Choice of Catheter Size for Infants in Continuous Renal Replacement Therapy: Bigger Is Not Always Better.

OBJECTIVES: Renal replacement therapy in infants and small children is the treatment of choice for severe oligoanuric renal dysfunction, with an increasing consensus that early initiation might contribute to preventing acute kidney injury complications. Safer renal replacement therapy devices specifically designed for neonates may contribute to ameliorating outcomes and increasing chances of survival. One of the crucial factors to achieve an effective renal replacement therapy in small infants is adequate vascular access. The interaction of small size central vascular catheters with renal replacement therapy devices has never been investigated. The aim of this study was to characterize both the operating conditions and performance of three different central vascular catheters sizes (4F, 5F, and 7F) connected to two different extracorporeal blood circulation models (adult and pediatric). The rheologic performance of each vascular access size in combination with the adult and pediatric renal replacement therapy models was described. DESIGN: Series of experimental extracorporeal circulation circuit tests were conducted with different setups. A two-roller pump was used to simulate a standard adult dialysis machine, whereas a small three-roller pump served as pediatric renal replacement therapy device. SETTING: A pressure-flow setup aimed to collect pressure and flow values under different test conditions. A second experiment focused on hemolysis estimation induced by the extracorporeal system. Hemolysis exclusively induced by the 4F catheter was also evaluated. Finally, our data were applied to estimate the optimal catheter size theoretically capable of delivering adequate doses basing on anthropometric data (patient weight and cannulation site) in absence of direct ultrasound vessel measurement. SUBJECTS: In vitro tests conducted on simulated extracorporeal circuit models of continuous pediatric and neonatal renal replacement therapy. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: When 4F and 5F catheters are used, maximal blood flows within safe circuit pressures can be set at the values of 13 and 29 mL/min, respectively, when a small pump is used. Differently, when using adult roller pumps, only maximal flows of 10 and 20 mL/min are reached. However, hemolysis is higher when using a three-roller pump compared with the two-roller. The clinical impact of this increased hemolytic burden is likely not relevant. CONCLUSIONS: Small size central vascular catheters display optimal rheologic performances in terms of pressures and flows particularly when the renal replacement therapy device is equipped with pumps proportional to central vascular catheters sizes, and even when relatively high blood flows are set. This is achieved at the risk of a higher hemolysis rate.

Corneal Nerve Migration Rate in a Healthy Control Population.

PURPOSE: The purpose of this study was to establish an age-dependent normative range and factors affecting the migration rate of the corneal subbasal nerve plexus in a healthy control population. METHODS: Corneal nerve migration rate was measured in 60 healthy participants grouped by age: A, aged 20 to 39 years (n = 20); B, 40 to 59 years (n = 20); and C, 60 to 79 years (n = 20). Laser-scanning corneal confocal microscopy was performed on the right eye of all participants at baseline and again after 3 weeks. Fully automated software was used to montage the frames. Distinctive nerve landmarks were manually reidentified between the two montages, and a software program was developed to measure the migration of these landmark points to determine corneal nerve migration rate in micrometers per week (µm/wk). RESULTS: The mean ± SD age of all participants in the study was 47.5 ± 15.5 years; 62% of participants were male. The average corneal nerve migration rates of groups A, B, and C were 42.0 ± 14.0, 42.3 ± 15.5, and 42.0 ± 10.8 µm/wk, respectively (P = .99). There was no difference in corneal nerve migration rate between male (41.1 ± 13.5 µm/wk) and female (43.7 ± 13.2 µm/wk) participants (P = .47). There was no significant correlation between age (P = .97), smoking (P = .46), alcohol use (P = .61), and body mass index (P = .49, respectively) with corneal nerve migration rate. However, exercise frequency correlated significantly (P = .04) with corneal nerve migration rate. CONCLUSIONS: Corneal nerve migration rate varies in healthy individuals and is not affected by age, sex, or body mass index but is related to physical activity.

Dynamic remodeling of arteriolar collaterals after acute occlusion in chick chorioallantoic membrane.

OBJECTIVE: After arteriolar occlusion, collaterals enlarge and initially elevated WSS normalizes. While most previous studies focused on endpoints of such adaptive changes in larger collaterals, the present investigation aimed to continuously determine the relation between WSS and diameter in microvascular collaterals during adaptive reactions. METHODS: In Hamburger-Hamilton stage 40 CAMs, junction points between arteriolar segments were identified and the third upstream segment on one side was occluded. Intravital microscopy recordings were taken for 24 hours post-occlusion. Segment diameter and blood velocity were measured: WSS and capillary density were calculated. RESULTS: After occlusion, vascular diameters exhibited an immediate decrease, then increased with a time constant of 2.5 ± 0.8 hours and reached a plateau of up to 60% above baseline after about 7 hours. Vascular tone showed no significant change. WSS exhibited an immediate increase post-occlusion and linearly returned to baseline after about 12 hours. Local WSS change and diameter change rate showed similar patterns during the initial but not the later phase of post-occlusive adaptation. CONCLUSIONS: CAM collaterals undergo fast structural remodeling within 24 hours post-occlusion. This remodeling might be driven by local WSS and by other regulators within the vascular network.

Impact of temporary hyperthermia on corneal endothelial cell survival during organ culture preservation.

To evaluate temporary exposure to hyperthermia for its impact on endothelial cell density of porcine corneas in organ culture medium containing dextran with regards to possible negative influences of high temperatures during the storage and transport of corneal grafts. Four groups of central discs (diameter 8 mm) from the corneas of both eyes in 40 pigs were first organ-cultured (MEM with 6% dextran 500) for 24 h at 32°C. Ten corneas were then exposed to 40°C in group 1, to 42°C in group 2, to 44°C in group 3, and to 50°C in group 4 for 12 h each. The paired corneal discs for all groups were not treated, stored at 32°C and served as controls. After further organ culture of all corneas for 48 h at 32°C to allow regenerative processes, corneal endothelium was stained with Alizarin Red S and examined by light microscopy. The endothelial cell densities were determined on three central images using a system for the automatic estimation of morphometric parameters of corneal endothelium. Exposure for 12 h to 40°C as well as to 42°C induced no endothelial cell loss. Statistical analysis showed no significant difference of the endothelial cell density between corneas exposed to 40°C and 42°C and the control corneas (40°C treatment: 4736 ± 426 cells/mm(2) and control: 4762 ± 344 cells/mm(2), p = 0.74; 42°C treatment: 4240 ± 363 cells/mm(2) and control: 4176 ± 448 cells/mm(2), p = 0.40). Exposure to 44°C and 50°C lead to total necrosis of the endothelial cell layer. Exposure of organ cultured porcine corneas in dextran containing medium up to 42°C for 12 h does not compromise the endothelial cell density in a clinically relevant manner. Temperatures above 42°C, as it might be the case during transports from the cornea bank to the ophthalmic surgeon, must be strictly avoided as they damage the endothelial cell layer.

Evaluating the efficacy of Quantum Molecular Resonance (QMR) electrotherapy in mixed-type dry eye patients.

PURPOSE: To evaluate the efficacy and safety of the low-power, high-frequency electrical current treatment administered by the Rexon-Eye device, in a cohort of patients affected by mixed-type dry eye disease (DED) of medium to severe level. PATIENTS AND METHODS: In this prospective, non-randomized, interventional clinical study, eighteen mixed type DED patients were treated. Treatment was a specific type of electrotherapy, Quantum Molecular Resonance (QMR®), administered by means of the Rexon-Eye® device (Resono Ophthalmic, Sandrigo, Italy) with a protocol of one 20-min session per week, for 4 weeks. Patients were examined at baseline and one month after the last treatment, utilizing the Ocular Surface Disease Index (OSDI) questionnaire and clinical signs: non-invasive tear break-up time (NIBUT), Oxford staining, meibum quality, meibography, meibomian gland expressibility, tear meniscus height (TMH), Schirmer's test, ocular inflammation expressed by MMP-9 concentration. RESULTS: Subjective benefit in OSDI was reported (p = 0.013). Improvement was also observed in NIBUT (p < 0.001), Oxford staining (p = 0.002), expressible meibomian glands number (p = 0.001) and meibum quality (p < 0.001). A remarkable benefit was present in inflammation, as evidenced by the reduction of MMP-9 (p = 0.003). Changes, although not statistically significant, were also present in TMH (p = 0.076) and Schirmer's test (p = 0.675), whereas no change was observed in meibography score. No adverse event was reported. CONCLUSION: In this mixed-type DED patients' cohort, Rexon-Eye proved to be effective and safe in improving subjective and objective ocular parameters, as well as capable to normalize inflammatory markers.

Corneal and Epidermal Nerve Quantification in Chemotherapy Induced Peripheral Neuropathy.

Chemotherapy-induced neurotoxicity is an increasingly recognized clinical issue in oncology. in vivo confocal microscopy (IVCM) of corneal nerves has been successfully used to diagnose peripheral neuropathies, including diabetic neuropathy. The purpose of this study was to test if the combination of corneal nerve density and morphology assessed by IVCM is useful to monitor the neurotoxic effects of chemotherapy compared to epidermal nerve quantification. Overall, 95 adult patients with different cancer types were recruited from the oncology and hematology departments of the San Raffaele Hospital. Neurological examination, including clinical Total Neuropathy Score, and in vivo corneal confocal microscopy (IVCM), were performed before and after chemotherapy. In a group of 14 patients, skin biopsy was performed at the first and last visit. In the group of 14 patients who underwent both skin biopsy and corneal nerve imaging, clinical worsening (+69%, p = 0.0018) was paralleled by corneal nerve fiber (CNF) density reduction (-22%, p = 0.0457). Clinical Total neuropathy score significantly worsened from the first to the last visit (+62%, p < 0.0001). CNF length was not significantly reduced overall. However, CNF density/tortuosity ratio significantly decreased after therapy. Correlation analysis showed that the CNF density/tortuosity ratio was also correlated with the number of chemotherapy cycles (r = -0.04790, P = 0.0009). Our data confirm that in vivo corneal confocal microscopy is a helpful, non-invasive tool which shows promise for the diagnosis of chemotherapy-induced peripheral neuropathies. IVCM could allow a rapid, reproducible and non-invasive quantification of peripheral nerve pathology in chemotherapy-associated neuropathy.

Multiple-Image Deep Learning Analysis for Neuropathy Detection in Corneal Nerve Images.

PURPOSE: Automated classification of corneal confocal images from healthy subjects and diabetic subjects with neuropathy. METHODS: Over the years, in vivo confocal microscopy has established itself as a rapid and noninvasive method for clinical assessment of the cornea. In particular, images of the subbasal nerve plexus are useful to detect pathological conditions. Currently, clinical information is derived through a manual or semiautomated process that traces corneal nerves and achieves their descriptors (eg, density and tortuosity). This is tedious and subjective. To overcome this limitation, a method based on a convolutional neural network (CNN) for the classification of images from healthy subjects and diabetic subjects with neuropathy is proposed. The CNN simultaneously analyzes 3 nonoverlapping images, from the central region of the cornea. The algorithm automatically extracts features, without the need for neither nerve tracing nor parameter extraction nor montage/mosaicking, and provides an overall classification for each image trio. RESULTS: On a dataset composed by images from 50 healthy subjects and 50 subjects with neuropathy, the algorithm achieves a classification accuracy of 96%. The proposed method improves the results obtained using a traditional method that traces nerves and evaluates their density and tortuosity. CONCLUSIONS: The proposed method provides a completely automated analysis of corneal confocal images. Results demonstrate the potentiality of the CNN in identifying clinically useful features for corneal nerves by analysis of multiple images.

Reduced corneal nerve fibre length in prediabetes and type 2 diabetes: The Maastricht Study.

PURPOSE: In individuals with diabetes, injury to the corneal nerve fibres predisposes to delayed corneal epithelial healing, reduced corneal sensitivity and corneal erosion. We investigated to what extent a reduction in corneal nerve fibre length (CNFL) is present in individuals with prediabetes or type 2 diabetes (DM2) compared with individuals with normal glucose metabolism (NGM). METHODS: Using composite images acquired by corneal confocal microscopy, we assessed total CNFL per mm2 in the subbasal nerve plexus of the cornea in 134 participants (mean age 59 ± 8 years, 49% men, 87 NGM, 20 prediabetes, 27 DM2). Multivariable linear regression was used to assess the association between CNFL and glucose metabolism status, adjusted for age and sex. RESULTS: In individuals with type 2 diabetes, the mean CNFL was significantly reduced [ß = -1.86 mm/mm2 (95% CI -3.64 to -0.08), p = 0.04], as compared with individuals with normal glucose metabolism after adjustment for age and sex. Part of the reduction was present in individuals with prediabetes [ß = -0.96 mm/mm2 (95% CI -2.91 to 0.99), p = 0.34], with a linear trend of corneal nerve fibre reduction with severity of glucose metabolism status (p trend = 0.04). CONCLUSIONS: A significant reduction in CNFL was found in individuals with DM2 compared with individuals with NGM. A trend of reduction in CNFL was observed between individuals with NGM and prediabetes. The reduction in corneal nerve fibre length could contribute to a delayed corneal healing and an increased risk for corneal complications after surgery.

Application of wavelet analysis to the phonocardiographic signal of mechanical heart valve closing sounds.

Heart valve disorders, caused by congenital defects, rheumatic fever, calcification, myocardial infarction and other cardiovascular diseases, often require native valves to be replaced by bio-prosthetic devices or mechanical heart valves (MHVs). Among MHVs, bileaflet valves are usually preferred for their hemodynamic features, similar to physiological ones, and their durability, but they are prone to complications due to thromboembolic events. Due to the asynchronous closure of the leaflets, bileaflet MHVs are also known to produce closing sounds typically characterized by the presence of two peaks in the time domain. The detection of this "double click" in the signal may be useful for the early diagnosis of bileaflet MHV malfunction. The closing sound is actually a non-stationary signal that can be properly explored by means of time-frequency analysis. This paper describes a preliminary approach to the investigation of bileaflet MHV closing sounds performed by Continuous Wavelet Transform (CWT) analysis. Signals were collected from 3 patients immediately after surgery by means of the Myotis 3C, which is a traditional phonocardiographic apparatus. Signals were analyzed by two algorithms: one embedded in the Myotis 3C, based on the Fast Fourier Transform (FFT); and one specifically created for the purposes of the present study, based on CWT. The performance of these algorithms was compared and the results showed that the proposed CWT technique correctly classifies as ''double'' a large number of clicks that are recognized as ''single'' by the Myotis 3C.

High Frequency Electrotherapy for the Treatment of Meibomian Gland Dysfunction.

PURPOSE: To test the safety and efficacy of high frequency electrotherapy (ET) on the clinical signs and symptoms of patients affected by dry eye and meibomian gland dysfunction (MGD). METHODS: Twenty-five patients affected by MGD were enrolled. Quantum Molecular Resonance ET was administered by means of the Rexon-Eye device 4 times, once per week for 4 weeks. Patients were reexamined 1 month after the last treatment. The primary endpoint was reduction in corneal fluorescein staining. Additional endpoints were tear break-up time, Ocular Surface Disease Index score, meibomian gland secretion score, and the number of expressible meibomian glands. Safety endpoints were Logarithm of the Minimum Angle of Resolution (LogMar) best spectacle-corrected visual acuity and intraocular pressure. RESULTS: Corneal fluorescein staining improved by 62.5% (P < 0.0001), tear breakup time increased by 30.9% (P < 0.0001), and the Ocular Surface Disease Index score improved by 37% (P < 0.001). The meibum quality and the number of expressible meibomian glands also increased (35.7% and 12%, P < 0.001 and P < 0.0001, respectively). Schirmer test scores increased after treatment by 16.5% (P = 0.01). No adverse events were observed. CONCLUSIONS: Quantum Molecular Resonance ET appears to be safe and significantly reduces symptoms and signs associated with MGD. It may have a relevant role in the treatment of evaporative dry eye disease.

A novel method for the automatic grading of retinal vessel tortuosity.

Tortuosity is among the first alterations in the retinal vessel network to appear in many retinopathies, such as those due to hypertension. An automatic evaluation of retinal vessel tortuosity would help the early detection of such retinopathies. Quite a few techniques for tortuosity measurement and classification have been proposed, but they do not always match the clinical concept of tortuosity. This justifies the need for a new definition, able to express in mathematical terms the tortuosity as perceived by ophthalmologists. We propose here a new algorithm for the evaluation of tortuosity in vessels recognized in digital fundus images. It is based on partitioning each vessel in segments of constant-sign curvature and then combining together each evaluation of such segments and their number. The algorithm has been compared with other available tortuosity measures on a set of 30 arteries and one of 30 veins from 60 different images. These vessels had been preliminarily ordered by a retina specialist by increasing perceived tortuosity. The proposed algorithm proved to be the best one in matching the clinically perceived vessel tortuosity.

Evaluating the efficacy of Quantum Molecular Resonance (QMR) electrotherapy in mixed-type dry eye patients / Evaluación de la eficacia de la electroterapia de resonancia molecular cuántica (QMR) en pacientes con ojo seco de tipo mixto

Purpose: To evaluate the efficacy and safety of the low-power, high-frequency electrical current treatment administered by the Rexon-Eye device, in a cohort of patients affected by mixed-type dry eye disease (DED) of medium to severe level. Patients and methods: In this prospective, non-randomized, interventional clinical study, eighteen mixed type DED patients were treated. Treatment was a specific type of electrotherapy, Quantum Molecular Resonance (QMR®), administered by means of the Rexon-Eye® device (Resono Ophthalmic, Sandrigo, Italy) with a protocol of one 20-min session per week, for 4 weeks. Patients were examined at baseline and one month after the last treatment, utilizing the Ocular Surface Disease Index (OSDI) questionnaire and clinical signs: non-invasive tear break-up time (NIBUT), Oxford staining, meibum quality, meibography, meibomian gland expressibility, tear meniscus height (TMH), Schirmer's test, ocular inflammation expressed by MMP-9 concentration. Results: Subjective benefit in OSDI was reported (p = 0.013). Improvement was also observed in NIBUT (p < 0.001), Oxford staining (p = 0.002), expressible meibomian glands number (p = 0.001) and meibum quality (p < 0.001). A remarkable benefit was present in inflammation, as evidenced by the reduction of MMP-9 (p = 0.003). Changes, although not statistically significant, were also present in TMH (p = 0.076) and Schirmer's test (p = 0.675), whereas no change was observed in meibography score. No adverse event was reported. Conclusion: In this mixed-type DED patients’ cohort, Rexon-Eye proved to be effective and safe in improving subjective and objective ocular parameters, as well as capable to normalize inflammatory markers.(AU)

Wide-field corneal subbasal nerve plexus mosaics in age-controlled healthy and type 2 diabetes populations.

A dense nerve plexus in the clear outer window of the eye, the cornea, can be imaged in vivo to enable non-invasive monitoring of peripheral nerve degeneration in diabetes. However, a limited field of view of corneal nerves, operator-dependent image quality, and subjective image sampling methods have led to difficulty in establishing robust diagnostic measures relating to the progression of diabetes and its complications. Here, we use machine-based algorithms to provide wide-area mosaics of the cornea's subbasal nerve plexus (SBP) also accounting for depth (axial) fluctuation of the plexus. Degradation of the SBP with age has been mitigated as a confounding factor by providing a dataset comprising healthy and type 2 diabetes subjects of the same age. To maximize reuse, the dataset includes bilateral eye data, associated clinical parameters, and machine-generated SBP nerve density values obtained through automatic segmentation and nerve tracing algorithms. The dataset can be used to examine nerve degradation patterns to develop tools to non-invasively monitor diabetes progression while avoiding narrow-field imaging and image selection biases.

Evaluation of repeatability for the automatic estimation of endothelial cell density in donor corneas.

BACKGROUND/AIMS: The repeatability of an automatic system for estimation of endothelial cell density (ECD) from microscopy images in donor corneas was assessed. METHODS: A computer program for the automatic ECD estimation from frequency analysis was previously presented. An evaluation of its repeatability was performed on a data set containing 200 corneas by assessing the accuracy and precision of automatic versus manual values. For each cornea, 2-21 images (1536 total) at 100x for automatic ECD and one image at 200x for manual ECD were available. RESULTS: Accuracy of automatic ECDs was -45 (SD 99) cells/mm(2) (-2% (4%)). Precision of repeated automatic ECDs on the same cornea was 62 (30) cells/mm(2) (3% (1%)). The algorithm was also capable of identifying all non-processable images. CONCLUSION: The proposed automatic technique proved to be reliable for its routine use in a typical eye bank setting like the one considered here.

Transcutaneous periorbital electrical stimulation in the treatment of dry eye.

PURPOSE: To evaluate efficacy and safety of transcutaneous application of electrical current on symptoms and clinical signs of dry eye (DE). METHODS: 27 patients with DE underwent transcutaneous electrostimulation with electrodes placed onto the periorbital region of both eyes and manual stimulation with a hand-piece conductor moved by the operator. Each patient underwent 12 sessions of 22 min spread over 2 months, two sessions per week in the first month and one session per week in the second month. Ocular Surface Disease Index (OSDI) questionnaire, tear break-up time (TBUT), fluorescein staining of the cornea, Schirmer I test and adverse events were evaluated at baseline, at end of treatment and at 6 and 12 months. RESULTS: OSDI improved from 43.0±19.2 at baseline to 25.3±22.1 at end of treatment (mean±SD, p=0.001). These effects were substantially maintained at 6-month and 12-month follow-up evaluations. Improvement of the values of TBUT was recorded for the right eye at the end of treatment (p=0.003) and found in the left eye after 12 months (p=0.02). The Oxford scores changed in both eyes at the end of treatment and at the 6-month evaluation (p<0.001), and in the right eye at the 12-month evaluation (p=0.035). Schirmer I improved significantly at the end of treatment in the left eye (p=0.001) and in both eyes at the 12-month evaluation (p=0.004 and p=0.039 for the left and right eye, respectively). A significant reduction of the use of tear substitutes was found at the end of treatment (p=0.003), and was maintained during the follow-up (p<0.001).No complications occurred and patients found the treatment satisfying. CONCLUSIONS: Transcutaneous electrical stimulation was shown to improve DE, both subjectively and objectively, without any adverse effects and has the potential to enlarge the armamentarium for treating DE.

Reduced Corneal Nerve Fiber Density in Type 2 Diabetes by Wide-Area Mosaic Analysis.

Purpose: To determine if corneal subbasal nerve plexus (SBP) parameters derived from wide-area depth-corrected mosaic images are associated with type 2 diabetes. Methods: One hundred sixty-three mosaics were produced from eyes of 82 subjects by laser-scanning in vivo confocal microscopy (IVCM). Subjects were of the same age, without (43 subjects) or with type 2 diabetes (39 subjects). Mosaic corneal nerve fiber length density (mCNFL) and apical whorl corneal nerve fiber length density (wCNFL) were quantified and related to the presence and duration of diabetes (short duration < 10 years and long duration ≥ 10 years). Results: In mosaics with a mean size of 6 mm2 in subjects aged 69.1 ± 1.2 years, mCNFL in type 2 diabetes was reduced relative to nondiabetic subjects (13.1 ± 4.2 vs. 15.0 ± 3.2 mm/mm2, P = 0.018). Also reduced relative to nondiabetic subjects was mCNFL in both short-duration (14.0 ± 4.0 mm/mm2, 3.2 ± 3.9 years since diagnosis) and long-duration diabetes (12.7 ± 4.2 mm/mm2, 15.4 ± 4.2 years since diagnosis; ANOVA P = 0.023). Lower mCNFL was associated with presence of diabetes (P = 0.032) and increased hemoglobin A1c (HbA1c) levels (P = 0.047). By contrast, wCNFL was unaffected by diabetes or HbA1c (P > 0.05). Global SBP patterns revealed marked degeneration of secondary nerve fiber branches outside the whorl region in long-duration diabetes. Conclusions: Wide-area mosaic images provide reference values for mCNFL and wCNFL and reveal a progressive degeneration of the SBP with increasing duration of type 2 diabetes.

Development of a Reliable Automated Algorithm for the Morphometric Analysis of Human Corneal Endothelium.

PURPOSE: Corneal images acquired by in vivo microscopy provide important clinical information on the health state of the corneal endothelium. However, the reliable estimation of the clinical morphometric parameters requires the accurate detection of cell contours in a large number of cells. Thus, for the practical application of this analysis in clinical settings, an automated method is needed. METHODS: We propose the automatic segmentation of corneal endothelial cells contour through an innovative technique based on a genetic algorithm, which combines information about the typical regularity of endothelial cells shape with the pixels intensity of the actual image. The developed procedure is applied to 30 images acquired with the SP-3000P Topcon specular microscope. Automatic assessment of the clinical parameters is then performed by estimating endothelial cell density (ECD, number of cells per unit area), pleomorphism (fraction of hexagonal cells), and polymegethism (fractional standard deviation of cell areas). Ground truth values for these clinical parameters were obtained from cell contours manually drawn by 2 experts. RESULTS: The mean percent absolute difference between the manual and the automated estimation was 0.6% for ECD, 3.1% for pleomorphism, and 5.3% for polymegethism. Comparable differences were obtained between the estimations provided by the 2 experts (0.5% for ECD, 2.6% for pleomorphism, and 2.9% for polymegethism). No statistically significant difference (P-value > 0.2) was found between automatic and manual assessments of each clinical parameter (power ≥ 77%). CONCLUSIONS: The proposed totally automatic method seems capable of obtaining a reliable estimation of the relevant morphometric parameters used in clinical practice.

Automatic estimation of corneal nerves focused tortuosities.

The correlation between corneal nerve tortuosity and pathology has been shown multiple times. However, because there isn't any defacto definition of tortuosity, reproducibility is poor. Indeed, many studies still rely on the manual observation and judgment of tortuosity. Recently, two distinct forms of corneal nerve tortuosity have been identified, describing either short-range or long-range directional changes. In this study we were able to develop automatic corneal nerve tortuosity measurements that correctly and independently represent these two tortuosity definitions. Furthermore, we show that a combination of mathematical tortuosity measurements improves on single metric results.

A Fast and Efficient Technique for the Automatic Tracing of Corneal Nerves in Confocal Microscopy.

PURPOSE: We describe a novel fully automatic method capable of tracing the subbasal plexus nerves from human corneal confocal images. METHODS: Following an increasing interest in the automatic analysis of corneal nerves, a few approaches have been proposed. These, however, cannot cope with large images, such as mosaics, in due time. The rationale of the proposed method is to minimize required computing time while still providing accurate results. Our method consists of two sequential steps - a thresholding step followed by a supervised classification. For the classification we use a support vector machines (SVM) approach. Initially, a large set of features is computed, which is later reduced using a backward-elimination based on segmentation accuracy. To validate the obtained tracings, we evaluated the tracing accuracy and reliability of extracted clinical parameters (corneal nerves density and tortuosity). RESULTS: The proposed algorithm proved capable to correctly trace 0.89 ± 0.07 of the corneal nerves. The obtained performance level was comparable to a second human grader. Furthermore, the proposed approach compares favorably to other methods. For both evaluated clinical parameters the proposed approach performed well. An execution time of 0.61 ± 0.07 seconds per image was achieved. The proposed algorithm was applied successfully to mosaic images, with run times of the order of tens of seconds. CONCLUSIONS: The achieved quality and processing time of the proposed method appear adequate for the application of this technique to clinical practice. TRANSLATIONAL RELEVANCE: The automatic tracing of corneal nerves is an important step for the quantitative analysis of corneal nerves in daily clinical practice. The proposed fast technique allows features, such as corneal nerve density and tortuosity, to be computed in a few seconds. The application of nerve tracing to mosaics covering a large area can be a key component in clinical studies aimed at investigating neuropathy influence in various ocular or systemic diseases.

Early detection of diabetic neuropathy by investigating CNFL and IENFD in thy1-YFP mice.

Small fiber neuropathy is one of the most common and painful long-term complications of diabetes mellitus. Examination of the sub-basal corneal nerve plexus is a promising surrogate marker of diabetic neuropathy. To investigate the efficacy, reliability and reproducibility of in vivo corneal confocal microscopy (IVCCM), we used thy1-YFP mice, which express yellow fluorescence protein (YFP) in nerve fibers. 4 weeks after multiple low-dose injections of streptozotocin, thy1-YFP mice showed manifest diabetes. Subsequent application of insulin-releasing pellets for 8 weeks resulted in a significant reduction of blood glucose concentration and HbA1c, a significant increase in body weight and no further increase in advanced glycation end products (AGEs). IVCCM, carried out regularly over 12 weeks and analyzed both manually and automatically, revealed a significant loss of corneal nerve fiber length (CNFL) during diabetes manifestation and significant recovery after insulin therapy. Ex vivo analyses of CNFL by YFP-based microscopy confirmed the IVCCM results (with high sensitivity between manual and automated approaches) but demonstrated that the changes were restricted to the central cornea. Peripheral areas, not accessible by IVCCM in mice, remained virtually unaffected. Because parallel assessment of intraepidermal nerve fiber density revealed no changes, we conclude that IVCCM robustly captures early signs of diabetic neuropathy.