Abstract
Purpose:
To test a new method for the detection and visualization of macular RNFL loss in eyes affected by glaucoma at different stages (mild, moderate and severe) confirmed against standard automated perimetry.
Methods:
20 eyes of 20 patients (mean age 69±9 years old) were enrolled into the study. 10 eyes were normal and 10 were affected by a glaucomatous field defect at different stages (MD from -4 to -15 dB) confirmed performing a Humphrey 24-2 SITA standard visual field . All eyes underwent retinal nerve fiber layer (RNFL) imaging with Spectralis SD-OCT (Heidelberg Engineering, Heidelberg, Germany). Each patient underwent the standard RNFL analysis by Spectralis SD-OCT. In addition we performed a dense volume scan consisting in 391 horizontal sections within a 20X15 degree rectangle centered on the fovea. Averaging was set to 16 frames. B-scans were separated by 11 microns intervals. Using the incorporated analysis software (Heidelberg Eye Explorer version 5.7.0.1) we obtained transversal scan images showing the RNFL.
Results:
In normal eyes Spectralis SD-OCT revealed hyperreflective arched shaped bundles from the temporal periphery above and below the fovea to the optic disc, sparing a horizontal line passing trough the fovea and the optic disc. The papillo-macular bundle could also be appreciated. In glaucomatous eyes at early and moderate stage the hyperreflective bundles were not visible in the area corresponding to the visual field defect. In eyes at advanced stage of the disease, the RNFL was so reduced that the whole area appeared darker. In these patients no hyperreflectant lines were detectable, suggesting a wide loss of RNF corresponding to visual field loss.
Conclusions:
The study shows that our dense volume scan protocol associated with the new transversal section provided by the Spectralis OCT software, is able to identify retinal fiber bundles in normal eyes and can detect RNFL loss, from early to advanced stage of glaucoma. This defects visualization follows the same visual field damage shape respecting anatomical RNFL distribution. The increased acquisition speed, could make this new approach a useful tool in clinical practice.
Keywords: 627 optic disc •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
691 retina: proximal (bipolar, amacrine, and ganglion cells)