Patterns of Retinal Damage and Visual Long-Term Consequences in Patients With Idiopathic Intracranial Hypertension

BACKGROUND AND OBJECTIVES: Persistent visual impairment is a feared complication of idiopathic intracranial hypertension (IIH). However, the structural and functional retinal changes beyond papilledema and their visual long-term consequences are less well studied. Therefore, we aimed to map patterns of structural and functional retinal damage according to papilledema severity to explain when and by what mechanisms patients with IIH lose vision.

METHODS: A prospective cohort study was conducted at 2 tertiary headache centers in Denmark from January 2018 to September 2022. Patients with suspected IIH were consecutively included. Eligibility criteria included clinical suspicion of IIH, age 18 years or older, and written informed consent. The standardized longitudinal diagnostic workup included a structured interview, neurologic and ophthalmologic investigation, lumbar puncture, magnetic resonance imaging, venography, routine blood samples, and diagnostic classification. The primary end point was mechanisms of retinal damage resulting in visual field and acuity impairment according to papilledema severity. A visual outcome score was designed using the desirability of outcome ranking approach.

RESULTS: We included 154 patients with IIH (149 women [96.8%], median age 28.0 [interquartile range 23.0-34.0] years). We found 2 different mechanisms of structural and functional retinal damage according to papilledema severity: (1) Impairment of the retinal nerve fiber layer: increasing papilledema severity was paralleled by increasing atrophy of the retinal nerve fiber layer and atrophy of the ganglion cell layer and resulted in peripheral scotomata without affecting visual acuity. (2) Macular impairment: grade 4 papilledema combined with macular edema, macular exudate, or disorganization of the inner retinal layer resulted in persisting reduction of visual acuity. Using modified desirability of outcome ranking, we proposed a score to predict visual outcome. The score correlated with papilledema severity (Spearman ρ = 0.30; p = 0.016) and disorganization of the inner retinal layer (p = 0.02), but not with lumbar puncture opening pressure, neurofilament light chain, or IIH-associated magnetic resonance imaging characteristics.

DISCUSSION: Our findings suggest 2 different mechanisms of structural and functional retinal impairment depending on papilledema severity. A visual outcome score was proposed, and papilledema severity and disorganization of the inner retinal layer were identified as major predictors of persistent functional retinal impairment.