Assessment of dynamic corneal nerve changes using static landmarks by large-area confocal microscopy-a longitudinal proof-of-concept study.

Background: The purpose of the present proof-of-concept study was to use large-area confocal laser scanning microscopy (CLSM) mosaics to determine the migration rates of nerve branching points in the human corneal subbasal nerve plexus (SNP).

Methods: Three healthy individuals were examined roughly weekly over a total period of six weeks by large-area confocal microscopy of the central cornea. An in-house developed prototype system for guided eye movement with an acquisition time of 40 s was used to image and generate large-area mosaics of the SNP.

Atypical Cellular Elements of Unknown Origin in the Subbasal Nerve Plexus of a Diabetic Cornea Diagnosed by Large-Area Confocal Laser Scanning Microscopy.

In vivo large-area confocal laser scanning microscopy (CLSM) of the human eye using EyeGuidance technology allows a large-scale morphometric assessment of the corneal subbasal nerve plexus (SNP). Here, the SNP of a patient suffering from diabetes and associated late complications was analyzed. The SNP contained multiple clusters of large hyperintense, stellate-shaped, cellular-like structures.

Comparative Anatomy of the Mammalian Corneal Subbasal Nerve Plexus.

Purpose: The subbasal nerve plexus (SNP) is the densest and most recognizable component of the mammalian corneal innervation; however, the anatomical configuration of the SNP in most animal models remains incompletely described. The purpose of the current study is to describe in detail the SNP architecture in eight different mammals, including several popular animal models used in cornea research.

Methods: Corneal nerves in mouse, rat, guinea pig, rabbit, dog, macaque, domestic pig, and cow eyes were stained immunohistochemically with antiserum directed against neurotubulin.

Comparative quantitative assessment of the human corneal sub-basal nerve plexus by in vivo confocal microscopy and histological staining.

PurposeThis study was designed to compare and contrast quantitative data of the human corneal sub-basal nerve plexus (SBP) evaluated by two different methods: in vivo confocal microscopy (IVCM), and immunohistochemical staining of ex vivo donor corneas.MethodsSeven parameters of the SBP in large-scale IVCM mosaicking images from healthy subjects were compared with the identical parameters in ex vivo donor corneas stained by β-III-tubulin immunohistochemistry. Corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), average weighted corneal nerve fiber tortuosity (CNFTo), corneal nerve connection points (CNCP), average corneal nerve single-fiber length (CNSFL), and average weighted corneal nerve fiber thickness (CNFTh) were calculated using a dedicated, published algorithm and compared.

Femtosecond laser cutting of human corneas for the subbasal nerve plexus evaluation.

Assessment of various morphological parameters of the corneal subbasal nerve plexus is a valuable method of documenting the structural and presumably functional integrity of the corneal innervation in health and disease. The aim of this work is to establish a rapid, reliable and reproducible method for visualization of the human corneal SBP using femtosecond laser cut corneal tissue sections. Trephined healthy corneal buttons were fixed and processed using TissueSurgeon-a femtosecond laser based microtome, to obtain thick tissue sections of the corneal epithelium and anterior stroma cut parallel to the ocular surface within approximately 15 min.

Hyperosmolar Tears Induce Functional and Structural Alterations of Corneal Nerves: Electrophysiological and Anatomical Evidence Toward Neurotoxicity.

Purpose: In an effort to elucidate possible neural mechanisms underlying diminished tearing in dry eye disease, this study sought to determine if hyperosmolar tears, a ubiquitous sign of dry eye disease, produce functional changes in corneal nerve responses to drying of the cornea and if these changes correlate with alterations in corneal nerve morphology.

Methods: In vivo extracellular electrophysiological recordings were performed in rat trigeminal ganglion neurons that innervated the cornea before, and up to 3 hours after, the ocular application of continuous hyperosmolar tears or artificial tears. In corollary experiments, immunohistochemical staining was performed to compare corneal nerve morphology in control and in eyes treated with hyperosmolar solutions.

Gross anatomy and morphometric evaluation of the canine lacrimal and third eyelid glands.

Objective: The lacrimal gland (LG) and the third eyelid gland (TELG) are two intraorbital glands that, in dogs, secrete the aqueous component of the tear film. Despite the central importance of these structures for maintaining ocular surface health, the gross anatomy of the glands remains understudied. We investigated the macroscopic morphometric characteristics of the LG and TELG in three different dog breeds.

Loss of corneal sensory nerve fibers in SIV-infected macaques: an alternate approach to investigate HIV-induced PNS damage.

Peripheral neuropathy is the most frequent neurological complication of HIV infection, affecting more than one-third of infected patients, including patients treated with antiretroviral therapy. Although emerging noninvasive techniques for corneal nerve assessments are increasingly being used to diagnose and monitor peripheral neuropathies, corneal nerve alterations have not been characterized in HIV. Here, to determine whether SIV infection leads to corneal nerve fiber loss, we immunostained corneas for the nerve fiber marker βIII tubulin.

The TFOS International Workshop on Contact Lens Discomfort: report of the subcommittee on neurobiology.

This report characterizes the neurobiology of the ocular surface and highlights relevant mechanisms that may underpin contact lens-related discomfort. While there is limited evidence for the mechanisms involved in contact lens-related discomfort, neurobiological mechanisms in dry eye disease, the inflammatory pathway, the effect of hyperosmolarity on ocular surface nociceptors, and subsequent sensory processing of ocular pain and discomfort have been at least partly elucidated and are presented herein to provide insight in this new arena. The stimulus to the ocular surface from a contact lens is likely to be complex and multifactorial, including components of osmolarity, solution effects, desiccation, thermal effects, inflammation, friction, and mechanical stimulation.

Metaherpetic corneal disease in a dog associated with partial limbal stem cell deficiency and neurotrophic keratitis.

Objective: To describe clinical, in vivo confocal microscopic, histopathologic, and immunohistochemical features of a dog with metaherpetic corneal disease that developed subsequent to a protracted episode of canine herpesvirus-1 (CHV-1) dendritic ulcerative keratitis.

Case Description: A 7-year-old, spayed-female, Miniature Schnauzer was treated for bilateral CHV-1 dendritic ulcerative keratitis. Following resolution of ulcerative keratitis, sectoral peripheral superficial corneal gray opacification, vascularization, and pigmentation slowly migrated centripetally to the axial cornea of both eyes.

Anatomy of the human corneal innervation.

The anatomy of the human corneal innervation has been the subject of much investigation; however, a comprehensive description remains elusive. The purpose of the present study was to provide a detailed description of the human corneal innervation using a novel approach involving immunohistochemically stained anterior-cornea whole mounts. Sixteen donor corneas aged 19-78 years were cut with a 6.

Age-related changes in rat corneal epithelial nerve density.

Purpose: To determine the effect of aging on corneal epithelial nerve density in an animal model.

Methods: Corneal whole mounts from rats aged 6, 12, 18, and 24 months were stained immunohistochemically with antisera against the pan-neuronal marker neurotubulin. Epithelial nerve terminals and subbasal nerves in standardized 1-mm(2) central and peripheral zones from each cornea were drawn using a drawing tube attached to a light microscope.

Nerve growth factor and corneal wound healing in dogs.

Nerve growth factor in the tear film and corneal epithelium is hypothesized to play an important role in ocular surface maintenance and corneal wound healing. The purpose of this study was to determine the expression of nerve growth factor and its high affinity (trkA) receptor in tears, cornea, and lacrimal glands of normal dogs, the modulation of nerve growth factor and its trkA receptor during corneal wound healing, and the effect of topical nerve growth factor application on canine corneal epithelial wound healing. In the first of three experiments, the nerve growth factor content of tears, corneal epithelium, lacrimal gland, and 3rd eyelid gland was determined in normal dogs by enzyme-linked immunosorbent assay and the expression of nerve growth factor and its trkA receptor were evaluated in the cornea and lacrimal glands by immunohistochemistry.

Expression and immunolocalization of plasma membrane calcium ATPase isoforms in human corneal epithelium.

Purpose: Plasma membrane Ca2+-ATPases (PMCAs) are integral membrane proteins essential to the control of intracellular Ca2+ ([Ca2+]i) concentration. Four genes encode PMCA proteins termed PMCA1-PMCA4. Little is known about the expression of these isoforms in corneal epithelium (CE).

Corneal nerves: structure, contents and function.

This review provides a comprehensive analysis of the structure, neurochemical content, and functions of corneal nerves, with special emphasis on human corneal nerves. A revised interpretation of human corneal nerve architecture is presented based on recent observations obtained by in vivo confocal microscopy (IVCM), immunohistochemistry, and ultrastructural analyses of serial-sectioned human corneas. Current data on the neurotransmitter and neuropeptide contents of corneal nerves are discussed, as are the mechanisms by which corneal neurochemicals and associated neurotrophins modulate corneal physiology, homeostasis and wound healing.

Effects of cyclophotocoagulation with a neodymium:yttrium-aluminum-garnet laser on corneal sensitivity, intraocular pressure, aqueous tear production, and corneal nerve morphology in eyes of dogs.

Objective: To determine effects of cyclophotocoagulation via administration of 100 J with a neodymium:yttrium aluminum garnet (Nd:YAG) laser on corneal touch threshold (CTT), intraocular pressure (IOP), aqueous tear production, and corneal nerve morphology in eyes of dogs.

Animals: 15 dogs.

Procedure: Noncontact Nd:YAG laser was transsclerally applied (10 applications; 25 W for 0.

Spontaneous chronic corneal epithelial defects (SCCED) in dogs: clinical features, innervation, and effect of topical SP, with or without IGF-1.

Purpose: To delineate the clinical features and alterations in innervation and substance P (SP) content in spontaneous chronic corneal epithelial defects (SCCED) in dogs and to conduct a preliminary investigation evaluating the efficacy of topical SP, with or without insulin-like growth factor (IGF)-1, in the treatment of this disorder.

Methods: Complete ophthalmic examinations, including Cochet-Bonnet aesthesiometry, were performed in 45 canine patients that had spontaneous corneal epithelial defects of at least 3 weeks' duration and with no identifiable cause. Eighteen patients had superficial keratectomies performed, and the corneal nerves were labeled immunohistochemically with antibodies against protein gene product (PGP)-9.

Morphology and neurochemistry of canine corneal innervation.

Purpose: To determine the architectural pattern and neuropeptide content of canine corneal innervation.

Methods: Corneal nerve fibers in normal dog eyes were labeled immunohistochemically with antibodies against protein gene product (PGP)-9.5, calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and tyrosine hydroxylase (TH).

Effect of norepinephrine on proliferation, migration, and adhesion of SV-40 transformed human corneal epithelial cells.

Purpose: To determine the ability of norepinephrine to modulate proliferation, adhesion, and migration of SV-40 transformed human corneal epithelial cells.

Methods: Assays were performed using SV-40 transformed human corneal epithelial cells. For proliferation assays, cells were plated in 96-well plates coated with fibronectin and collagen (FNC).

Parasympathetic innervation of the rat cornea.

The mammalian cornea receives a dense sensory innervation and a modest sympathetic innervation. The purpose of the current study was to determine if the rat cornea is also innervated by parasympathetic nerves. In the first set of experiments, unilateral combined sympathetic and sensory ocular denervations were performed in adult rats by surgical removal of the superior cervical ganglion and intracranial transection of the trigeminal ophthalmomaxillary nerve.

Peptidergic innervation of the rat cornea.

Corneal nerves regulate corneal epithelial integrity, proliferation, and wound healing. The mechanisms by which the nerves mediate their effects remain poorly understood; however, the release of biologically active neuropeptides has been hypothesized. The purpose of the current investigation was to determine the relative densities, distribution patterns, and origins of rat corneal nerves containing each of eight different neuropeptides, calcitonin gene-related peptide (CGRP), substance P (SP), galanin (GAL), neuropeptide Y (NPY), methionine-enkephalin (M-ENK), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), and cholecystokinin (CCK).

Topical substance P and corneal epithelial wound closure in the rabbit.

Purpose: The authors determined the effect of topically applied substance P (SP) on the rate of corneal epithelial wound closure in the rabbit.

Methods: Uniform circular lesions, 6.5 mm in diameter, were made bilaterally in the corneal epithelium of 24 rabbits using N-heptanol.

Sympathetic stimulation of corneal epithelial proliferation in wounded and nonwounded rat eyes.

Purpose: To determine the effect of ocular sympathetic nerves on corneal epithelial proliferation in the rat.

Methods: Osmotic pumps filled with bromodeoxyuridine (BrdU) were implanted subcutaneously in adult rats to label corneal epithelial cells entering the S-phase of the cell cycle during a 24-hour period. Corneas in some animals were wounded with n-heptanol.

Local anesthetic effects in the presence of chronic osteomyelitis (necrosis) of the mandible: implications for localizing the etiologic sites of referred trigeminal pain.

The aims of this study were: (1) to demonstrate how reproducible variations in incomplete anesthesia of the inferior alveolar nerve can be used as a guide to locate the etiologic sites of referred trigeminal pain emanating from the mandible; (2) to describe the salient histopathologic features of a lowgrade, nonsuppurative osteomyelitis seen in this patient population. Forty-six patients with idiopathic facial pain were subjected to a specific protocol of local anesthetic injections to sequentially block branches of the mandibular nerve to determine the effects on his/her pain. If this significantly reduced or altered the pain on three separate appointments, then exploratory surgery was conducted near identified zones of unanesthetized gingiva.

The effect of diabetes on neuropeptide content in the rat cornea and iris.

Purpose: To determine the effect of diabetes mellitus on the levels of substance P (SP), calcitonin gene-related peptide (CGRP), and vasoactive intestinal polypeptide (VIP) in the rat cornea and iris.

Methods: Corneas and irides from control and diabetic rats were processed for neuropeptide radioimmunoassay 3 months after induction of diabetes with streptozotocin. Corneas and irides also were processed for SP and CGRP immunohistochemistry and were evaluated qualitatively.