The Difficulty with Diagnosing Keratoconus

March 2023 Update Newsletter

March 14, 2023

Dr. Brooke Messer OD, a keratoconus expert at Vance Thompson Vision in West Fargo, North Dakota lectured at the recent Global Specialty Lens Symposium in Las Vegas.  She reminded eye care professionals there are several myths and misunderstandings about keratoconus and offered evidence why this disease is so often misdiagnosed.  While doctors may create a mental checklist of clues to the disease, she cautioned that not all signs are present for all patients.  Here are some of the reasons why keratoconus may not be so easy for your doctor to diagnose:

  • You don’t need to have a steep cornea. Finding out the curvature of a cornea gives doctors insight into the quality of a patient’s vision. Higher keratometry (k) readings indicate steeper corneas; anything above k=48 is suspected keratoconus.  However, Dr. Messer noted a high k reading is not essential to be diagnosed with keratoconus, and showed examples of average corneal curvatures in patients that had KC.
  • Your cornea doesn’t need to be thin. Again, evidence of a thin cornea is a way some doctors discover KC.  Normal corneas have an average thickness of about 550Β΅m, anything less than 500Β΅m may indicate a corneal irregularity or keratoconus.  Messer noted there are numerous individuals with documented KC whose cornea thickness falls in the normal range.
  • Both eyes need not be affected. While keratoconus is considered a bilateral (both eyes) disease, it often has an asymmetrical presentation.  One eye may show absolutely no signs of disease, while the fellow eye has irregularities.  Messer cautioned that keratoconus could be the diagnosis even if it appears to be unilateral, and that doctors need to monitor both eyes at every eye exam.
  • You don’t age out of keratoconus. While most patients are diagnosed in their teens or twenties, there are individuals who develop symptoms of KC later in life.  Messer reported people in their 30s, 40s, or even 50s may learn they have keratoconus for the first time or experience new onset of disease progression.  She advised doctors to continue to think about keratoconus as a possible diagnosis for patients with unexplained vision findings well into middle-age.
  • You can have perfect vision and still have keratoconus. Another myth is that patients with keratoconus can’t achieve 20/20 reading an eye chart.  On a simple vision screen, some patients appear to have perfect vision, but they may complain of excessive glare or trouble driving at night. In these cases, doctors are encouraged to think about keratoconus and to go beyond a simple vision test.

Dr. Messer’s presentation showed that no single data point can guarantee a patient has keratoconus.  She described how some indicators of the disease can be absent; a patient may have a combination of normal and abnormal test results.  It underlines why this condition is often misdiagnosed, and why doctors need to gather all the information they can about the cornea strength, structure, and vision to make a definite diagnosis.

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