Purchase this article with an account.
Andrew Turpin, Siyuan Chen, Juan Alejandro Sepulveda Ulloa, Allison M McKendrick; Customizing Macular Structure-Function Maps for Individuals. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):632.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To develop a model of Henle fibre length that is readily customizable to an individual based on their OCT images. By adjusting for an individual's Henle fibre length, it is anticipated that structural and functional measures of the macular will better correlate in glaucoma patients.
We begin with the model of Drasdo et al (Vision Research 47, 2007) as a basis, which uses population-based estimates of the density of retinal ganglion cells (RGCs) and the density of 'inputs' to those ganglion cells (RFs) in the macular region, combined with a simple counting argument, to predict Henle fiber length. In order to customize the computations to an individual, we adjust the density of both RGC and RF in proportion to the ratio of the appropriate layers in a spectral domain OCT image for a person to the population average. For RGCs we use the GCL+ layer (IPL less RNFL using the segmentation scheme of the Spectralis OCT, Heidelberg Engineering), and for the RF we use the Outer Nuclear Layer (ONL) (OPL less ELM).<br /> <br /> For an individual, the OCT data was collected with high resolution radial line scans at 45 degree intervals, and both the GCL+ and ONL thickness was fitted and interpolated to the whole retina with the model of Scheibe et al (Experimental Eye Research 119, 2014) using our own software. For examining the structure-function concordance, we used the RNFL layer of a cube scan of the macular.<br /> <br /> Individual Henle fiber-length maps for 30 control eyes were derived. To explore the utility of the model for structure-function computations in the macular, we fitted the model to the normal area (HFA 10-2 TD within normal limits) of 6 glaucomatous patients with known 10-2 hemifield-loss, extrapolated this to their damaged area, and examined the structure-function relationship both with and without Henle fiber correction.
In the normal eyes, the location of some 10-2 test points when projected onto the retina shifted by more than one degree, and the range of shift between individuals was over one degree. For the glaucomatous eyes, the RNFL thickness of locations that were damaged (10-2 TD below normal limits) generally decreased when mapped to areas of the retina according to our model of Henle fibre length.
Using segmented OCT images to customize macular structure-function mapping for individuals is possible, and may lead to better quantification of macular damage in individuals with glaucoma.
This PDF is available to Subscribers Only