Rating papilloedema: an evaluation of the Frisen classification in idiopathic intracranial hypertension

The appearance of the optic disc is a key measure of disease status in idiopathic intracranial hypertension (IIH). The Fris,n classification describes stages of optic disc swelling (grades 0-5). It is the only classification of papilloedema, and is used internationally in clinical and research practice. Despite this, there has been very limited evaluation of the scale. We assessed the inter-rater reproducibility and ability to discriminate optic disc changes over time using the Fris,n classification compared with a system of ranking papilloedema severity in patients with IIH. Paired disc photographs (before and after treatment) were obtained from 47 patients with IIH (25 acute and 22 chronic). Six neuro-ophthalmologists blinded to patient identity, clinical information and chronology of the photographs reviewed the discs and allocated a Fris,n grade and ranked the paired discs in order of papilloedema severity (disc ranking). A total of 188 optic disc photographs were reviewed. All six reviewers agreed in only three comparisons (1.6%) when using the Fris,n classification, compared with 42 comparisons (45.2%) when using disc ranking. The probability of agreement between any two reviewers was 36.1% for Fris,n grade and 70.0% for disc ranking. Disc ranking had significantly greater sensitivity for finding differences in degree of disc oedema, identifying a difference in 75.3% of paired photographs compared to 53.2% detected using the Fris,n classification (p < 0.001). This study demonstrated the limited reproducibility and discriminative ability of the Fris,n classification in identifying changes in serial optic disc photographs in IIH. Simple optic disc ranking appears to be a more sensitive and reliable tool to monitor changes in optic disc appearance. The use of disc ranking in clinical practice and research studies is recommended to monitor alterations in optic disc appearance until alternative schemes, specific to IIH, have been developed.