Validation of an automated method for studying retinal capillary blood flow.

Two major approaches for tracking cellular motion across a range of biological tissues are the manual labelling of cells, and automated analysis of spatiotemporal information represented in a kymograph. Here we compare these two approaches for the measurement of retinal capillary flow, a particularly noisy application due to the low intrinsic contrast of single red blood cells (erythrocytes). Image data were obtained using a flood-illuminated adaptive optics ophthalmoscope at 750 nm, allowing the acquisition of flow information over several cardiac cycles which provided key information in evaluating tracking accuracy. Our results show that in addition to being much faster, the automated method is more accurate in the face of rapid flow and reduced image contrast. This study represents the first validation of commonly used kymograph approaches to capillary flow analysis.

Mapping the human parafoveal vascular network to understand flow variability in capillaries.

Capillary flow is known to be non-homogenous between vessels and variable over time, for reasons that are poorly understood. The local properties of individual vessels have been shown to have limited explanatory power in this regard. This exploratory study investigates the association of network-level properties such as vessel depth, branch order, and distance from the feeding arteriole with capillary flow. Detailed network connectivity analysis was undertaken in 3 healthy young subjects using flood-illuminated adaptive optics retinal imaging, with axial depth of vessels determined via optical coherence tomography angiography. Forty-one out of 70 vessels studied were of terminal capillary type, i.e. fed from an arterial junction and drained by a venous junction. Approximately half of vessel junctions were amenable to fitting with a model of relative branch diameters, with only a few adhering to Murray's Law. A key parameter of the model (the junction exponent) was found to be inversely related to the average velocity (r = -0.59, p = 0.015) and trough velocity (r = -0.67, p = 0.004) in downstream vessels. Aspects of cellular flow, such as the minimum velocity, were also moderately correlated (r = 0.46, p = 0.009) with distance to the upstream feeding arteriole. Overall, this study shows that capillary network topology contributes significantly to the flow variability in retinal capillaries in human eyes. Understanding the heterogeneity in capillary flow is an important first step before pathological flow states can be properly understood. These results show that flow within capillary vessels is not affected by vessel depths but significantly influenced by the upstream feeder distance as well as the downstream vessel junction exponents, but there remains much to be uncovered regarding healthy capillary flow.

Flow Heterogeneity and Factors Contributing to the Variability in Retinal Capillary Blood Flow.

Purpose: Capillary flow plays an important role in the nourishment and maintenance of healthy neural tissue and can be observed directly and non-invasively in the living human retina. Despite their importance, patterns of normal capillary flow are not well understood due to limitations in spatial and temporal resolution of imaging data. Methods: Capillary flow characteristics were studied in the retina of three healthy young individuals using a high-resolution adaptive optics ophthalmoscope. Imaging with frame rates of 200 to 300 frames per second was sufficient to capture details of the single-file flow of red blood cells in capillaries over the course of about 3 seconds. Results: Erythrocyte velocities were measured from 72 neighboring vessels of the parafoveal capillary network for each subject. We observed strong variability among vessels within a given subject, and even within a given imaged field, across a range of capillary flow parameters including maximum and minimum velocities, pulsatility, abruptness of the systolic peak, and phase of the cardiac cycle. The observed variability was not well explained by "local" factors such as the vessel diameter, tortuosity, length, linear cell density, or hematocrit of the vessel. Within a vessel, a moderate relation between the velocities and hematocrit was noted, suggesting a redistribution of plasma between cells with changes in flow. Conclusions: These observations advance our fundamental understanding of normal capillary physiology and raise questions regarding the potential role of network-level effects in explaining the observed flow heterogeneity.

A comparison of macular ganglion cell and retinal nerve fibre layer optical coherence tomographic parameters as predictors of visual outcomes of surgery for pituitary tumours.

PURPOSE: The prognostic value of optical coherence tomography (OCT) of the macular ganglion cell layer (mGGL) versus peripapillary retinal nerve fibre layers (pRNFL) following chiasmal decompression is unclear. This study is the largest comparison of the two parameters to date and aims to clarify how their performance as covariates compare in predictive models of long-term visual outcomes following pituitary or parasellar tumour surgical resection. METHODS: This was a prospective, two-year, longitudinal cohort study in a single centre tertiary hospital setting. Participants with MRI evidence of pituitary or parasellar tumour compression of the optic chiasm who underwent surgical decompression, were enrolled. Associations between pre-operative OCT parameters and long-term visual outcomes were assessed using multivariable generalised linear mixed models and an age matched normative database. RESULTS: Final analysis included 216 eyes of 108 participants with a mean age (standard deviation) of 51.6 (17.04) years, of whom 58 (49%) were female. The superior inner mGCL was the best predictor of long-term visual field recovery, with an area under the curve of 0.90, a sensitivity of 80%, specificity of 88%, positive predictive value of 86%, and negative predictive value of 83%. CONCLUSION: mGCL performed better in predicting long-term visual field recovery post-pituitary or parasellar surgical resection. The superior inner mGCL was the best specific measure which may provide clinical utility in pre-operative counselling. In this study we clarify previously variable comparisons of mGCL and pRNFL parameters in post-operative predictive modelling.

Temporal patterns of visual recovery following pituitary tumor resection: A prospective cohort study.

Significant restoration of visual function can occur following pituitary tumor resection, although the time course of visual recovery remains poorly understood. This single-centre, two-year, prospective cohort study investigated the temporal patterns of visual recovery in consecutive patients undergoing pituitary tumor resection, between 2009 and 2018. Eyes were stratified based on pre-operative optical coherence tomography (OCT) retinal nerve fibre layer (RNFL) thickness measurements, with thin RNFL being defined as those within the fifth-percentile of age-matched normative values, and normal RNFL as those above the fifth-percentile. Visual function and OCT parameters were assessed pre-operatively, and at 6 weeks, 6 months, and 2 years post-operatively. 456 eyes of 228 patients (mean ± SD age, 53 ± 15 years) were included, of which 114 (25%) eyes had thin RNFL pre-operatively. Visual field recovery was observed in both groups during the first 6 weeks post-operatively (all Q ≤ 0.02), although improvements in visual field parameters between 6 weeks to 6 months were limited to eyes with thin RNFL (both Q < 0.05). No further improvements in visual function were detected beyond 6 months in both groups (both Q > 0.50). Similar trends were observed in linear regression analysis according to baseline visual function in both groups. In summary, eyes with normal RNFL thickness at baseline experienced most of their recovery within the first six weeks following surgery, while eyes with thin RNFL exhibited gradual improvements during the first six months. These findings have important implications when providing patient counselling and prognostication in the pre-operative setting.

ASYMMETRIC HYDROXYCHLOROQUINE MACULAR TOXICITY WITH APHAKIC FELLOW EYE.

BACKGROUND/PURPOSE: Retinal toxicity associated with antimalarial drug use in inflammatory conditions is well described and may be more common than previously recognized. Antimalarial drugs bind to melanin in ocular tissues, particularly the retinal pigment epithelium, but the mechanism of toxicity and its relation to light is unclear. METHODS: Case report. RESULTS: A 62-year-old white woman with erosive rheumatoid arthritis developed hydroxychloroquine toxicity in her phakic eye, with her aphakic fellow eye only mildly affected. CONCLUSION: We report the clinical evaluation of this rare case of asymmetrical hydroxychloroquine retinopathy and present a hypothesis regarding the mechanism of drug toxicity.

Prognostic Utility of Optical Coherence Tomography for Long-Term Visual Recovery Following Pituitary Tumor Surgery.

PURPOSE: To investigate the association between optical coherence tomography (OCT) parameters and long-term visual recovery following optic chiasm decompression surgery. DESIGN: Prospective cohort study. METHODS: Consecutive patients who underwent pituitary or parasellar tumor resection between January 2009 to December 2018 were recruited in a single-center, 2-year prospective, longitudinal cohort study. Best-corrected visual acuity, visual fields, and OCT retinal nerve fiber layer (RNFL) thickness, macular thickness and volume were assessed preoperatively, and at 6 weeks, 6 months, and 2 years postoperatively. Long-term visual field recovery and maintenance were defined as a mean deviation of >-3 at 24 months, and visual acuity recovery and maintenance were defined as a logarithm of minimal angle of resolution (logMAR) of 0 (Snellen 20/20) or better at 24 months. RESULTS: A total of 239 patients (129 men, 110 women; mean ± SD age: 52 ± 16 years) were included. Multiple logistic regression analysis demonstrated that increased inferior RNFL thickness (per 10 µm) was associated with higher odds of long-term visual field recovery and maintenance (odds ratio [OR]: 1.26; 95% confidence interval [CI]: 1.12-1.41; Q < 0.001), and greater superior RNFL thickness (per 10 µm) was associated with higher odds of visual acuity recovery and maintenance (OR: 1.13; 95% CI: 1.03-1.27; Q = 0.031). A multivariable risk prediction model developed for long-term visual field recovery and maintenance that incorporated age, preoperative visual function, and RNFL thickness demonstrated C-statistics of 0.83 (95% CI: 0.72-0.94). CONCLUSION: Preoperative RNFL thickness was associated with long-term visual recovery and maintenance following chiasmal decompression. The multivariable risk prediction model developed in the present study may assist with preoperative patient counseling and prognosis.

Optical coherence tomography analysis of patients with untreated diabetic macular edema.

PURPOSE: Diabetic macular edema (DME) is a major cause of vision loss. Diabetes patients with mild macular edema and good visual acuity are often observed carefully so that treatment can be instituted when central vision is threatened. Optimal frequency of monitoring of these patients is unknown. Our study aimed to gather more information to determine a safe interval for monitoring of patients with eyes that were not undergoing active treatment for DME and to correlate outcomes with clinical risk factors. METHODS: Study population: Ninety-seven eyes with optical coherence tomography (OCT) evidence of DME of 97 patients with diabetes. Study procedures: Retrospective review of medical records and macular OCT scans at a 6-12-month interval. Primary outcomes: Change in visual acuity and change in central subfield thickness (CSFT) between the initial and follow-up OCT scans. RESULTS: There was no significant change from median baseline visual acuity 6/9 (inter-quartile range 6/6-6/12) or from median baseline CSFT (290 µm, inter-quartile range 270-312 µm) over a median duration of 8 months (inter-quartile range 7-10 months). The numbers of eyes where CSFT had increased ≥ 25 µm, reduced ≥ 25 µm, or remained unchanged were 16 (16%), 6 (6%), and 74 (76%), respectively. Patients with hemoglobin A1c ≥ 8.5% were 5.7 times more likely to develop central subfield thickening (95% CI 1.1-30.1, P = 0.038). CONCLUSIONS: Majority of eyes with DME on OCT had stable CSFT without treatment over a median duration of 8 months. Hemoglobin A1c may be useful for risk stratification.

Bull's eye maculopathy and subfoveal deposition in two mucopolysaccharidosis type I patients on long-term enzyme replacement therapy.

PURPOSE: To report retinal findings in two patients with mucopolysaccharidosis type I (MPS I) receiving human recombinant alpha-l-iduronidase (Laronidase) as enzyme replacement therapy. OBSERVATIONS: Patient 1 had visual acuity 20/20 right eye, 20/25 left eye and unremarkable anterior segment and retinal examination. Optical coherence tomography (OCT) scanning demonstrated parafoveal thinning and subfoveal hyperreflectant material. Patient 2 had visual acuity 20/20 both eyes, with dense nuclear cataract both eyes. Retinal examination demonstrated bull's eye maculopathy both eyes. OCT scanning confirmed parafoveal atrophy and demonstrated similar appearing subfoveal hyperreflectant material, more prominent than in case 1. CONCLUSIONS AND IMPORTANCE: These two patients with MPS I receiving Laronidase treatment have developed bull's eye maculopathy changes and subfoveal deposition of hyperreflectant material despite excellent compliance and good tolerance of the standard dose of enzyme therapy for this disorder. Further studies are required to determine the nature of the material, the incidence and the effect of enzyme replacement therapy on these findings in patients with MPS I.

Retinal disease in the C3 glomerulopathies and the risk of impaired vision.

BACKGROUND: Dense deposit disease and atypical hemolytic uremic syndrome are often caused by Complement Factor H (CFH) mutations. This study describes the retinal abnormalities in dense deposit disease and, for the first time, atypical haemolytic uremic syndrome. It also reviews our understanding of drusen pathogenesis and their relevance for glomerular disease. METHODS: Six individuals with dense deposit disease and one with atypical haemolytic uremic syndrome were studied from 2 to 40 years after presentation. Five had renal transplants. All four who had genetic testing had CFH mutations. Individuals underwent ophthalmological review and retinal photography, and in some cases, optical coherence tomography, and further tests of retinal function. RESULTS: All subjects with dense deposit disease had impaired night vision and retinal drusen or whitish-yellow deposits. Retinal atrophy, pigmentation, and hemorrhage were common. In late disease, peripheral vision was restricted, central vision was distorted, and there were scotoma from sub-retinal choroidal neovascular membranes and atypical serous retinopathy. Drusen were present but less prominent in the young person with atypical uremic syndrome due to a heterozygous CFH mutation. CONCLUSIONS: Drusen are common in forms of C3 glomerulopathy caused by compound heterozygous or heterozygous CFH mutations. They are useful diagnostically but also impair vision. Drusen have an identical composition to glomerular deposits. They are also identical to the drusen of age-related macular degeneration, and may respond to the same treatments. Individuals with a C3 glomerulopathy should be assessed ophthalmologically at diagnosis, and monitored regularly for vision-threatening complications.

Incidence and clinical predictors of ocular candidiasis in patients with Candida fungemia.

Purpose. The aim of this study is to determine the incidence and the predictors of ocular candidiasis among patient with Candida fungemia. Methods. We retrospectively reviewed the charts of all patients diagnosed with candidemia at the University of Kansas Medical Center during February 2000-March 2010. Data regarding patients' demographics, clinical characteristics, laboratory results, and ophthalmology examination findings were collected. Results. A total of 283 patients with candidemia were enrolled. The mean age (± standard deviation) was 55 ± 18 years; 66% were male. The most commonly isolated Candida species were C. albicans (54%), C. parapsilosis (20%), C. glabrata (13%), and C. tropicalis (8%). Only 144 (51%) patients were evaluated by ophthalmology; however, the proportion of patients who were formally evaluated by an ophthalmologist increased during the study period (9%in 2000 up to 73%in 2010; P < 0.0001). Evidence of ocular candidiasis was present in 18 (12.5%) patients. Visual symptoms were reported by 5 of 18 (28%) patients. In multivariable analysis, no predictors of ocular candidiasis were identified. Conclusions. The incidence of ocular candidiasis among patients with fungemia remains elevated. Most patients are asymptomatic and therefore all patients with candidemia should undergo fundoscopic examination to rule out ocular involvement.

Bilateral retrobulbar optic neuropathy in the setting of interferon alpha-2a therapy.

The development of biopharmaceutical agents, including the interferons (IFN), offers new treatment options for a wide range of medical conditions. Such advancements, however, have not come without risk to patients. Optic neuropathy in the setting of IFN therapy has been previously documented and is usually attributed to anterior ischaemic optic neuropathy; however, the pathophysiology remains poorly understood. Retrobulbar optic neuropathy associated with IFN treatment has not been described in the medical literature to date. We report the case of a 38-year-old Caucasian female with refractory acute myeloid leukaemia who developed painless bilateral blurred vision within 2 weeks of commencing a course of IFN alpha-2a. Extensive clinical workup demonstrated bilateral retrobulbar optic neuropathy. We report the clinical evaluation of this first documented case and discuss the possible aetiologies of her presentation.

Cytokine profiles in clinical subtypes of ophthalmic Graves' disease.

PURPOSE: To examine the association of cytokines in the two clinical subtypes of ophthalmic Graves' disease by comparing cytokine expression in the fat and ethmoid tissue of type I and type II patients. METHODS: Patients needing orbital decompression or eyelid surgery were identified and enrolled into a prospective study. Patients were assigned to the type I or type II subclassification, based on the presence of diplopia. Orbital fat, sinus tissue or muscle removed during surgery was evaluated. The mRNA expression profiles of Th1 cytokines (TNF-alpha/beta, IFN-gamma, IL-2) and Th2 cytokines (IL-4, IL-5, IL-6, IL-10) were analyzed using real time PCR. RESULTS: 30 patients were enrolled in the study: 5 type I (80% female), 14 type II (71% female) and 11 controls (73% female). There were 14 decompressions (3 type I and 11 type II), 17 lid procedures (2 type I, 4 type II and 11 controls) and 10 ethmoidectomies (3 type I and 7 type II). The average ages were 45, 56 and 66 in the type I, type II and control groups, respectively. There was more TNF-alpha (p value 0.009) and IL-6 (p value 0.04) in ethmoid sinus cells of type II patients compared to ethmoid sinus cells of type I patients and a trend of higher expression of all cytokines in type II patients. CONCLUSIONS: There is a trend towards greater mRNA expression of both Th1 and Th2 cytokines in both orbital fat and ethmoidal sinus tissue of type II patients compared to type I patients.

CHD7 deficiency in "Looper", a new mouse model of CHARGE syndrome, results in ossicle malformation, otosclerosis and hearing impairment.

CHARGE syndrome is a rare human disorder caused by mutations in the gene encoding chromodomain helicase DNA binding protein 7 (CHD7). Characteristics of CHARGE are varied and include developmental ear and hearing anomalies. Here we report a novel mouse model of CHD7 dysfunction, termed Looper. The Looper strain harbours a nonsense mutation (c.5690C>A, p.S1897X) within the Chd7 gene. Looper mice exhibit many of the clinical features of the human syndrome, consistent with previously reported CHARGE models, including growth retardation, facial asymmetry, vestibular defects, eye anomalies, hyperactivity, ossicle malformation, hearing loss and vestibular dysfunction. Looper mice display an otosclerosis-like fusion of the stapes footplate to the cochlear oval window and blepharoconjunctivitis but not coloboma. Looper mice are hyperactive and have vestibular dysfunction but do not display motor impairment.

Honokiol inhibits pathological retinal neovascularization in oxygen-induced retinopathy mouse model.

Aberrant activation of the hypoxia inducible factor (HIF) pathway is the underlying cause of retinal neovascularization, one of the most common causes of blindness worldwide. The HIF pathway also plays critical roles during tumor angiogenesis and cancer stem cell transformation. We have recently shown that honokiol is a potent inhibitor of the HIF pathway in a number of cancer and retinal pigment epithelial cell lines. Here we evaluate the safety and efficacy of honokiol, digoxin, and doxorubicin, three recently identified HIF inhibitors from natural sources. Our studies show that honokiol has a better safety to efficacy profile as a HIF inhibitor than digoxin and doxorubicin. Further, we show for the first time that daily intraperitoneal injection of honokiol starting at postnatal day (P) 12 in an oxygen-induced retinopathy (OIR) mouse model significantly reduced retinal neovascularization at P17. Administration of honokiol also prevents the oxygen-induced central retinal vaso-obliteration, characteristic feature of the OIR model. Additionally, honokiol enhanced physiological revascularization of the retinal vascular plexuses. Since honokiol suppresses multiple pathways activated by HIF, in addition to the VEGF signaling, it may provide advantages over current treatments utilizing specific VEGF antagonists for ocular neovascular diseases and cancers.

The genetic control of avascular area in mouse oxygen-induced retinopathy.

PURPOSE: The C57BL/6ByJ and BALB/cByJ inbred strains of mice are, respectively, susceptible and resistant to oxygen-induced retinopathy (OIR). The purpose of this work was to investigate the genetic control of the retinal avascular area in mouse OIR using a mapping cross. METHODS: The central retinal avascular area was measured on postnatal day 16 (P16) in C57BL/6ByJ, BALB/cByJ, 101 (C57BL/6ByJ x BALB/cByJ)F2, and 116 (BALB/cByJ x C57BL/6ByJ)F2 mice that had been subjected to the OIR protocol. A genome-wide scan was performed of selected albino and non-albino mice to determine quantitative trait loci associated with weight and avascular area. RESULTS: C57BL/6ByJ mice had significantly larger avascular areas than BALB/cByJ ones. Albino mice of the F2 generation had smaller avascular areas than the non-albino mice. Genotyping was performed at 856 informative single nucleotide polymorphisms approximately evenly distributed across the genome from each of 85 selected F2 mice. Weight, sex, and the paternal grandmother were found to act as additive covariates associated with the avascular area on P16; mapping analyses that used a model incorporating these covariates found a quantitative trait locus on chromosome 7 related to avascular area. Mapping analyses that used a model that did not incorporate covariates found a quantitative trait locus on chromosome 9 related to avascular area. A quantitative trait locus for bodyweight on P16 was mapped to chromosome 5. CONCLUSIONS: The retinal avascular area in the mouse OIR model is under genetic control. Revascularization in OIR is related to the weight, strain of paternal grandmother, sex, and albinism. Our data support the existence of a quantitative trait locus on chromosome 5 that influences weight after exposure to hyperoxia, as well as quantitative trait loci on chromosomes 7 and 9 that modify susceptibility to OIR.

RNAi-based treatment for neovascular age-related macular degeneration by Sirna-027.

PURPOSE: To assess the safety, tolerability, pharmacokinetics, and dose-limiting toxicity of single intravitreal injection of Sirna-027, a small interfering RNA targeting vascular endothelial growth factor receptor-1, in patients with choroidal neovascularization (CNV) resulting from neovascular age-related macular degeneration (AMD). Secondary objectives included assessment of anatomic changes in retinal thickness, size of CNV, and changes in visual acuity. DESIGN: Prospective, open-label, single-dose, dose-escalation phase 1 study. METHODS: Twenty-six eyes of 26 patients with a median age of 82 years and CNV resulting from AMD who had previous treatments with other therapies were treated at 2 academic retinal practices. Patients received a single dose of Sirna-027 (100, 200, 400, 800, 1200, or 1600 microg/eye). Blood was sampled for pharmacokinetic analysis at 1, 4, and 24 hours after injection and on day 7. Patients underwent ophthalmic examinations including visual acuity, fluorescein angiography, and optical coherence tomography at screening and days 7, 14, 28, and 84. The main outcome measures were adverse reactions and dose-limiting toxicities. RESULTS: Intravitreal injection of a single dose of Sirna-027 from 100 to 1600 microg was well tolerated in patients with AMD, with no dose-limiting toxicity found. Adverse events were mild to moderate in severity. Adjusted mean foveal thickness decreased within 2 weeks after study treatment. The decrease was most pronounced in the 100- and 200-microg doses. CONCLUSIONS: A single intravitreal dose of Sirna-027 up to 1600 microg/eye was well tolerated in patients with CNV resulting from neovascular AMD that had been refractory to other therapies. Stabilization or improvement in visual acuity and foveal thickness was observed. No dose-response or dose-limiting effects were noted.

Intravenous bevacizumab causes regression of choroidal neovascularization secondary to diseases other than age-related macular degeneration.

PURPOSE: To investigate the safety, tolerability, and bioactivity of intravenous infusions of bevacizumab in patients with choroidal neovascularization (CNV) attributable to causes other than age-related macular degeneration. DESIGN: Nonrandomized clinical trial. METHODS: Ten patients with CNV received infusions of 5 mg/kg of bevacizumab. The primary efficacy outcome measure was change in visual acuity (VA; Early Treatment Diabetic Retinopathy Study letters read at 4 meters) at 24 weeks and secondary measures were changes from baseline in excess foveal thickness (center subfield thickness), area of fluorescein leakage, and area of CNV. RESULTS: Infusions were well tolerated and there were no ocular or systemic adverse events. At baseline, median VA was 25.5 letters read at 4 meters (20/80) and median foveal thickness was 346 mum. At the primary endpoint (24 weeks), median VA was 48.5 letters (20/32), representing four lines of improvement from baseline (P = .005), median foveal thickness was 248 mum representing a 72% reduction in excess foveal thickness (P = .007). Four of nine patients had complete elimination of fluorescein leakage, three had near complete elimination (reductions of 91%, 88%, and 87%), two had modest reductions, and one had no reduction. All patients except one showed a reduction in area of CNV with a median reduction of 43%. CONCLUSIONS: Despite the small number of patients studied, the marked improvement in VA accompanied by prominent reductions in foveal thickness, fluorescein leakage, and area of CNV suggest a beneficial effect. It may be worthwhile to consider further evaluation of systemic bevacizumab in young patients with CNV.

Common ophthalmic emergencies.

Ophthalmic emergencies are immediate threats to the visual system that can lead to permanent loss of visual function if left untreated. These emergencies should be detected by physicians and immediately treated and referred to an ophthalmologist if necessary. This article reviews the most common ophthalmic emergency room presentations, the history and physical examination for an ophthalmic emergency, and the diagnosis and management of each condition.