Tudor Tepelus

Repeatability of automated vessel density measurements using optical coherence tomography angiography

Aims To determine the repeatability of optical coherence tomography angiography (OCT-A)-derived automated vessel density measurements in the superficial retinal layer (SRL) and deep retinal layer (DRL) in healthy individuals. Methods 41 eyes of 21 healthy individuals were included in this study. OCT-A was performed using the NIDEK RS-3000 Advance with prototype OCT-A software. Each subject underwent two scanning sessions with 5–10 min in between. En face images of the retinal vasculature were generated using the default segmentation for SRL and DRL. Automated vessel density measurements were compared between the two sessions. The intraclass correlation coefficients (ICCs) and coefficient of repeatability were used as a measure for repeatability. Results The mean±SD age of the subjects was 36.8±7.5 years. Overall vessel density measured in the first and second session was 19.43±3.10 and 19.72±3.78 for the SRL, and 34.67±1.801 and 34.55±1.64 for the DRL, respectively. The mean difference in vessel density between sessions was −0.3 (95% CI 3.3 to −3.9) for the SRL and 0.1 (95% CI 2.6 to −2.5) for the DRL. The two measurements were highly correlated with an ICC=0.90 (p=0.33) for the SRL and 0.83 (p=0.589) for the DRL. The coefficient of variation was 0.052 for the SRL and 0.02 for the DRL. Conclusions Commercial automated vessel density measurements using OCT-A showed excellent repeatability in healthy individuals. Although repeatability will also need to be established in the setting of disease, the level of reproducibility should be useful for assessing the significance of differences in capillary density over time or under different conditions.

Quantitative Comparison of Swept-Source and Spectral-Domain OCT Angiography in Healthy Eyes

BACKGROUND AND OBJECTIVE To compare macular vessel density (VD) and foveal avascular zone (FAZ) area in healthy individuals using two different optical coherence tomography angiography (OCTA) devices. PATIENTS AND METHODS In this prospective, comparative study, 25 eyes of 14 healthy subjects underwent fovea-centered 3 mm × 3 mm OCTA-imaging using the Triton (Topcon, Tokyo, Japan) and RS-3000 (Nidek, Gamagori, Japan) OCTA devices. Superficial and deep retinal layers (SRL/DRL) and FAZ were manually graded after threshold standardization to determine macular VD and area of the FAZ. RESULTS The mean difference in the VD between the two devices was 0.105 and 0.096, and the coefficient of variation (CV) was 19.59% and 16.90% for the SRL and DRL, respectively. After skeletonization of vessels to remove variation related to vessel width, the mean difference was 0.174 mm-1 and 0.516 mm-1, and the CV was 3.49% and 1.07% for SRL and DRL, respectively. The mean difference of FAZ area was 0.001 mm2 and 0.010 mm2 in the SRL and DRL, respectively, and the CV was 2.17% and 5.74% for the SRL and DRL, respectively. CONCLUSION Macular VD using skeletonized mapping and FAZ area in SRL and DRL were statistically similar between the two devices, demonstrating a possible comparison of quantitative values between different OCTA devices. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:385-391.].

Characterization of Corneal Involvement in Eyes with Mucous Membrane Pemphigoid by in vivo Confocal Microscopy

Purpose: To describe the morphological features of the corneal epithelial layers, subbasal nerve plexus, stroma, and endothelium in patients with mucous membrane pemphigoid (MMP) as shown by in vivo confocal microscopy (IVCM). Methods: Central corneal images were captured from 10 healthy age-matched control eyes and 30 eyes with clinically diagnosed MMP by in vivo laser scanning confocal microscopy (HRT III RCM). Morphological changes of the corneal epithelial layers, stroma, and endothelium, characteristics of corneal nerves, and presence of inflammatory dendritic cells (DCs) were evaluated. Results: Images obtained by IVCM from 40 eyes were analyzed. The eyes with MMP were divided into 2 groups based on clinical staging: 16 eyes with end-stage MMP and 14 eyes with non–end-stage MMP. Compared with controls, IVCM in eyes with end-stage MMP displayed severe conjunctivalization and neovascularization of the cornea, with otherwise limited identifiable cellular or structural elements. Those with non–end-stage MMP showed metaplasia of the corneal epithelial layers, presence of hyperreflective cells similar to conjunctival cells, intraepithelial defects, fibrosis of anterior stroma, and hyperreflective endothelial deposits. Images of the subbasal nerve plexus demonstrate significant reduction in density (1251.3 ± 806.9 &mgr;m/frame vs. 2688.8 ± 607.33 &mgr;m/frame, P < 0.001), increased tortuosity (2.76 ± 0.6 vs. 2.3 ± 0.42, not significant), decreased reflectivity (2.73 ± 0.4 vs. 3.46 ± 0.52, P < 0.01), and increased density of DCs (115 ± 88 cells/mm2 vs. 43.9 ± 28.14 cells/mm2, P < 0.05) in MMP-affected eyes compared with controls. Conclusions: IVCM reveals profound and variable microstructural changes in the corneas of patients with MMP compared with normal controls. Our study demonstrated decreased corneal nerve density and elevated DC density in eyes with non–end-stage MMP compared with normal controls. Frequent scarring, conjunctivalization, and neovascularization observed in eyes with end-stage MMP preclude recognition by IVCM of the morphologic architecture of the corneal layers. Our findings suggest implications for using IVCM to evaluate and monitor patients with MMP.

Comparison of Noncontact Specular and Confocal Microscopy for Evaluation of Corneal Endothelium

Purpose: To compare endothelial cell analysis obtained by noncontact specular and confocal microscopy, using the Konan NSP-9900 and Nidek ConfoScan4 systems, respectively. Methods: Three groups including 70 healthy eyes, 49 eyes with Fuchs endothelial corneal dystrophy (FECD), and 78 eyes with glaucoma were examined with both the Konan NSP-9900 specular microscope and the Nidek ConfocScan4 confocal microscope. Certified graders at the Doheny Image Reading Center compared corneal endothelial images from both instruments side by side to assess image quality. Endothelial cell density (ECD) measurements were calculated and compared using three different modalities: (1) each instruments fully automated analysis; (2) each instruments semiautomatic analysis with grader input; and (3) manual grading methods by certified grader. Results: All normal eyes yielded gradable endothelial images, and most but not all glaucomatous eyes yielded images with high enough image quality to allow grading. In addition, in corneas with severe FECD, poor image quality precluded ECD grading by specular microscopy in 20 eyes (40.8%) but in only 4 (8.2%) confocal images from the same eyes. For the gradable images, the ECD values obtained using the manual grading method from either device were comparable with no statistically significant difference (P>0.05) between specular and confocal devices. Machine-generated ECD values were significantly different from manual results, measuring greater in all cases with specular microscopy. Machine-generated ECD values from confocal microscopy also differed significantly from manual determinations, but not in a consistent direction. Semiautomatic methods for both instruments obtained clinically acceptable ECD values. Conclusions: Automatic machine-generated ECD measurements differed significantly from manual assessments of corneal endothelium by both specular and confocal microscopy, suggesting that automated results should be used with caution. But ECD values derived manually were comparable between the two devices in both normal and glaucomatous eyes, suggesting that manually graded images from the two instruments can be used interchangeably for reliable ECD measurements. Because of a higher proportion of gradable images, confocal microscopy may be superior to specular microscopy for ECD measurements in FECD.

Reproducibility of Central Corneal Thickness Measurements in Normal Eyes Using the Zeiss Cirrus 5000 HD-OCT and Pentacam HR

Objectives: To determine the repeatability and reproducibility of Central Corneal Thickness (CCT) measurements using two different anterior segment imaging modalities, including those obtained with the new anterior segment lens attachments for the Cirrus 5000 HD-OCT. Methods: A total of 32 eyes from 16 normal volunteers (8 male, 8 female) were enrolled in this prospective study. CCT was measured by the same examiner using the Cirrus 5000 HD-OCT and Pentacam HR. The results of CCT obtained by each method were averaged and compared using t-test analysis. The agreement between the measurement methods was evaluated. Coefficient of Repeatability (CoR) and Intra-Class Correlation Coefficient (ICC) were computed. Results: The mean measurements taken with the Cirrus OCT anterior chamber lens (CCTAC), HD cornea lens (CCTHDC) and pachymetry scans (CCTPach) were 545.35 ± 31.02, 537.87 ± 26.82, and 532.04 ± 29.82 µm, respectively. The mean CCT obtained with the Pentacam (CCTPent) was 545.51 ± 30.71 µm. CCTPent were significantly higher than CCTHDC and CCTPach (p< 0.0001). In contrast, the CCTPent and CCTAC were similar (p=0.87). CCT, as evaluated by the two different instruments, showed excellent correlation (r > 0.98, p< 0.0001) with an ICC > 0.99 (95% CI, 0.97 – 0.99). CoR was the highest for CCTPach (3.7 ± 1.4, 95% CI (3.0- 4.6)). Conclusion: CCT measurements from the Cirrus OCT using the new anterior segment lens attachments and the Pentacam HR are highly correlated. This should allow the use of a standardized correction factor if necessary to inter-relate the measurements between the two devices.

Distinct Retinal Capillary Plexuses in Normal Eyes as Observed in Optical Coherence Tomography Angiography Axial Profile Analysis

Optical coherence tomography angiography (OCTA) allows the retinal microvasculature to be visualized at various retinal depths. Previous studies introduced OCTA axial profile analysis and showed regional variations in the number and location of axially distinct vascular retinal plexuses. OCTA acquisition and processing approaches, however, vary in terms of their resulting transverse and axial resolutions, and especially the latter could potentially influence the profile analysis results. Our study imaged normal eyes using the Spectralis OCT2 with a full-spectrum, probabilistic OCTA algorithm, that, in marked contrast to split-spectrum approaches, preserves the original high OCT axial resolution also within the resulting OCTA signal. En face OCTA images are generally created by averaging flow signals over a finite axial depth window. However, we assessed regional OCTA signal profiles at each depth position at full axial resolution. All regions had two sharp vessel density peaks near the inner and outer boundaries of the inner nuclear layer, indicating separate intermediate and deep capillary plexuses. The superficial vascular plexus (SVP) separated into two distinct peaks within the ganglion cell layer in the parafoveal zone. The nasal, superior, and inferior perifovea had a deeper SVP peak that was shifted anteriorly compared to the parafoveal zone. Axial vascular density analysis with high-resolution, full spectrum OCTA thus allows healthy retinal vasculature to be precisely reconstructed and may be useful for clinically assessing retinal pathology.

Reproducibility of Macular Thickness Measurements in Eyes Affected by Dry Age-Related Macular Degeneration From Two Different SD-OCT Instruments

BACKGROUND AND OBJECTIVE To compare macular thickness measurement algorithms of two different spectral-domain optical coherence tomography (SD-OCT) devices in eyes affected by dry age-related macular degeneration (AMD). PATIENTS AND METHODS Patients with dry AMD and healthy volunteers from the retina clinic of the Doheny Eye Center - UCLA were imaged using two different SD-OCT devices: the RS-3000 Advance (Nidek, Padova, Italy) and the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA). All patients had been previously diagnosed with drusen or geographic atrophy due to AMD. The commercial instrument software was used to generate the macular retinal thickness measurements, and measurements were compared between devices. RESULTS Eighty-five diseased eyes from 49 patients and 16 healthy control eyes from eight normal volunteers were included in this study. The macular thickness measurements generated by the two instruments in eyes with AMD differed significantly in mean retinal thickness in the foveal center subfield (257.34 μm ± 51.72 μm using the Nidek OCT vs. 238.20 μm ± 51.89 μm using the Cirrus OCT; P < .001). The mean difference in macular thickness between the two devices was 19.14 μm ± 5.84 μm for diseased eyes and 17.06 μm ± 5.28 μm in normal control eyes, and this was not statistically different between the two groups (P > .05). The macular thickness measurements in diseased eyes, as evaluated by the two different instruments, however, showed excellent correlation (r = 0.99; P < .001), with an intraclass correlation coefficient of 0.99 (95% confidence interval, 0.98-0.99). Post hoc evaluation of cases with larger differences also showed differences in foveal center selection and variabilities in boundary selection with specific pathology. CONCLUSION Macular thickness measurements provided by the Nidek and Cirrus OCT instruments in eyes with dry AMD are highly correlated but show a consistent difference, which may allow the use of a standard correction factor to be applied to better interrelate measurements between the devices. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:410-415.].

Assessment of Corneal Changes Associated with Topical Antiglaucoma Therapy Using in vivo Confocal Microscopy

Purpose: Ocular surface disease (OSD) is highly prevalent in eyes treated with chronic, topical antiglaucoma (A/G) therapy. The purpose of this study was to utilize in vivo confocal microscopy (IVCM) to evaluate the corneal morphology, including characteristics of corneal epithelial cells, presence of epithelial dendritic cells (DCs), and characteristics of subbasal nerve plexus, of eyes under topical A/G therapy versus normal eyes. Methods: Central corneal images were prospectively captured from 30 eyes of 16 patients under topical A/G therapy (>6 months) and 20 normal control eyes, using IVCM (HRT 3 RCM, Heidelberg, Germany). Demographic data were collected, as well as information on the types and duration of A/G therapy. In addition, OSD index (OSDI) score, tear film breakup time, Schirmer 1 test results, density of epithelial wing cells (WCs) and basal cells (BCs), subbasal nerve features (density, tortuosity, and reflectivity), and presence of DCs were all assessed and recorded by trained Doheny Image Reading Center graders. Results: IVCM findings of 30 glaucomatous eyes and 20 normal control eyes were analyzed. The mean OSDI score was 8.72 in controls and 32.06 in patients under A/G therapy (p = 0.002). Nerve fiber density, nerve fiber reflectivity, and BC density were all decreased in the A/G group (1,789.07 ± 785.70 μm/frame, 2.79 ± 0.83, 6,457.67 ± 692.55 cells/mm2, respectively) as compared to controls (2,815.981 ± 563.77 μm/frame, 3.52 ± 0.50, 7,854.13 ± 1,073.69 cells/mm2, respectively) (p < 0.05), whereas the decrease in WC density was statistically nonsignificant (p = 0.5). Nerve tortuosity and DC density were both significantly greater in the A/G eyes (3.00 ± 0.57, 71.24 ± 61.74 cells/mm2, respectively) compared to controls (2.10 ± 0.42, 34.08 ± 11.70 cells/mm2, respectively) (p < 0.05). Tear film breakup time and Schirmer 1 test results were significantly lower in the A/G group as compared to controls (p < 0.001). Conclusions: Using IVCM, our study identified significant microstructural alterations in the corneas of eyes treated with topical A/G therapy. In addition, our study also revealed that glaucoma patients treated with topical A/G therapy report significantly higher OSDI scores compared to controls. Thus, IVCM may be a useful tool in providing structural parameters to correlate with the functional OSDI assessments in the evaluation of ocular surface toxicity associated with topical A/G therapy.

Analysis of ocular inflammation in anterior chamber—involving uveitis using swept-source anterior segment OCT

AbstractPurposeTo evaluate the utility of swept-source (SS) optical coherence tomography (OCT) to objectively analyze the degree of anterior chamber (AC) inflammation.MethodsThirty-eight eyes of 32 patients with uveitis and 20 control eyes were enrolled. SS OCT B-scans were obtained, and the number of cells in the B-scans was counted using two methods: (1) manual grading by Point Picker plug-in of Image J (http://bigwww.epfl.ch/thevenaz/pointpicker/) and (2) automated grading by the Image J Particle Analysis algorithm (http://imagej.net/Particle_Analysis). The automated and manual AC cell counts were correlated with the Standardization of Uveitis Nomenclature score. ResultsThe average numbers of AC inflammatory cells counted by the automated method were 8 ± 4.0, 18 ± 3.0, 42 ± 14.0, 81 ± 32.0, 117 ± 57.0, and 275 ± 67.0 cells/mm2 for grades 0, 0.5 + , 1 + , 2 + , 3 + , and 4 + , respectively. For the same clinical categories, the average manual cell counts were 6 ± 4.0, 18 ± 3.0, 34 ± 14.0, 72 ± 32.0, 92 ± 43.0, and 168 ± 65.0 cells/mm2, respectively. Zero cells were detected in the AC of healthy eyes. The automated and manual methods were highly correlated (R = 0.98, p < 0.001) and showed good correlation with the clinical grading (R = 0.88, p < 0.001). A mean AC particle size of 117.4 ± 108.8 μm was obtained by the automated method.ConclusionsQuantification of the AC cells imaged by SS AS-OCT shows good correlation with categorical clinical severity assessments in uveitis eyes. This approach may provide a more objective method for monitoring uveitis and response to uveitis therapy.

Comparison of manual & automated analysis methods for corneal endothelial cell density measurements by specular microscopy

Purpose To determine the reliability of corneal endothelial cell density (ECD) obtained by automated specular microscopy versus that of validated manual methods and factors that predict such reliability. Methods Sharp central images from 94 control and 106 glaucomatous eyes were captured with Konan specular microscope NSP-9900. All images were analyzed by trained graders using Konan CellChek Software, employing the fully- and semi-automated methods as well as Center Method. Images with low cell count (input cells number <100) and/or guttata were compared with the Center and Flex-Center Methods. ECDs were compared and absolute error was used to assess variation. The effect on ECD of age, cell count, cell size, and cell size variation was evaluated. Results No significant difference was observed between the Center and Flex-Center Methods in corneas with guttata (p = 0.48) or low ECD (p = 0.11). No difference (p = 0.32) was observed in ECD of normal controls <40 yrs old between the fully-automated method and manual Center Method. However, in older controls and glaucomatous eyes, ECD was overestimated by the fully-automated method (p = 0.034) and semi-automated method (p = 0.025) as compared to manual method. Conclusion Our findings show that automated analysis significantly overestimates ECD in the eyes with high polymegathism and/or large cell size, compared to the manual method. Therefore, we discourage reliance upon the fully-automated method alone to perform specular microscopy analysis, particularly if an accurate ECD value is imperative.