Subbasal Plexus Research Articles

The Severity of Diabetic Retinopathy Corresponds with Corneal Nerve Alterations and Ocular Discomfort of the Patient.

Diabetic retinopathy (DR) remains the leading cause of blindness in the working-age population. Its progression causes gradual damage to corneal nerves, resulting in decreased corneal sensitivity (CS) and disruption of anterior-eye-surface homeostasis, which is clinically manifested by increased ocular discomfort and dry eye disease (DED). This study included 52 DR patients and 52 sex- and age-matched controls. Ocular Surface Disease Index (OSDI) survey, tear film-related parameters, CS, and in vivo corneal confocal microscopy (IVCM) of the subbasal plexus were performed. Furthermore, all patients underwent tear sampling for neurotrophin and cytokine analysis. OSDI scores were greater in DR patients than in controls (p = 0.00020). No differences in the Schirmer test score, noninvasive tear film-break-up time (NIBUT), tear meniscus or interferometry values, bulbar redness, severity of blepharitis or meibomian gland loss were found. In the DR group, both the CS (p < 0.001), and the scotopic pupil diameter (p = 0.00008) decreased. IVCM revealed reduced corneal nerve parameters in DR patients. The stage of DR was positively correlated with the OSDI (Rs = +0.51, 95% CI: + 0.35-+0.64, p < 0.001) and negatively correlated with IVCM corneal nerve parameters and scotopic pupillometry (Rs = -0.26, 95% CI: -0.44--0.06, p = 0.0097). We found negative correlations between the OSDI and IVCM corneal innervation parameters. The DR group showed lower tear film-brain-derived neurotrophic factor (BDNF) levels (p = 0.0001) and no differences in nerve growth factor (NGF)-β, neurotrophin (NT)-4, vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-4, IL-5, IL-6, or IL-12 concentrations. Tumor necrosis factor (TNF)-α, IL-2, IL-8, IL-10, granulocyte macrophage colony-stimulating factor (GM-CSF), and interferon (IFN)-γ levels were decreased among patients with DR. Corneal innervation defects have a direct impact on patients' subjective feelings. The evolution of DR appears to be associated with corneal nerve alterations, emphasizing the importance of IVCM.

A pilot study on Langerhans cells in keratoconus patients by in vivo confocal microscopy before and after corneal cross-linking and correlation with eye rubbing

PurposeThe aim of this study was to investigate the corneal microstructure and Langerhans cells using in vivo confocal microscopy in keratoconus patients before and after cross-linking, and to correlate the morphologic findings with clinical and patient-reported outcomes, including eye rubbing (ER) behavior. MethodsPatients with progressive keratoconus undergoing iontophoresis-assisted epithelium-on cross-linking (I-CXL) were consecutively enrolled. In vivo confocal microscopy was performed before and 6 months after treatment. Patients were asked to quantify their ER behavior on a Visual Analogue Scale (VAS) and completed the Keratoconus Outcomes Research Questionnaire and the Ocular Surface Disease Index questionnaires at the same time points. Visual acuity, tear osmolarity, topography, aberrometry, and pachymetry of both eyes were assessed. ResultsThirteen patients were included in this pilot study. Preoperatively, the mean Langerhans cells density was 35,615 cells per mm2, and the median morphology was 3. The mean ER VAS before treatment was 7,077 out of 10. The ER VAS showed significant positive correlations with both Langerhans cells density and morphology of the study eye. After treatment, a statistically significant reduction in ER VAS and in Langerhans cells variables was observed. The mean sub-basal plexus nerve density was comparable to pre-operative values 6 months after I-CXL. ConclusionsBased on this preliminary evidence, the presence of high density of mature Langerhans cells in the central cornea of keratoconus patients and its correlation with eye rubbing support the role of inflammation in keratoconus. The reduction in these markers after treatment may suggest a potential of CXL in moderating immune-related inflammation and eye rubbing in the medium term.

Topical Insulin for Ocular Surface Disease.

Background: Insulin and insulin-like growth factor (IGF)-1 receptors are present in ocular tissues such as corneal epithelium, keratocytes, and conjunctival cells. Insulin plays a crucial role in the growth, differentiation, and proliferation of corneal epithelial cells, as well as in wound healing processes in various tissues. Purpose: This review explores the potential role of topical insulin in the treatment of ocular surface diseases. Specifically, it examines its impact on corneal nerve regeneration, sub-basal plexus corneal nerves, and its application in conditions like corneal epithelial defects, dry eye disease, and diabetic keratopathy. Methods: The review analyzes studies conducted over the past decade that have investigated the use of topical insulin in ocular surface diseases. It focuses on indications, drug preparation methods, side effects, efficacy outcomes, and variations in insulin concentrations and dosages used. Results: While off-label use of topical insulin has shown promising results in refractory corneal epithelial defects, its efficacy in dry eye disease is yet to be demonstrated. Variations in concentrations, dilutions, and dosing guidelines have been reported. However, limited data on ocular penetration, ocular toxicity, and systemic side effects pose challenges to its widespread utility. Conclusion: This review synthesizes findings from ocular investigations on topical insulin to assess its potential applicability in treating ocular surface and corneal diseases. By highlighting indications, preparation methods, side effects, and efficacy outcomes, it aims to provide insights into the current status and future prospects of using topical insulin in ophthalmic practice.

Effects of Diabetes Mellitus on Corneal Immune Cell Activation and the Development of Keratopathy.

Diabetes mellitus (DM) is one of the most prevalent diseases globally, and its prevalence is rapidly increasing. Most patients with a long-term history of DM present with some degree of keratopathy (DK). Despite its high incidence, the underlying inflammatory mechanism of DK has not been elucidated yet. For further insights into the underlying immunopathologic processes, we utilized streptozotocin-induced mice to model type 1 DM (T1D) and B6.Cg-Lepob/J mice to model type 2 DM (T2D). We evaluated the animals for the development of clinical manifestations of DK. Four weeks post-induction, the total frequencies of corneal CD45+CD11b+Ly-6G- myeloid cells, with enhanced gene and protein expression levels for the proinflammatory cytokines TNF-α and IL-1β, were higher in both T1D and T2D animals. Additionally, the frequencies of myeloid cells/mm2 in the sub-basal neural plexus (SBNP) were significantly higher in T1D and T2D compared to non-diabetic mice. DK clinical manifestations were observed four weeks post-induction, including significantly lower tear production, corneal sensitivity, and epitheliopathy. Nerve density in the SBNP and intraepithelial terminal endings per 40x field were lower in both models compared to the normal controls. The findings of this study indicate that DM alters the immune quiescent state of the cornea during disease onset, which may be associated with the progressive development of the clinical manifestations of DK.

Three Strategies to Induce Neurotrophic Keratitis and Nerve Regeneration in Murine Cornea.

The cornea is a transparent tissue that covers the eye and is crucial for clear vision. It is the most innervated tissue in the body. This innervation provides sensation and trophic function to the eye and contributes to preserving corneal integrity. The pathological disruption of this innervation is termed neurotrophic keratitis. This can be triggered by injury to the eye, surgery, or disease. In this study, we propose three different protocols for inflicting damage on the innervation in ways that recapitulate the three types of cases generally encountered in the clinic. The first method consists in making an abrasion of the epithelium with an ophthalmic burr. This involves the removal of the epithelial layer, the free nerve endings, and the subbasal plexus in a manner similar to the photorefractive keratectomy surgery performed in the clinic. The second methodonly targets the innervation by sectioning it at the periphery with a biopsy punch, maintaining the integrity of the epithelium. This method is similar to the first steps of lamellar keratoplasty and leads to a degeneration of the innervation followed by regrowth of the axons in the central cornea. The last method damages the innervation of a transgenic mouse model using a multiphoton microscope, which specifically localizes the site of cauterization of the fluorescent nerve fibers. This method inflicts the same damage as photokeratitis, an overexposure to UV light. This study describes different options for investigating the physiopathology of corneal innervation, particularly the degeneration and regeneration of the axons. Promoting regeneration is crucial for avoiding such complications as epithelium defects or even perforation of the cornea. The proposed models can help test new pharmacological molecules or gene therapy that enhance nerve regeneration and limit disease progression.

Analysis of the ocular surface functional unit in episodic migraine

AimMigraine is a chronic neurovascular disease that affects the trigeminovascular system. The purpose of this study was to evaluate corneal subbasal nerve fibers, dendritic cells and to measure tear film parameters in migraine.Patients and methods87 eyes of 44 patients suffering from migraine with a mean age of 33.23 ± 11.41 years were included in our study. 25 age-matched controls (mean age of 30.16 ± 12.59 years; P = 0.162) were recruited. The corneal subbasal plexus and the dendritic cells (DC) were analyzed using in vivo confocal microscopy (Heidelberg Retina Tomograph II Rostock Cornea Module; Heidelberg Engineering GmbH), and the tear film was imaged using LacryDiag (Quantel Medical, France).ResultsRegarding the subbasal nerve fibers of the cornea, none of the examined parameters differed significantly in migraine patients from controls. We found a significant increase in the corneal DC density (P < 0.0001) and DC area (P < 0.0001) in migraine patients compared to healthy volunteers. DC density showed a positive correlation with the monthly attack frequency (r = 0.32, P = 0.041) and the DC area a negative correlation with corneal nerve branch density (r = -0.233, P = 0.039), nerve fiber length (r = -0.232, P = 0.04) and total branch density (r = -0.233, P = 0.039). Using LacryDiag a significant loss of Meibomian gland area could be detected on the superior eyelid (P = 0.005) in migraine.ConclusionsOur results suggest the presence of neuroinflammation in the cornea of migraine patients affecting the peripheral trigeminal system. Dendritic cells surrounding the subbasal plexus may be involved in the activation and modulation of pain in migraine.

CLINICAL AND IN VIVO CONFOCAL MICROSCOPY FINDINGS IN MGUS - A CASE REPORT

Purpose The purpose of this study was to describe a case of paraproteinemic keratopathy (PPK) in a patient with monoclonal gammopathy of undetermined significance (MGUS) Methods A 56 years old man was assessed using a slit lamp and in vivo confocal microscopy (IVCM) with Heidelberg HRT Rostock II. Results The patient showed bilateral diffuse, symmetric, non-polychromatic, punctiform crystals in all layers of the cornea. The remaining part of the ophthalmic clinical assessment was normal. Esthesiometry was normal in all quadrants. Anterior segment OCT confirmed diffused hyperreflectivity of the epithelium and corneal stroma. IVCM was then executed, showing polymorphic (granular, needle-like, stellate) hyperreflective crystals in all layers of corneal epithelium and anterior stroma, subbasal plexus nerves beading, cytoplasmatic hyperreflectivity of the keratocytes of the posterior stroma without any endothelial involvement After considering the age, health status, and ocular signs the primary entities to be investigated were adult benign cystinosis and paraproteinemic disorder. All the diagnostic tests were negative except for a monoclonal component IgG/k of 1.37 d/dl. A hematological examination was then performed with the resulting diagnosis of MGUS. In this paper, we analyzed 11 articles about IVCM in PPK in MGUS and other paraproteinemias highlighting IVCM features compatible with our findings allowing us to generalize a first diagnostic IVCM pattern for PPK. Conclusions In this case report we suggest the IVCM diagnostic patterns that may be used to identify PPK without corneal biopsy.

Insights into mustard gas keratopathy- characterizing corneal layer-specific changes in mice exposed to nitrogen mustard

Exposure to mustard agents, such as sulfur mustard (SM) and nitrogen mustard (NM), often results in ocular surface damage. This can lead to the emergence of various corneal disorders that are collectively referred to as mustard gas keratopathy (MGK). In this study, we aimed to develop a mouse model of MGK by using ocular NM exposure, and describe the subsequent structural changes analyzed across the different layers of the cornea. A 3 μL solution of 0.25 mg/mL or 5 mg/mL NM was applied to the center of the cornea via a 2-mm filter paper for 5 min. Mice were evaluated prior to and after exposure on days 1, 3, 7, 14, and 28 for 4 weeks using slit lamp examination with fluorescein staining. Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) tracked changes in the epithelium, stroma, and endothelium of the cornea. Histologic evaluation was used to examine corneal cross-sections collected at the completion of follow-up. Following exposure, mice experienced central corneal epithelial erosion and thinning, accompanied by a decreased number of nerve branches in the subbasal plexus and increased activated keratocytes in the stroma in both dosages. The epithelium was recovered by day 3 in the low dose group, followed by exacerbated punctuate erosions alongside persistent corneal edema that arose and continued onward to four weeks post-exposure. The high dose group showed persistent epitheliopathy throughout the study. The endothelial cell density was reduced, more prominent in the high dose group, early after NM exposure, which persisted until the end of follow-up, along with increased polymegethism and pleomorphism. Microstructural changes in the central cornea at 4 weeks post-exposure included dysmorphic basal epithelial cells and reduced epithelial thickness, and in the limbal cornea included decreased cellular layers. We present a mouse model of MGK using NM that successfully replicates ocular injury caused by SM in humans who have been exposed to mustard gas.

Collagen mimetic peptide repair of the corneal nerve bed in a mouse model of dry eye disease.

The intraepithelial sub-basal nerve plexus of the cornea is characterized by a central swirl of nerve processes that terminate between the apical cells of the epithelium. This plexus is a critical component of maintaining homeostatic function of the ocular surface. The cornea contains a high concentration of collagen, which is susceptible to damage in conditions such as neuropathic pain, neurotrophic keratitis, and dry eye disease. Here we tested whether topical application of a collagen mimetic peptide (CMP) is efficacious in repairing the corneal sub-basal nerve plexus in a mouse model of ocular surface desiccation. We induced corneal tear film reduction, epithelial damage, and nerve bed degradation through a combination of environmental and pharmaceutical (atropine) desiccation. Mice were subjected to desiccating air flow and bilateral topical application of 1% atropine solution (4× daily) for 2 weeks. During the latter half of this exposure, mice received topical vehicle [phosphate buffered saline (PBS)] or CMP [200 μm (Pro-Pro-Gly)7, 10 μl] once daily, 2 h prior to the first atropine treatment for that day. After euthanasia, cornea were labeled with antibodies against βIII tubulin to visualize and quantify changes to the nerve bed. For mice receiving vehicle only, the two-week desiccation regimen reduced neuronal coverage of the central sub-basal plexus and epithelial terminals compared to naïve, with some corneas demonstrating complete degeneration of nerve beds. Accordingly, both sub-basal and epithelial βIII tubulin-labeled processes demonstrated increased fragmentation, indicative of nerve disassembly. Treatment with CMP significantly reduced nerve fragmentation, expanded both sub-basal and epithelial neuronal coverage compared to vehicle controls, and improved corneal epithelium integrity, tear film production, and corneal sensitivity. Together, these results indicate that topical CMP significantly counters neurodegeneration characteristic of corneal surface desiccation. Repairing underlying collagen in conditions that damage the ocular surface could represent a novel therapeutic avenue in treating a broad spectrum of diseases or injury.

WITHDRAWN: Insights into mustard gas keratopathy: Characterizing corneal layer-specific changes in mice exposed to nitrogen mustard

Exposure to mustard agents, such as sulfur mustard (SM) and nitrogen mustard (NM), often results in ocular surface damage. This can lead to the emergence of various corneal disorders that are collectively referred to as mustard gas keratopathy (MGK). In this study, we aimed to develop a mouse model of MGK by using ocular NM exposure, and describe the subsequent structural changes analyzed across the different layers of the cornea. A 3 μL solution of 0.25 mg/mL NM was applied to the center of the cornea via a 2-mm filter paper for 5 min. Mice were evaluated prior to and after exposure on days 1 and 3, and weekly for 4 weeks using slit lamp examination with fluorescein staining. Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) tracked changes in the epithelium, stroma, and endothelium of the cornea. Histologic evaluation and immunostaining were used to examine corneal cross-sections collected at the completion of follow-up. A biphasic ocular injury was observed in mice exposed to NM, most prominent in the corneal epithelium and anterior stroma. Following exposure, mice experienced central corneal epithelial erosions and thinning, accompanied by a decreased number of nerve branches in the subbasal plexus and increased activated keratocytes in the stroma. The epithelium was recovered by day 3, followed by exacerbated punctuate erosions alongside persistent stromal edema that arose and continued onward to four weeks post-exposure. The endothelial cell density was reduced on the first day after NM exposure, which persisted until the end of follow-up, along with increased polymegethism and pleomorphism. Microstructural changes in the central cornea at this time included dysmorphic basal epithelial cells, and in the limbal cornea included decreased cellular layers and p63+ area, along with increased DNA oxidization. We present a mouse model of MGK using NM that successfully replicates ocular injury caused by SM in humans who have been exposed to mustard gas. Our research suggests DNA oxidation contributes to the long-term effects of nitrogen mustard on limbal stem cells.

Methods for evaluation of corneal nerve fibres in diabetes mellitus by in vivo confocal microscopy: a scoping review protocol

IntroductionGlobally, 422 million people have diabetes. Late complications of diabetes are blindness, kidney failure, heart attack, stroke and lower limb amputation. The prevalence of diabetic peripheral neuropathy and diabetic retinopathy...

Clinically Based Automated Tracing and Tortuosity Estimation of Corneal Nerve Fibers From Confocal Microscopy Images

The purpose of this study was the development of an algorithm able to automatically trace corneal nerves and to estimate a nerve tortuosity index that is useful in clinical practice. In vivo confocal microscopy is an imaging technique that allows the clinical assessment of corneal and systemic diseases. Many studies have demonstrated a correlation between the tortuosity level of nerve fibers in the subbasal plexus layer and some pathologies. We developed an algorithm that provides fully automatic tracing of nerve fibers. It also includes a new way of dealing with bifurcations, separating the main paths from the secondary ones. Based on this automated tracing, the tortuosity was estimated as the absolute curvature, tortuosity density, and fractal dimension. These metrics were considered first individually and then as a linear combination of 2 or 3 of them. We investigated the capability of the estimated tortuosity to emulate the clinical classification into low, mid, and high tortuosity levels. Furthermore, we investigated its ability to distinguish healthy subjects from pathological subjects. Excellent agreement between manual and automated grouping of tortuosity (96.6% accuracy) was obtained. Moreover, the proposed algorithm could differentiate between healthy and pathological subjects with an accuracy of 77.1% by analyzing each image individually. The accuracy improved to 86.31% by considering 3 images of the same subject simultaneously. The proposed framework provides completely automated analysis of corneal nerve images. The results demonstrate the ability of our method to emulate the clinical classification of tortuosity levels and its potential for identifying healthy and pathological subjects.

Corneal confocal microscopy in patients with distal symmetric polyneuropathy compared to controls.

Diabetic neuropathy (DN) is a very common clinical condition throughout the world. The diagnostic tests currently recommended have low sensitivity, such as electromyography, or are invasive, such as skin biopsy. New techniques have been developed to identify the early involvement of the peripheral nerve. With the advent of corneal confocal microscopy (CCM), a reduction in corneal innervation in patients with DN has been observed. To compare, through CCM, diabetic patients with symptomatic distal symmetric polyneuropathy (DSP) and controls. In the present study, through CCM, we compared the morphological changes in the sub-basal epithelial corneal plexus of 35 diabetic patients with symptomatic DSP with 55 controls. Moreover, we sought to determine a pattern of change regarding the severity stages of DSP, comparing the clinical, laboratory, and nerve-conduction (NC) variables. Differences between the control and diabetic groups were observed for the following variables, respectively: age (44.9 ± 13.24 years versus 57.02 ± 10.4 years; p < 0.001); fiber density (29.7 ± 10.2 versus 16.6 ± 10.2; p < 0.001); number of fibers (4.76 ± 1.30 versus 3.14 ± 1.63; p < 0.001); number of Langerhans cells (4.64 ± 8.05 versus 7.49 ± 10.3; p = 0.035); tortuosity (p < 0.05); and thickness (p < 0.05). Furthermore, inverse relationships were found regarding fiber density and age (p < 0.01) and fiber density and the severity of the disease (p < 0.05). A positive relationship between the conduction velocity of the fibular nerve and fiber density (p < 0.05) was also observed. Corneal confocal microscopy proved to be a fast, noninvasive and reproducible method for the diagnosis, staging, and monitoring of diabetic DSP.

Small fiber neuropathy in the cornea of Covid-19 patients associated with the generation of ocular surface disease

PurposeTo describe the association between Sars-CoV-2 infection and small fiber neuropathy in the cornea identified by in vivo corneal confocal microscopy. MethodsTwenty-three patients who had overcome COVID-19 were recruited to this observational retrospective study. Forty-six uninfected volunteers were also recruited and studied as a control group. All subjects were examined under in vivo confocal microscopy to obtain images of corneal subbasal nerve fibers in order to study the presence of neuroma-like structures, axonal beadings and dendritic cells. The Ocular Surface Disease Index (OSDI) questionnaire and Schirmer tear test were used as indicators of Dry Eye Disease (DED) and ocular surface pathology. ResultsTwenty-one patients (91.31%) presented alterations of the corneal subbasal plexus and corneal tissue consistent with small fiber neuropathy. Images from healthy subjects did not indicate significant nerve fiber or corneal tissue damage. Eight patients reported increased sensations of ocular dryness after COVID-19 infection and had positive DED indicators. Beaded axons were found in 82.60% of cases, mainly in patients reporting ocular irritation symptoms. Neuroma-like images were found in 65.22% patients, more frequently in those with OSDI scores >13. Dendritic cells were found in 69.56% of patients and were more frequent in younger asymptomatic patients. The presence of morphological alterations in patients up to 10 months after recovering from Sars-CoV-2 infection points to the chronic nature of the neuropathy. ConclusionsSars-CoV-2 infection may be inducing small fiber neuropathy in the ocular surface, sharing symptomatology and morphological landmarks with DED and diabetic neuropathy.

Corneal Subbasal Plexus in Eyes with Fuchs' Endothelial Corneal Dystrophy after Two Different Endothelial Surgeries.

Purpose To evaluate the morphological features and density of corneal subbasal plexus (SBP) using in vivo corneal confocal microscopy (IVCCM) in patients affected by Fuchs' endothelial corneal dystrophy (FECD) six months after Descemet membrane endothelial keratoplasty (DMEK) and Descemet-stripping automated endothelial keratoplasty (DSAEK). Methods We included patients affected by FECD, requiring corneal endothelial surgery due to corneal oedema occurred from 3 to 6 months. 7 eyes underwent DMEK and 7 eyes DSAEK. All patients performed IVCCM preoperative and in six months postoperative. We analyzed SBP parameters, using CS4 Nerves Tracking Tool, and we studied the differences between the two endothelial keratoplasties. Results Comparing the eyes treated with DMEK with those treated with DSAEK, preoperative corneal thickness, corrected distance visual acuity (CDVA), and age were similar in both groups. SBP was not detectable at preoperative IVCCM in any eye. Postoperatively, the nerve fibers length, the nerve fibers density, the tortuosity, and the number of fibers and of branching did not differ in the eyes that underwent DMEK compared to DSAEK. The corneal beadings density was higher after DMEK than DSAEK, and this difference was statistically significant (P = 0.004). The type of endothelial keratoplasty was not associated with the presence or absence of postoperative corneal SBP (Pearson' chi-square, 0.755). Conclusions Postoperative corneal reinnervation should be easily and noninvasively studied using IVCCM. Morphological postoperative features of SBP did not differ between two different types of endothelial keratoplasty, DMEK and DSAEK, despite the different sizes of the corneal incision. The lower beading density in the DSAEK group should be the consequence of a different distribution of mitochondria along the nerve fibers, as expression of a supposed higher metabolic distress in the DSAEK group.

The pattern of the inferocentral whorl region of the corneal subbasal nerve plexus is altered with age

PurposeTo describe the pattern of the nerves in the inferocentral whorl region of the human corneal subbasal nerve plexus (SBNP) in health and diseases known to affect the subbasal nerves. MethodsLaser-scanning in vivo confocal microscopy (IVCM) was used to image the SBNP bilaterally in 91 healthy subjects, 39 subjects with type 2 diabetes mellitus (T2DM), and 43 subjects with Parkinson's disease (PD). Whorl regions were classified according to nerve orientation relative to age and health/disease status. ResultsOf 346 examined eyes, 300 (86.7%) had an identifiable whorl pattern. In healthy subjects, a clockwise nerve orientation of the whorl was most common (67.9%), followed by non-rotatory or ‘seam’ morphology (21.4%), and counterclockwise (10.7%). The clockwise orientation was more prevalent in healthy subjects than in T2DM or PD (P < 0.001). Healthy individuals below 50 years of age had a predominantly clockwise orientation (93.8%) which was reduced to 51.9% in those over 50 years (P < 0.001). Age but not disease status explained whorl orientation in T2DM and PD groups. Moreover, whorl orientation is bilaterally clockwise in the young, but adopts other orientations and becomes asymmetric across eyes with age. Finally, we report reflective ‘dot-like’ features confined to the whorl region of the subbasal plexus, sometimes appearing in close association with subbasal nerves and present in 84–93% of examined eyes regardless of disease status, eye or sex. ConclusionSubbasal nerves in the inferocentral whorl region are predominantly clockwise in young, healthy corneas. With aging and conditions of T2DM and PD, counterclockwise and non-rotatory configurations increase in prevalence, and bilateral symmetry is lost. Mechanisms regulating these changes warrant further investigation.

Corneal Neurotization in the Setting of Facial Paralysis: A Comprehensive Review of Surgical Techniques.

Neurotrophic keratopathy is characterized by decreased corneal sensitivity, decreased reflex tearing, and poor corneal healing resulting in corneal injury. Without proper sensory innervation, the cornea undergoes continuous epithelial injury, ulceration, infection and eventually results in vision loss. In situations where patients have concomitant facial paralysis, such as after resection of a large vestibular schwannoma, the ocular health is further impaired by paralytic lagophthalmos with decreased eye closure and blink reflex, decreased tearing, and potential lower eyelid malposition. In patients with a dual nerve injury, the ocular surface is in significant danger, as there is increased environmental exposure in conjunction with the inability to sense damage when it occurs. Immediate recognition and care of the eye are critical for maintaining ocular health and preventing irreversible vision loss. The first modern corneal neurotization procedure was described in 2009. The ultimate goal in corneal neurotization is to establish sub-basal plexus regeneration via transferring a healthy nerve to the corneo-limbal region. Corneal neurotization can be achieved either via a direct transfer of healthy nerve (direct approach) or via nerve graft interpositions (indirect approach). This is an emerging concept in the treatment of neurotrophic/exposure keratitis and over the past decade multiple direct and indirect approaches have been described in the attempt to restore corneal sensation and to prevent the devastating outcomes of neurotrophic keratitis. Knowledge of these techniques, their advantages, and disadvantages is required for proper management of patients suffering from neurotrophic keratitis in the setting of facial paralysis.

Correlation Between Corneal Nerve Density and Symptoms of Small Fiber Neuropathy in Patients With Fibromyalgia: The Confounding Role of Severe Anxiety or Depression.

A consistent line of investigation proposes fibromyalgia as a dysautonomia-associated neuropathic pain syndrome. Comorbid anxiety or depression amplifies fibromyalgia symptoms. The recent recognition of small fiber neuropathy in fibromyalgia patients supports the neuropathic nature of the illness. Corneal confocal microscopy accurately identifies small nerve fiber pathology. The newly developed Small-Fiber Symptom Survey captures the spectrum of small fiber neuropathy symptoms. We aimed to correlate corneal nerve density with different fibromyalgia disease severity questionnaires including the Small-Fiber Symptom Survey. We defined the possible confounding role of comorbid anxiety or depression severity in the clinical-pathological association. This is a case series of 28 women with fibromyalgia. A single ophthalmologist quantified corneal subbasal plexus nerve density. Corneal innervation was correlated (Spearman ρ) with the following clinical questionnaires scores: Small-Fiber Symptom Survey, Revised Fibromyalgia Impact Questionnaire, and COMPASS-31 (Composite Autonomic Symptom Survey 31-Item Score). Validated inquiry forms assessed the comorbid anxiety and/or depression severity. There were no clinical-pathological correlations in the group as a whole. In the subgroup of fibromyalgia women without severe anxiety or depression (n = 13), there was a strong negative correlation between corneal nerve density with the Small-Fiber Symptom Survey score (ρ = -0.771, p = 0.002) and COMPASS-31 score (ρ = -0.648, p = 0.017). Patients with profound anxiety or depression (n = 15) had more intense symptoms but had not clinical-pathological correlations. Small fiber neuropathy and dysautonomia symptoms correlate with corneal denervation in women with fibromyalgia without severe anxiety or depression. This clinical-pathological association reinforces fibromyalgia as a dysautonomia-related neuropathic pain syndrome. Severe anxiety or depression distorts fibromyalgia symptoms. Corneal confocal microscopy may become a useful procedure to study fibromyalgia patients.

Structural changes associated to orthokeratology: A systematic review

PurposeTo summarize the peer-reviewed literature on corneal structural changes after orthokeratology (OK) and to analyze the quality of the studies published. MethodsAn exhaustive search was carried out in the databases Pubmed MEDLINE, Web of Science and Scopus. Original studies in English, with a cohort or experimental design and analyzing the cellular and structural changes of the cornea after OK fitting for myopia correction were selected. The NewCastle-Ottawa Assessment Scale (NOS) tool was used to analyze the quality of the studies selected. ResultsThe search provided a total of 1837 articles, of which 12 were selected following the inclusion and exclusion criteria. All studies had good quality according to the NOS tool (mean 7.58 ± 1.31). The mean ± standard deviation follow-up period of lens wear in the studies evaluated was 19.27 ± 33.97 months. The following reversible changes after OK have been reported: reduction in central epithelial basal cells, an increase in height and especially in width of superficial epithelial cells, as well as an increase in central stromal thickness and in the number of active keratocytes. Concerning corneal endothelium, only changes in terms of polymegathism were reported that were compatible with those observed for other types of contact lens wear. In relation to corneal sensitivity, there was a reduction during the use of OK, as well as in the nervous density of the sub-basal plexus at the central level, with some contradictory outcomes concerning the reversibility of these changes. ConclusionOK produces reversible structural changes in the central epithelium and central anterior corneal stroma, as well as a decrease in the nerve density of the sub-basal plexus and corneal sensitivity. The quality of published studies evaluating these aspects is good, although more studies are needed to evaluate longer follow-up changes.

Micro-optical coherence tomography for high-resolution morphologic imaging of cellular and nerval corneal micro-structures.

We demonstrate the highest resolution (1.5×1.5×1 µm) micrometer optical coherence tomography (µOCT) imaging of the morphologic micro-structure of excised swine and non-human primate corneas. Besides epithelial, stromal, and endothelial cell morphology, this report focuses on investigating the most peripheral corneal nerve fibers, the nerve fibers of the subbasal plexus (SBP). Alterations of SBP nerve density and composition are reportedly linked to major neurologic disorders, such as diabetic neuropathy, potentially indicating earliest onsets of denervation. Here, the fine, hyperreflective, epithelial nerve structures located just above Bowman's membrane, are i) visualized using our µOCT prototype, ii) validated by comparison to fluorescence confocal microscopy (including selective immunohistochemical staining), and iii) segmented using state-of-the-art image processing. Here, we also introduce polarization sensitive (PS) µOCT imaging, demonstrating, to the best of our knowledge, the highest resolution corneal PS-OCT scans reported to date.