Novel Index for Detecting Keratoconus

How does the newly developed Corvis Biomechanical Index (CBI) work in clinical practice to distinguish normal from keratoconic eyes? Riccardo Vinciguerra, MD, discussed application of the CBI—as well as its initial development and validation—during Refractive Surgery Subspecialty Day. 

Rationale for the CBI. Dr. Vinciguerra said that he and his colleagues developed the CBI with 2 goals in mind—“to detect those who are at high risk of developing ectasia after LASIK, as well as those who need corneal cross-linking (CXL) as soon as possible for keratoconus.”

 Study background. The researchers used 16 different corneal thickness profile and deformation parameters obtained from the Corvis ST (Oculus), a device incorporating tonometry and Scheimpflug imaging.¹ They evaluated the CBI in a group of 329 patients and then validated it in a second group of 329 patients. All told, 478 eyes were healthy and 180 were keratoconic; the CBI proved to be highly specific and sensitive in differentiating them. (In additional research, the investigators have evaluated a second biomechanical index for assessing ectasia risk.²) Dr. Vinciguerra received the 2017 Troutman Prize for the paper.

Into the clinic. Clinicians can use the CBI in everyday practice, along with topography and tomography, to diagnose ectasia, Dr. Vinciguerra said. “You can see when findings go outside of normative values.” He then presented a series of examples drawn from his clinical practice, to illustrate the application of the index.—Jean Shaw

1 Vinciguerra R et al. J Refract Surg. 2016;32(12):803-810.

2 Ambrósio R Jr. et al. J Refract Surg. 2017;33(7):434-443.

Financial disclosures. Oculus: C.

Disclosure key. C = Consultant/Advisor; E = Employee; L = Speakers bureau; O = Equity owner; P = Patents/Royalty; S = Grant support.