Swept-source optical coherence tomography (SS-OCT) demonstrates better repeatability in obtaining anterior corneal measurements in patients with keratoconus (KC) compared with a rotating Scheimpflug camera (RSC), according to a study published in Eye and Vision.

Researchers enrolled 57 patients with KC (16 mild, 41 moderate) and 43 control individuals in a study to assess the repeatability and agreement of the SS-OCT and RSC methods. They performed a total of 3 consecutive measurements on each participant with each device. The team obtained RSC measurements first, and the same operator performed each measurement for each device. Investigators assessed simulated keratometry (SimK), central corneal thickness, and the thinnest corneal thickness.

The team determined that RSC and SS-OCT exhibited similar repeatability in the anterior cornea (repeatability < 0.5 D) for patients with mild and moderate KC for all measurements. The repeatability for maximum keratometry (Kmax) was 1.33 D and 0.78 D for RSC and SS-OCT, respectively, in patients with moderate KC. The researchers noted that repeatability for posterior corneal parameters was consistently better with SS-OCT than RSC. They also noted significant offsets and wide ranges of limits of agreement between the devices for SimK and corneal thickness values in both devices, according to the report. 


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“The SS-OCT seems to be a better tool for assessing corneal tomography (SimK and corneal thickness) in follow-up examinations in normal eyes as well as mild and moderate KC eyes,” according to the researchers. The team emphasizes the need for consistency in using these devices and urges “due to significant offsets and wide ranges of LoA [levels of agreement] between two devices, interchangeability is not recommended.”

Study limitations include the non-randomized order of measuring corneal parameters and failure to match age and sex between the groups. 

Reference

Herber R, Lenk J, Pillunat LE, Raiskup F. Comparison of corneal tomography using a novel swept-source optical coherence tomographer and rotating Scheimpflug system in normal and keratoconus eyes: repeatability and agreement analysis. Eye Vis (Lond). Published online May 23, 2022. doi:10.1186/s40662-022-00290-6