Cornea specialists published a consensus paper on the diagnosis of keratoconus in 2015 that included three characteristics of keratoconus. Patients should have changes (steepening) to the front and the back of the cornea, and the cornea must show thinning or variations in thickness. Today, improvements in imaging enable doctors to pick up subtle characteristics of the disease before vision is lost, or the cornea changes become too extreme.
These experts also concluded that because there are genetic and biomechanical elements to KC, the disease is bilateral (both eyes) even if the condition is worse in one eye.
Clinicians in France recently described a 19-year-old man who was diagnosed with KC in his left eye, with a cornea that was significantly thinner and steeper than his right eye. The patient admitted that he rubbed his left eye, and he has advised to stop. The doctors completed a battery of diagnostic tests to both eyes.
The authors found this case noteworthy because they documented diagnostic test results for the next 14 years. Now 33 years old, the patient still shows no signs of disease in his right eye. The patient was presented as a possible case of unilateral keratoconus.
We asked two cornea experts if they believe the unicorn of unilateral keratoconus is real. Dr. Marjan Farid MD is Clinical Professor of Ophthalmology at the Gavin Herbert Eye Institute at University of California, Irvine. Dr. Joseph Ciolino MD is Associate Professor of Ophthalmology at Harvard’s Massachusetts Eye & Ear Infirmary:
Is there such a thing as unilateral keratoconus?
Farid: In my opinion, there is no such thing as unilateral keratoconus. Although the disorder may not be at all apparent in the fellow eye, the underlying susceptibility is there.
Ciolino: In general, keratoconus is thought to be a bilateral disease, but can have an asymmetrical presentation with one eye sometimes much more involved than the other.
How would you manage the care of a patient where one eye appears unaffected?
Farid: This is why it is very important that BOTH eyes always be monitored in a patient with “unilateral” or “asymmetric” keratoconus. I also always educate patients on the importance of not rubbing either eye in these cases.
Ciolino: Sometimes one eye is more affected than the other. In some cases, one eye isn’t affected nearly at all. There has been recent reports that after unilateral crosslinking (CXL) the other eye did not show evidence of progression and never required CXL. I have seen this in some of my patients as well.