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Asymmetry of pachymetry, keratometry values helps detect corneas at risk for refractive surgery
PARIS — An asymmetry index evaluating the difference in pachymetry and keratometry findings between the left eye and right eye of the same patient provides additional reliable information to identify corneas at risk for refractive surgery, according to a specialist.
“Both topography and artificial intelligence systems help us identifying abnormal corneas and keratoconus suspects but only consider each eye separately. They do not compare right and left eyes, and yet we know that asymmetry between eyes is an indicator of corneal abnormality,” Alain Saad, MD, said at the meeting of the French Society of Ophthalmology.
Alain Saad
Normal eyes, he explained, tend to be symmetric. Central pachymetry or thinnest pachymetry differ by an average of 6 µm between the right and left eyes in normal subjects, while in keratoconus eyes, the mean difference is 35 µm.
“In normal patients, the difference is never more than 18 µm in thinnest pachymetry. Whenever the difference is above that, you should look in more details for other signs of abnormality,” he said.
“By combining thinnest pachymetry and keratometry indexes of the two eyes, we can obtain a score of similarity or asymmetry between the two eyes. A high score shows high asymmetry, and a negative score shows that the cornea is normal,” Saad said.
A study is currently in press. Saad and Damien Gatinel, MD, hold the patent of this new tool.
Disclosure: Saad has no relevant financial disclosures.