FL-41 Tint Reduces Activation of Neural Pathways of Photophobia in Patients with Chronic Ocular Pain

PURPOSE

To assess the therapeutic effect of tinted lenses (FL-41) on photophobia and light-evoked brain activity using functional magnetic resonance imaging (fMRI) in individuals with chronic ocular surface pain.

DESIGN

Prospective case series.

METHODS

25 subjects from the Miami veterans affairs (VA) eye clinic were recruited based on the presence of chronic ocular pain, dry eye symptoms, and photophobia. Using a 3T MRI scanner, subjects underwent 2 fMRI scans using an event-related design based on light stimuli: one scan while wearing FL-41 lenses and one without. Unpleasantness ratings evoked by the light stimuli were collected after each scan.

RESULTS

With FL-41 lenses, subjects reported decreased (n = 19), maintained (n = 2), or increased (n = 4) light-evoked unpleasantness ratings. Group analysis at baseline (no lens) revealed significant light evoked responses in bilateral primary somatosensory (S1), bilateral secondary somatosensory (S2), bilateral insula, bilateral frontal pole, visual, precuneus, paracingulate, and anterior cingulate cortices (ACC) as well as cerebellar vermis, bilateral cerebellar hemispheric lobule VI, and bilateral cerebellar crus I and II. With FL-41 lenses, light-evoked responses were significantly decreased in bilateral S1, bilateral S2, bilateral insular, right temporal pole, precuneus, ACC, and paracingulate cortices as well as bilateral cerebellar hemispheric lobule VI.

CONCLUSION

FL-41 lenses modulated photophobia symptoms in some individuals with chronic ocular pain. In conjunction, FL-41 lenses decreased activation in cortical areas involved in processing affective and sensory-discriminative dimensions of pain. Further research into these relationships will advance the ability to provide precision therapy for individuals with ocular pain.

Patient Experiences and Insights on Chronic Ocular Pain: Social Media Listening Study

BACKGROUND

Ocular pain has multifactorial etiologies that affect activities of daily life, psychological well-being, and health-related quality of life (QoL). Chronic ocular surface pain (COSP) is a persistent eye pain symptom lasting for a period longer than 3 months.

OBJECTIVE

The objective of this social media listening study was to better understand COSP and related symptoms and identify its perceived causes, comorbidities, and impact on QoL from social media posts.

METHODS

A search from February 2020 to February 2021 was performed on social media platforms (Twitter, Facebook, blogs, and forums) for English-language content posted on the web. Social media platforms that did not provide public access to information or posts were excluded. Social media posts from Australia, Canada, the United Kingdom, and the United States were retrieved using the Social Studio platform-a web-based aggregator tool.

RESULTS

Of the 25,590 posts identified initially, 464 posts about COSP were considered relevant; the majority of conversations (98.3%, n=456) were posted by adults (aged >18 years). Work status was mentioned in 52 conversations. Patients' or caregivers' discussions across social media platforms were centered around the symptoms (61.9%, n=287) and causes (58%, n=269) of ocular pain. Patients mentioned having symptoms associated with COSP, including headache or head pressure, dry or gritty eyes, light sensitivity, etc. Patients posted that their COSP impacts day-to-day activities such as reading, driving, sleeping, and their social, mental, and functional well-being.

CONCLUSIONS

Insights from this study reported patients' experiences, concerns, and the adverse impact on overall QoL. COSP imposes a significant burden on patients, which spans multiple aspects of daily life.

Electroacupuncture Alleviates Dry Eye Ocular Pain Through TNF-ɑ Mediated ERK1/2/P2X3R Signaling Pathway in SD Rats

Purpose

This study aimed to examine electroacupuncture's influence on ocular pain and its potential modulation of the TNF-ɑ mediated ERK1/2/P2X3R signaling pathway in dry eye-induced rat models.

Methods

Male Sprague-Dawley rats with induced dry eye, achieved through extraorbital lacrimal gland removal, were treated with electroacupuncture. Comprehensive metrics such as the corneal mechanical perception threshold, palpebral fissure height, eyeblink frequency, eye wiping duration, behavioral changes in the open field test, and the forced swimming test were employed. Additionally, morphological changes in microglia and neurons were observed. Expression patterns of key markers, TNF-ɑ, TNFR1, p-ERK1/2, and P2X3R, in the trigeminal ganglion (TG) and spinal trigeminal nucleus caudalis (SpVc) regions, were studied with etanercept serving as a control to decipher the biochemistry of electroacupuncture's therapeutic effects.

Results

Electroacupuncture treatment demonstrated a notable decrease in the corneal mechanical perception threshold, improvement in palpebral fissure height, and significant reductions in both eyeblink frequency and eye wiping duration. Moreover, it exhibited a promising role in anxiety alleviation. Notably, the technique effectively diminished ocular pain by curbing microglial and neuronal activation in the TG and SpVc regions. Furthermore, it potently downregulated TNF-ɑ, TNFR1, p-ERK1/2, and P2X3R expression within these regions.

Conclusion

Electroacupuncture attenuated damage to sensory nerve pathways, reduced pain, and eased anxiety in dry eye-afflicted rats. The findings suggest a crucial role of TNF-ɑ mediated ERK1/2/P2X3R signaling pathway inhibition by electroacupuncture in these benefits.

A novel animal model of neuropathic corneal pain-the ciliary nerve constriction model

Introduction

Neuropathic pain arises as a result of peripheral nerve injury or altered pain processing within the central nervous system. When this phenomenon affects the cornea, it is referred to as neuropathic corneal pain (NCP), resulting in pain, hyperalgesia, burning, and photoallodynia, severely affecting patients' quality of life. To date there is no suitable animal model for the study of NCP. Herein, we developed an NCP model by constriction of the long ciliary nerves innervating the eye.

Methods

Mice underwent ciliary nerve constriction (CNC) or sham procedures. Safety was determined by corneal fluorescein staining to assess ocular surface damage, whereas Cochet-Bonnet esthesiometry and confocal microscopy assessed the function and structure of corneal nerves, respectively. Efficacy was assessed by paw wipe responses within 30 seconds of applying hyperosmolar (5M) saline at Days 3, 7, 10, and 14 post-constriction. Additionally, behavior was assessed in an open field test (OFT) at Days 7, 14, and 21.

Results

CNC resulted in significantly increased response to hyperosmolar saline between groups (p < 0.0001), demonstrating hyperalgesia and induction of neuropathic pain. Further, animals that underwent CNC had increased anxiety-like behavior in an open field test compared to controls at the 14- and 21-Day time-points (p < 0.05). In contrast, CNC did not result in increased corneal fluorescein staining or decreased sensation as compared to sham controls (p > 0.05). Additionally, confocal microscopy of corneal whole-mounts revealed that constriction resulted in only a slight reduction in corneal nerve density (p < 0.05), compared to naïve and sham groups.

Discussion

The CNC model induces a pure NCP phenotype and may be a useful model for the study of NCP, recapitulating features of NCP, including hyperalgesia in the absence of ocular surface damage, and anxiety-like behavior.

Disentangling the neurological basis of chronic ocular pain using clinical, self-report, and brain imaging data: use of K-means clustering to explore patient phenotypes

Introduction

The factors that mediate the expression of ocular pain and the mechanisms that promote chronic ocular pain symptoms are poorly understood. Central nervous system involvement has been postulated based on observations of pain out of proportion to nociceptive stimuli in some individuals. This investigation focused on understanding functional connectivity between brain regions implicated in chronic pain in persons reporting ocular pain symptoms.

Methods

We recruited a total of 53 persons divided into two cohorts: persons who reported no ocular pain, and persons who reported chronic ocular pain, irrespective of ocular surface findings. We performed a resting state fMRI investigation that was focused on subcortical brain structures including the trigeminal nucleus and performed a brief battery of ophthalmological examinations.

Results

Persons in the pain cohort reported higher levels of pain symptoms relating to neuropathic pain and ocular surface disease, as well as more abnormal tear metrics (stability and tear production). Functional connectivity analysis between groups evinced multiple connections exemplifying both increases and decreases in connectivity including regions such as the trigeminal nucleus, amygdala, and sub-regions of the thalamus. Exploratory analysis of the pain cohort integrating clinical and brain function metrics highlighted subpopulations that showed unique phenotypes providing insight into pain mechanisms.

Discussion

Study findings support centralized involvement in those reporting ocular-based pain and allude to mechanisms through which pain treatment services may be directed in future research.

Pain control and subconjunctival haemorrhage after intravitreal injection using cooled anaesthetic eyedrops and antiseptics: A prospective, double-blind, randomized controlled trial

PURPOSE

To evaluate whether cooled anaesthetic eyedrops and antiseptics alleviate pain and minimise subconjunctival haemorrhage following intravitreal injection.

METHODS

A prospective, double-masked, randomised controlled trial of 100 participants receiving either cooled (n = 50) or room temperature (n = 50) topical anaesthetic eyedrops and antiseptics before receiving an injection of bevacizumab. Baseline tolerability was estimated using a self-reported pain sensitivity questionnaire.

RESULTS

Overall tolerability was comparable between the study group and the control group (0.75 ± 0.13 vs. 0.74 ± 0.14, respectively, p = 0.99). Subconjunctival haemorrhage incidence was similar in both groups (80% vs. 86%, respectively, p = 0.113), as was subconjunctival haemorrhage size (2.75 ± 5.51 mm2 vs. 5.53 ± 10.72 mm2 , respectively, p = 0.11). Sub-group analysis demonstrated that the participants taking daily ocular eyedrops who received cooled anaesthetic eyedrops and antiseptics reported less pain at 10 min and less burning sensation at 24 h compared with matched controls (0.67 ± 1.50 vs. 2.50 ± 3.03, respectively, p = 0.040 and 0.00 ± 0.00 vs. 1.44 ± 2.96, respectively, p = 0.045). Participants who received cooled eyedrops and did not use antithrombotic therapy had smaller-sized subconjunctival haemorrhages compared with matched controls (1.55 ± 1.87 mm2 vs. 8.29 ± 14.61 mm2 , respectively, p = 0.038). Participants with hypertension who received cooled eyedrops had smaller-sized subconjunctival haemorrhage compared with matched controls (2.33 ± 4.99 mm2 vs. 6.89 ± 12.41 mm2 , respectively, p = 0.045).

CONCLUSION

The benefit of using cooled anaesthetic eyedrops and antiseptics to alleviate pain and minimise subconjunctival haemorrhage following intravitreal injection was not proven in the general population. It may be beneficial in part for some patients, such as those who regularly use eyedrops, patients with hypertension or those not on antithrombotic therapy.

Self-reported symptoms of everyday executive dysfunction, daytime sleepiness, and fatigue and health status among adults with congenital aniridia: a descriptive study

Background

Congenital aniridia is a rare genetic disorder of the eye characterized by visual impairment and progressive vision loss. While prior research has focused on ocular manifestations in individuals with aniridia, there is a dearth of research on impacts on cognition and mental health. The aims of this study were to describe subjective symptoms of everyday executive functioning, fatigue and sleepiness in adults with aniridia and to compare self-reported health status with that of a normative reference group.

Methods

Twenty-nine adults (aged 18-79 years) with congenital aniridia were included in this online survey, of whom 52% were females. Participants completed self-report measures of executive functioning (The Behavior Rating Inventory of Executive Function-Adult Version), sleepiness, fatigue, and health status (EQ-5D-5L).

Results

Participants reported relatively few problems in everyday executive functioning, with only 14% experiencing impaired executive functioning. Scores on the five EQ-5D-5L domains (mobility, self-care, usual activities, pain, and anxiety/depression) did not differ from those of the normative reference group. The frequencies of excessive daytime sleepiness and severe fatigue were 17% and 38%, respectively. Ocular pain was experienced by 62% of participants.

Conclusions

The findings show that cognitive problems are related to and reflect self-reported health status and extent of fatigue. Moreover, those who suffered from ocular pain reported more difficulties with executive functioning, sleepiness and fatigue. These findings are important for understanding this disorder and supporting patients.

Chemical toxic exposures and chronic ocular pain

Chronic ocular pain is a common, debilitating chronic pain condition with significant morbidity and negative impact in patients' quality of life. Several, diverse types of insults to the ocular surface can lead to acute, and under certain conditions to chronic ocular pain, and these include toxic irritants. Exposure of ocular surface to toxic irritants, in addition to direct tissue injury, carries the capacity to generated intense immune and neuronal responses with hyper-excitability, sensitization and chronic pain. Because, chronic ocular pain subsequent to toxic exposures is relatively unrecognized clinical entity, this brief review highlights pertinent concepts of its epidemiology, pathogenesis/pathophysiology, clinical progression, with recommendations for its clinical management that clinicians may find helpful. Suppression of pain signaling, generating neuronal sensitization, and prevention of chronicity of neuropathic pain is particularly emphasized in this respect.

Botulinum toxin A decreases neural activity in pain-related brain regions in individuals with chronic ocular pain and photophobia

Introduction

To examine the effect of botulinum toxin A (BoNT-A) on neural mechanisms underlying pain and photophobia using functional magnetic resonance imaging (fMRI) in individuals with chronic ocular pain.

Methods

Twelve subjects with chronic ocular pain and light sensitivity were recruited from the Miami Veterans Affairs eye clinic. Inclusion criteria were: (1) chronic ocular pain; (2) presence of ocular pain over 1 week recall; and (3) presence of photophobia. All individuals underwent an ocular surface examination to capture tear parameters before and 4-6 weeks after BoNT-A injections. Using an event-related fMRI design, subjects were presented with light stimuli during two fMRI scans, once before and 4-6 weeks after BoNT-A injection. Light evoked unpleasantness ratings were reported by subjects after each scan. Whole brain blood oxygen level dependent (BOLD) responses to light stimuli were analyzed.

Results

At baseline, all subjects reported unpleasantness with light stimulation (average: 70.8 ± 32.0). Four to six weeks after BoNT-A injection, unpleasantness scores decreased (48.1 ± 33.6), but the change was not significant. On an individual level, 50% of subjects had decreased unpleasantness ratings in response to light stimulation compared to baseline ("responders," n = 6), while 50% had equivalent (n = 3) or increased (n = 3) unpleasantness ("non-responders"). At baseline, several differences were noted between responders and non-responders; responders had higher baseline unpleasantness ratings to light, higher symptoms of depression, and more frequent use of antidepressants and anxiolytics, compared to non-responders. Group analysis at baseline displayed light-evoked BOLD responses in bilateral primary somatosensory (S1), bilateral secondary somatosensory (S2), bilateral anterior insula, paracingulate gyrus, midcingulate cortex (MCC), bilateral frontal pole, bilateral cerebellar hemispheric lobule VI, vermis, bilateral cerebellar crus I and II, and visual cortices. BoNT-A injections significantly decreased light evoked BOLD responses in bilateral S1, S2 cortices, cerebellar hemispheric lobule VI, cerebellar crus I, and left cerebellar crus II. BoNT-A responders displayed activation of the spinal trigeminal nucleus at baseline where non-responders did not.

Discussion

BoNT-A injections modulate light-evoked activation of pain-related brain systems and photophobia symptoms in some individuals with chronic ocular pain. These effects are associated with decreased activation in areas responsible for processing the sensory-discriminative, affective, dimensions, and motor responses to pain.

Novel Treatments for Chronic Ocular Surface Pain

ABSTRACT

Several etiologies can contribute to ocular surface pain including nociceptive, peripheral neuropathic, and central neuropathic mechanisms. Clinical clues can help identify contributors to ocular surface pain in a patient. In individuals whose pain persists despite targeting nociceptive contributors, neuropathic mechanisms should be considered and addressed using oral, topical, and/or adjuvant agents.

Nav1.7 P610T mutation in two siblings with persistent ocular pain after corneal axon transection: impaired slow inactivation and hyperexcitable trigeminal neurons

Despite extensive study, the mechanisms underlying pain after axonal injury remain incompletely understood. Pain after corneal refractive surgery provides a model, in humans, of the effect of injury to trigeminal afferent nerves. Axons of trigeminal ganglion neurons that innervate the cornea are transected by laser-assisted in situ keratomileusis (LASIK). Although most patients do not experience postoperative pain, a small subgroup develop persistent ocular pain. We previously carried out genomic analysis and determined that some patients with persistent pain after axotomy of corneal axons during refractive surgery carry mutations in genes that encode the electrogenisome of trigeminal ganglion neurons, the ensemble of ion channels and receptors that regulate excitability within these cells, including SCN9A, which encodes sodium channel Nav1.7, a threshold channel abundantly expressed in sensory neurons that has been implicated in a number of pain-related disorders. Here, we describe the biophysical and electrophysiological profiling of the P610T Nav1.7 mutation found in two male siblings with persistent ocular pain after refractive surgery. Our results indicate that this mutation impairs the slow inactivation of Nav1.7. As expected from this proexcitatory change in channel function, we also demonstrate that this mutation produces increased spontaneous activity in trigeminal ganglion neurons. These findings suggest that this gain-of-function mutation in Nav1.7 may contribute to pain after injury to the axons of trigeminal ganglion neurons.NEW & NOTEWORTHY Mechanisms underlying pain after axonal injury remain elusive. A small subgroup of patients experience pain after corneal refractive surgery, providing a human pain model after well-defined injury to axons. Here we analyze a mutation (P610T) in Nav1.7, a threshold sodium channel expressed in nociceptors, found in two siblings with persistent ocular pain after refractive surgery. We show that it impairs channel slow inactivation, thereby triggering inappropriate repetitive activity in trigeminal ganglion axons that signal eye pain.

Transient Receptor Potential Channels: Important Players in Ocular Pain and Dry Eye Disease

Dry eye disease (DED) is a multifactorial disorder in which the eyes respond to minor stimuli with abnormal sensations, such as dryness, blurring, foreign body sensation, discomfort, irritation, and pain. Corneal pain, as one of DED’s main symptoms, has gained recognition due to its increasing prevalence, morbidity, and the resulting social burden. The cornea is the most innervated tissue in the body, and the maintenance of corneal integrity relies on a rich density of nociceptors, such as polymodal nociceptor neurons, cold thermoreceptor neurons, and mechano-nociceptor neurons. Their sensory responses to different stimulating forces are linked to the specific expression of transient receptor potential (TRP) channels. TRP channels are a group of unique ion channels that play important roles as cellular sensors for various stimuli. These channels are nonselective cation channels with variable Ca²⁺ selectivity. TRP homologs are a superfamily of 28 different members that are subdivided into 7 different subfamilies based on differences in sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells, where they affect various stress-induced regulatory responses essential for normal vision maintenance. This article reviews the current knowledge about the expression, function, and regulation of TRPs in ocular surface tissues. We also describe their implication in DED and ocular pain. These findings contribute to evidence suggesting that drug-targeting TRP channels may be of therapeutic benefit in the clinical setting of ocular pain.

Clinical Characteristics of Idiopathic Orbital Inflammation Syndrome in Relation to Intraocular Pressure

Purpose

To investigate the clinical characteristics of idiopathic orbital inflammation and changes in intraocular pressure (IOP) before and after its treatment.

Patients and Methods

We retrospectively studied 20 eyes from the medical records of 19 patients who were diagnosed with idiopathic orbital inflammation between April 1, 2004, and April 30, 2019, at Toyama University Hospital. The inflammation site (type of disease), treatment provided, IOP before and after treatment, and the symptoms (proptosis, decreased ocular movements or diplopia, periorbital edema, and ocular pain) were analyzed.

Results

The types of idiopathic orbital inflammation were dacryoadenitis in 14, myositis in 7, diffuse-type in 3, and posterior periscleritis in 1 case. The mean IOP after treatment was 15.4±3.9 mm Hg, which was significantly lower than the mean pretreatment IOP of 19.0±5.3 mm Hg (p = 0.009). Before treatment, all cases with the diffuse-type had high IOPs of 21 mm Hg or more. Ocular pain and eye movement disorders were present in 86% and 100% of subjects in the group with an IOP of 21 mm Hg or higher, but 38% and 31% in the group with an IOP of 20 mm Hg or lower, respectively.

Conclusion

Diffuse-type of idiopathic orbital inflammation is prone to develop high IOP. Patients with idiopathic orbital inflammation and high IOP exhibit many symptoms such as decreased ocular movements, diplopia, and ocular pain.

Self-Report of Severity of Ocular Pain Due to Light as a Predictor of Altered Central Nociceptive System Processing in Individuals With Symptoms of Dry Eye Disease

Dry eye disease (DED) is a diagnosis given to individuals with a heterogeneous combination of symptoms and/or signs, including spontaneous and evoked ocular pain. Our current study evaluated whether and which ocular pain assessments could serve as screening tools for central sensitization in individuals with DED. A cohort of individuals with DED symptoms (n = 235) were evaluated for ocular pain, DED signs (tear production, evaporation), evoked sensitivity to mechanical stimulation at the cornea, and evidence of central sensitization. Central sensitization was defined for this study as the presence of pain 30 seconds after termination of a thermal noxious temporal summation protocol (ie, aftersensations) presented at a site remote from the eye (ventral forearm). We found that combining ratings of average intensity of ocular pain, ratings of average intensity of pain due to light, response to topical anesthetic eye drops, and corneal mechanical pain thresholds produced the best predictive model for central sensitization (area under the curve of .73). When examining ratings of intensity of ocular pain due to light alone (0-10 numerical rating), a cutoff score of 2 maximized sensitivity (85%) and specificity (48%) for the presence of painful aftersensations at the forearm. Self-reported rating of pain sensitivity to light may serve as a quick screening tool indicating the involvement of central nociceptive system dysfunction in individuals with DED. PERSPECTIVE: This study reveals that clinically-relevant variables, including a simple 0 to 10 rating of ocular pain due to light, can be used to predict the contribution of central sensitization mechanisms in a subgroup of individuals with DED symptoms. These findings can potentially improve patient stratification and management for this complex and painful disease.

An Experimental Model of Neuro-Immune Interactions in the Eye: Corneal Sensory Nerves and Resident Dendritic Cells

The cornea is an avascular connective tissue that is crucial, not only as the primary barrier of the eye but also as a proper transparent refractive structure. Corneal transparency is necessary for vision and is the result of several factors, including its highly organized structure, the physiology of its few cellular components, the lack of myelinated nerves (although it is extremely innervated), the tightly controlled hydration state, and the absence of blood and lymphatic vessels in healthy conditions, among others. The avascular, immune-privileged tissue of the cornea is an ideal model to study the interactions between its well-characterized and dense sensory nerves (easily accessible for both focal electrophysiological recording and morphological studies) and the low number of resident immune cell types, distinguished from those cells migrating from blood vessels. This paper presents an overview of the corneal structure and innervation, the resident dendritic cell (DC) subpopulations present in the cornea, their distribution in relation to corneal nerves, and their role in ocular inflammatory diseases. A mouse model in which sensory axons are constitutively labeled with tdTomato and DCs with green fluorescent protein (GFP) allows further analysis of the neuro-immune crosstalk under inflammatory and steady-state conditions of the eye.

Beyond dry eye: how co-morbidities influence disease phenotype in dry eye disease

Dry Eye Disease (DED) is a complex and multifactorial disorder of tear homoeostasis that results in pain, visual disturbance, and ocular surface damage. It is highly prevalent around the world and is associated with many co-morbidities that may contribute to or exacerbate symptoms and signs of disease and affect disease phenotype. However, DED is not one disease and can manifest with a variety of symptoms and/or signs. In this review, we discuss relationships between various co-morbidities and DED phenotypes. For example, individuals with immune mediated diseases, like Sjögren's Syndrome and Graft versus Host Disease, often present with aqueous tear deficiency (ADDE) in the setting of lacrimal gland dysfunction. Individuals with disorders that affect the periocular skin, like rosacea and seborrhoeic dermatitis, often present with evaporative dry eye (EDE) in the setting of eyelid and/or meibomian gland abnormalities. Individuals with pain related disorders, such as chronic pain syndrome and migraine, often present with ocular pain out of proportion to tear film abnormalities, often with accompanying corneal nerve hypersensitivity. Individuals with diabetes mellitus often present with an epitheliopathy in the setting of decreased sensation (neurotrophic keratitis). While not absolute, understanding relationships between co-morbidities and DED phenotypes can help tailor a therapeutic plan to the individual patient.

Mechanisms of Peripheral and Central Pain Sensitization: Focus on Ocular Pain

Persistent ocular pain caused by corneal inflammation and/or nerve injury is accompanied by significant alterations along the pain axis. Both primary sensory neurons in the trigeminal nerves and secondary neurons in the spinal trigeminal nucleus are subjected to profound morphological and functional changes, leading to peripheral and central pain sensitization. Several studies using animal models of inflammatory and neuropathic ocular pain have provided insight about the mechanisms involved in these maladaptive changes. Recently, the advent of new techniques such as optogenetics or genetic neuronal labelling has allowed the investigation of identified circuits involved in nociception, both at the spinal and trigeminal level. In this review, we will describe some of the mechanisms that contribute to the perception of ocular pain at the periphery and at the spinal trigeminal nucleus. Recent advances in the discovery of molecular and cellular mechanisms contributing to peripheral and central pain sensitization of the trigeminal pathways will be also presented.

Evaluation of Same-Day versus Next-Day Implantation of Intracanalicular Dexamethasone for the Control of Postoperative Inflammation and Pain Following Cataract Surgery

Purpose

To evaluate the safety and efficacy of a sustained-release intracanalicular dexamethasone insert for postoperative inflammation and pain implanted in a clinical setting preoperatively or on postoperative day 1.

Methods

Single-site, retrospective, contralateral eye study of patients undergoing cataract surgery. Included were subjects with a dexamethasone intracanalicular insert implanted in the clinic immediately prior to surgery in one eye (same-day) and on postoperative day 1 (POD1) in the contralateral eye. The primary outcome measure was the resolution of anterior chamber inflammation at 1 week postoperative. Secondary outcome measures included proportion of eyes requiring additional therapy for pain and inflammation through 1 month as well as the number of eyes with IOP spikes above baseline. Safety measures included adverse events through 1 month postoperative.

Results

Sixty-two eyes of 31 subjects were included in the case series. At 1 week postoperative, 52% of the eyes (n = 16) achieved complete resolution of inflammation in the same-day group and 58% (n = 18) met this endpoint at 1 week in the POD1 group. One subject in the same-day group required additional therapy for rebound inflammation and no eyes required additional therapy in the POD1 group. There were no reports of pain at 1 week or 1 month in either group. There were no implant-related adverse events in either group.

Conclusion

The favorable results of this study indicate that the sustained-release dexamethasone insert can be safely implanted in the clinic either preoperatively on the day of surgery or on postoperative day 1 for the control of pain and inflammation following cataract surgery.

Immunity and pain in the eye: focus on the ocular surface

Most ocular diseases are associated with pain. While pain has been generally considered a mere (deleterious) additional symptom, it is now emerging that it is a key modulator of innate/adaptive immunity. Because the cornea receives the highest nerve density of the entire body, it is an ideal site to demonstrate interactions between pain and the immune response. Indeed, most neuropeptides involved in pain generation are also potent regulators of innate and adaptive leukocyte physiology. On the other hand, most inflammatory cells can modulate the generation of ocular pain through release of specific mediators (cytokines, chemokines, growth factors, and lipid mediators). This review will discuss the reciprocal role(s) of ocular surface (and specifically: corneal) pain on the immune response of the eye. Finally, we will discuss the clinical implications of such reciprocal interactions in the context of highly prevalent corneal diseases.

Cerebrofacial vascular metameric syndrome is caused by somatic pathogenic variants in PIK3CA

Disorganized morphogenesis of arteries, veins, capillaries, and lymphatic vessels results in vascular malformations. Most individuals with isolated vascular malformations have postzygotic (mosaic), activating pathogenic variants in a handful of oncogenes within the PI3K–RAS–MAPK pathway (Padia et al., Laryngoscope Investig Otolaryngol 4: 170–173 [2019]). Activating pathogenic variants in the gene PIK3CA, which encodes for the catalytic subunit of phosphatidylinositol 3-kinase, are present in both lymphatic and venous malformations as well as arteriovenous malformations in other complex disorders such as CLOVES syndrome (congenital, lipomatous, overgrowth, vascular malformations, epidermal anevi, scoliosis) (Luks et al., Pediatr Dev Pathol 16: 51 [2013]; Luks et al., J Pediatr 166: 1048–1054.e1–5 [2015]; Al-Olabi et al., J Clin Invest 128: 1496–1508 [2018]). These vascular malformations are part of the PIK3CA-related overgrowth spectrum, a spectrum of entities that have regionalized disordered growth due to the presence of tissue-restricted postzygotic PIK3CA pathogenic variants (Keppler-Noreuil et al., Am J Med Genet A 167A: 287–295 [2015]). Cerebrofacial vascular metameric syndrome (CVMS; also described as cerebrofacial arteriovenous metameric syndrome, Bonnet–Dechaume–Blanc syndrome, and Wyburn–Mason syndrome) is the association of retinal, facial, and cerebral vascular malformations (Bhattacharya et al., Interv Neuroradiol 7: 5–17 [2001]; Krings et al., Neuroimaging Clin N Am 17: 245–258 [2007]). The segmental distribution, the presence of tissue overgrowth, and the absence of familial recurrence are all consistent with CVMS being caused by a postzygotic mutation, which has been hypothesized by previous authors (Brinjiki et al., Am J Neuroradiol 39: 2103–2107 [2018]). However, the genetic cause of CVMS has not yet been described. Here, we present three individuals with CVMS and mosaic activating pathogenic variants within the gene PIK3CA. We propose that CVMS be recognized as part of the PIK3CA-related overgrowth spectrum, providing justification for future trials using pharmacologic PIK3CA inhibitors (e.g., alpelisib) for these difficult-to-treat patients.

Deciphering the Action of Perfluorohexyloctane Eye Drops to Reduce Ocular Discomfort and Pain

Perfluorohexyloctane (F6H8) eyedrops have been recently introduced in Europe as a product to treat dry eye disease, based on its ability to reduce tear film instability in Meibomian gland dysfunction and evaporative dry eye disease, although its mechanism of action is still unknown. In the present pilot study, we evaluated the effects of the ocular instillation of a single drop of commercial F6H8 eyedrops in 20 healthy humans (9 women/11 men), measuring: (a) Corneal surface temperature (CST) from infrared video images; (b) tear volume using phenol red threads; (c) blinking frequency; and (d) ocular surface sensations (cold, dryness, pricking, foreign body, burning, itching, gritty, eye fatigue, watering eyes, and light-evoked discomfort sensations; scored using 10 cm Visual Analog Scales), before and 5–60 min after F6H8 or saline treatment. CST decreased and tearing and blinking frequency increased significantly after F6H8 but not after saline solution. When applied unilaterally, CST decreased only in the F6H8-treated eye. No sensations were evoked after F6H8 or saline. The corneal surface temperature reduction produced by topical F6H8 does not evoke conscious ocular sensations but is sufficient to increase the activity of corneal cold thermoreceptors, leading to an increased reflex lacrimation and blinking that may relieve dry eye condition thus reducing ocular discomfort and pain.

Same-Day versus Next-Day Dexamethasone Intracanalicular Insert Administration for Inflammation and Pain Control Following Cataract Surgery: A Retrospective Analysis

Background

The dexamethasone 0.4mg intracanalicular insert (Dextenza, Ocular Therapeutix, Bedford, MA) is approved for control of postoperative pain and inflammation following ocular surgery. This study compared pain and inflammation resolution following phacoemulsification in eyes that received the insert immediately postoperatively versus the next day.

Methods

This was a retrospective analysis of existing electronic health records. Consecutive qualifying eyes were included for analysis. All patients received perioperative antibiotics and nonsteroidal anti-inflammatory drugs. Pain and inflammation were assessed at baseline and on postoperative days 1, 7, and 30. Pain was assessed by dichotomous patient report (present/absent). Anterior chamber cell (0, 0.5+, 1–4+) and flare (0–4+) were graded using the Standardization of Uveitis Nomenclature rubric.

Results

Data from 17 eyes of 17 subjects were analyzed; 8 received the insert immediately postoperative and 9 in the office the next day. In both groups, trace cell was present in all eyes at day 1 and had resolved in all but 1 eye in each group at days 7 and 30. Flare was absent in all eyes at every time point, and transient pain was reported in a single same-day eye on day 7. No insert-related adverse events were observed, and no eyes required rescue corticosteroid therapy or insert removal.

Conclusion

Similar rates of inflammation and pain resolution after phacoemulsification were observed with the dexamethasone intracanalicular insert placed either immediately postoperatively or the next day.

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Comprehensive Review and Update of Burning Eye Syndrome

Keratoconjunctivitis sicca ("dry eye") is a common (14%-30% of adults over age 48) though difficult to treat condition that causes both discomfort and disability with associated dryness, pain, and visual disturbances. Etiology is not clearly understood but is likely varied, with a subset of patients suffering from chronic neuropathic pain referred to as "burning eye syndrome." This review of existing literature summarizes the clinical presentation, natural history, pathophysiology, and treatment modalities of burning eye syndrome. Chronicity of burning eye syndrome is likely secondary to increased nociception from the cornea, decrease in inhibitory signals, and nerve growth factor expression alterations. Treatment centers around symptomatic alleviation and reduction of inflammation. Conservative treatments focus on well-being and perception and include exercise, acupuncture, and cognitive behavioral therapy. Topical treatment consists of the anti-adhesion T-cell antagonist lifitegrast, corticosteroids, and cyclosporine; all have moderate efficacy and good safety. Autologous serum eye drops are a second-line topical that may promote corneal and neural healing on top of symptomatic relief. When these treatments fail, patients may trial neuromodulation with transcranial magnetic stimulation. Despite general treatment safety, more research is needed to develop novel approaches to this condition, possibly focusing more directly on the neurological component.

KPI-121 1% for pain and inflammation in ocular surgery

Pain and inflammation are common experiences following ocular surgery and, if uncontrolled, can compromise patients' vision, functioning and quality of life. Corticosteroid drugs are available to manage inflammation and discomfort but have limitations in penetrating the ocular mucus barrier to reach the target ocular tissues. KPI-121 1% (INVELTYS^®) is a novel formulation of loteprednol etabonate that employs innovative proprietary technology to deliver nanoparticle-sized mucus-penetrating particles to the cornea. Results from clinical trials demonstrate that KPI-121 1% is effective and well tolerated. KPI-121 1% uses mucopenetrative technology for ophthalmic use and is the only US FDA-approved twice-daily ocular corticosteroid indicated for the treatment of inflammation and pain after ocular surgery.

A 4-week, randomized, double-masked study to evaluate efficacy of deproteinized calf blood extract eye drops versus sodium hyaluronate 0.3% eye drops in dry eye patients with ocular pain

BACKGROUND

To evaluate the clinical efficiency of the treatment of dry eye disease (DED) with ocular pain using deproteinized calf blood extract (DCBE) eye drops as compared to 0.3% sodium hyaluronate (SH) eye drops.

METHODS

This prospective, single-center, masked (double-blind), randomized controlled study included 53 patients divided into two groups: DCBE (n=22) and SH (n=31) group. The DCBE group received DCBE eye drops for 4 weeks, and the SH group received 0.3% SH eye drops for 4 weeks. Corneal fluorescein staining (CFS) scores, tear break up time (TBUT), Schirmer test and the ocular surface disease index (OSDI) scores were evaluated in all patients before treatment, 2 and 4 weeks post-treatment.

RESULTS

The DCBE group showed better improvement in the OSDI light sensitivity scores and ocular pain scores compared with the SH group (P<0.05). At 2 and 4 weeks post-treatment, the DCBE group and the SH group showed significant improvement in TBUT, Schirmer test, CFS, OSDI score, light sensitivity score and ocular pain score (P<0.05) compared with the data from before treatment.

CONCLUSIONS

This study indicates that DCBE eye drops can relieve ocular pain and light sensitivity in dry eye patients better than SH eye drops.

Ocular Neuropathic Pain: An Overview Focusing on Ocular Surface Pains

Objective

This paper reviews ocular pain with the main focus on ocular surface discomfort and dry eye pain. Anatomy, physiology, epidemiology, assessment, and treatment are discussed in this paper.

Methods

A PubMed search was conducted for studies published from 2000 to 2019 on the anatomy, pathophysiology, epidemiology, assessment, and treatment of ocular pain. Reviews, meta-analyses, and randomized clinical trials were included. Inclusion criteria focused on ocular surface discomfort, dry eye pain and neuropathic pain.

Results

A total of 112 articles were found through searches, 45 of which were selected and studied in this review.

Discussion

Pain in general can be acute or chronic. Acute pain is usually a physiologic response to a serious damage to the tissues and alleviates with pain relief treatments. Chronic pain is defined as the persistence of pain for more than three months. From another point of view, pain has been classified into either nociceptive or neuropathic. Nociceptive pain is a physiologic response to a noxious stimulus. Both central and peripheral nervous systems can be involved in the development of a neuropathic pain, which is characterized by positive or negative sensory signs, a pain perceived disproportionate to a noxious stimulus, and/or not responsive to analgesics. Chronic pain usually has a neuropathic component. Ocular surface pain is a well-known complaint after any corneal surgery. This is mainly due to abnormal regeneration of damaged corneal nerve endings and abnormal connections with adjacent nerve endings which produce spontaneous activity. Tear hyperosmolarity and the resultant ocular surface inflammation can also trigger voluntary activity of corneal nerve endings. Referral pain to the first and second division of the trigeminal nerve has been reported. Interference with vision and even sleep, which is out of proportion to the examination are among patients' complaints. All of these elements proposed the new concept of ocular neuropathic pain syndrome. The first step in conventional evaluation of ocular discomfort is search for tear insufficiency. Pathologies of lid and blinking as well as conjunctival irregularities should be addressed. Anti-inflammatory agents and, in resistant cases, systemic neuromodulators are shown to be helpful. Education on behavioral changes and reassurance are essential steps. Considering the neuropathic origin for the ocular pain, treatment modalities used for such pain in other parts of the body can be considered for this syndrome.

Differential diagnosis of acute ocular pain: Teleophthalmology during COVID-19 pandemic - A perspective

Ocular pain is a common complaint which forces the patient to seek immediate medical attention. It is the primeval first response of the body to any severe condition of the eye such as trauma, infections and inflammation. The pain can be due to conditions directly affecting the eye and ocular adnexa; or indirect which would manifest as referred pain from other organ structures such as the central nervous system. Paradoxically, there are several minor and non-sight threatening conditions, which also leads to ocular pain and does not merit urgent hospital visits. In this perspective, we intend to provide guidelines to the practising ophthalmologist for teleconsultation when a patient complains of pain with focus on how to differentiate the various diagnoses that can be managed over teleconsultation and those requiring emergency care in the clinic. These guidelines can decrease unnecessary hospital visits, which is the need of the hour in the pandemic era and also beyond. Patients who are under quarantine and those who are unable to travel would be benefitted, and at the same time, the burden of increased patient load in busy hospital systems can be reduced.

Glaucoma-associated pain results in mechanical sensitivity changes in dogs: A pilot study

PURPOSE

To explore the effects of chronic, uncontrolled glaucoma on pressure sensitivity in dogs before and after enucleation of the painful globe.

METHODS

Client-owned dogs undergoing enucleation for chronic glaucoma with no other sources of pain were enrolled. Normal dogs of similar breeds and skull morphology were enrolled as controls. Craniofacial ratio (CFR) and relative palpebral fissure width (RPFW) were assessed in all patients. Serial mechanical quantitative sensory testing (QST) was performed the day before surgery, and 14, 30, 60, and 120 days after surgery. QST consisted of electronic Von Frey (eVF), and blunt algometry (BA) performed above and below the nonglaucomatous eye, the metacarpus, and metatarsus. Cochet-Bonnet esthesiometry (CB) was also performed on the remaining eye.

RESULTS

Twelve dogs (6 per group) were included. Compared to baseline values, sensitivity tended to decrease over time (increased thresholds) in treatment dogs while it stayed constant or increased slightly in control dogs. The difference in change from baseline sensitivity between control and treatment groups was significant at day 120 using BA at supraorbital (P = .0153), infraorbital (P = .0209), and metacarpal sites (P = .007) and overall (P = .0470). This divergence was also significant using CB (P = .0470) on the opposite cornea. As patient CFR and RPFWV increased, both eVF (P = .005-.023) and BA (P = .004-.041) increased.

CONCLUSIONS

Sensitivity to mechanical stimuli decreased both locally and at remote sites in dogs following enucleation for painful chronic glaucoma. Cranial conformation is associated with differences in sensitivity.

Evaluation of Potential Pain Biomarkers in Saliva and Pain Perception After Corneal Advanced Surface Ablation Surgery

Purpose

To evaluate the evolution of a set of proposed pain biomarkers in the saliva of subjects following Advanced Surface Ablation (ASA), in order to determine their validity as objective pain measures.

Methods

A multicenter, prospective, and descriptive study was carried out to assess the variations between biomarkers and perceived pain. The Inclusion criteria were healthy subjects who underwent a bilateral, alcohol-assisted surface ablation with epithelial removal (ASA). Pain intensity before and after surgery was assessed by Visual Analog Scale (VAS) and the Numeric Pain Rating Scale (NPRS). Cortisol, sAA, sIgA, testosterone, and sTNFαRII were assayed at four-time points (V0, baseline; V1, pre-surgery; V2, 1 hr post-surgery, and V3, 72 hrs post-surgery). Comorbidities and Hospital Anxiety and Depression (HADS) questionnaires were administrated before and at 6 hrs after the surgery. All patients were treated with cold patches, topical steroids, topical cold antibiotics, and benzodiazepines after ASA surgery. A descriptive analysis of biomarkers and pain intensity evolution and the agreement between biomarkers and pain was performed.

Results

Concentration of sIgA and sTNFαRII post-surgery was significantly higher at each visit compared to baseline (p-value: 0.053, p-value: <0.001, respectively). Relations between VAS scale score and putative biomarker variations were not statistically significant except for the sIgA but only at visit 0 (p-value: 0.024). The HADS questionnaire showed anxiety scores between 0 and 7 in all patients before and at 6 hrs after surgery.

Conclusion

In this study, sIgA and sTNFαRII are the two potential biomarkers that present correlation with the VAS and these salivary substances showed acceptable levels of reproducibility in healthy subjects.

Dexamethasone 0.4mg Sustained-Release Intracanalicular Insert in the Management of Ocular Inflammation and Pain Following Ophthalmic Surgery: Design, Development and Place in Therapy

Inflammation and pain are two prevalent findings after ocular surgery. Corticosteroids are widely administrated as a core treatment to control post-surgical inflammation and pain. Improper patient adherence to post-operative eye drop regimens, limited bioavailability of topical eye drops, and the negative impact of preservatives used in many of these eye drops, has made a strong case for novel therapies in the treatment of post-operative pain and inflammation. This review of the literature will focus on the role of intracanalicular sustained-release dexamethasone (Dextenza, Ocular Therapeutix, Bedford, MA, USA) for the management of ocular inflammation and pain.

Pregabalin Failed to Prevent Dry Eye Symptoms after Laser-Assisted in Situ Keratomileusis (LASIK) in a Randomized Pilot Study

PURPOSE

Perioperative pregabalin administration has been found to reduce the risk of persistent pain after a variety of surgical procedures. However, this approach has not been tested in relation to eye surgery. As such, the purpose of this study was to evaluate whether perioperative pregabalin can reduce the presence of dry eye (DE) symptoms, including eye pain, six months after laser-assisted in situ keratomileusis (LASIK).

METHODS

Prospective, masked, randomized single-center pilot study. Patients were treated with either pregabalin (oral solution of pregabalin 150 mg twice daily, first dose prior to surgery, continued for a total of 28 doses over 14 days) or placebo solution. The primary outcome was dry eye symptoms as measured by the Dry Eye Questionnaire 5 (DEQ-5). Secondary outcome measures included pain-related eye symptoms.

RESULTS

In total, 43 individuals were enrolled in the study and randomized to pregabalin (n = 21) or placebo (n = 22). Of those, 42 individuals completed the final visit after six months of follow-up. Some differences were noted between the two groups at baseline, including a higher frequency of females in the pregabalin group. At 6-months, there were no significant differences in the percentage of patients with DE symptoms (DEQ5 ≥ 6, 57% vs. 33%, p = 0.14), DE symptom severity (DEQ5, 6.6 ± 5.0 vs. 4.5 ± 4.2, p = 0.14), ocular pain intensity (numerical rating scale, 1.10 ± 1.48 vs. 0.38 ± 0.97, p = 0.08), or neuropathic pain complaints (Neuropathic Pain Symptom Inventory-Eye, 2.81 ± 4.07 vs. 3.14 ± 5.85, p = 0.83) between the pregabalin and control groups. Ocular signs were likewise similar between the groups, and of note, did not correlate with DE symptoms. The strongest predictor of DE symptoms six months post-surgery was the presence of DE symptoms prior to surgery.

CONCLUSIONS

Perioperative pregabalin did not reduce the frequency or severity of DE symptoms at a six month follow-up after LASIK in this small pilot study.

Dry Eye Symptoms and Ocular Pain in Veterans with Glaucoma

Dry eye and glaucoma are two frequently encountered ocular conditions, which can lead to substantial morbidity and decreased quality of life. Patients on topical glaucoma medications are known to be at greater risk for ocular surface symptoms. Veterans seen in the eye clinics at the Miami Veterans Affairs Hospital from January to July 2016 completed surveys assessing dry eye and ocular pain symptoms, including the five item Dry Eye Questionnaire (DEQ5). A total of 62 patients with glaucoma completed the survey. Of those, 52 were on glaucoma medications at the time of the survey, with the majority requiring more than one medication to control intraocular pressure. The frequency of mild or greater dry eye symptoms (defined as DEQ5 >6) tended to increase with increasing medication burden, and patients on brimonidine were more likely to report a DEQ5 >6. Patients on three or more glaucoma medications were more likely to report symptoms of shooting pain, dryness, and itchiness. Patients using timolol were more likely to report throbbing and pain by light, while those on latanoprost reported stinging. Our data support an association between increasing number of glaucoma medications and worsening of dry eye symptoms. Patient and medication-associated symptoms can be used to tailor individual medication regimens.

The effect of cold tetracaine on the severity of burning sensation upon instillation

Purpose

Tetracaine is one of the most common eye drops that are used for analgesia in clinical practice. However, it causes ocular burning sensation when instilled. This study aimed to compare the effects of the cold and room temperature tetracaine on burning sensation.

Patients and methods

We conducted a prospective, double-blinded, randomized controlled trial at the ophthalmology outpatient clinic, Phramongkutklao Hospital during January 2016–February 2017. In this study, 424 consecutive patients (those with a history of keratopathy or neuropathy were excluded) who received dilated fundus examination were randomized to receive cold tetracaine (4°C) in one eye and room temperature tetracaine (22.5°C) in the other eye. Each patient was asked to answer the questionnaire on the severity of burning sensation using 100 mm visual analog scale.

Results

Patients reported less burning sensation on the eye that received cold tetracaine (visual analog scale 20.50±18.8 vs 22.70±20 mm; P=0.025). In the subgroup analysis, young patients (≤40 years old), female subjects, patients who received tetracaine for the first-time and those who had no previous ocular surgery reported more benefit from cold tetracaine. The subgroup of patients who had normal corneal sensation, identified by using a Cochet–Bonnet esthesiometer, also showed greater benefit from cold tetracaine compared to those with impaired corneal sensation.

Conclusion

Cold tetracaine caused less burning sensation than room temperature solution. Its benefit was greater in the subgroup of patients who reported more severe burning sensation. We recommend using cold tetracaine in routine practice, especially in those who are anticipated to have this common side effect.

Proinflammatory Markers, Chemokines, and Enkephalin in Patients Suffering from Dry Eye Disease

Dry eye symptoms are among the leading complaints in ophthalmology. Dry eye disease (DED) is associated with significant pain affecting quality of life. Cellular and molecular mechanisms underlying ocular pain associated with DED are not fully understood. In this study, we investigated the ocular surface of patients with DED using in vivo confocal microscopy (IVCM) to quantify corneal nerve density and its relation with corneal inflammation. Gene expression of the proinflammatory markers HLA-DR, IL-6, CXCL12, and CCL2 and the receptors CXCR4 and CCR2, as well as PENK (enkephalin precursor), was therefore quantified in conjunctival impression cytology specimens. Thirty-two patients with DED and 15 age-matched controls were included. Subbasal nerve density was significantly lower in DED patients compared to controls. IVCM analysis revealed that DED patients had a significantly higher corneal dendritic cell density compared to controls. Conjunctival impression cytology analysis revealed that HLA-DR, IL-6, CXCR4, and CCL2/CCR2 mRNA levels were significantly increased in DED patients compared to controls, whereas PENK mRNA levels were significantly decreased. Similar results were obtained in vitro on immortalized human conjunctiva-derived epithelial cells challenged with osmotic stress that mimics the DED condition. These results demonstrate that proinflammatory molecules and endogenous enkephalin have opposite gene regulation during DED.

Intraorbital ancient pilocytic astrocytoma of the optic nerve in neurofibromatosis type 1 patient presenting with sudden ocular pain

Optic nerve pilocytic astrocytoma is an uncommon but well-known entity; however, intraorbital ancient pilocytic astrocytoma of the optic nerve is extremely rarely reported. To our knowledge, this is the first detailed description regarding the intraorbital ancient pilocytic astrocytoma, reported in available English literature, to date. We presented an extremely unusual neurofibromatosis type 1 case of a 17-year-old male’s sudden ocular pain secondary to intraorbital pilocytic astrocytoma of the optic nerve with markedly cystic degeneration, fluid production, and hemorrhage, due to ancient and possibly ruptured glioma. Future prospective studies are required to validate the significance of intraorbital ancient pilocytic astrocytoma arising from the optic nerve and the close correlation with ruptured cystic degeneration and ocular pain, after collecting and investigating a larger number of its cases examined.

Noninvasive Electrical Stimulation for the Treatment of Chronic Ocular Pain and Photophobia

INTRODUCTION

"Dry eye" or "keratoconjunctivitis sicca" is a multifactorial disease estimated to have a worldwide prevalence of 5-33%. Conventional therapies targeting the ocular surface with artificial tears, anti-inflammatories, punctal closure, eyelid hygiene, and antibiotics do not provide relief in all patients, especially those with neuropathic-like ocular complaints (wind hyperalgesia and photophobia). We anticipated that ocular transcutaneous electrical nerve stimulation (TENS) would alleviate symptoms of ocular pain, photophobia, and dryness in these latter individuals.

METHODS

All individuals who received electrical stimulation between May 10, 2016 and April 6, 2017 for the treatment of chronic ocular pain at the oculofacial pain clinic of the Miami Veterans Administration Hospital were included in this retrospective review. All patients had symptoms of dryness along with other neuropathic-like symptoms (e.g., photophobia) and minimal signs of tear dysfunction. Ocular pain intensity, symptoms of dryness, and light sensitivity were compared pre-treatment and five min post-treatment via a two-tailed paired Student's t-test.

RESULTS

The use of TENS significantly reduced the mean pain intensity in both the right and left eyes five min after treatment compared to prior to treatment (p < 0.05, paired t-test). The use of TENS significantly decreased light sensitivity in both eyes (p < 0.05). The findings for symptoms of dryness, however, were equivocal with a significant decrease in the left eye but not the right (p < 0.05, paired t-test).

DISCUSSION

Our data indicate that TENS may similarly provide analgesia in patients with dry eye symptoms as it does for many other chronic pain conditions. Furthermore, the noted effect on symptoms of photophobia and dryness suggest that all may be linked by similar trigeminal-thalamic-cortical pathways. Prospective studies with electrical stimulation of dry eye are needed to further elucidate its benefit and mechanism of action.

Pain perception description after advanced surface ablation

Purpose

The objective of this study was to characterize the evolution of ocular pain after advanced surface ablation (ASA) to improve strategies in postoperative pain management.

Methods

This was a multicenter, prospective, descriptive, cohort study. The inclusion criteria were healthy individuals ≥18 years old receiving bilateral alcohol-assisted surface ablation with epithelial removal. Pain intensity was evaluated with the visual analog scale (VAS) and the numeric pain rating scale before and after surgery. Comorbidities (photophobia, burning, tearing, and foreign body sensation) and Hospital Anxiety and Depression (HAD) questionnaire were evaluated before and at 6 hours after surgery. Postoperative treatments included cold patch, topical cold antibiotics, topical steroids, and benzodiazepines.

Results

Thirty-two consecutive patients having similar profiles of postoperative pain evolution were included. At 0.5 hour after ASA, the pain score by VAS was 37±20 mm, and the maximum pain, 61±31 mm, occurred at 24 hours. Afterward, it decreased progressively until 72 hours after surgery (19±20 mm). Most patients (81%) scored >60 mm, and 44% required rescue medication. Among the comorbidities, all patients had photophobia and 84% had burning sensation. At 6 hours, the HAD score was 5.4±3.9, within the range of values considered as normal.

Conclusion

Postoperative acute ocular pain after ASA showed a characteristic evolution over time. Recognition of the pattern could be important for improving the acceptance of ASA and for improving strategies in pain management in the postoperative period.

Turning Down the Thermostat: Modulating the Endocannabinoid System in Ocular Inflammation and Pain

The endocannabinoid system (ECS) has emerged as an important regulator of both physiological and pathological processes. Notably, this endogenous system plays a key role in the modulation of pain and inflammation in a number of tissues. The components of the ECS, including endocannabinoids, their cognate enzymes and cannabinoid receptors, are localized in the eye, and evidence indicates that ECS modulation plays a role in ocular disease states. Of these diseases, ocular inflammation presents a significant medical problem, given that current clinical treatments can be ineffective or are associated with intolerable side-effects. Furthermore, a prominent comorbidity of ocular inflammation is pain, including neuropathic pain, for which therapeutic options remain limited. Recent evidence supports the use of drugs targeting the ECS for the treatment of ocular inflammation and pain in animal models; however, the potential for therapeutic use of cannabinoid drugs in the eye has not been thoroughly investigated at this time. This review will highlight evidence from experimental studies identifying components of the ocular ECS and discuss the functional role of the ECS during different ocular inflammatory disease states, including uveitis and corneal keratitis. Candidate ECS targeted therapies will be discussed, drawing on experimental results obtained from both ocular and non-ocular tissue(s), together with their potential application for the treatment of ocular inflammation and pain.

Pain and sickness behavior associated with corneal lesions in dairy calves

Infectious bovine keratoconjunctivitis (IBK) is a common corneal disease of calves that adversely affects animal welfare by causing pain and weight loss. Identifying behavioral indicators of pain and sickness in calves with IBK is necessary for designing studies that aim to identify effective means of pain mitigation. Consistent with principles of the 3Rs for animal use in research, data from a randomized blinded challenge study was used to identify and describe variation of behaviors that could serve as reliable indicators of pain and sickness in calves with corneal injuries. Behavioral observations were collected from 29 Holstein calves 8 to 12 weeks of age randomly allocated to one of three treatments: (1) corneal scarification only, (2) corneal scarification with inoculation with Moraxella bovoculi and (3) corneal scarification with inoculation with Moraxella bovis. Behavior was continuously observed between time 1230 - 1730 h on day -1 (baseline time period) and day 0 (scarification time period). Corneal scarification and inoculation occurred between 0800 - 1000 h on day 0. Frequency of head-directed behaviors (head shaking, head rubbing, head scratching) and durations of head rubbing, feeding, standing with head lifted, lying with head lifted and sleeping were compared between study days and groups. Following scarification, the frequency of head-directed behavior significantly increased (p = 0.0001), as did duration of head rubbing (p=0.02). There was no significant effect of trial, trial day, treatment or treatment-day interaction on other behaviors studied. Our study demonstrated that head-directed behavior, such as head shaking, rubbing and scratching, was associated with scarification of eyes using an IBK challenge model, but sickness behavior was not observed.

A practical approach to ocular pain for the non-ophthalmologist

Pain involving the eye has numerous etiologies and is a feared challenge of many clinicians. Between a fear of the patient losing vision and a lack of familiarity with the ophthalmic equipment necessary to diagnose the problem, working up eye pain can be a daunting task. While the ophthalmologist can be indispensable in challenging cases of eye pain, this article will help clarify the unique clinical features of each etiology that can help clinicians narrow down the differential and arrive at a diagnosis.

Trigeminal pathways for hypertonic saline- and light-evoked corneal reflexes

Cornea-evoked eyeblinks maintain tear film integrity on the ocular surface in response to dryness and protect the eye from real or potential damage. Eyelid movement following electrical stimulation has been well studied in humans and animals; however, the central neural pathways that mediate protective eyeblinks following natural nociceptive signals are less certain. The aim of this study was to assess the role of the trigeminal subnucleus interpolaris/caudalis (Vi/Vc) transition and subnucleus caudalis/upper cervical cord (Vc/C1) junction regions on orbicularis oculi electromyographic (OOemg) activity evoked by ocular surface application of hypertonic saline or exposure to bright light in urethane anesthetized male rats. The Vi/Vc and Vc/C1 regions are the main sites of termination for trigeminal afferent nerves that supply the ocular surface, while hypertonic saline (saline=0.15-5M) and bright light (light=5k-20klux) selectively activate ocular surface and intraocular trigeminal nerves, respectively, and excite second-order neurons at the Vi/Vc and Vc/C1 regions. Integrated OOemg activity, ipsilateral to the applied stimulus, increased with greater stimulus intensities for both modalities. Lidocaine applied to the ocular surface inhibited OOemg responses to hypertonic saline, but did not alter the response to light. Lidocaine injected into the trigeminal ganglion blocked completely the OOemg responses to hypertonic saline and light indicating a trigeminal afferent origin. Synaptic blockade by cobalt chloride of the Vi/Vc or Vc/C1 region greatly reduced OOemg responses to hypertonic saline and bright light. These data indicate that OOemg activity evoked by natural stimuli known to cause irritation or discomfort in humans depends on a relay in both the Vi/Vc transition and Vc/C1 junction regions.

Posterior hypothalamic modulation of ocular-responsive trigeminal subnucleus caudalis neurons is mediated by Orexin-A and Orexin1 receptors

Orexin-A (OxA) is synthesized in posterior and lateral regions of the hypothalamus and contributes to homeostatic regulation of body functions including pain modulation. To determine if orexinergic mechanisms contribute to posterior hypothalamus (PH)-induced modulation of ocular input to subnucleus caudalis/upper cervical (Vc/C1) neurons, the orexin-1 receptor antagonist SB334867 was applied to the dorsal brainstem surface prior to PH disinhibition, by bicuculline methiodide, in male rats under isoflurane anesthesia. Ocular input to Vc/C1 units by bright light or hypertonic saline was markedly reduced by PH disinhibition and reversed completely by local Vc/C1 application of SB334867. OxA applied to the Vc/C1 surface mimicked the effects of PH disinhibition in a dose-dependent manner. OxA-induced inhibition was prevented by co-application of SB334867, but not by the orexin-2 receptor antagonist TCS Ox2 29. PH disinhibition and local OxA application also reduced the high threshold convergent cutaneous receptive field area of ocular units, suggesting widespread effects on somatic input to Vc/C1 ocular units. Vc/C1 application of OxA or SB334867 alone did not affect the background discharge of ocular units and suggested that the PH-OxA influence on ocular unit activity was not tonically active. Vc/C1 application of OxA or SB334867 alone also did not alter mean arterial pressure, whereas PH disinhibition evoked prompt and sustained increases. These results suggest that stimulus-evoked increases in PH outflow acts through OxA and orexin-1 receptors to alter the encoding properties of trigeminal brainstem neurons responsive to input from the ocular surface and deep tissues of the eye.

Nodular posterior scleritis mimicking choroidal metastasis: a report of two cases

Posterior scleritis is a rare underdiagnosed condition that can potentially cause blindness. Its varied presentations lead to delayed or incorrect treatment. We present here the cases of two patients with nodular posterior scleritis mimicking a choroidal metastasis. Two female patients presented with a sudden unilateral visual loss associated with ocular pain. Fundus examination revealed temporomacular choroidal masses with exudative detachments that, due to angiographic presentation, were suggestive of choroidal metastasis. Systemic examinations were unremarkable. In the two cases, a local or general anti-inflammatory treatment led to the complete recovery of the lesions, which were, thus, considered nodular posterior scleritis. The diagnosis of nodular posterior scleritis has to be evoked in all patients presenting with a choroidal mass in fundus examination. It represents the principal curable differential diagnosis of malignant choroidal tumor.