate your eye's projection and reflection of light.

    This test may include a measurement taken by a special instrument (automatic refractor), which automatically checks how light is projected and reflected by your eye.
  • Slit-lamp examination. In this test, your doctor directs a vertical beam of light on the surface of your eye and uses a low-powered microscope to view your eye. Your doctor will evaluate the shape of your cornea and look for other potential problems in your cornea or other parts of your eye.

    The test may be repeated after eyedrops are used to dilate your pupils so that the doctor can view the back of your cornea.
  • Keratometry. In this test, your eye doctor focuses a circle of light on your cornea. Your doctor measures the reflection to evaluate the curve of your cornea.
  • Computerized corneal mapping. Optical scanning techniques, such as optical coherence tomography and corneal topography, take images of your cornea. The tests create a topographical map of your cornea's surface and measure the thickness of your cornea.
Feb. 20, 2013