Abstract
Purpose:
To use pre-laminar neural tissue thickness values obtained trough enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT) to build new structural indices for glaucoma assessment
Methods:
We prospectively enrolled glaucomatous patients, glaucomatous suspects, and healthy controls. Exclusion criteria were the presence of significant media opacity or any ocular disease besides glaucoma. All participants underwent EDI-OCT (SD-OCT; Spectralis®, Wavelength: 870nm; Heidelberg Engineering Co., Heidelberg, Germany) and visual field assessment using the Humphrey Visual Field Analyzer (24-2; SITA-Standard). The following optic nerve head (ONH) parameters were evaluated: lamina cribrosa and pre-laminar neural tissue thicknesses (PLNTT), scleral canal diameter (Bruch’s membrane opening), and cup depth. Two independent examiners assessed all EDI-OCT images (poor quality images were not included in the analysis). Three PLNTT based parameters [PLNTT to disc ratio (PLNTT/D), PLNTT to cup depth ratio (PLNTT/CD), and the PLNTT values itself] were compared among groups using analysis of covariance (accounting for age differences). Areas under receiver operating characteristic curves (AUCs) were calculated for each index and compared using the DeLong test. Whenever both eyes were eligible, one was randomly selected for analysis
Results:
25 eyes of 25 patients were included. Glaucomatous patients (including those from the suspect group) were significantly older than controls (p=0.01). Average visual field mean deviation of glaucomatous eyes was -4.5±3.6dB. The three indices differed significantly between glaucomatous patients and controls (p≤0.01); all indicating a significant pre-laminar neural tissue loss in glaucomatous eyes. In addition, the three indices showed good discrimination ability, with no significant differences between their AUCs (PLNTT/D, =0.87; PLNTT/CD, 0.84; PLNTT, 0.91; p≥0.18)
Conclusions:
Using the EDI method to evaluate deep ONH structures in vivo, we found a significant reduction in pre-laminar neural tissue thickness in glaucomatous eyes. In this population with moderate glaucomatous damage, the three proposed indices showed good diagnostic performance. We believe these initial results deserve further evaluation, especially in a subset of patients with early functional damage
Keywords: 577 lamina cribrosa