Abstract
Purpose :
Combined photoplethysmographic (PPG) data from both eyes can predict intracranial pressure (ICP) with a mean absolute error accuracy of 3mmHg. Here, we determine if the degree of optic disk (OD) swelling influences the accuracy of ICP estimation.
Methods :
Objective measurement of OD swelling was done using optical coherence tomographic (Heidelberg Spectralis) measurement of Bruch’s membrane opening (BMO) minimum rim width. The severity of OD swelling was also graded by two independent observers using the modified Frisén Scale. Ophthalmodynamometry measurement of venous pulse amplitudes with modified photoplethysmography (PPG) was used to estimate intracranial pressure and this was compared to the opening pressure on lumbar puncture (LP) performed within 3 days after PPG. PPG data from each eye was used to calculate an ICP estimate using the zero amplitude extrapolated model previously described. The difference between LP opening pressure and estimates of ICP was calculated. This was then compared to OD swelling measures using linear mixed modelling and Frisén grading using the Poisson distribution.
Results :
31 participants with suspected idiopathic intracranial hypertension were examined with a mean BMO thickness of 505 um (sd=125, range: 254 to 745). Neither mean BMO thickness (p=0.64), mean absolute BMO thickness (p=0.60) nor Frisén grading scale (p=0.22) were significantly associated with the difference between estimated and LP measures. Additionally, prediction errors using combined PPG data from each eye to estimate ICP were not associated with mean BMO thickness from both eyes (p=0.84). BMO thickness was associated with subjective Frisén grading (p<0.0001).
Conclusions :
The degree of optic disk swelling is not associated with the difference between PPG estimates of ICP and LP measurements. PPG estimates of ICP appear robust in the face of the observed disk swelling.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.