Joanne C Wen

Peripapillary Retinal Nerve Fiber Layer Vascular Microcirculation in Glaucoma Using Optical Coherence Tomography–Based Microangiography

Purpose To investigate the vascular microcirculation changes in the retinal nerve fiber layer (RNFL) in normal, glaucoma suspect, and open-angle glaucoma (OAG) groups using optical coherence tomography–based microangiography (OMAG). Methods One eye from each subject was scanned with a Cirrus HD-OCT 5000–based OMAG prototype system montage scanning protocol centered at the optic nerve head (ONH). Blood flow signals were extracted using OMAG algorithm. Retinal nerve fiber layer vascular microcirculation was measured by calculating the blood flux index and vessel area density within a 1.2-mm width annulus centered at the ONH with exclusion of big retinal vessels. One-way ANOVA were performed to analyze the RNFL microcirculation among groups. Linear-regression models were constructed to analyze the correlation between RNFL microcirculation and clinical parameters. Discrimination capabilities of the flow metrics were assessed with the area under the receiver operating characteristic curve (AROC). Results Twenty normal, 26 glaucoma suspect, and 42 OAG subjects were enrolled. Eyes from OAG subjects and glaucoma suspects showed significantly lower blood flux index compared with normal eyes (P ≤ 0.0015). Retinal nerve fiber layer blood flow metrics showed significant correlations with visual field indices and structural changes in glaucomatous eyes (P ≤ 0.0123). Similar discrimination capability of blood flux index compared with RNFL thickness was found in both disease groups. Conclusions Peripapillary RNFL vascular microcirculation measured as blood flux index by OMAG showed significant differences among OAG, glaucoma suspect, and normal controls and was significantly correlated with functional and structural defects. Retinal nerve fiber layer microcirculation measurement using OMAG may help physicians monitor glaucoma.

Optic nerve head perfusion in normal eyes and eyes with glaucoma using optical coherence tomography-based microangiography.

BACKGROUND To investigate the differences of perfusion in the optic nerve head (ONH) between normal and glaucomatous eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique. METHODS One eye from each subject was scanned with a 68 kHz Cirrus 5000 HD-OCT-based OMAG prototype system centered at the ONH (Carl Zeiss Meditec Inc, Dublin, CA, USA). Microvascular images were generated from the OMAG dataset by detecting the differences in OCT signal between consecutive B-scans. The pre-laminar layer (preLC) was isolated by a semi-automatic segmentation program. En face OMAG images for preLC were generated using signals with highest blood flow signal intensity. ONH perfusion was quantified as flux, vessel area density, and normalized flux within the ONH. Standard t-tests were performed to analyze the ONH perfusion differences between normal and glaucomatous eyes. Linear regression models were constructed to analyze the correlation between ONH perfusion and other clinical measurements. RESULTS Twenty normal and 21 glaucoma subjects were enrolled. Glaucomatous eyes had significantly lower ONH perfusion in preLC in all three perfusion metrics compared to normal eyes (P≤0.0003). Significant correlations between ONH perfusion and disease severity as well as structural changes were detected in glaucomatous eyes (P≤0.012). CONCLUSIONS ONH perfusion detected by OMAG showed significant differences between glaucoma and normal controls and was significantly correlated with disease severity and structural defects in glaucomatous eyes. ONH perfusion measurement using OMAG may provide useful information for detection and monitoring of glaucoma.

Peripapillary Retinal Nerve Fiber Layer Vascular Microcirculation in Eyes With Glaucoma and Single-Hemifield Visual Field Loss

Importance Understanding the differences in vascular microcirculation of the peripapillary retinal nerve fiber layer (RNFL) between the hemispheres in eyes with glaucoma with single-hemifield visual field (VF) defects may provide insight into the pathophysiology of glaucoma. Objective To investigate the changes in the microcirculation of the peripapillary RNFL of eyes with glaucoma by using optical microangiography. Design, Setting, and Participants Eyes with glaucoma and single-hemifield VF defect and normal eyes underwent scanning using an optical microangiography system covering a 6.7 × 6.7-mm2 area centered at the optic nerve head. The RNFL microcirculation was measured within an annulus region centered at the optic nerve head divided into superior and inferior hemispheres. Blood flux index (the mean flow signal intensity in the vessels) and vessel area density (the percentage of the detected vessels in the annulus) were measured. Main Outcomes and Measures Differences in microcirculation between the hemispheres in eyes with glaucoma and normal eyes and correlations among blood flow metrics, VF thresholds, and clinical optical coherence tomography structural measurements were assessed. Results Twenty-one eyes from 21 patients with glaucoma (7 men and 14 women; mean [SD] age, 63.7 [9.9] years) and 20 eyes from 20 healthy control individuals (9 men and 11 women; mean [SD] age, 68.3 [10.7] years) were studied. In eyes with glaucoma, the abnormal hemisphere showed a thinner RNFL (mean [SE] difference, 23.5 [4.5] &mgr;m; 95% CI, 15.1-32.0 µm; P < .001), lower RNFL blood flux index (mean [SE] difference, 0.04 [0.01]; 95% CI, 0.02-0.05; P < .001), and less vessel area density (mean [SE] difference, 0.08% [0.02%]; 95% CI, 0.05%-0.10%; P < .001) than did the normal hemisphere. Compared with normal eyes, reduced RNFL microcirculation was found in the normal hemisphere of eyes with glaucoma, measured by mean [SE] differences in blood flux index (0.06 [0.01]; 95% CI, 0.04-0.09; P < .001) and vessel area density (0.04% [0.02%]; 95% CI, 0.02%-0.08%; P = .003) but not in RNFL thickness (3.4 [4.7] &mgr;m; 95% CI, −6.2 to 12.9 µm; P = .48). Strong correlations were found between the blood flux index and VF mean deviation (Spearman &rgr; = 0.44; P = .045) and RNFL thickness (Spearman &rgr; = 0.65; P = .001) in the normal hemisphere of the eye with glaucoma. Conclusions and Relevance Reduced RNFL microcirculation was detected in the normal hemisphere of eyes with glaucoma, with strong correspondence with VF loss and RNFL thinning. Although the results suggest that vascular dysfunction precedes structural changes seen in glaucoma, longitudinal studies would be needed to confirm this finding.

Microcystic Macular Changes in Primary Open-angle Glaucoma.

Purpose:To describe microcystic macular changes in patients with moderate to advanced primary open-angle glaucoma. Patients and Methods:Eleven eyes of 6 unrelated patients were retrospectively identified based on a disproportionately preserved macular thickness on optical coherence tomography (OCT) despite severe peripapillary retinal nerve fiber layer thinning. Patient demographic, history, and examination findings were reviewed. Results:All identified patients were African American, relatively young (mean age, 43.8 y) and 5 of the 6 patients were males. Examination of individual macular OCT sections through areas of disproportionately preserved macular thickness invariably demonstrated numerous small cystic cavities within the inner nuclear layer. These microcystic changes were seen in areas of the macula that corresponded with areas of glaucoma-related ganglion cell loss, therefore mimicking the normal appearance of retinal thickness in the macular region. No other retinal pathologies were identified on the macular OCT to account for these changes. Conclusions:This study describes microcystic macular changes in mostly young, African American males with moderate to advanced primary open-angle glaucoma. Vitreous adherence to the internal limiting membrane preventing retinal collapse is a proposed mechanism. The disproportionately preserved macular volume may confound the diagnosis of glaucoma in these patients.

Repeatability and reproducibility of optic nerve head perfusion measurements using optical coherence tomography angiography

Abstract. Optical coherence tomography angiography (OCTA) has increasingly become a clinically useful technique in ophthalmic imaging. We evaluate the repeatability and reproducibility of blood perfusion in the optic nerve head (ONH) measured using optical microangiography (OMAG)-based OCTA. Ten eyes from 10 healthy volunteers are recruited and scanned three times with a 68-kHz Cirrus HD-OCT 5000-based OMAG prototype system (Carl Zeiss Meditec Inc., Dublin, California) centered at the ONH involving two separate visits within six weeks. Vascular images are generated with OMAG processing by detecting the differences in OCT signals between consecutive B-scans acquired at the same retina location. ONH perfusion is quantified as flux, vessel area density, and normalized flux within the ONH for the prelaminar, lamina cribrosa, and the full ONH. Coefficient of variation (CV) and intraclass correlation coefficient (ICC) are used to evaluate intravisit and intervisit repeatability, and interobserver reproducibility. ONH perfusion measurements show high repeatability [CV≤3.7% (intravisit) and ≤5.2% (intervisit)] and interobserver reproducibility (ICC≤0.966) in all three layers by three metrics. OCTA provides a noninvasive method to visualize and quantify ONH perfusion in human eyes with excellent repeatability and reproducibility, which may add additional insight into ONH perfusion in clinical practice.

Comparison of Anterior Segment Optical Coherence Tomography Bleb Grading, Moorfields Bleb Grading System, and Intraocular Pressure After Trabeculectomy

Purpose: To compare a novel anterior segment optical coherence tomography (AS-OCT) bleb grading system with a clinical bleb grading system and both with intraocular pressure (IOP) following trabeculectomy surgery. Materials and Methods: A novel AS-OCT grading system based on bleb size and internal reflectivity was developed. An imaging center was tasked with masked grading of AS-OCT images acquired by multiple surgical sites at postoperative week (POW) 2, postoperative month (POM) 4, 6, and 12, respectively. The Moorfields Bleb Grading System was used by another independent imaging center to grade clinical photos. The results of the 2 grading systems were compared and correlated with IOP. Results: Blebs of 124 eyes were assessed in this study. Higher (worse) AS-OCT bleb grades was significantly associated with: decreased bleb height at POM4, 6, and 12 (P<0.001, 0.001, and 0.0001), increased central bleb vascularity at POM4 and 12 (P=0.0026;0.036) and decreased maximal bleb area at POM6 and 12 (P=0.026; 0.01). A higher AS-OCT bleb grade correlated with a higher IOP at POM4 and 6 (P=0.004; 0.02), though no longer significant at POM12 (P=0.1). Increased maximum bleb vascularity was associated with increased IOP at POM4 (P=0.003) though none of the remaining MGBS parameters correlated significantly with IOP. Eyes with a final IOP of ⩽12 mm Hg had significantly lower AS-OCT bleb grades at POM6 (P=0.045). Conclusion: A novel AS-OCT bleb grading system correlated well with a number of Moorfields Bleb Grading System variables throughout the 1-year postoperative period. Although the AS-OCT grades also correlated well with IOP throughout most of the postoperative period, it was limited in their abilities to predict final IOP.

Intravitreal Anti-VEGF Injections Reduce Aqueous Outflow Facility in Patients With Neovascular Age-Related Macular Degeneration

Purpose We assess the effect of intravitreal anti-VEGF injections on tonographic outflow facility. Methods Patients with age-related macular degeneration who had received unilateral intravitreal anti-VEGF injections were recruited into two groups, those with ≤10 and those with ≥20 total anti-VEGF injections. Intraocular pressure and tonographic outflow facility of injected and uninjected fellow eyes were measured and compared between groups. Risk factors for development of reduced outflow facility also were assessed. Results Outflow facility was 12% lower in the injected eyes of patients who received ≥20 anti-VEGF injections, compared to contralateral uninjected eyes (P = 0.02). In contrast, there was no facility reduction for patients with ≤10 anti-VEGF injections (P = 0.4). In patients with ocular hypertension in the uninjected eye (IOP > 21 mm Hg, n = 5), the outflow facility of injected eyes was on average 46% lower (P = 0.01) than in the uninjected fellow eyes. This was significantly greater than the difference observed in patients with IOP ≤ 21 mm Hg in the uninjected eye (P = 2 × 10−4). In patients with ocular hypertension in the injected eye (n = 6) the differences in facility and IOP between contralateral eyes were significantly greater than in patients with IOP ≤ 21 mm Hg in the injected eye (P = 2 × 10−4 and P = 7 × 10−4, respectively). Conclusions Chronic anti-VEGF injections significantly reduce outflow facility in patients with AMD. The greatest facility reduction is observed in patients with baseline ocular hypertension. Ophthalmologists who administer anti-VEGF injections should be aware of these findings and monitor patients closely for changes in IOP or evidence of glaucoma, especially in those with pre-existing ocular hypertension.

VEGF as a Paracrine Regulator of Conventional Outflow Facility

Purpose Vascular endothelial growth factor (VEGF) regulates microvascular endothelial permeability, and the permeability of Schlemms canal (SC) endothelium influences conventional aqueous humor outflow. We hypothesize that VEGF signaling regulates outflow facility. Methods We measured outflow facility (C) in enucleated mouse eyes perfused with VEGF-A164a, VEGF-A165b, VEGF-D, or inhibitors to VEGF receptor 2 (VEGFR-2). We monitored VEGF-A secretion from human trabecular meshwork (TM) cells by ELISA after 24 hours of static culture or cyclic stretch. We used immunofluorescence microscopy to localize VEGF-A protein within the TM of mice. Results VEGF-A164a increased C in enucleated mouse eyes. Cyclic stretch increased VEGF-A secretion by human TM cells, which corresponded to VEGF-A localization in the TM of mice. Blockade of VEGFR-2 decreased C, using either of the inhibitors SU5416 or Ki8751 or the inactive splice variant VEGF-A165b. VEGF-D increased C, which could be blocked by Ki8751. Conclusions VEGF is a paracrine regulator of conventional outflow facility that is secreted by TM cells in response to mechanical stress. VEGF affects facility via VEGFR-2 likely at the level of SC endothelium. Disruption of VEGF signaling in the TM may explain why anti-VEGF therapy is associated with decreased outflow facility and sustained ocular hypertension.

DYNAMIC CHANGES OF THE ANTERIOR CHAMBER ANGLE PRODUCED BY INTRAVITREAL ANTI-VASCULAR GROWTH FACTOR INJECTIONS.

Purpose: To use anterior segment optical coherence tomography (AS-OCT) to evaluate the anterior chamber after intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections. Methods: Preinjection and immediate postinjection AS-OCT images were taken and measurements were compared including angle opening distance (AOD) and trabeculo-iris space area (TISA) at 500 &mgr;m and 750 &mgr;m from the scleral spur (AOD500, AOD750, TISA500 and TISA750, respectively), and the scleral spur angle. Results: Twenty-one eyes from 21 patients were studied. There was significant narrowing of the temporal AOD500, AOD750, and temporal angle after injection (P = 0.03, 0.01, and 0.02, respectively). The percentage of narrowing of the nasal TISA500 and TISA750 was significantly greater in phakic versus pseudophakic eyes (P = 0.03 and 0.02, respectively). A higher postinjection IOP was correlated with increased narrowing of the nasal AOD500, TISA500, TISA750, and nasal angle (R2 = 0.22, 0.28, 0.34 and 0.20; P = 0.03, 0.01, 0.005 and 0.04, respectively) and a smaller preinjection anterior chamber depth in phakic eyes (R2 = 0.53, P = 0.01). Conclusion: After an anti-vascular endothelial growth factor injection, there is significant narrowing of the temporal anterior chamber angle in all eyes and increased narrowing of the nasal angle in phakic compared with pseudophakic eyes. Physicians performing intravitreal injections should be aware of these associations as they may contribute to our understanding of prolonged elevation of IOP after injections.

Cytokine biomarkers in tear film for primary open-angle glaucoma.

Purpose To determine the utility of tear film cytokines as biomarkers for early primary open-angle glaucoma (POAG). Methods Patients without POAG and eye drop-naïve patients with newly diagnosed POAG were recruited from an academic hospital-based glaucoma practice. Tear films of recruited patients were obtained and analyzed using a multiplex, high-sensitivity electrochemiluminescent enzyme-linked immunosorbent assay for proinflammatory cytokines (IFNγ, IL-10, IL-12p70, IL-13, IL-1β, IL-2, IL-4, IL-6, IL-8, and TNFα). Results Mean concentrations of tear film cytokines were lower in the glaucoma group for 8 of 10 cytokines tested. IL-12p70 (3.94±2.19 pg/mL in control vs 2.31±1.156 pg/mL in POAG; P=0.035) was significantly lower in the tear film of patients with newly diagnosed POAG. Conclusion Proinflammatory cytokines were lower in eye drop-naïve newly diagnosed glaucoma patients. Tear film cytokine profiles may be used as biomarkers of early POAG.