Optical coherence tomography angiography and arterial hypertension: A role in identifying subclinical microvascular damage?

INTRODUCTION: To evaluate retinal microvasculature modifications by means of optical coherence tomography angiography in human subjects diagnosed with arterial hypertension and to assess potential clinical relevance for early diagnosis. METHODS: A cross-sectional study of 30 subjects affected by arterial hypertension compared to a matched cohort of healthy patients was conducted. Patients were evaluated by the Outpatient Clinic for Hypertension and the Retina Center, University of Insubria, Varese, Italy. Patients were divided into three groups: Group 1-healthy subjects, Group 2-patients first diagnosed with hypertension, and Group 3-patients with treated hypertension. Optical coherence tomography angiography was performed applying different analysis protocols for macula and optic disk, using an AngioVue OCTA System on an Optovue device. Morphological data were compared to and correlated with clinical vascular parameters, to evaluate preclinical microvascular damage. RESULTS: A significant reduction in deep vascular layer density (Group 1: 59.2% ± 1.5% standard deviation; Group 2: 59.2% ± 2.2% standard deviation; Group 3: 57.8% ± 2.6% standard deviation; p < 0.05) as well as an enlargement of the deep foveal avascular zone area (Group 1: 0.34 ± 0.09 mm2; Group 2: 0.36 ± 0.07 mm2; Group 3: 0.39 ± 0.1 mm2; p < 0.05) was measured in patients with first diagnosed hypertension and in treated patients compared to healthy subjects. We also observed a significant decrease in mean foveal choroidal thickness in affected patients compared to controls (Group 1: 319.68 ± 61.72 µm standard deviation; Group 2: 251.04 ± 63.1 µm standard deviation; Group 3: 262.65 ± 51.08 µm standard deviation; p < 0.05). Our preliminary data did not show a significant correlation with microalbuminuria levels. DISCUSSION: Retinal vascular density showed pathological modifications between healthy subjects and hypertensive patients. These preliminary findings suggest that optical coherence tomography angiography may identify pathological markers of an early hypertensive damage and help monitor disease progression with potential therapeutic advantages.

Comparison between invasive and noninvasive techniques of evaluation of microvascular structural alterations.

BACKGROUND: The evaluation of the morphological characteristics of small resistance arteries in humans is challenging. The gold standard method is generally considered to be the measurement by wire or pressure micromyography of the media-to-lumen ratio of subcutaneous small vessels obtained by local biopsies. However, noninvasive techniques for the evaluation of retinal arterioles were recently proposed; in particular, two approaches, scanning laser Doppler flowmetry (SLDF) and adaptive optics, seem to provide useful information; both of them provide an estimation of the wall-to-lumen ratio (WLR) of retinal arterioles. Moreover, a noninvasive measurement of basal and total capillary density may be obtained by videomicroscopy/capillaroscopy. No direct comparison of these three noninvasive techniques in the same population was previously performed; in particular, adaptive optics was never validated against micromyography. METHODS: In the current study, we enrolled 41 controls and patients: 12 normotensive lean controls, 12 essential hypertensive lean patients, nine normotensive obese patients and eight hypertensive obese patients undergoing elective surgery. All patients underwent a biopsy of subcutaneous fat during surgery. Subcutaneous small resistance artery structure was assessed by wire micromyography and the media-to-lumen ratio was calculated. WLR of retinal arterioles was obtained by SLDF and adaptive optics. Functional (basal) and structural (total) microvascular density was evaluated by capillaroscopy before and after venous congestion. RESULTS AND CONCLUSION: Our data suggest that adaptive optics has a substantial advantage over SLDF in terms of evaluation of microvascular morphology, as WLR measured with adaptive optics is more closely correlated with the M/L of subcutaneous small arteries (r = 0.84, P < 0.001 vs. r = 0.52, P < 0.05, slopes of the relations: P < 0.01 adaptive optics vs. SLDF). In addition, the reproducibility of the evaluation of the WLR with adaptive optics is far better, as compared with SLDF, as intraobserver and interobserver variation coefficients are clearly smaller. This may be important in terms of clinical evaluation of microvascular morphology in a clinical setting, as micromyography has substantial limitations in its clinical application due to the local invasiveness of the procedure.

New Methods to Study the Microcirculation.

Essential hypertension is associated with structural alterations in the microvessels; in particular, an increase in the media thickness to internal lumen ratio of small resistance arteries (MLR) and a reduction in capillary density have been observed. The evaluation of the morphological characteristics of small resistance arteries in humans is challenging. The gold-standard method is generally considered to be the measurement by wire or pressure micromyography of MLR of subcutaneous small vessels obtained by local biopsies. However, noninvasive techniques for the evaluation of retinal arterioles were recently proposed; in particular, 2 approaches, scanning laser Doppler flowmetry (SLDF) and adaptive optics (AO), seem to provide useful information. Both of them provide an estimation of the wall to lumen ratio (WLR) of retinal arterioles. Moreover, a noninvasive measurement of basal and total capillary density may be obtained by videomicroscopy/capillaroscopy. It has been recently demonstrated that AO has a substantial advantage over SLDF in terms of evaluation of microvascular morphology, since WLR measured with AO is more closely correlated with the M/L of subcutaneous small arteries. The possibility to noninvasively assess in a reliable way, microvascular morphology in a clinical setting may represent a major advancement, since micromyography has substantial limitations in its application due to the local invasiveness of the procedure.

Relationship between media-to-lumen ratio of subcutaneous small arteries and wall-to-lumen ratio of retinal arterioles evaluated noninvasively by scanning laser Doppler flowmetry.

BACKGROUND: Structural alterations of subcutaneous small resistance arteries, as indicated by an increased media-to-lumen ratio, are frequently present in hypertensive and/or diabetic patients, and may represent the earliest alteration observed. Furthermore, media-to-lumen ratio of small arteries evaluated by micromyography has a strong prognostic significance; however, its extensive evaluation is limited by the invasivity of the assessment, since a biopsy of subcutaneous fat is needed. Noninvasive measurement of wall-to-lumen of retinal arterioles using scanning laser Doppler flowmetry (SLDF) has recently been introduced. However, this new technique has not yet been compared to micromyographic measurement, generally considered the gold standard approach. METHODS AND RESULTS: We investigated 40 individuals and patients, 24 of them were hypertensive patients and 16 normotensive individuals. All patients underwent a biopsy of subcutaneous fat during an elective surgical intervention. Subcutaneous small resistance arteries were dissected and mounted on a wire myograph, and media-to-lumen ratio was measured. In addition, an evaluation of wall-to-lumen ratio of retinal arterioles by SLDF was performed (Heidelberg Retina Flowmeter, Heidelberg Engineering). A close correlation was observed between media-to-lumen ratio of subcutaneous small arteries and wall-to-lumen ratio of retinal arterioles (r = 0.76, P < 0.001; P < 0.001, r(2) = 0.57). CONCLUSION: A noninvasive and easily repeatable procedure (intraobserver and interobserver variation coefficient <13%) such as an evaluation of the arterioles in the fundus oculi by SLDF may provide similar information regarding microvascular morphology compared with an invasive, accurate and prognostically relevant micromyographic measurement of media-to-lumen ratio of subcutaneous small arteries.

State-of-The-Art and Applications of 3D Imaging Sensors in Industry, Cultural Heritage, Medicine, and Criminal Investigation.

3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a "sensor fusion" approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications.

Effects of bonded composites vs. amalgam on resistance to cuspal deflection for endodontically-treated premolar teeth.

PURPOSE: To determine, by means of a non-destructive experimental procedure, the extent to which tooth cusps are weakened by endodontic procedures and the effectiveness of adhesive bonding restoration in reducing cuspal deflection as a function of different restorative procedures. METHODS: A mechanically controlled loading device induced cuspal deflection by axial force (range 98-294 N) on an occlusal surface while LTS laser twin sensors registered the amount of deflection. Cusp deflection values, in microns, were recorded for each tooth. Thirty sound maxillary premolars teeth were sequentially evaluated in the following conditions: A) intact tooth; B) completion of endodontic and restorative procedures. Teeth were randomly divided into five groups and restored respectively with: A) amalgam (Dispersalloy); B) Spectrum TPH; C) Surefil; D) Esthet-X; E) Esthet-X + Dyract Flow. RESULTS: The average loading force needed to induce 1 microm cusp deflection was evaluated, for all groups, in intact teeth (range 49.52-58.76 N/microm) and in restored teeth (range 8.56 - 47.05 N/microm). Statistical analysis (ANOVA for repeated measures) has been performed. Mean structural recovery values after restorative treatment were 17% with amalgam, 60% with Spectrum TPH, 59% with SureFil, 54% with Esthet-X, and 99% with Esthet-X/Dyract.

Autofluorescence methods in ophthalmology.

An overview of the fluorophores of the eye, the methods used to measure ocular fluorescence, and the existing or ready-to-market instrumentation for the early diagnosis and monitoring of ophthalmic pathologies is presented. Emphasis is given to the impact that a more detailed knowledge of the fluorophores of the eye, their age and pathology relationship, and the considerable technology-driven progress in optical devices and components has had on the development of new compact yet powerful instruments for population screening and for patient follow-ups, using fluorometry alone or in combination with other optical techniques such as light scattering.