Choroidal Microvascular Alterations in COVID-19 Patients.

OBJECTIVE: To evaluate alterations in the choroidal angioarchitecture of COVID-19 patients using optical Coherence Tomography (OCT) based surrogate markers. METHODS: This prospective case-control study recruited 56 COVID-19 patients (111 eyes) and 61 healthy individuals (120 eyes). Choroidal thickness (CT) and Choroidal vascularity index (CVI) were derived from OCT images using a purpose-built automated software for choroidal image segmentation. A linear mixed model with age and gender as covariates was employed to compare CVI and CT between groups. RESULTS: COVID-19 patients had significantly higher subfoveal (81.3um vs 86.8um, p = .02), temporal (78.8um vs 84.3um, p = .005), nasal (87.5um vs 95.1um, p = .001) and average CT (82.5um vs 88.7um, p = .001). COVID-19 patients had significantly lower subfoveal (64.0 vs 63.5, p = .02) and average CVI (63.5 vs 63.1, p = .02). CONCLUSION: COVID-19 results in significantly thicker choroid with reduced relative vascularity. This may be attributable to increased vascular permeability secondary to inflammation, resulting in choroidal stromal edema.

Investigating mental rehearsal's applicability in guiding independent E-learning (IMAGINE) of eye examination skills during the pandemic.

BACKGROUND: COVID-19's infection control policies have hindered the Deliberate Practice of clinical examinations. Guided Mental Rehearsal (GMR) may overcome this obstacle by facilitating independent, repetitive practice. Underpinned by the 'Motor Simulation Theory,' GMR reinforces similar neuro-circuit activations during physical practice and was proven effective in surgical training. METHODS: This prospective, randomized controlled study evaluated the efficacy of GMR versus 'peer-learning' of Confrontational Visual Field Examination (CVFE). Third-year medical-students without clinical Ophthalmology experience were recruited. Controls (n = 40) watched an e-learning instructional video (8-min CVFE tutorial) followed by 6-min of 'peer-learning.' GMR-students (n = 40) had 'peer-learning' replaced by a 6-min GMR audio-recording (CVFE running commentary). Pre-test and post-test MCQs were administered to determine baseline knowledge and knowledge acquisition, respectively. 28 controls and 26 GMR-students performed CVFE on simulated patients with right homonymous hemianopia. Four Ophthalmologists graded their performances using a checklist-based marking scheme. RESULTS: Both groups did not exhibit a significant difference in pre-test scores (8.550 vs. 7.947, p = 0.266); outcome of sub-group analysis of CVFE-performing candidates was similar (8.214 vs. 7.833, p = 0.561). Post-test scores were significantly higher than pre-test in both groups (all p < .001), without inter-group difference (14.000 vs. 15.000, p = 0.715). GMR-group had significantly higher scores on CVFE performance than controls (85.354 vs. 73.679%, p = .001). CONCLUSIONS: GMR improved psychomotor but not cognitive aspect of learning CVFE. This may be attributable to GMR's theoretical resemblance with physical practice, with additional expert guidance. By enabling independent learning, GMR may also reduce the demand for teaching manpower and thus education cost in the future.

Clinical Features and CD4+ T Cells Count in AIDS Patients with CMV Retinitis: Correlation with Mortality.

PURPOSE: To explore the all-cause mortality in patients with acquired immune deficiency syndrome (AIDS) and Cytomegalovirus (CMV) retinitis. METHODS: A retrospective cohort study of patients with CMV retinitis (CMVR) presented to a tertiary referral center in Singapore from January 1, 2004, through December 31, 2015. RESULTS: A total of 144 patients were studied (87 survived, 11 lost to follow up, 46 died). Patients with bilateral CMVR and six-month follow up CD4 + T cell count < 50 cells/mm3 have shorter time to mortality, compared to patients with CD4 + T cell count > 50 cells/mm3 (p < .001) and unilateral disease (p = .043). Baseline CD4 + T cell count, size and zone of initial primary retinitis lesions, recurrences of retinitis, and timing of combined antiretroviral therapy (cART) are not significantly associated with mortality. CONCLUSION: Bilateral ocular involvement and lack of immune recovery in patients with AIDS and CMVR are associated with shorter survival time.

Choroidal vascularity index: a step towards software as a medical device.

The choroidal vascularity index (CVI) is a relatively new parameter, calculated off optical coherence tomography (OCT) images, for the quantitative evaluation of choroid vascularity. It is defined as the ratio of vascular area to the total choroidal area, presented as a percentage. The choroid is an important vascular bed, often implicated in ocular and systemic conditions. Since the introduction of CVI, multiple studies have evaluated its efficacy as a tool for disease prognostication and monitoring progression, with promising results. The CVI was born out of the need for more robust and accurate evaluations of choroidal vasculature, as prior parameters such as choroidal thickness and choroidal vessel diameter had their limitations. In this review, we summarise current literature on the CVI, explain how the CVI is derived and explore its potential integration into future research and translation into clinical care. This includes the application of CVI in various disease states, and ongoing attempts to produce an automated algorithm which can calculate CVI from OCT images.

Perinatal risk factors associated with central retinal changes in former preterm children on optical coherence tomography angiography.

PURPOSE: To assess the association between perinatal risk factors for retinopathy of prematurity (ROP) and central retinal structures of former preterm children seen on optical coherence tomography angiography (OCTA). METHODS: This prospective cohort study included 40 children with a history of preterm birth and 33 healthy full-term children. We documented their birth weight, gestational age, other significant risk factors for ROP development and presence of ROP. Imaging was performed using swept-source OCTA, and quantitative evaluation was performed. Analytic parameters included the area of foveal avascular zone (FAZ), foveal depth (FD), central subfoveal retinal thickness (CSFT) and capillary density index (CDI) of the deep and superficial capillary plexus. RESULTS: Preterm children had significantly smaller FAZ, lower FD and higher CSFT compared to controls (all p < 0.001). Both groups exhibited no differences in total CDI at the superficial (p = 0.969) and deep capillary plexus (p = 0.370). The duration of mechanical ventilation correlated negatively with FAZ and FD but positively with CSFT. The duration of supplemental oxygen treatment correlated negatively with FD. The presence of intraventricular haemorrhage correlated negatively with FAZ and FD but positively with CSFT. Regression analysis found that the duration of mechanical ventilation and the presence of bronchopulmonary dysplasia were associated with lower FD (p = 0.002 and 0.01, respectively) and higher CSFT (p = 0.002 and 0.028, respectively). CONCLUSION: Central retinal anomalies were identified in former preterm children using OCTA. Macular changes were associated with several risk factors for ROP development.

The performance of iPad-based noise-field perimeter versus Humphrey Field Analyser in detecting glaucomatous visual field loss.

BACKGROUND: To conduct a preliminary evaluation of the feasibility of visual field fast (VFF), a free iPad-based noise-field perimeter, in detecting glaucomatous scotomas versus the clinical-standard Humphrey visual field (HVF) test. VFF confronts subjects with a screen of flickering stimulus, allowing the immediate perception of scotomas. METHODS: This was a cross-sectional observational study of 66 glaucoma patients (66 eyes) and 30 healthy controls (30 eyes). All patients had no other visual field disorders. VFF was compared against HVF in terms of whole field and quadrants for the following: (1) correspondence in scotoma detection. (2) Agreement and correlation of the scotoma size (percentage of abnormal visual field area). (3) Test duration. Other domains tested included: (1) correlation of VFF scotoma area with the severity of visual field loss on HVF (mean deviation, MD; visual field index, VFI). (2) Repeatability of VFF. (3) Patient descriptors of scotomas. RESULTS: Using HVF pattern deviation plot as a reference, VFF detected 52/57 (91.2%) of glaucoma subjects with 1 false-positive (control) (kappa = 0.86). 146/184 (79.3%) of abnormal quadrants (visual field defect present) were localized and 23/157 (14.6%) healthy quadrants were falsely identified as abnormal (kappa = 0.61). VFF underestimated scotoma area as compared to HVF (21.0% versus 44.0%, p < 0.01) but correlated positively (r = 0.268, p = 0.044) with HVF area and negatively with VFI (r = -0.340, p = 0.01) and MD (r = -0.398, p < 0.01). Using HVF total deviation plot as reference, VFF's glaucoma detection rate remained unchanged (kappa = 0.86) with similar quadrant detection (kappa = 0.68). However, a greater underestimation of scotoma area was observed (21.0% versus 85.4%, p < 0.01). VFF's quantitative repeatability was excellent for whole field (intraclass correlation coefficient, ICC: 0.96; p < 0.0001) and quadrants (ICC: 0.82-0.96; all p < 0.001). Qualitatively, 35/37 (94.6%) of subjects reported reduced luminance and flicker in scotomas, with similar morphologies on retests. VFF is faster than HVF SITA-Standard in glaucoma (3.60 ± 1.85 min versus 6.92 ± 1.12 min, p < 0.01) and control (1.12 ± 0.486 min versus 5.16 ± 0.727 min, p < 0.01). CONCLUSION: This early model of VFF accurately detected scotomas with high repeatability. However, its accuracy in localizing and quantifying the scotoma can be improved. Considering its portability and cost-effectiveness, VFF demonstrated potential as a general screening tool for moderate-to-severe glaucoma.

Choroidal Structural Changes in Sympathetic Ophthalmia on Swept-Source Optical Coherence Tomography.

Purpose: To analyze choroidal angioarchitecture in sympathetic ophthalmia (SO) using swept-source optical coherence tomography (SS-OCT) images.Methods: Case-control study of six patients with SO. Qualitative changes and quantitative parameters, including choroidal thickness (CT) and choroidal vascularity index (CVI), were analyzed.Results: Qualitative findings in the acute phase of SO on SS-OCT included retinal serous detachment with hyperreflective septa, choroidal folds, alterations in angioarchitecture with loss of vascular lacunae, and Dalen-Fuchs nodules. There was significantly higher CT in SO (284.05 ± 24.12 µm) compared to healthy controls (229.57 ± 46.67 µm, p = 0.04) and also increased CVI in SO (62.06 ± 2.07% vs 56.79 ± 3.15%, p = 0.006).Conclusions: CVI was significantly increased in SO, representing a novel noninvasive biomarker of disease activity. SS-OCT provides a useful qualitative and quantitative parameter, which can be potentially explored in the diagnosis and monitoring of patients with SO.

Exploring choroidal angioarchitecture in health and disease using choroidal vascularity index.

The choroid is one of the most vascularized structures of the human body and plays an irreplaceable role in nourishing photoreceptors. As such, choroidal dysfunction is implicated in a multitude of ocular diseases. Studying the choroid can lead to a better understanding of disease pathogenesis, progression and discovery of novel management strategies. However, current research has produced inconsistent findings, partly due to the physical inaccessibility of the choroid and the lack of reliable biomarkers. With the advancements in optical coherence tomography technology, our group has developed a novel quantitative imaging biomarker known as the choroidal vascularity index (CVI), defined as the ratio of vascular area to the total choroidal area. CVI is a potential tool in establishing early diagnoses, monitoring disease progression and prognosticating patients. CVI has been reported in existing literature as a robust marker in numerous retinal and choroidal diseases. In this review, we will discuss the current role of CVI with reference to existing literature, and make postulations about its potential and future applications.

Choroidal structural changes in preterm children with and without retinopathy of prematurity.

PURPOSE: Evaluate choroidal structural changes in preterm children with and without retinopathy of prematurity (ROP) using image binarization technique on swept-source optical coherence tomography (SS-OCT) scans. METHODS: Prospective case-control study. Forty-one (79 eyes) children aged 5-15 years with a history of preterm birth and 33 (63 eyes) age-matched full-term children were recruited. Demographics including gestational age at birth, birth weight and history of ROP were documented. All subjects had undergone complete eye examinations, including best-corrected visual acuity and SS-OCT imaging. Subfoveal choroidal thickness (SFCT) was calculated, and images were binarized to obtain stromal and luminal areas (LA). The choroidal vascularity index (CVI) was derived from the proportion of LA to the total subfoveal choroidal area. RESULTS: There were no significant differences in SFCT between the preterm children with (286.63 ± 83.98 µm) or without (306.59 ± 77.29 µm) ROP and the full-term children (311.82 ± 42.87; p = 0.20 and 0.67, respectively). The CVI was significantly reduced in the preterm children with ROP (68.66 ± 3.24%; p = 0.005) compared with the CVI in the full-term control group (71.37 ± 3.63%); however, the CVI in the preterm children without ROP (71.68 ± 3.09%; p = 0.93) was not significantly affected. CONCLUSION: The reduced CVI in preterm children with ROP may indicate compromised choroidal vascularity. The CVI was found to be a more sensitive OCT biomarker than the SFCT and may be helpful in evaluating associated choroidal structural changes in preterm children, especially those with a history of ROP.

Choroidal Structural Changes in Smokers Measured Using Choroidal Vascularity Index.

Purpose: Cigarette smoking is a known risk factor for vascular dysfunction. This study evaluated choroidal structural changes in smokers using the choroidal vascularity index (CVI) derived from image binarization on spectral domain optical coherence tomography scans with enhanced depth imaging (EDI-OCT). Methods: This cross-sectional study included 39 smokers and 44 non-smokers. Choroidal images on EDI-OCT were binarized into luminal area (LA) and stromal area (LA). CVI was calculated as the ratio of LA to total choroid area (TCA). CVI, foveal retinal thickness (FRT), and subfoveal choroidal thickness (SFCT) between smokers and non-smokers were compared using likelihood ratio test with linear mixed model. Trend and subgroup analysis were performed to investigate the dose-dependent relationship between CVI/FRT/SFCT and pack-years. Results: CVI in smokers (65 ± 2%) was lower compared to non-smokers (67 ± 2%, P = 0.0001). The difference remained significant after adjusting for age (P = 0.001). There was no significant association between cigarette smoking and FRT/SFCT. CVI decreased by 0.12% with each unit increase in smoking measured by pack-year (P = 0.0009). In subgroup analysis, those who smoked 8 to 12 and >12 pack-years had significantly lower CVI compared to non-smokers (both P < 0.05). Conclusions: Cigarette smoking is associated with decreased choroidal vascularity in healthy subjects, and this association appears to be dose dependent. CVI might be a non-invasive marker of vascular health in smokers.

A longitudinal study of choroidal changes following cataract surgery in patients with diabetes.

OBJECTIVE: To study the structural changes in the choroid of diabetic patients following cataract surgery, using choroidal vascularity index and choroidal thickness. METHODS: A prospective case-control study was conducted in 18 diabetic and 18 non-diabetic patients undergoing cataract surgery (phacoemulsification) in one eye. Enhanced depth imaging optical coherence tomography images were obtained before and after surgery. Niblack's image binarization of images was performed to derive the choroidal vascularity index. Independent sample T-test compared the differences of choroidal vascularity index and choroidal thickness between diabetic and non-diabetic patients. RESULTS: The baseline choroidal vascularity index was significantly lower in diabetic patients for both operated (mean difference vs non-diabetic: 0.0184, 95% CI: 0.004-0.0324, p = 0.012) and non-operated (mean difference vs non-diabetic: 0.0145, 95% CI: 0.003-0.0256, p = 0.012) eyes. Choroidal thickness increased following cataract surgery (diabetes: mean difference = 12.4, 95% CI: 0.70-24.0, adjusted p = 0.036; non-diabetic: mean difference = 21.0, 95% CI: 4.39-37.6, adjusted p = 0.011). CONCLUSION: Diabetic patients have reduced choroidal vascularity index than non-diabetic patients, suggestive of possible reduction in choroidal vascularity in diabetes. Choroidal thickness increased following cataract surgery in both diabetic and non-diabetic patients.

[Relationship of I/D polymorphism of angiotensin converting enzyme gene with hypertension in Xinjiang Kazakh isolated group].

OBJECTIVE: To investigate whether the insertion/deletion(I/D) polymorphism in the angiotensin converting enzyme(ACE) gene is associated with essential hypertension in Xinjiang Kazakh isolated population. METHODS: The study covered 201 hypertensives and 151 normotensive controls in Xinjiang Barlikun Kazakh population. The I/D polymorphism of ACE gene was determined by polymerase chain reaction. RESULTS: The frequencies of D and I in the hypertensive group (0.44 and 0.56, respectively) were not significantly different from the controls(0.39 and 0.61, respectively, P=0.16). The frequencies of ACE genotypes of DD, ID, and II were 0.18, 0.52, 0.30 in hypertensives respectively and 0.17, 0.43, 0.40 in control group respectively. There was no significant difference in genotypes between hypertensive group and normotensive group (P=0.14). CONCLUSION: The results suggested that the I/D polymorphism of ACE gene might not be associated with hypertension in the Kazakh population of Xinjiang Barlikun area.