Fabrication of infrared linear arrays of InAs planar avalanche photodiodes

We report a, to the best of our knowledge, new device fabrication process for 128-pixel linear arrays of InAs planar avalanche photodiodes, utilizing selective area implantation of Beryllium ions into epitaxially-grown InAs wafers. The pixels exhibited uniform avalanche gain and responsivity. Room temperature responsivity values at 1550 and 2004 nm wavelengths are 0.49 ± 0.017 and 0.89 ± 0.024 A/W, respectively. Reverse dark current-voltage and avalanche gain measurements were carried out at different temperatures (from room temperature to 150 K). At 200 K at -15 V reverse bias, the pixels exhibited an avalanche gain of 22.5 ± 1.18 and dark current density of 0.68 ± 0.48 A/cm².

Comparison of Polypoidal Choroidal Vasculopathy Lesion Sizes Measured on Multicolor Imaging and Indocyanine Green Angiography

Purpose

To evaluate the areas of lesion components of polypoidal choroidal vasculopathy (PCV) measured using multicolor imaging compared to indocyanine green angiography (ICGA).

Methods

In a prospective study of 50 consecutive treatment-naïve PCV patients, multicolor imaging and ICGA were performed. The images were independently graded by reading center-certified retinal specialists to confirm the diagnosis of PCV and identify lesion components. The areas of the respective lesion components were compared.

Results

The mean age of the participants was 67.8 years. PCV was diagnosed in 96% of eyes using multicolor imaging. The mean numbers of polypoidal lesions identified using ICGA and multicolor were 4.0 and 2.1, respectively (P < 0.001), with mean total polypoidal lesion areas of 0.32 mm² versus 0.30 mm² (P = 0.727). The area of the branching vascular network (BVN) on ICGA was 7.8 mm² compared to 5.7 mm² on multicolor imaging (P = 0.289). Patients with four or more polypoidal lesions on ICGA had larger differences in total lesion area between ICGA and multicolor imaging (4.07 vs. –0.70 mm², p = 0.039). Those with total lesion area ≥ 2.0 mm² on ICGA had larger differences in mean polypoidal lesion number compared to those with smaller areas (2.2 vs. 0.5; P = 0.026).

Conclusions

Multicolor imaging is a useful, noninvasive adjunct for detecting PCV lesion components, revealing lesion areas similar to but generally smaller than those seen on ICGA. This is important to consider when making treatment decisions with different imaging modalities

Translational Relevance

New features seen on multicolor imaging can aid in the diagnosis and treatment of PCV.

Acute Onset of Bilateral Follicular Conjunctivitis in two Patients with Confirmed SARS-CoV-2 Infections

PURPOSE

To report bilateral follicular conjunctivitis in two confirmed Coronavirus (COVID-19) patients with the presence of Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) in conjunctival swab specimens.

PARTICIPANTS AND METHODS

Two unrelated patients with confirmed SARS-CoV-2 infection and bilateral acute conjunctivitis were examined. Conjunctival swabs were assessed for the presence of SARS-CoV-2 by quantitative real-time polymerase chain reaction (RT-PCR) and viral culture.

RESULTS

Both patients developed eye redness 3 days after the onset of COVID-19 symptoms. Slit lamp examination showed bilateral acute follicular conjunctivitis, which was resolved within 6 days. RT-PCR demonstrated the presence of viral RNA in conjunctival specimens from both eyes, which was unrelated to viral RNA from throat swabs.

CONCLUSION

SARS-CoV-2 may cause ocular manifestations such as viral conjunctivitis. Conjunctival sampling may be useful for infected patients with conjunctivitis and fever. Precautionary measures are recommended when examining infected patients throughout the clinical course of the infection.

Predictors of persistent disease activity following anti-VEGF loading dose for nAMD patients in Singapore: the DIALS study

Background

To determine the frequency of persistent disease activity following 3 loading doses of anti- vascular endothelial growth factor (VEGF) agents, and the anatomic and demographic predictors of early persistent disease activity among patients with neovascular age-related macular degeneration (nAMD).

Methods

In a retrospective real-world cohort study, 281 consecutive patients with nAMD were reviewed at baseline and after 3 anti-VEGF injections for pre-defined indicators of disease activity. Optical coherence tomography (OCT) features such as subretinal fluid, intraretinal cysts and intraretinal fluid were assessed by reading-center certified graders. Multiple logistic regression was performed on demographic and anatomic factors.

Results

At month 3, 66.1% of patients had persistent disease activity. The best-corrected visual acuity (BCVA) improvement was 0.16 LogMAR for those with no disease activity compared to 0 for patients with persistent activity (p < 0.001). The significant risk factors for persistent activity at 3 months were male gender (odds ratio [OR] 0.54, 95% confidence interval [CI] 0.32–0.93, p = 0.025), intraretinal cysts at baseline (OR 2.95, 95% CI 1.67–5.20, p < 0.001) and subretinal fluid at baseline (OR 3.17, 95% CI 1.62–6.18, p = 0.002). At 3 months, 58% of patients had features of activity on OCT. Patients with intraretinal cysts and intraretinal fluid at baseline had worse BCVA at month 3 compared to patients without these OCT features (0.69 vs. 0.43, p < 0.001, and 0.62 vs. 0.43, p < 0.001, respectively).

Conclusions

In a real-world study, 66.1% of nAMD patients have persistent disease activity after the initial loading dose, with poorer BCVA compared to those without. Baseline OCT features (intraretinal cysts and subretinal fluid) are useful predictors of persistent disease activity at month 3.

Classification of Andrographis paniculata extracts by solvent extraction using HPLC fingerprint and chemometric analysis

Objective

Andrographis paniculata, widely used as an antidiabetic in Indonesian traditional medicines (jamu), contains chemical compounds whose concentration is related to its therapeutic effects. The concentration of solvents used for extraction will also affect the number of compounds extracted. Therefore, a quality control method is needed to ensure consistency in quantifying these compounds in A. paniculata to improve its therapeutic application. High-performance liquid chromatography fingerprint analysis combined with chemometrics was used to evaluate extracts from different solvent extraction treatments. The content of andrographolide, the main bioactive compound in A. paniculata, and the level of α-glucosidase inhibition activity, an indicator of its antidiabetic activity, were also determined.

Results

Fingerprint chromatograms of A. paniculata extracts from different treatments exhibited a similar pattern with several peaks in common, only differing in area and intensity value. The A. paniculata extracts were classified using HPLC fingerprint and principal component analysis to allow grouping according to their respective solvent extraction treatments. The highest andrographolide content and α-glucosidase inhibition activity occurred in the 50% ethanol extract and the lowest in the water extract. HPLC fingerprint analysis could be used for identifying A. paniculata extracts based on solvent extraction, thus improving quality control for their therapeutic application.

EVEREST study report 4: Fluorescein angiography features predictive of polypoidal choroidal vasculopathy

Importance

It is important to identify features of polypoidal choroidal vasculopathy (PCV) that differentiate it from typical neovascular age‐related macular degeneration (nAMD) on various imaging modalities, including fluorescein angiography (FA).

Background

PCV was thought to be indistinguishable from nAMD using FA alone. In real‐world practice, indocyanine‐green angiography may often be unavailable or contraindicated.

Design

Analysis of FA images from a prospective, multicentre study.

Participants

Study images of both PCV and nAMD patients from the EVEREST study.

Methods

FA features at baseline were independently graded by masked graders (fellowship‐trained ophthalmologists) using standardized diagnostic algorithms.

Main Outcome Measures

Predictive indicators (sensitivity, specificity, positive and negative predictive values) for PCV.

Results

Of the 95 patients screened, 61 had PCV. Of the 34 screening failures, 15 were diagnosed as nAMD. Hyperfluorescent nodules on FA were observed in 80% of patients with PCV vs 20% with nAMD (P < 0.001). Blocked fluorescence on FA, which corresponded to the presence of subretinal haemorrhage, occurred more frequently among patients with PCV vs nAMD (61.7% vs 13.3%, P = 0.001). Similarly, the leakage characteristic of occult choroidal neovascularization occurred more frequently among patients with PCV vs nAMD (95.0% vs 73.3%, P = 0.026). The positive predictive value for PCV was 94.1% for hyperfluorescent nodules, 94.9% for blocked fluorescence, 83.8% for occult choroidal neovascularization and 82.0% for pigment epithelial detachment.

Conclusions and Relevance

This study demonstrated that certain FA features can be predictive of PCV and may be considered as an indication for retina specialists to perform indocyanine green angiography as confirmatory test.

EVEREST Report 5: Clinical Outcomes and Treatment Response of Polypoidal Choroidal Vasculopathy Subtypes in a Multicenter, Randomized Controlled Trial

Purpose

The purpose of this study was to describe the characteristics of polypoidal choroidal vasculopathy (PCV) subtypes among patients from a multicenter randomized controlled trial and to determine the impact of PCV subtypes on clinical outcomes.

Methods

This was a prospective cohort study of 61 patients with macular PCV from the EVEREST study. Indocyanine green (ICGA) and fluorescein angiography (FA) obtained using standardized imaging protocols were graded to classify PCV into three subtypes. Type A PCV had polyps with interconnecting channels, type B had polyps with branching vascular networks, but no significant leakage on FA, and type C had polyps with branching vascular networks and leakage on FA. The best-corrected visual acuity (BCVA) and proportion of patients with BCVA ≥ 20/40 were compared among the three PCV subtypes.

Results

Of the 61 patients, 54 were gradable for PCV subtype. Among these, 8 had type A PCV (14.8%), 27 had type B (50%), and 19 had type C (35.2%). At baseline, BCVA was 67.1 letters for type A, 58.7 for type B, and 43.5 for type C (P < 0.001). At 6 months, BCVA was highest among patients with type A compared with types B and C (80.1 letters versus 67.2 versus 50.4, respectively; P < 0.001). Type A PCV gained 13 letters compared with 8.5 (type B) and 6.9 (type C). BCVA ≥ 20/40 was highest for type A compared with types B and C (100% vs. 51.9% vs. 10.5%; P < 0.001). On performing ANCOVA, PCV subtype and baseline BCVA significantly affected final BCVA.

Conclusions

The visual outcome following treatment varies with PCV subtype classification. The distinction in clinical outcomes between the PCV subtypes is observed in the initial months following the start of treatment.

A novel and faster method of manual grading to measure choroidal thickness using optical coherence tomography

PurposeChoroidal thickness (CT) measurements are typically obtained from manual segmentation of optical coherence tomography (OCT) B-scans. This method is time-consuming. We aimed to describe a novel and faster technique to obtain CT measurements.Patients and methodsIn a prospective cohort study of 200 healthy eyes, Spectral-Domain OCT with enhanced depth imaging were performed with the Spectralis OCT using standardised imaging protocols. The OCT scans were independently graded by reading centre-certified graders. The standard method of manual adjustment of segmentation boundaries was performed. The new method consisted of adjusting the lower segmentation line to the choroid-scleral boundary to generate the combined choroid-retina thickness, and subtracting the original retinal thickness (RT) from it to measure CT. Mean CT in the respective Early Treatment Diabetic Retinopathy Study (ETDRS) subfields was measured via the two methods, and were compared with intraclass correlation coefficients (ICC) and Bland-Altman plots.ResultsThe mean central subfield CT was 324.4 μm using the original method, compared with 328.8 μm using the new method, with a mean difference of 4.5 μm (range: -14.0 to +4.0 μm; P<0.001), and ICC for agreement of 0.9996 (P<0.001). Similar comparability was achieved for mean CT across other ETDRS subfields, with mean differences ranging from 2.4 to 3.7 μm, and ICCs ranging from 0.9993 to 0.9995 (all P<0.001).ConclusionsMean CT can be measured by subtracting the original RT from the combined choroid-retina thickness. Only one segmentation line needs to be adjusted, instead of two, reducing time required for segmentation. This method is faster and reliable.

Optical Coherence Tomography Angiography Evaluation of the Parafoveal Vasculature and Its Relationship With Ocular Factors

PURPOSE

To determine the size and characteristics of the superficial and deep foveal avascular zone (FAZ) in healthy adults by using optical coherence tomography angiography (OCT-A), and to ascertain the effects of demographic and ocular parameters on the FAZ size.

METHODS

In a prospective cohort study of 117 healthy volunteers, foveal-centered 3 × 3-mm OCT-A scans were manually graded by certified graders to determine the size of the superficial and deep FAZ. Multiple linear regression analyses were performed to evaluate the impact of demographics and ocular factors, including central retinal thickness (CRT), choroidal thickness, axial length (AL), and spherical equivalent (SE) on superficial and deep FAZ areas.

RESULTS

The mean age of the participants was 22.5 years, with mean AL of 25.4 mm and mean SE of -4.3 diopters. The mean CRT was 262.8 μm (range, 220-316 μm). The mean superficial FAZ area was 0.24 mm2, while the deep FAZ area was 0.38 mm2 (P < 0.001). Females had a larger superficial (P < 0.001) and deep FAZ (P < 0.001). On univariate linear regression, both superficial and deep FAZ areas had significant correlations with CRT, sex, AL, and SE, but not with age. By multiple linear regression analysis, in normal eyes, superficial FAZ area varied significantly with CRT and sex. Among eyes with high myopia, both superficial and deep FAZ varied significantly with CRT, sex, and choroidal thickness.

CONCLUSIONS

The superficial and deep FAZ areas varied significantly among healthy eyes. Factors such as CRT, sex, SE, AL, and choroidal thickness influence the size of the FAZ.

Relationship between Myopia Severity and Macular Retinal Thickness on Visual Performance under Different Lighting Conditions

OBJECTIVE

To evaluate the relationship between both spherical equivalent (SE) and retinal thickness (RT) on best-corrected visual acuity (BCVA) among young Asian adult men under photopic, mesopic, and simulated night-vision goggle (NVG) lighting conditions.

DESIGN

Community-based cross-sectional study.

PARTICIPANTS

Total of 698 myopic and 148 emmetropic subjects.

METHODS

All participants underwent a complete ophthalmic examination and color fundus photography. BCVA and subjective refraction were assessed under standardized photopic, mesopic, and simulated NVG lighting conditions. Retinal thickness in various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields was measured using spectral-domain OCT using a standardized protocol. Univariate and multiple linear regression analyses were performed to assess the relationship between BCVA and both SE and RT.

MAIN OUTCOME MEASURES

Relationship between BCVA and both SE and RT.

RESULTS

The mean age of all subjects was 21.1 years, with mean SE of -8.44 diopter (D) among the myopic subjects (range, -3.75 D to -23.0 D) and +0.10 among the emmetropic subjects (range, -0.49 D to +1.00 D). BCVA worsened progressively with increasing myopia under all lighting conditions (standardized coefficient -0.581 under photopic conditions, P < 0.001). RT was thickest among participants with LogMAR VA ≤0.00, and became thinner in the groups including those with VA >0.00 to ≤0.10 and >0.10 (mean inner subfield RT: 342.7 μm vs. 338.1 μm vs. 331.0 μm, respectively, P < 0.001) under all lighting conditions. When multiple linear regression was performed, higher degrees of myopia and decreasing RT were associated with reduced BCVA (all P < 0.05). For each diopter increase in myopia, mean BCVA decreased by 0.01 LogMAR in photopic conditions and 0.02 LogMAR in mesopic conditions (both P < 0.001). The mean BCVA reduced by 0.05 LogMAR (P = 0.003) and 0.04 LogMAR (P = 0.037), under photopic and scotopic lighting conditions respectively, for each 100-μm decrease in RT.

CONCLUSIONS

Both the severity of myopia and macular RT independently affect visual performance under photopic, mesopic, and simulated NVG conditions.

EVEREST study report 3: diagnostic challenges of polypoidal choroidal vasculopathy. Lessons learnt from screening failures in the EVEREST study

Purpose

To describe screening failures in the EVEREST study by examining the imaging characteristics that enabled differentiation of polypoidal choroidal vasculopathy (PCV) from cases that were subsequently diagnosed not to be PCV.

Methods

Post-hoc analysis of 34 patients with PCV reported as screening failures from EVEREST study. Standardised confocal scanning laser indocyanine green angiography (ICGA) images were graded by the Central Reading Centre to confirm PCV diagnosis based on the presence of early focal sub-retinal hyperfluorescence on ICGA and at least one of the following six diagnostic criteria: (1) nodular appearance of polyp(s) on stereoscopic examination, (2) hypofluorescent halo around nodule(s), (3) presence of a branching vascular network, (4) pulsation of polyp(s) on dynamic ICGA, (5) orange sub-retinal nodules on colour fundus photography, or (6) massive sub-macular haemorrhage (≥4 disc areas in size). Additional detailed image grading was performed with stereo-imaging and dynamic early-phase ICGA.

Results

Of the 95 screened PCV cases, 34 were excluded: (1) cases not suitable for recruitment as per the study protocol (n = 14), (2) equivocal lesions on ICGA characterised by small hyperfluorescent dots (n = 9), and (3) cases that were definitely not PCV (non-PCV, n = 11), identified by definitive diagnoses which included one case each of micro-aneurysm, retinal angiomatous proliferation, retino-choroidal anastomosis, small type-2 choroidal neovascularisation, retinal pigment epithelial (RPE) window defect and disciform scar; two cases of lesions where the choroidal vessel changed its course; and three cases of late-onset RPE staining.

Conclusions

Standardised image grading techniques used in EVEREST study enabled effective differentiation of non-PCV from actual PCV.

Electronic supplementary material

The online version of this article (doi:10.1007/s00417-016-3333-y) contains supplementary material, which is available to authorized users.

Comparison of macular choroidal thicknesses from swept source and spectral domain optical coherence tomography

BACKGROUND

Choroidal thickness (CT) measurements differ between swept source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT) devices for point thickness measurements. We aimed to assess the comparability of mean macular CT measurements between SS-OCT and SD-OCT devices.

METHODS

In a prospective cohort study of 25 healthy volunteers, OCT scans were performed sequentially with the deep range imaging (DRI) OCT-1 and Spectralis OCT using standardised imaging protocols. These OCT scans were independently graded by reading centre-certified graders to obtain mean CT in the various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields. Paired t tests and intraclass correlation coefficients (ICCs) were used to compare the measurements.

RESULTS

The difference in mean central subfield CT between DRI OCT-1 and Spectralis was 49.3 µm (p<0.001), while differences in CT in various ETDRS subfields varied from 42.1 to 67.2 µm. After manual adjustment of the segmentation boundaries for the central subfield in the DRI OCT-1, the mean central subfield CT for DRI OCT-1 increased from 263.1 to 293.3 µm (p<0.001), and the resultant difference between DRI OCT-1 and Spectralis decreased from 49.3 to 19.1 µm (a decrease of 61.3%; p<0.001). CT between the three-dimensional and radial scanning protocols of the DRI OCT-1 were highly comparable, with differences generally under 10 µm and ICC of 0.888 for the central subfield.

CONCLUSIONS

CT measurements between automated segmentations from the DRI OCT-1 and manual segmentations on the Spectralis OCT may differ by more than 50 µm. This difference can be reduced, but not eliminated, by manual adjustment of segmentation boundaries by trained graders, and should be accounted for when comparing results between the two devices.

Topographic variation of choroidal and retinal thicknesses at the macula in healthy adults

BACKGROUND/AIMS

To determine the topographic variation of macular choroidal and retinal thicknesses (RTs) in normal eyes and their relationship with refractive error.

METHODS

Spectral domain optical coherence tomography with enhanced depth imaging was performed on 124 healthy participants using a standardised imaging protocol. Manual segmentation of choroidal boundaries was performed by trained graders, and mean choroidal thickness (CT) was compared with mean RT in corresponding sectors of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid.

RESULTS

Mean central subfield CT was 322.2 µm. The choroid was thickest at the temporal and superior sectors (323.1-338.1 µm), followed by inferior sectors (314.0-321.8 µm), and thinnest at the nasal sectors (232.8-287.8 µm). In contrast, the retina was thicker nasally (343.4 µm) and thinner temporally (287.1 µm). CT was thickest among emmetropes in all ETDRS subfields and became thinner progressively among low, moderate and high myopes (p<0.001). The variation of both choroidal and RTs among refractive error groups resulted in different topographic patterns at the macula.

CONCLUSION

There is significant topographic variation of choroidal and RTs at different regions of the macula, with progressive change of choroidal thickness in all sectors based on the refractive status of the eye.