Baseline OCT measurements in the idiopathic intracranial hypertension treatment trial, part I: quality control, comparisons, and variability.

PURPOSE: Optical coherence tomography (OCT) has been used to investigate papilledema in single-site, mostly retrospective studies. We investigated whether spectral-domain OCT (SD-OCT), which provides thickness and volume measurements of the optic nerve head and retina, could reliably demonstrate structural changes due to papilledema in a prospective multisite clinical trial setting. METHODS: At entry, 126 subjects in the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) with mild visual field loss had optic disc and macular scans, using the Cirrus SD-OCT. Images were analyzed by using the proprietary commercial and custom 3D-segmentation algorithms to calculate retinal nerve fiber layer (RNFL), total retinal thickness (TRT), optic nerve head volume (ONHV), and retinal ganglion cell layer (GCL) thickness. We evaluated variability, with interocular comparison and correlation between results for both methods. RESULTS: The average RNFL thickness > 95% of normal controls in 90% of eyes and the RNFL, TRT, ONH height, and ONHV showed strong (r > 0.8) correlations for interocular comparisons. Variability for repeated testing of OCT parameters was low for both methods and intraclass correlations > 0.9 except for the proprietary GCL thickness. The proprietary algorithm-derived RNFL, TRT, and GCL thickness measurements had failure rates of 10%, 16%, and 20% for all eyes respectively, which were uncommon with 3D-segmentation-derived measurements. Only 7% of eyes had GCL thinning that was less than fifth percentile of normal age-matched control eyes by both methods. CONCLUSIONS: Spectral-domain OCT provides reliable continuous variables and quantified assessment of structural alterations due to papilledema. (ClinicalTrials.gov number, NCT01003639.).

Baseline OCT measurements in the idiopathic intracranial hypertension treatment trial, part II: correlations and relationship to clinical features.

PURPOSE: The accepted method to evaluate and monitor papilledema, Frisén grading, uses an ordinal approach based on descriptive features. Part I showed that spectral-domain optical coherence tomography (SD-OCT) in a clinical trial setting provides reliable measurement of the effects of papilledema on the optic nerve head (ONH) and peripapillary retina, particularly if a 3-D segmentation method is used for analysis.(1) We evaluated how OCT parameters are interrelated and how they correlate with vision and other clinical features in idiopathic intracranial hypertension (IIH) patients. METHODS: A total of 126 subjects in the IIH Treatment Trial (IIHTT) OCT substudy had Cirrus SD-OCT optic disc and macula scans analyzed by using a 3-D segmentation algorithm to derive retinal nerve fiber layer (RNFL) thickness, total retinal thickness (TRT), retinal ganglion cell layer plus inner plexiform layer (GCL+IPL) thickness, and ONH volume. The SD-OCT parameter values were correlated with high- and low-contrast acuity, perimetric mean deviation, Frisén grading, and IIH features. RESULTS: At study entry, the average RNFL thickness, TRT, and ONH volume showed significant strong correlations (r ≥ 0.90) with each other. The same OCT parameters showed a strong (r > 0.76) correlation with Frisén grade and a mild (r > 0.24), but significant, correlation with lumbar puncture opening pressure. For all eyes at baseline, neither visual acuity (high or low contrast) nor mean deviation correlated with any OCT measure of swelling or GCL+IPL thickness. CONCLUSIONS: In newly diagnosed IIH, OCT demonstrated alterations of the peripapillary retina and ONH correlate with Frisén grading of papilledema. At presentation, OCT measures of papilledema, in patients with newly diagnosed IIH and mild vision loss, do not correlate with clinical features or visual dysfunction. (ClinicalTrials.gov number, NCT01003639.).