Is point wise analysis of the Humphrey visual field feasible as a primary outcome in idiopathic intracranial hypertension?

PurposeUsing the Idiopathic Intracranial Hypertension Weight Trial (IIH:WT) data, this study aimed to determine if point analysis of the Humphrey visual field (HVF) could be more informative than the perimetric mean deviation (PMD) as an IIH trial outcome measure. MethodsIIH:WT was a randomized controlled trial that recruited 66 people with active IIH (mean {+/-} standard deviation age 32 {+/-} 7.8 years). Event-based analysis using a pointwise analysis of the numerical sensitivity data was performed. The number of participants that would be eligible for analysis was calculated when the data were enriched to reflect a medically treated cohort defined as a PMD between -2dB to -7dB. ResultsThe HVF 24-2 mean {+/-} standard deviation PMD in the worse eye was 3.5 {+/-} 1.1dB, (range,2.0 to 6.4dB), and point sensitivity showed a preference for peripheral and blind spot locations. Those points between 0 and -10dB demonstrated negligible ability to improve compared with those between -10dB and -25dB. In evaluating feasibility for a medical intervention trial, 346 points were available for analysis between -10dB and -25dB bilaterally compared with 4123 in baseline sensitivities of 0 to -10dB. ConclusionsMildly affected baseline sensitivities were unlikely to show considerable change over 24 months. There were fewer points available for analysis and greater variability if moderately affected baseline points were chosen. If point analysis was used as an outcome measure in a medical intervention trial, the majority of points would not demonstrate clinically meaningful change, thus offering little advantage over PMD.