A comparison of retinal nerve fiber layer (RNFL) thickness obtained with frequency and time domain optical coherence tomography (OCT).

To diagnose glaucoma and other diseases of the retinal ganglion cell/ optic nerve, the thickness of the retinal nerve fiber layer (RNFL) is routinely measured with optical coherence tomography. Until recently, these OCT measurements were made almost exclusively with a time domain OCT (tdOCT) machine from a single manufacturer. Recently, a number of OCT machines, based upon an improved frequency domain OCT technology (fdOCT), have appeared. We compared measurements made using a new fdOCT machine to those from the older tdOCT machine. The results were comparable. More importantly, we learned that the key factor determining whether results from different machines will be comparable is the algorithm used to segment RNFL thickness, not the type of OCT.