Purpose
Idiopathic intracranial hypertension (IIH) frequently manifests as papilledema associated with visual loss. Recent studies suggest that increased intraocular pressure (IOP) may counteract the effect of elevated intracranial pressure (ICP) at the level of the lamina cribosa, possibly mitigating damage to axonal transport and subsequent visual function. The current retrospective, cross-sectional, paired-eye, comparison study aimed to test the hypothesis that eyes with increased IOP are associated with superior visual function in those with papilledema secondary to IIH.
Methods
A consecutive series of newly diagnosed patients with IIH from a single Neuro-ophthalmology specialist practice between January 2006 and January 2014 were assessed. Included subjects had baseline bilateral IOP measurements obtained by Goldmann applanation tonometry and concurrent Humphrey Visual Field (HVF) perimetry. Major exclusion criteria were any previous treatment for IIH (ICP-lowering surgery, medical therapy >1 month in duration), a record of any asymmetric ocular comorbidity, or the presence of atrophic papilledema. Patients were divided into two groups for analysis. The first group had symmetric IOPs (+/-1 mmHg) bilaterally whereas the second group had asymmetric IOPs (>= 2mmHg) between eyes. All comparisons were performed between each pair of eyes, with the primary outcome being Mean Deviation (MD) as measured by the HVF analyzer.
Results
A total of 77 patients were assessed for inclusion. Fourty-four patients were analyzed, with 31 in the symmetric group and 13 in the asymmetric group. Baseline demographic features were similar between both groups. In the group with symmetric IOPs, there was no significant difference in MD (p = 0.89). In the group with asymmetric IOPs, there was a significant difference in MD (p = 0.007). Specifically, the eyes with the higher IOP (mean, 15.77 SD 2.52 mmHg) had less visual loss (MD: -5.72 SD 7.13 dB) compared to the fellow eyes with lower IOP (mean, 12.77 SD 2.92 mmHg) and greater visual loss (MD: -7.04 SD 7.66 dB).
Conclusions
Patients presenting with papilledema from IIH with asymmetric IOPs display better visual function in the eye with higher IOP. This observation suggests that IOP may be a factor in the pathophysiology of visual loss from IIH. Further investigation into this relationship is warranted.