Ocular Hypertension Treatment Study: Effect of Time After Incident Glaucoma on OCT Optic Nerve Head and Macula Measurements.

Abstract

The objectives of this report are to compare optical coherence tomography (OCT) based retinal nerve fiber layer (RNFL) and ganglion cell / inner plexiform layer (GCIPL) thickness in participants who developed primary open-angle glaucoma (POAG) in the Ocular Hypertension Treatment Study (OHTS) to RNFL and GCIPL thickness in those who did not develop POAG (ie, a parallel control group) and to elucidate the relationship between duration after reaching an OHTS POAG endpoint and RNFL and GCIPL thickness. Clinical cohort study using OCT data. Six hundred and forty six OHTS participants who completed OHTS 3 visit OCT imaging were included. Cirrus and Spectralis parapapillary RNFL and GCIPL thickness measurements were compared between 450 eyes that developed POAG and 723 eyes in the control group that did not develop POAG. In eyes that developed POAG compared to eyes that did not develop POAG, mean global RNFL thickness was between 11.1 and 12.7 µm thinner and mean global GCIPL was between 4.5 and 7.6 µm thinner using Spectralis and Cirrus OCT, respectively (all comparisons P < .001). The 10+ years after POAG diagnosis POAG eyes had ∼10% thinner mean global RNFL thickness and GCIPL thickness than eyes with shorter durations after POAG diagnosis. In the OHTS, the ocular hypertensive eyes that developed POAG had significantly thinner RNFL and GCIPL measurements compared with the ocular hypertensive eyes that did not develop glaucoma. In addition, longer duration of POAG was associated with thinner RNFL/GCIPL independent of POAG treatment status and IOP level. These results characterize the magnitude of RNFL and GCIPL thinning associated with increasing POAG duration and reinforce the role of OCT as a key tool for monitoring glaucomatous structural change in eyes with OH.