Dynamic Ranges of Retinal Nerve Fiber and Optic Nerve Head Parameters Measured Using Optical Coherence Tomography in Glaucoma: A Longitudinal Study

Abstract

Purpose: To evaluate the dynamic range of retinal nerve fiber layer (RNFL) and optic nerve head (ONH) parameters measured using optical coherence tomography (OCT) in conditions ranging from nonglaucomatous status to advanced glaucoma by longitudinal observation.Methods: A total of 15 eyes of 12 participants with glaucoma progression from a non-glaucomatous status to advanced glaucoma were included. The RNFL and ONH parameters were compared between the non-glaucomatous and advanced stages within the same eye. The absolute and relative changes in OCT parameters were analyzed. Results:The median (interquartile range) highest intraocular pressure was 42.5 (37.5, 54.5) mmHg, and the final mean deviation of the visual field test was -24.68 (-23.93, -31.13) dB. The median relative changes in RNFL thickness were -40.6%, -51.9%, -21.4%, -51.1%, and -41.8% in the overall area and the superior, nasal, inferior, and temporal quadrants, respectively (all p < 0.05). Relative changes in rim area, disc area, average cup-to-disc ratio, vertical cup-to-disc ratio, and cup volume were -56.64%, 0.59%, 62.10%, 66.0%, and 337.90%, respectively (all p < 0.05, except for disc area with a p value of 0.753). Conclusion:The dynamic range of the RNFL thickness ranged from 40.6% to 51.9%, and the dynamic range of the ONH parameters ranged from 56.64% to 337.90%. During the course of glaucoma progression, the cup volume showed the widest dynamic range. However, the disc area did not show significant changes.