Spontaneous Venous Pulsations Detected With Infrared Videography

Autonomous assessment of spontaneous retinal venous pulsations in fundus videos using a deep learning framework

The presence or absence of spontaneous retinal venous pulsations (SVP) provides clinically significant insight into the hemodynamic status of the optic nerve head. Reduced SVP amplitudes have been linked to increased intracranial pressure and glaucoma progression. Currently, monitoring for the presence or absence of SVPs is performed subjectively and is highly dependent on trained clinicians. In this study, we developed a novel end-to-end deep model, called U3D-Net, to objectively classify SVPs as present or absent based on retinal fundus videos. The U3D-Net architecture consists of two distinct modules: an optic disc localizer and a classifier. First, a fast attention recurrent residual U-Net model is applied as the optic disc localizer. Then, the localized optic discs are passed on to a deep convolutional network for SVP classification. We trained and tested various time-series classifiers including 3D Inception, 3D Dense-ResNet, 3D ResNet, Long-term Recurrent Convolutional Network, and ConvLSTM. The optic disc localizer achieved a dice score of 95% for locating the optic disc in 30 milliseconds. Amongst the different tested models, the 3D Inception model achieved an accuracy, sensitivity, and F1-Score of 84 ± 5%, 90 ± 8%, and 81 ± 6% respectively, outperforming the other tested models in classifying SVPs. To the best of our knowledge, this research is the first study that utilizes a deep neural network for an autonomous and objective classification of SVPs using retinal fundus videos.

Autonomous Stabilization of Retinal Videos for Streamlining Assessment of Spontaneous Venous Pulsations

Spontaneous retinal Venous Pulsations (SVP) are rhythmic changes in the caliber of the central retinal vein and are observed in the optic disc region (ODR) of the retina. Its absence is a critical indicator of various ocular or neurological abnormalities. Recent advances in imaging technology have enabled the development of portable smartphone-based devices for observing the retina and assessment of SVPs. However, the quality of smartphone-based retinal videos is often poor due to noise and image jitting, which in return, can severely obstruct the observation of SVPs. In this work, we developed a fully automated retinal video stabilization method that enables the examination of SVPs captured by various mobile devices. Specifically, we first propose an ODR Spatio-Temporal Localization (ODR-STL) module to localize visible ODR and remove noisy and jittering frames. Then, we introduce a Noise-Aware Template Matching (NATM) module to stabilize high-quality video segments at a fixed position in the field of view. After the processing, the SVPs can be easily observed in the stabilized videos, significantly facilitating user observations. Furthermore, our method is cost-effective and has been tested in both subjective and objective evaluations. Both of the evaluations support its effectiveness in facilitating the observation of SVPs. This can improve the timely diagnosis and treatment of associated diseases, making it a valuable tool for eye health professionals.

Noninvasive methods to monitor intracranial pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) is determined by the production of and outflow facility of cerebrospinal fluid. Since alterations in ICP are implicated in several vision-threatening and life-threatening diseases, measurement of ICP is necessary and common. All current clinical methods to measure ICP are invasive and carry the risk for significant side effects. Therefore, the development of accurate, reliable, objective, and portal noninvasive devices to measure ICP has the potential to change the practice of medicine. This review discusses recent advances and barriers to the clinical implementation of noninvasive devices to determine ICP.

RECENT FINDINGS

Many noninvasive methods to determine ICP have been developed. Although most have significant limitations limiting their clinical utility, several noninvasive methods have shown strong correlations with invasively obtained ICP and have excellent potential to be developed further to accurately quantify ICP and ICP changes.

SUMMARY

Although invasive methods remain the mainstay for ICP determination and monitoring, several noninvasive biomarkers have shown promise to quantitatively assess and monitor ICP. With further refinement and advancement of these techniques, it is highly possible that noninvasive methods will become more commonplace and may complement or even supplant invasively obtained methods to determine ICP in certain situations.

Near infra-red reflectance videography in the evaluation of retinal artery macroaneurysm pulsatility

Purpose

To describe pulsations of the retinal arteries detected in the course of evaluation of an exudative non-pulsatile retinal arterial macroaneurysm using near infra-red reflectance videography.

Observations

A 68-year-old patient underwent slit lamp examination, color retinal imaging, optical coherence tomography, fluorescein videography, short wave-length and near infrared fundus autofluorescence of the left, and near infrared reflectance videography of both eyes. A 1309.3 × 955.1 μm exudative lesion with intraretinal hemorrhage and retinal edema secondary to a retinal arterial macroaneurysm was observed along the superior temporal arcade between the retinal artery and vein. Bilateral serpentine and expansile spontaneous retinal artery pulsations were detected along the retinal vascular tree and imaged using near infrared reflectance videography. Fluorescein video-angiography showed an irregular filling defect of the lesion with minimal angiographic leakage. Whereas pulsations of the retinal arteries were visualized, no pulsations of the retinal arterial macroaneurysm were detected with either dynamic imaging modality, therefore observation was recommended. Significant spontaneous lesion regression was observed at one month follow-up.

Conclusionand Importance

Detection of spontaneous retinal artery pulsation and the assessment of exudative maculopathy due to an underlying retinal arterial macroaneurysm could be facilitated by near infrared reflectance videography. This imaging modality can aid in clinical decision-making where a non-pulsatile macroaneurysm would favor conservative management.

Linear interactions between intraocular, intracranial pressure, and retinal vascular pulse amplitude in the fourier domain

Purpose

To compare the retinal vascular pulsatile characteristics in subjects with normal (ICP_n) and high (ICP_h) intracranial pressure and quantify the interactions between intraocular pressure, intracranial pressure, and retinal vascular pulse amplitude in the Fourier domain.

Materials and methods

Twenty-one subjects were examined using modified photoplethysmography with simultaneous ophthalmodynamometry. A harmonic regression model was fitted to each pixel in the time-series, and used to quantify the retinal vascular pulse wave parameters including the harmonic regression wave amplitude (HRW_a). The pulse wave attenuation was measured under different ranges of induced intraocular pressure (IOP_i), as a function of distance along the vessel (V_Dist). Intracranial pressure (ICP) was measured using lumbar puncture. A linear mixed-effects model was used to estimate the correlations between the Yeo-Johnson transformed harmonic regression wave amplitude (HRW_a-YJt) with the predictors (IOP_i, V_Dist and ICP). A comparison of the model coefficients was done by calculating the weighted Beta (β_x) coefficients.

Results

The median HRW_a in the ICP_n group was higher in the retinal veins (4.563, interquartile range (IQR) = 3.656) compared to the retinal arteries (3.475, IQR = 2.458), p<0.0001. In contrast, the ICP_h group demonstrated a reduction in the median venous HRW_a (3.655, IQR = 3.223) and an elevation in the median arterial HRW_a (3.616, IQR = 2.715), p<0.0001. Interactions of the pulsation amplitude with ICP showed a significant disordinal interaction and the loss of a main effect of the Fourier sine coefficient (b_n1) in the ICP_h group, suggesting that this coefficient reflects the retinal vascular response to ICP wave. The linear mixed-effects model (LME) showed the decay in the venous (HRW_a-YJt) was almost twice that in the retinal arteries (−0.067±0.002 compared to −0.028±0.0021 respectively, p<0.00001). The overall interaction models had a total explanatory power of (conditional R²) 38.7%, and 42% of which the fixed effects explained 8.8%, and 5.8% of the variance (marginal R²) for the venous and arterial models respectively. A comparison of the damping effect of V_Dist and ICP showed that ICP had less influence on pulse decay than distance in the retinal arteries (β_ICP = -0.21, se = ±0.017 compared to βVDist=-0.26, se = ±0.019), whereas the mean value was equal for the retinal veins (venous βVDist=-0.42, se = ±0.015, β_ICP = -0.42, se = ±0.019).

Conclusion

The retinal vascular pulsation characteristics in the ICP_h group showed high retinal arterial and low venous pulsation amplitudes. Interactions between retinal vascular pulsation amplitude and ICP suggest that the Fourier sine coefficient b_n1 reflects the retinal vascular response to the ICP wave. Although a matrix of regression lines showed high linear characteristics, the low model explanatory power precludes its use as a predictor of ICP. These results may guide future predictive modelling in non-invasive estimation of ICP using modified photoplethysmography.

Idiopathic intracranial hypertension: Pathophysiology, diagnosis and management

Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure, manifested by papilledema and radiological findings, in the absence of an identifiable casual factor. The primary symptoms include headache, vision loss, and pulsatile tinnitus, and are recognized to have profound impacts on quality of life and visual function. IIH demonstrates a strong predilection towards obese women of reproductive age, and the population incidence is rising with the growing prevalence of obesity worldwide. The pathophysiology involves dysregulation of cerebrospinal fluid (CSF) dynamics and venous sinus pressure, and recent studies highlighting the pathogenic role of metabolic and hormonal factors have led to the identification of several pharmacological targets and development of novel therapeutic agents. The overarching treatment goals include symptomatic alleviation and prevention of permanent vision loss. The Idiopathic Intracranial Hypertension Treatment Trial, the first of its kind randomized controlled trial on IIH, provides class I evidence for treatment with weight loss and acetazolamide. In medically refractive or fulminant cases, optic nerve sheath fenestration, CSF diversion, and venous sinus stenting, have been successfully implemented. However, there are few high-quality prospective studies investigating the treatment and natural history of IIH, highlighting the compelling need for further research to determine the optimal treatment regimen.

At the Pulse of Time: Machine Vision in Retinal Videos

Spontaneous venous pulsations (SVP) are a common finding in healthy people. The absence of SVP is associated with rapid progression in glaucoma and increased intracranial pressure. Traditionally, SVP has been documented qualitatively by clinicians during biomicroscopy. Nowadays numerous imaging devices recording the fundus exist. Hence, video data for objectification of SVP is readily available. Still, these clinical datasets are afflicted with various quality issues and artifacts. In this machine vision based study, we explore methods to overcome challenges in identifying SVP in fundus videos of varying quality and provide a detailed protocol thereof. Hereby, we aim to lower the burden of access of implementing machine vision in clinical video datasets and quantification of SVP.

Non-invasive detection of intracranial pressure related to the optic nerve

Intracranial pressure (ICP) is associated with a variety of diseases. Early diagnosis and the timely intervention of elevated ICP are effective means to clinically reduce the morbidity and mortality of some diseases. The detection and judgment of reduced ICP are beneficial to glaucoma doctor and neuro ophthalmologist to diagnose optic nerve disease earlier. It is important to evaluate and monitor ICP clinically. Although invasive ICP detection is the gold standard, it can have complications. Most non-invasive ICP tests are related to the optic nerve and surrounding tissues due to their anatomical characteristics. Ultrasound, magnetic resonance imaging, transcranial Doppler, papilledema on optical coherence tomography, visual evoked potential, ophthalmodynamometry, the assessment of spontaneous retinal venous pulsations, and eye-tracking have potential for application. Although none of these methods can completely replace invasive technology; however, its repeatable, low risk, high accuracy, gradually attracted people's attention. This review summarizes the non-invasive ICP detection methods related to the optic nerve and the role of the diagnosis and prognosis of neurological disorders and glaucoma. We discuss the advantages and challenges and predict possible areas of development in the future.

Brain MRI and Ophthalmic Biomarkers of Intracranial Pressure

OBJECTIVE

To evaluate the utility of brain MRI and ophthalmic biomarkers for the prediction of intracranial hypertension, we have studied the association between 6 biomarkers and 24-hour intracranial pressure (ICP) monitoring results in 45 patients.

METHODS

This single-center observational study includes patients who underwent 24-hour ICP monitoring, brain MRI (within 3 months), and ophthalmic assessment (during ICP monitoring). Six biomarkers were investigated: pituitary gland shape, vertical tortuosity of the optic nerve, distension of the optic nerve sheath, optic disc protrusion (MRI), papilledema (slit lamp biomicroscopy), and spontaneous venous pulsations (SVP, infrared video recordings).

RESULTS

Forty-five patients (mean age 39 ± 14 years, 38 women) met the inclusion criteria. All 6 biomarkers had a significant association with 24-hour ICP. Concave pituitary gland was observed with moderately elevated median ICP. Protrusion of the optic disc (MRI), papilledema, and absence of SVP were associated with the highest median ICP values. Twenty patients had raised ICP (median 24-hour ICP >5.96 mm Hg, cutoff obtained through Youden index calculation). Patients with all normal biomarkers had normal median ICP in 94% (standard error 6%) of the cases. All patients with ≥3 abnormal biomarkers had intracranial hypertension. The combination of at least 1 abnormal biomarker in MRI and ophthalmic assessments was highly suggestive of intracranial hypertension (area under the curve 0.94, 95% confidence interval 0.93-0.94) CONCLUSIONS: Brain MRI and ophthalmic biomarkers can noninvasively guide the management of patients with suspected CSF dynamics abnormalities. Patients with multiple abnormal biomarkers (≥3) or a combination of abnormal MRI and ophthalmic biomarkers are likely to have intracranial hypertension and should be managed promptly.

Current Perspectives on Idiopathic Intracranial Hypertension without Papilloedema

The pseudotumor cerebri syndrome embraces disorders characterised by raised intracranial pressure, where the commonest symptom is headache (90%). Idiopathic intracranial hypertension without papilloedema (IIHWOP) is increasingly recognised as a source of refractory headache symptoms and resultant neurological disability. Although the majority of patients with IIHWOP are phenotypically similar to those with idiopathic intracranial hypertension (IIH), it remains uncertain as to whether IIHWOP is nosologically distinct from IIH. The incidence, prevalence, and the degree of association with the world-wide obesity epidemic is unknown. Establishing a diagnosis of IIHWOP can be challenging, as often lumbar puncture is not routinely part of the work-up for refractory headaches. There are published diagnostic criteria for IIHWOP; however, some report uncertainty regarding a pathologically acceptable cut off for a raised lumbar puncture opening pressure, which is a key criterion. The literature provides little information to help guide clinicians in managing patients with IIHWOP. Further research is therefore needed to better understand the mechanisms that drive the development of chronic daily headaches and a relationship to intracranial pressure; and indeed, whether such patients would benefit from therapies to lower intracranial pressure. The aim of this narrative review was to perform a detailed search of the scientific literature and provide a summary of historic and current opinion regarding IIHWOP.

An Update on Imaging in Idiopathic Intracranial Hypertension

Neuroimaging plays an essential role in the diagnostic workup of idiopathic intracranial hypertension with the aims to exclude secondary causes of elevated intracranial pressure and to identify imaging signs that are commonly observed in this disorder. As a valuable expansion of brain imaging, the imaging of the retina using optical coherence tomography has been of increasing value. In particular, this is the case with the latest devices that allow a more accurate distinction between a reduction in retinal nerve fiber layer thickness due to an improvement of papilledema or due to a worsening caused by optic nerve atrophy. Although optical coherence tomography does not yet replace the other elements of the diagnostic workup, it is likely to play an increasing role in diagnosis and follow-up of idiopathic intracranial hypertension. The review focuses on the main findings in neuroimaging, including structural and vascular alterations as well as on the relevance of optical coherence tomography.