Optic disc appearance is a key measure of disease status in Idiopathic Intracranial Hypertension (IIH). Frisen classification describes stages of papilloedema (grades 0–5) and is used internationally, in clinical and research practice. No studies have evaluated Frisen classification since its original description. We assess the inter-rater reproducibility and sensitivity of Frisen classification, compared with our system of ranking papilloedema severity, in IIH. Six masked neuro-ophthalmologists reviewed paired disc photographs (before and after treatment) from 47 patients with IIH (25 acute and 22 chronic) and assigned a Frisen grade. Additionally paired discs were ranked in order of papilloedema severity, (disc ranking). 188 discs were reviewed. Agreement among all reviewers was noted in only three instances (1.6%) when using Frisen classification, compared with 40 instances of exact agreement (44.6%) for disc ranking. The probability of agreement between any two reviewers was 36.1% for Frisen grade and 70.0% for disc ranking. Disc ranking had significantly greater sensitivity, identifying a difference in 75.3% of paired photographs compared to 53.2% for Frisen grade (p<0.001). We demonstrate the limited sensitivity and reproducibility of Frisen classification in IIH. Simple optic disc ranking was more sensitive and reproducible. The use of disc ranking in clinical practice and research studies is recommended until alternative schemes, specific to IIH, have been developed.
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