To diagnose keratoconus, your eye doctor (ophthalmologist) will review your medical and family history and conduct an eye exam. He or she may conduct other tests to determine more details regarding the shape of your cornea. Tests to diagnose keratoconus include:
- Eye refraction. In this test your eye doctor uses special equipment that measures your eyes to check for vision problems. He or she may ask you to look through a device that contains wheels of different lenses (phoropter) to help judge which combination gives you the sharpest vision. Some doctors may use a hand-held instrument (retinoscope) to evaluate your eyes.
- 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. He or she evaluates the shape of your cornea and looks for other potential problems in your eye. The doctor may repeat the test after you've had eyedrops applied to dilate your pupils. This helps with viewing the back of your eye.
- Keratometry. In this test your eye doctor focuses a circle of light on your cornea and measures the reflection to determine the basic shape of your cornea.
- Computerized corneal mapping. Special photographic tests, such as optical coherence tomography and corneal topography, record images of your cornea to create a detailed shape map of your cornea's surface. The tests can also measure the thickness of your cornea.