Abstract
Structural differences between optic nerve head (ONH) parameters in glaucomatous and non-glaucomatous eyes has been documented, however the association between such parameters in patients with different disease stages is yet to be elucidated. We investigated the relationship between different laminar and prelaminar ONH structures using enhanced depth imaging spectral-domain optical coherence tomography (EDI OCT) in a population with and without glaucoma. In this observational case-control study, we prospectively enrolled healthy individuals and glaucomatous patients with different disease stages. All participants underwent EDI OCT imaging (Heidelberg Engineering). Following ONH parameters were measured on serial vertical B-scans by two examiners masked to patient’s clinical data: lamina cribrosa (LC) and prelaminar neural tissue (PLNT) thicknesses, Bruch’s membrane opening (BMO) and cup depth. Associations between cup depth, and laminar and prelaminar parameters were evaluated controlling for possible confounding factors such as axial length and disc size. Sixty-four eyes of 64 patients were included (30 with glaucoma and 34 controls). Eyes with glaucoma had significantly lower mean LC and PLNT thickness, and greater mean cup depth than controls (p<0.01). There was a significant negative association between PLNT thickness and cup depth in glaucomatous eyes (R2 = 0.158, p = 0.029). In addition, LC thickness correlated significantly with cup depth (R2 = 0.135, p = 0.045). Eyes with thinner LCs presented deeper cups. Overall, cup depth and BMO had the best and LC thickness had the worst intraobserver and interobserver reproducibility grading. In conclusion, significant associations were seen between cup depth, LC and PLNT thickness. Eyes with deeper cups not only had less neural tissue, but also thinner LCs, independent of disc size and axial length. Best reproducibility was found for prelaminar parameters compared to deeper ONH structures.
Highlights
The lamina cribrosa (LC) within the scleral canal in the optic nerve head (ONH) is thought to be the primary site of axonal insult in glaucoma [1,2,3]
Even though glaucomatous changes of different ONH parameters have been documented with enhanced depth imaging spectral-domain optical coherence tomography (EDI optical coherence tomography (OCT)), the relationship between such parameters in patients with different disease stages is yet to be elucidated, i.e. which ONH parameter has a greater influence on disc cupping in eyes with glaucoma—prelaminar neural tissue loss or LC thinning? The main goal of this study was to investigate the relationship between optic disc cupping and lamina cribrosa and prelaminar neural tissue thickness using the enhanced depth imaging (EDI) modality of spectral domain (SD)-OCT in a population with and without glaucoma
PLNTT, prelaminar neural tissue thicknesses; BMO, Bruch’s membrane opening; LCT, lamina cribrosa thickness. *Normally distributed variables represented by mean±standard deviation; non-normally distributed variables represented by median
Summary
The lamina cribrosa (LC) within the scleral canal in the optic nerve head (ONH) is thought to be the primary site of axonal insult in glaucoma [1,2,3]. Even though glaucomatous changes of different ONH parameters have been documented with EDI OCT, the relationship between such parameters in patients with different disease stages is yet to be elucidated, i.e. which ONH parameter has a greater influence on disc cupping in eyes with glaucoma—prelaminar neural tissue loss or LC thinning? The main goal of this study (our primary outcome) was to investigate the relationship between optic disc cupping (cup depth) and lamina cribrosa and prelaminar neural tissue thickness using the EDI modality of SD-OCT in a population with and without glaucoma. As secondary outcomes we determined the interobserver and intraobserver reproducibility of the analyzed EDI OCT parameters
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