Eye Movements, Strabismus, Amblyopia, and Neuro-Ophthalmology Baseline OCT Measurements in the Idiopathic Intracranial Hypertension Treatment Trial, Part I: Quality Control, Comparisons, and Variability OCT Sub-Study Committee for the NORDIC Idiopathic Intracranial Hypertension Study Group Icahn School of Medicine at Mount Sinai, NORDIC Headquarters, New York, New York, United States Correspondence: Mark J. Kuper- smith, Icahn School of Medicine at Mount Sinai, NORDIC Headquarters, 1000 10th Avenue, New York, NY 10019, USA; mkuper@chpnet.org. P URPOSE . 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. Submitted: June 5, 2014 Accepted: October 13, 2014 M ETHODS . 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. Citation: OCT Sub-Study Committee for the NORDIC Idiopathic Intracra- nial Hypertension Study Group. Base- line OCT measurements in the Idiopathic Intracranial Hypertension Treatment Trial, part I: quality control, comparisons, and variability. Invest Ophthalmol Vis Sci. 2014;55:8180– 8188. DOI:10.1167/iovs.14-14960 R ESULTS . 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. See the appendix for the members of the OCT Sub-Study Committee for the NORDIC Idiopathic Intracranial Hy- pertension Study Group. C ONCLUSIONS . Spectral-domain OCT provides reliable continuous variables and quantified assessment of structural alterations due to papilledema. (ClinicalTrials.gov number, NCT01003639.) Keywords: papilledema, intracranial hypertension, optical coherence tomography, OCT I diopathic intracranial hypertension (IIH) is a disorder that affects overweight women of childbearing age, 1,2 with a rising incidence in parallel with the current obesity epidemic in the United States. 3 Patients have headaches, pulsatile tinnitus, transient visual obscurations, and diplopia in association with optic disc edema (papilledema). Some degree of vision loss occurs in 86% of patients and 10% develop severe visual loss. 2 The effectiveness of treatment had not been verified by properly designed clinical trials until the implementation of the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT), sponsored by the National Eye Institute. This trial has shown that acetazolamide plus weight management improves the visual fields more than weight management plus placebo at the 6-month study outcome. 4 The accepted objective method for evaluating papilledema and monitoring the alterations in the optic nerve head (ONH) is the Fris´en scale, a noncontinuous ordinal grading based on specific features described in fundus photographs or on ophthalmoscopy. 5 The scale has been clinically useful but lacks sensitivity to small changes in the degree of disc edema and varies among observers. 6,7 In contrast, optical coherence tomography (OCT) measurement of the peripapillary retina nerve fiber layer (RNFL) thickness provides a continuous quantitative assessment of papilledema that correlates with Fris´en grading. 6,8,9 Typically, OCT assessments are used to evaluate thinning of the RNFL due to optic nerve injury from many causes. 10–12 Although prior smaller studies of IIH have shown that lower-resolution time-domain OCT imaging of the RNFL thickness can monitor changes in papilledema over time, 13,14 other studies 15 suggest the commercially available algorithms used in both time-domain and newer spectral- domain (SD) OCT units to calculate RNFL thickness can be unreliable and fail with severe papilledema (Mandel G, et al. IOVS 2010;51:ARVO E-Abstract 555). The OCT substudy of the IIHTT was designed to systemat- ically explore potential continuous measures of alterations in the structures of the ONH and macula due to papilledema, and monitor changes in the ONH, peripapillary and macular retinal layer thicknesses during treatment. Since the SD-OCT instru- ment and proprietary two-dimensional segmentation software methods are not designed to measure swelling of the ONH or the peripapillary retina, we evaluated a variety of approaches via a pilot study. We explored SD-OCT parameters and procedures that could be applied across multiple study sites to provide uniform data collection that measured the effects of papilledema (see Supplementary Appendix Pilot study file). In Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc. www.iovs.org j ISSN: 1552-5783 Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/Journals/IOVS/933678/ on 02/10/2016