Central optic nerve head thickness changes are consistent with changes to intracranial pressure (ICP), researchers out of the United Kingdom revealed in a study. This means that changes to ICP can be measured using optical coherence tomography (OCT), offering a long-awaited noninvasive option to gather this metric, according to investigators.
Traditionally, ICP has been measured using lumbar puncture (LP). However, this technique is quite invasive and is associated with a number of side effects. An investigation published in JAMA Ophthalmology demonstrates that OCT imaging can provide clinicians a way to monitor symptoms of idiopathic intracranial hypertension (IIH) and papilledema.
The longitudinal cohort study used data from 3 randomized clinical trials that examined 104 female participants between the ages of 18 and 45 who were diagnosed with IIH. Patients were recruited from 5 National Health Service hospitals in the United Kingdom between 2014 and 2019 and were divided into 2 cohorts.
Cohort 1 consisted of participants who had been diagnosed with papilledema secondary to IIH and who received a telemetric implant to monitor ICP over a 12-week period. Cohort 1 participants underwent evaluation by neuro ophthalmologist via dilated fundus slit lamp exam 1 week after the device was implanted and their ICP was continually monitored at home. The data was then compared with the patients’ OCT measurements.
The findings from cohort 1 demonstrated that mean ICP measurements from a sitting position, as recorded via the telemetric implant, was closely correlated with measurements of optical nerve head volume, maximum height anywhere, central thickness and central volume. Higher ICP corresponded to increased volume and increased central thickness, the report shows. No significant correlation was noted between ICP and RNFL, macular thickness, and other optical nerve head measurement components. This data helped refine parameters for cohort 2.
Cohort 2 underwent a baseline evaluation, and another at 3, 12, and 24 months. Cohort 2 also received an LP assessment of ICP. Researchers then correlated OCT measurements of the optic nerve head, nerve fiber layer, and macular volume scans to ICP levels using Frisén grading and perimetric mean deviation.
The data from cohort 2 confirmed the correlation between central optic nerve head thickness and ICP longitudinally. Investigators say this shows a positive association between central thickness and change in ICP at the follow up points at 12 and 24 months with a decrease in central thickness by 50 μm being associated with an ICP decrease of 5 cm H2O. This correlation can help doctors gauge ICP based solely on OCT data and help track changes without the need for LP, the study says.
Researchers point to a number of limitations, including OCT’s potential to fail in the cases of higher-grade papilledema.
While more studies are required to fully understand the correlation between OCT measurements and ICP, researchers say, OCT imaging measures can be used to assess ICP and “are directly translatable to routine clinical practice.”
Vijay V, Mollan S, Mitchell J, et al. Using optical coherence tomography as a surrogate of measurements of intracranial pressure in idiopathic intracranial hypertension. JAMA Ophthalmol. Published online October 22, 2020. doi:10.1001/jamaophthalmol.2020.4242