IMPORTANCE Accurate measurements of choroidal thickness (CT) using enhanced-depth imaging optical coherence tomography (EDI-OCT) require a well-defined choroid-scleral junction (CSJ), which may appear in some eyes as a hyporeflective band corresponding to the suprachoroidal layer (SCL). OBJECTIVE To identify factors associated with the presence and thickness of the SCL in healthy participants and determine how different CSJ boundary definitions impact CT measurements. DESIGN, SETTING, AND PARTICIPANTS Secondary analysis of EDI-OCT images obtained prospectively from 74 eyes of 74 controls (mean age, 68.6 years) from the Age-Related Eye Disease Study 2 Ancillary SDOCT Study. MAIN OUTCOMES AND MEASURES The CSJ appearances were categorized as either having no visible SCL or a hyporeflective band corresponding to the SCL. Ocular parameters associated with the presence and thickness of the SCL were identified. Subfoveal CT was measured using 3 different posterior boundaries: (1) the posterior vessel border (vascular CT [VCT]), (2) inner border of the SCL (stromal CT [StCT]), and (3) inner border of the sclera (total CT [TCT]). Manual segmentation using custom software was used to compare VCT, StCT, and TCT across the macula. RESULTS The SCL was visible in 33 eyes (44.6%). Factors associated with SCL presence and thickness included hyperopic refractive error (R 2 = 0.123; P = .045) and increased TCT (R 2 = 0.215; P = .004), but not age, visual acuity, intraocular pressure, retinal foveal thickness, VCT, or StCT. In eyes where the SCL was not visible, mean [SD] subfoveal VCT was 222.3 [101.5] μm and StCT and TCT were 240.0 [99.0] μm, with a difference of 17.7 [16.0] μm (P < .001). In eyes where the SCL was visible, mean [SD] subfoveal VCT, StCT, and TCT were 221.9 [83.1] μm, 257.7 [97.3] μm, and 294.1 [104.8] μm, respectively, with the greatest difference of 72.2 [30.4] μm between VCT and TCT (P < .001). All 3 CT measurements were significantly different along all points up to 3.0 mm nasal and temporal to the fovea. CONCLUSIONS AND RELEVANCE A hyporeflective SCL is visible at the CSJ on EDI-OCT in nearly half of healthy individuals, and its presence correlates with hyperopia. Different posterior boundary definitions may result in significant differences in CT measurements and should be explicitly identified in future choroidal studies and segmentation algorithms.

The DISCOVER iOCT study demonstrated both generalized feasibility and usefulness based on the surgeon-reported impact on surgical decision making. This large-scale study confirmed similar findings from other studies on the potential value and impact of iOCT on ophthalmic surgery.

In this study, we examined the effects of mechanical stress induced by elevated hydrostatic pressure (HP) on the migration of human optic nerve head (ONH) astrocytes, using an in vitro model that follows repopulation of a cell-free area (CFA) created on a monolayer of cultured astrocytes. alpha-Tubulin staining detected phenotypic changes in astrocytes exposed to HP. The influence of proliferation in closure of the CFA was determined by incorporation of BrdU under 1.5-cm H2O, control pressure (CP), and 10-cm H2O HP with or without 5-fluorouracil. Under control and experimental conditions, closure of the CFA occurred mostly by migration and less by proliferation. Exposure to 10-cm H2O HP induced faster closure of the CFA at 1, 3, and 5 days. The signaling pathways involved in responses to HP were determined using genistein, tyrphostin A25, AG1478, and AG1295, inhibitors of receptor tyrosine kinases; wortmannin and LY294002, inhibitors of phosphatidyl inositol 3-kinase (PI-3K); and SC58236, an inhibitor of inducible cyclooxygenase-2 (COX2). Genistein and tyrphostin A25 blocked HP-induced migration at 1, 3, and 5 days, but did not affect closure of the CFA under CP. AG1478 and AG1295 blocked HP-induced migration and partially inhibit closure of the CFA under CP. LY294002 blocked HP-induced migration. SC58236 markedly inhibited closure of the CFA under CP by inhibiting COX2 activity. Exposure to HP, a physical stress, induced faster closure of the CFA via activation of members of the epidermal growth factor receptor (EGFR) family and PI-3K pathways. Under CP, closure of the CFA in response to denudation, a form of injury, is due to activation of COX2 in ONH astrocytes.

There is clinical and experimental evidence that elevated intraocular pressure (IOP), a mechanical stress, is involved in the pathogenesis of glaucomatous optic neuropathy. The mechanism by which astrocytes in the optic nerve head (ONH) respond to changes in IOP is under study. Gene transcription by ONH astrocytes exposed either to 60 mmHg hydrostatic pressure (HP) or control ambient pressure (CP) for 6, 24, and 48 h was compared using Affymetrix GeneChip microarrays to identify HP-responsive genes. Data were normalized across arrays within each gene. A linear regression model applied to test effect of time and HP on changes in expression level identified 596 genes affected by HP over time. Using GeneSpring analysis we selected genes whose average expression level increased or decreased more than 1.5-fold at 6, 24, or 48 h. Expression of selected genes was confirmed by real-time RT-PCR; protein levels were detected by Western blot. Among the genes highly responsive to HP were those involved in signal transduction, such as Rho nucleotide exchange factors, Ras p21 protein activator, tyrosine kinases and serine threonine kinases, and genes involved in transcriptional regulation, such as c-Fos, Egr2, and Smad3. Other genes that increased expression included ATP-binding cassettes, solute carriers, and genes associated with lipid metabolism. Among the genes that decreased expression under HP were genes encoding for dual activity phosphatases, transcription factors, and enzymes involved in protein degradation. These HP-responsive genes may be important in the establishment and maintenance of the ONH astrocyte phenotype under conditions of elevated IOP in glaucoma.