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The lamina cribrosa (LC) and sclera both are considered important structures contributing to the optic nerve head (ONH) changes in glaucoma. To better understand the contribution of the LC and sclera to glaucoma pathogenesis, investigating their structures should be imperative.
Two instruments are commercially available to image the deep ONH tissues in vivo; the enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT) and swept-source (SS) OCT. Park et al. compared the detection rates of identifying the posterior border of the sclera and the LC and measurement reproducibility of sclera and LC thickness using the EDI SD-OCT and SS-OCT. They found that the visibility of the sclera was significantly improved using SS-OCT than using EDI SD-OCT with a significantly improved detection rate of the posterior scleral border using SS-OCT (53% vs. 31%, P = 0.008), while the visibility of the LC was similar between the two devices (81% vs. 75%). Although the interobserver reproducibility was comparable between the two devices both for measurement of the sclera and LC thickness, the intersystem agreement was lower for scleral thickness, with a larger scleral thickness obtained using SS-OCT than EDI SD-OCT (650.26 ± 222.30 vs. 464.32 ± 213.24 µm, P = 0.018). They speculated that the thicker sclera as observed by SS-OCT might be attributable to a deeper tissue penetration of SS-OCT, and concluded that because of the better deep tissue visibility, SS-OCT may facilitate investigation of the contribution of the sclera and LC to glaucoma pathogenesis. Although this study is limited by including only a small subset of myopic glaucoma patients and lack of histologic confirmation, the study is still valuable in that it is the first one that evaluated the sclera and LC using both EDI SD-OCT and SS-OCT and compared their reproducibility. Future studies with a larger subset of eyes are warranted to validate the study results.