Abstract Vitreoretinal Symposium Frankfurt / Marburg 2003
6th session: OCT


Volumetric optical coherence tomography for macular edema

Glenn J. Jaffe (Durham)


Purpose: Optical coherence tomography (OCT) is a useful ancillary test to diagnose and manage a variety of retinal disorders. It is particularly useful for characterizing
macular diseases. Here, the volumetric OCT technique (VOCT) to manage patientswith macular edema is described.
Methods: Volumetric OCT is a term used to denote the data obtained from the Retinal Thickness Map or Fast Macular Thickness Map scan modes. To perform VOCT, 6 radial scans, approximately 6 mm in length, centered on the fovea are done to produce a series of “optical sections” through the cortical vitreous, retina, RPE and choroid. 100 – 256 points are sampled along the length of each radial scan. The retinal thickness at each of these points
is calculated by measuring the distance between the retinal pigment epithelial layer and the nerve fiber layer. The typical volumetric scan obtained in this manner includes an area in the posterior pole bounded by the major
temporal vascular arcades, the optic nerve, and a point equidistant to the foveal center on the temporal side of the fovea. These scans are reconstructed to form an interpolated surface contour map of the retina that indicates
the retinal thickness at various points in the posterior pole.
Results: Data obtained from VOCT include 6 cross sectional radial macular images, a measurement of mean (± SD) central foveal thickness, a measurement of average thickness in the central, and 8 paracentral macular
regions, and a measurement of volume under the area enclosed by the surface map. Measurements are quite reproducible, and retinal thickness measurements correlate well with leakage observed on fluorescein angiography
and qualitative thickness analysis of stereoscopic fundus photographs. The quantitative and morphological data obtained from VOCT are extremely useful to evaluate and monit the course of macular edema. Typical clinical situations for which this test may be appropriate include cystoid macular edema caused by uveitis, retinal degenerative diseases, drug toxicity, macular edema associated with diabetic retinopathy, and macular edema associated with choroidal neovascularization. Artifacts can be produced by operator error, hazy media, inner and outer retinal boundary misidentification by the software.
Conclusions: VOCT is a very useful, non-invasive method to evaluate eyes with macular edema, and to determine response to therapy. This technique provides morphological and quantitative data that are not readily obtained with alternative techniques such as fluorescein angiography and stereo fundus photography.



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