Abstract
Purpose:
To investigate the ability of glaucoma specialists to identify different laminar and pre-laminar optic nerve head (ONH) structures using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT) in a population with and without glaucoma.
Methods:
We prospectively enrolled glaucomatous patients (glaucomatous optic neuropathy and reproducible visual field defect) and healthy individuals from August 2012 to October 2012. Those with significant media opacity or any ocular disease (besides glaucoma) were excluded. All participants underwent EDI-OCT (SD-OCT; Spectralis®, Wavelength: 870nm; Heidelberg Engineering Co., Heidelberg, Germany). We investigated the ability of three glaucoma specialists to identify the following ONH parameters in each EDI-OCT image: anterior and posterior surfaces of the lamina cribrosa, anterior surface of the pre-laminar neural tissue, Bruch’s membrane opening (scleral canal diameter), and anterior and posterior margins of the choroid (choroidal thickness) measured 500µm distant from the inferior border of the Bruch’s membrane opening. Whenever both eyes were eligible, the right eye was arbitrarily chosen for analysis. Identification of each parameter was graded as easy, difficult or impossible.
Results:
A total of 19 eyes of 19 patients were included (mean age, 54.3±25.2 years). Overall, the anterior surface of the pre-laminar neural tissue and the borders of the Bruch’s membrane opening were the landmarks most clearly identified (graded as easy in over 90% of the eyes on average). On the other hand, the anterior and posterior surfaces of the lamina cribrosa were clearly identified in less than 35% of the cases on average. Comparing the eyes in which most parameters were easily identified with those that showed poor visibility, the former group was mostly composed by eyes with glaucoma, with larger cup-to-disc ratio (mean of 0.72 vs 0.30; p<0.05) and a thinner pre-laminar neural tissue layer (mean of 188 vs 390 µm; p<0.5).
Conclusions:
Most pre-laminar ONH structures could be clearly identified by different glaucoma specialists using EDI-OCT. Identification of deeper structures such as the lamina cribrosa seems to be not always feasible, especially in cases of normal eyes with healthy ONH.
Keywords: 627 optic disc •
577 lamina cribrosa •
419 anatomy