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Heather Moss, Kiran Malhotra, megh patel, Zainab Shirazi; Optic nerve head geometry as a function of chronic intracranial pressure. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3317.
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© ARVO (1962-2015); The Authors (2016-present)
Chronic elevations in intracranial pressure(ICP) are associated with ophthalmic geometric changes including optic nerve head(ONH) swelling and peripapillary Bruch's membrane(BM) displacement. The objectives of this project were 1.to determine the quantitative relationship between ICP magnitude and geometric ophthalmic features and 2.to evaluate the suitability of geometric ophthalmic features for discriminating high from normal ICP.
6 OCT B-scans of the ONH(radial scan pattern, Spectralis, Heidelberg Engineering) were obtained in both eyes of 20 subjects(age 23-86yrs) prior to lumbar puncture(LP). ICP was measured as LP opening pressure(10-55 cm H2O). Inner limiting membrane(ILM) and BM were manually segmented on each image by two raters. ONH volume(ONHV) was defined as tissue between ILM and BM in in a 3mm diameter circle centered on the ONH and was calculated for each eye by interpolating between images. Perpendicular distances between each of the two BM opening points and the secant line intersecting BM 2mm on either side of the ONH center were calculated for each image and summed across images to generate BM opening distance(BMOD) for each eye. Relationships between ICP and geometric features were modeled using generalized estimating equations(GEE). Area under the curve(AUC) from receiver operating characteristic analysis evaluated the ability to discriminate high(≥ 25 cm H2O) from normal(≤ 20cm H2O) ICP and to confirm normal ICP using geometric features.
Segmentation of ILM and BM was feasible in all scans for 36 eyes(90%). ICP was linearly related to both ONHV (0.010 mm3/cm H2O 95%CI[0.005-0.015], p<0.0005, GEE) and BMOD (39μm into the globe/cm H2O 95%CI[25-54], p<0.0005, GEE). The probability of correctly classifying a subject as having high ICP(AUC for high vs. normal ICP, excluding borderline ICP) was 0.98 95%CI[0.91-1.0] using ONHV and 0.87[0.73-1.0] using BMOD. The probability of correctly classifying a subject as having normal ICP (AUC for normal vs. borderline or high ICP) was 0.86[0.74-0.98] using ONHV and 0.77[0.61-0.93] using BMOD.
We build upon prior reports of qualitative relationships between high ICP, increased ONHV and BMOD by demonstrating a quantitative relationship between chronic ICP and ophthalmic geometric features. Distinguishing between ICP states may be possible based on geometric ophthalmic features. The basis of misclassified cases requires further study.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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