Modification of the Neuropathic Pain Symptom Inventory for use in eye pain (NPSI-Eye)

Impact of botulinum toxin type A on ocular pain with neuropathic features

PURPOSE

To investigate the impact of botulinum toxin type A (BoNT-A) on neuropathic/nociplastic ocular pain (NOP) and identify predictors of patient outcomes.

METHODS

A retrospective study of individuals with NOP symptoms (light sensitivity, wind/air sensitivity, persistent pain despite dry eye treatment) who received ≥1 BoNT-A injection. Primary outcome measures included if (responders vs. non-responders) and to what degree (none vs. mild vs. moderate vs. marked) individuals experienced pain improvement 4-6 weeks post-injection. Demographics and clinical exam information was compared between the groups.

RESULTS

27 individuals received BoNT-A for NOP symptoms. 74 % (n = 20) reported an improvement in pain and were classified as responders. Among responders, the degree of benefit varied, with 25 % reporting mild, 45 % moderate, and 30 % marked pain improvement. Improvements in light sensitivity (37 %), wind/air sensitivity (33 %), and quality of life (QoL) (59 %) were reported by fewer individuals. 80 % of responders and 0 % of non-responders reported QoL improvements afer BoNT-A. In a multivariable model that examined predictors of response (none to marked, 0-3), the presence of fibromyalgia (FM) (β = 0.50; p = 0.004) portended a better response, while shooting pain (β = -0.47; p = 0.007) portended a worse response to BoNT-A, (full model r2 = 0.53; p < 0.001). Degree of pain improvement significantly correlated with improvements in light sensitivity, wind/air sensitivity, and QoL (ρ range: 0.42-0.63; p < 0.05).

CONCLUSION

After BoNT-A, most individuals reported improved ocular pain and QoL, while fewer noted improved light and wind/air sensitivity. Some systemic and ocular factors predicted treatment response and may thus guide treatment.

CORONIS symposium 2023: Scientific and clinical frontiers in ocular surface innervation

The 5th CORONIS Symposium, held during the 2023 Congress of the European Association for Vision and Eye Research (EVER), highlighted the growing importance of ocular surface innervation in eye surface disorders. This article summarises the insights and perspectives shared during the symposium, which focused on the clinical relevance of ocular surface innervation, as well as on the development of innovative diagnostic and therapeutic approaches for ocular surface pathologies linked to disturbed sensory innervation. Through robust interdisciplinary collaborations, these developments hold great potential to improve patient outcomes and quality of life.

Is Meibomian Gland Dysfunction One Disease? Heterogeneity Among Phenotypes

PURPOSE

The purpose of this study was to examine ocular surface symptoms, tear metrics, and tear cytokines by Meibomian gland dysfunction (MGD) features.

METHODS

Symptom questionnaires and an ocular surface evaluation were performed on 40 individuals with varied MGD signs (Meibomian gland [MG] plugging, eyelid vascularity, meibum quality, and MG dropout). Tear proteins were extracted off Schirmer strips and analyzed for 23 human inflammation-related proteins. Statistical analysis was performed to examine associations between dry eye metrics inflammatory proteins and MGD features.

RESULTS

The study involved 40 South Florida veterans with a mean age of 61 ± 13 years; most individuals were male (95%), White (31%), and non-Hispanic (85%). MGD features differentially related to dry eye signs. Eyelid vascularity, meibum quality, and MG dropout, but not MG plugging, correlated with higher corneal staining and lower tear production. MGD features also differentially related to tear cytokines. Eyelid vascularity most closely related to inflammation with significant correlations for interferon-gamma-γ (r = 0.36, P = 0.02), interleukin-4 (IL-4) (r = 0.43, P = 0.006), IL-17A (r = 0.42, P = 0.007), matrix metalloproteinase-2 (r = 0.39, P = 0.01), C-X-C motif chemokine ligand 5 (Regulated upon Activation, Normal T-Cell Expressed and presumably Secreted [RANTES]) (r = 0.32, P = 0.04), and tumor necrosis factor α (r = 0.36, P = 0.02). The other 3 MGD signs were less related to inflammation. Multivariable models revealed IL-4 to be most closely related to eyelid vascularity (standardized β = 0.39, P < 0.0001).

CONCLUSIONS

Eyelid vascularity was the MGD sign most closely related to inflammatory cytokines, suggesting that different MGD features may be driven by different pathophysiological mechanisms.

Corneal neuropathic pain: a review to inform clinical practice

Corneal neuropathic pain (CNP) is a poorly defined disease entity characterised by an aberrant pain response to normally non-painful stimuli and categorised into having peripheral and central mechanisms, with the former responding to instillation of topical anaesthetic. CNP is a challenging condition to diagnose due to numerous aetiologies, an absence of clinical signs and ancillary tests (in vivo confocal microscopy and esthesiometry), lacking the ability to confirm the diagnosis and having limited availability. Symptomatology maybe mirrored by severe and chronic forms of dry eye disease (DED), often leading to misdiagnosis and inadequate treatment. In practice, patients with suspected CNP can be assessed with questionnaires to elicit symptoms. A thorough ocular assessment is also performed to exclude any co-existent ocular conditions. A medical and mental health history should be sought due to associations with autoimmune disease, chronic pain syndromes, anxiety and depression. Management begins with communicating to the patient the nature of their condition. Ophthalmologists can prescribe topical therapies such as autologous serum eyedrops to optimise the ocular surface and promote neural regeneration. However, a multi-disciplinary treatment approach is often required, including mental health support, particularly when there are central mechanisms. General practitioners, pain specialists, neurologists and psychologists may be needed to assist with oral and behavioural therapies. Less data is available to support the safety and efficacy of adjuvant and surgical therapies and the long-term natural history remains to be determined. Hence clinical trials and registry studies are urgently needed to fill these data gaps with the aim to improve patient care.

Prospective cohort study investigating frequency and risk factors for acute pain 1 day after refractive surgery

BACKGROUND/AIMS

To examine demographic and clinical factors associated with ocular pain 1 day after refractive surgery.

METHODS

Prospective study of individuals undergoing refractive surgery. Participants rated their ocular pain on a 0-10 numerical rating scale (NRS) presurgery and 1 day after surgery. Presurgery, participants completed questionnaires on demographics, comorbidities, medications and dry eye and ocular pain symptoms; and an anaesthetised Schirmer test was performed. Acute ocular pain 1 day after surgery was defined as an NRS score of worst pain since surgery ≥3 and this group was compared with individuals with NRS scores<3.

RESULTS

251 individuals underwent refractive surgery (89% laser-assisted in situ keratomileusis, n=222; 11% PRK, n=29). Mean age was 35±8 years (range 19 to 60); 60% (n=150) self-identified as female, 80% (n=203) as White, and 36% (n=89) as Hispanic. Thirteen (5%) individuals reported ocular pain (NRS ≥3) prior to surgery and 67% (n=168) reported ocular pain 1 day after surgery (nine individuals had pain at both time points). Factors that were associated with pain 1 day after surgery included Hispanic ethnicity (adjusted relative risk (aRR) 1.42, 95% CI 1.21 to 1.68, p<0.001) and the presence of eye pain presurgery (aRR 1.10, 95% CI 1.02 to 1.18, p=0.02).

CONCLUSION

A majority of individuals report moderate or greater pain within 24 hours of refractive surgery. Hispanic ethnicity and eye pain prior to surgery were associated with self-reported acute postsurgical pain.

Rethinking Sjögren Beyond Inflammation: Considering the Role of Nerves in Driving Disease Manifestations

ABSTRACT

Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease characterized by destruction of mucosal glands resulting in dry eye and dry mouth. Ocular presentations can be heterogenous in SS with corneal nerves abnormalities that are structural, functional, or both. Some individuals present with corneal hyposensitivity, with a phenotype of decreased tear production and epithelial disruption. Others present with corneal hypersensitivity, with a phenotype of neuropathic pain including light sensitivity and pain out of proportion to signs of tear dysfunction. A similar correlate can be found outside the eye, with dry mouth predominating in some individuals while pain conditions predominate in others. Understanding how nerve status affects SS phenotype is an important first step to improving disease management by targeting nerve abnormalities, as well as inflammation.

Associations between Corneal Nerve Structure and Function in a Veteran Population

Background: We evaluate the relationship between corneal nerve structure and function in a veteran population. Methods: 83 veterans (mean age: 55 ± 5 years) seen at the Miami Veterans Affairs (VA) eye clinic were included in this study. Each individual filled out questionnaires to evaluate ocular symptoms (5-Item Dry Eye Questionnaire, DEQ5; Ocular Surface Disease Index, OSDI) and ocular pain (Numerical Rating Scale, NRS; Neuropathic Pain Symptom Inventory modified for the Eye, NPSI-Eye). The individuals also underwent an ocular surface examination that captured functional nerve tests including corneal sensation, corneal staining, and the Schirmer test for tear production. Corneal sub-basal nerve analysis was conducted using in vivo confocal microscopy (IVCM) images with corneal nerve density, length, area, width, and fractal dimension captured. IVCM and functional corneal metrics from the right eye were examined using correlational and linear regression analysis. Results: Most corneal structural metrics were not related to functional metrics, except for weak correlations between various IVCM metrics and tear production. In addition, corneal nerve fiber area was positively related to corneal sensation (r = 0.3, p = 0.01). On linear regression analyses, only the corneal fractal dimension remained significantly related to tear production (β = -0.26, p = 0.02) and only the corneal nerve fiber area remained significantly related to corneal sensation (β = 0.3, p = 0.01). Conclusions: Most corneal nerve structural metrics did not relate to functional metrics in our veteran population, apart from a few weak correlations between structural metrics and tear production. This suggests that using corneal nerve anatomy alone may be insufficient for predicting corneal function.

Role of Polyunsaturated Fatty Acids (PUFAs) and Eicosanoids on Dry Eye Symptoms and Signs

Polyunsaturated fatty acids (PUFAs) generate pro- and anti-inflammatory eicosanoids via three different metabolic pathways. This study profiled tear PUFAs and their metabolites and examined the relationships with dry eye (DE) and meibomian gland dysfunction (MGD) symptoms and signs. A total of 40 individuals with normal eyelids and corneal anatomies were prospectively recruited. The symptoms and signs of DE and MGD were assessed, and tear samples (from the right eye) were analyzed by mass spectrometry. Mann-Whitney U tests assessed differences between medians; Spearman tests assessed correlations between continuous variables; and linear regression models assessed the impact of potential confounders. The median age was 63 years; 95% were male; 30% were White; and 85% were non-Hispanic. The symptoms of DE/MGD were not correlated with tear PUFAs and eicosanoids. DE signs (i.e., tear break-up time (TBUT) and Schirmer's) negatively correlated with anti-inflammatory eicosanoids (11,12-dihydroxyeicosatrienoic acid (11,12 DHET) and 14,15-dihydroxyicosatrienoic acid (14,15, DHET)). Corneal staining positively correlated with the anti-inflammatory PUFA, docosahexaenoic acid (DHA). MGD signs significantly associated with the pro-inflammatory eicosanoid 15-hydroxyeicosatetranoic acid (15-HETE) and DHA. Several relationships remained significant when potential confounders were considered. DE/MGD signs relate more to tear PUFAs and eicosanoids than symptoms. Understanding the impact of PUFA-related metabolic pathways in DE/MGD may provide targets for new therapeutic interventions.

Analysis of Clinical Characteristics and Neuropeptides in Patients with Dry Eye with and without Chronic Ocular Pain after FS-LASIK

INTRODUCTION

Chronic ocular pain, particularly prevalent in patients with dry eye disease and post-femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) surgery, presents with unclear clinical characteristics and an undefined pathogenesis. In this study, we aimed to compare clinical characteristics and tear neuropeptide concentrations in patients with dry eye disease (DED) with and without chronic ocular pain following FS-LASIK, and investigate correlations between ocular pain, clinical characteristics, and tear neuropeptide levels.

METHODS

Thirty-eight post-FS-LASIK patients with DED were assigned to two groups: those with chronic ocular pain and those without chronic ocular pain. Dry eye, ocular pain, and mental health-related parameters were evaluated using specific questionnaires and tests. The morphology of corneal nerves and dendritic cells (DCs) was evaluated by in vivo confocal microscopy. Function of corneal innervation was evaluated by corneal sensitivity. Concentrations of tear cytokines (interleukin [IL]-6, IL-23, IL-17A, and interferon-γ) and neuropeptides (α-melanocyte-stimulating hormone, neurotensin, β-endorphin, oxytocin, and substance P [SP]) were measured using the Luminex assay.

RESULTS

Most patients with chronic ocular pain experienced mild to moderate pain; the most common types included stimulated pain (provoked by wind and light), burning pain, and pressure sensation. More severe dry eye (P < 0.001), anxiety symptoms (P = 0.026), lower Schirmer I test values (P = 0.035), lower corneal nerve density (P = 0.043), and more activated DCs (P = 0.041) were observed in patients with ocular pain. Tear concentrations of SP and oxytocin were significantly higher in patients with ocular pain (P = 0.001, P = 0.021, respectively). Furthermore, significant correlations were observed among ocular pain severity, SP, and anxiety levels.

CONCLUSIONS

Patients with DED after FS-LASIK who have chronic ocular pain show more severe ocular and psychological discomfort and higher tear levels of neuropeptides. Furthermore, ocular pain severity is correlated with tear SP levels.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05600985.

How does ocular graft-versus-host disease fit under the dry eye umbrella? A review

Graft-versus-host disease (GVHD) is a systemic disease that can affect multiple organs as a consequence of an allogeneic haematopoietic stem cell transplant. One organ system that is often affected in GVHD is the eyes. Ocular GVHD (oGVHD) may involve various structures within the eye including the lacrimal glands, eyelids, conjunctiva, cornea, and nasolacrimal ducts, and is a source of morbidity in patients with GVHD. Common presenting features of GVHD overlap with dry eye disease (DED), including decreased tear production, epithelial disruption, and Meibomian gland dysfunction (MGD). In this review, we aim to compare oGVHD and DED to better understand the similarities and differences between the conditions, with a focus on pathophysiology, risk factors, clinical features, and treatments.

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.

Genome Wide Association Study of Neuropathic Ocular Pain

Purpose

To conduct a genome-wide association study (GWAS) of individuals with neuropathic ocular pain (NOP) symptoms to identify genomic variants that may predispose to NOP development.

Design

Prospective study of individuals with NOP.

Participants

Three hundred twenty-nine patients recruited from the Miami Veterans Affairs eye clinic.

Methods

The Neuropathic Pain Symptom Inventory modified for the eye (NPSI-Eye) was completed to calculate a NPSI-Eye-Sub-Score (summed ratings of burning and wind sensitivity) as an indicator of NOP severity. A GWAS was performed for the NPSI-Eye-Sub-Score with a significance threshold of P < 5 × 10-8. A gene-based analysis was performed using the multimarker analysis of genomic annotation software (in the functional mapping and annotation of GWAS online platform). The 13 865 778 single nucleotide polymorphisms (SNPs) from our GWAS analysis were mapped to 10 834 protein coding genes, and significant genes were run through gene set enrichment analysis.

Main Outcome Measures

Identification of SNPs and protein products that may be associated with the development of NOP.

Results

One hundred seventy-one SNPs reached a threshold of P < 10-5, of which 10 SNPs reached the suggestive level of significance of P < 5 × 10-7 and 1 SNP met our genome-wide significance threshold of P < 5 × 10-8. This lead SNP, rs140293404 (P = 1.23 × 10-8), is an intronic variant found within gene ENSG00000287251 coding for transcript ENST00000662732.1. Rs140293404 is in linkage disequilibrium with exon variant rs7926353 (r2 > 0.8) within ENSG00000279046 coding for transcript ENST00000624288.1. The most significant genes from gene-based tests were matrix metalloproteinase-19 (MMP19) (P = 1.12 × 10-5), zinc finger RNA-binding motif and serine/arginine rich-1 (ZRSR1) (P = 1.48 × 10-4), CTC-487M23.8 (P = 1.79 × 10-4), receptor expression-enhancing protein-5 (REEP5) (P = 2.36 × 10-4), and signal recognition particle-19 (SRP19) (P = 2.56 × 10-4). From gene set enrichment analysis, the sensory perception (false discovery rate = 6.57 × 10-3) and olfactory signaling (false discovery rate = 1.63 × 10-2) pathways were enriched with the most significant genes.

Conclusions

Our GWAS revealed genes with protein products that may impact sensory perception, lending biological plausibility to a role for SNPs identified by our GWAS in the development of NOP. A better understanding of the biological relevance of these genes and pathways in the pathophysiology associated with NOP may facilitate future novel mechanism-based treatments.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Coexistence of neuropathic corneal pain, corneal nerve abnormalities, depression, and low quality of life

PURPOSE

To evaluate the quality of life (QoL), mental health conditions and corneal morphology in neuropathic corneal pain (NCP) subjects without a significant ocular surface disease.

METHODS

A composite questionnaire was administered to 228 consecutive subjects, assessing the pain intensity, duration, and quality using a modified version of the Self-Administered Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and Pain Detect (PD) questionnaires. Subjects diagnosed with possible central NCP and two sub-groups of patients diagnosed with peripheral ocular pain completed an additional battery of mental health questionnaires and were examined by In Vivo Confocal Microscopy (IVCM).

RESULTS

Of the 76 subjects that reported chronic ocular pain (duration >1 month), 53 were classified with probable NCP. Nine subjects without signs that justify the pain and non-responding to topical anaesthesia, were considered affected by central NCP. In these patients, a significant negative correlation was found between the presence pain and the mental component of the QoL (R2 = 0.733), and a positive correlation between the severity of pain the presence post-traumatic stress disorder (R2 = 0.83) and depression (R2 = 0.93). Although neuromas and sprouting had higher frequency in the central NCP group compared the control groups, these differences was not statistically different.

CONCLUSIONS

The assessment of ocular pain characteristics using multiple questionnaires and IVCM may help to recognize differences between nociceptive and neuropathic pain. An association between pain intensity and mental health condition may guide the therapeutical choices.

Efficacy of topical 0.05% cyclosporine A and 0.1% sodium hyaluronate in post-refractive surgery chronic dry eye patients with ocular pain

BACKGROUND

The management of post-refractive surgery dry eye disease (DED) can be challenging in clinical practice, and patients usually show an incomplete response to traditional artificial tears, especially when it is complicated with ocular pain. Therefore, we aim to investigate the efficacy of combined topical 0.05% cyclosporine A and 0.1% sodium hyaluronate treatment in post-refractive surgery DED patients with ocular pain unresponsive to traditional artificial tears.

METHODS

We enrolled 30 patients with post-refractive surgery DED with ocular pain who were unresponsive to traditional artificial tears. Topical 0.05% cyclosporine A and 0.1% sodium hyaluronate were used for 3 months. They were evaluated at baseline and 1 and 3 months for dry eye and ocular pain symptoms and objective parameters, including Numerical Rating Scale (NRS), Neuropathic Pain Symptom Inventory modified for the Eye (NPSI-Eye), tear break-up time (TBUT), Schirmer I test (SIt), corneal fluorescein staining (CFS), corneal sensitivity, and corneal nerve morphology. In addition, tear levels of inflammatory cytokines and neuropeptides were measured using the Luminex assay.

RESULTS

After 3 months of treatment, patients showed a statistically significant improvement in the ocular surface disease index (OSDI), TBUT, SIt, CFS, and corneal sensitivity (all P < 0.01) using linear mixed models. As for ocular pain parameters, the NRS and NPSI-Eye scores were significantly reduced (both P < 0.05) and positively correlated with the OSDI and CFS scores. Additionally, tear IL-1β, IL-6, and TNF-α levels were improved better than pre-treatment (P = 0.01, 0.03, 0.02, respectively).

CONCLUSION

In patients with post-refractive surgery DED with ocular pain, combined topical 0.05% cyclosporine A and 0.1% sodium hyaluronate treatment improved tear film stability, dry eye discomfort, and ocular pain, effectively controlling ocular inflammation.

TRIAL REGISTRATION

Registration number: NCT06043908.

Associations between dry eye disease and sleep quality: a cross-sectional analysis

BACKGROUND/AIMS

To investigate relationships between dry eye (DE) disease and sleep quality, with a focus on which aspects of sleep most closely relate to DE.

METHODS

141 veterans (mean age: 56±5) seen at the Miami Veterans Affairs eye clinic filled out questionnaires to quantify the severity of DE symptoms (5-Item Dry Eye Questionnaire (DEQ-5) and Ocular Surface Disease Index (OSDI)) and ocular pain (Numerical Rating Scale (NRS) and Neuropathic Pain Symptom Inventory modified for the Eye (NPSI-E)). All individuals also underwent an ocular surface examination. Aspects of sleep quality were assessed using the Pittsburgh Sleep Quality Index (PSQI). DE metrics were examined by PSQI scores and subscores.

RESULTS

Most participants (76%) reported mild or greater DE symptoms (DEQ-5 ≥6). Overall, ocular symptoms were more related to sleep metrics than signs. The strongest DE symptom association was between the OSDI and sleep disturbances (PSQI subscore 5, r=0.49, p<0.0005). For DE signs, ocular surface inflammation and meibum quality were related to subjective sleep quality (PSQI subscore 1, r=0.29, p=0.03, for both). On linear regression analyses, most ocular symptom questionnaires remained associated with sleep disturbances (PSQI subscore 5: NRS (r=0.52, p<0.0005), DEQ-5 (r=0.36, p<0.0005), and OSDI (r=0.31, p<0.0005)). For DE signs, ocular surface inflammation and meibum quality remained associated with subjective sleep quality (r=0.26, p=0.01; r=0.46, p<0.0005, respectively).

CONCLUSION

DE symptom and ocular pain intensity were closely related to sleep metrics, most strongly to sleep disturbances. Relationships were weaker for DE signs, with subjective sleep quality relating to inflammation and meibum quality.

Dry eye symptoms and signs in United States Gulf War era veterans with myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

To examine ocular symptoms and signs of veterans with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) diagnosis, ME/CFS symptoms, and controls.

METHODS

This was a prospective, cross-sectional study of 124 South Florida veterans in active duty during the Gulf War era. Participants were recruited at an ophthalmology clinic at the Miami Veterans Affairs Hospital and evaluated for a diagnosis of ME/CFS, or symptoms of ME/CFS (intermediate fatigue, IF) using the Canadian Consensus criteria. Ocular symptoms were assessed via standardised questionnaires and signs via comprehensive slit lamp examination. Inflammatory blood markers were analysed and compared across groups.

RESULTS

Mean age was 55.1 ± 4.7 years, 88.7% identified as male, 58.1% as White, and 39.5% as Hispanic. Ocular symptoms were more severe in the ME/CFS (n = 32) and IF (n = 48) groups compared to controls (n = 44) across dry eye (DE; Ocular Surface Disease Index [OSDI]: 48.9 ± 22.3 vs. 38.8 ± 23.3 vs. 19.1 ± 17.8, p < 0.001; 5 item Dry Eye Questionnaire [DEQ-5]: 10.8 ± 3.9 vs. 10.0 ± 4.6 vs. 6.6 ± 4.2, p < 0.001) and pain-specific questionnaires (Numerical Rating Scale 1-10 [NRS] right now: 2.4 ± 2.8 vs. 2.4 ± 2.9 vs 0.9 ± 1.5; p = 0.007; Neuropathic Pain Symptom Inventory modified for the Eye [NPSI-E]: 23.0 ± 18.6 vs. 19.8 ± 19.1 vs. 6.5 ± 9.0, p < 0.001). Ocular surface parameters and blood markers of inflammation were generally similar across groups.

CONCLUSION

Individuals with ME/CFS report increased ocular pain but similar DE signs, suggesting that mechanisms beyond the ocular surface contribute to symptoms.

Identification of Subtypes of Dry Eye Disease, Including a Candidate Corneal Neuropathic Pain Subtype Through the Use of a Latent Class Analysis

PURPOSE

In the absence of a gold-standard diagnostic test for different subtypes of dry eye disease (DED), we aimed to identify latent subtypes of DED within a well-characterized cohort.

DESIGN

This is a cross-sectional study of participants enrolled in the Sjögren International Collaborative Clinical Alliance (SICCA).

METHODS

A latent class analysis was applied to different dry eye-related signs/tests and symptoms of ocular pain (particularly those that aligned with corneal neuropathic pain) giving relative specificities and sensitivities of each diagnostic test or symptom in the SICCA population.

RESULTS

Four subtypes of DED were identified with putative designations including normal, asymptomatic dry eye, symptomatic dry eye, and corneal neuropathic pain.

CONCLUSIONS

More specific classification criteria are needed for DED. Latent class analysis applied to the signs and symptoms captured in the SICCA cohort may allow for the development and refinement of classification criteria for specific subtypes of dry eye.

Individuals with Diabetes Mellitus Have a Dry Eye Phenotype Driven by Low Symptom Burden and Anatomic Abnormalities

Dry eye disease is an umbrella term that includes a variety of symptoms and signs. A link between diabetes mellitus and dry eye disease exists, but the associated phenotype needs further examination. Thus, our aim was to determine how diabetes mellitus relates to the dry eye disease phenotype. A prospective, cross-sectional study was conducted at the Miami Veteran Affairs Medical Center ophthalmology clinic between October 2013 and September 2019. Participants included a volunteer sample of 366 South Florida veterans with one or more symptoms or signs of dry eye disease [Dry Eye Questionnaire-5 ≥ 6 OR tear break-up time ≤ 5 OR Schirmer's test score ≤ 5 OR corneal fluorescein staining ≥ 2]. Participants were divided into three groups: (1) individuals without diabetes mellitus (controls); (2) individuals with diabetes mellitus but without end-organ complications; and (3) individuals with diabetes mellitus and end-organ complications. Dry eye metrics were compared across groups. The main outcome measures included ocular symptom questionnaires [e.g., 5-item Dry Eye Questionnaire, Ocular Surface Disease Index, and ocular pain assessment] and clinical parameters obtained from an ocular surface evaluation. A total of 366 individuals were included (mean age 59 ± 6 years; 89% males; 39% White; 11% diabetes mellitus and end-organ complications; 15% diabetes mellitus but without end-organ complications). Individuals with diabetes mellitus and end-organ complications had lower symptom scores on the dry eye disease and pain-specific questionnaires compared to individuals with diabetes mellitus but without end-organ complications and controls (Ocular Surface Disease Index: 42.1 ± 24.5 vs. 38.9 ± 25.1 vs. 23.6 ± 16.2; p < 0.001; numerical rating scale of ocular pain intensity: 4.9 ± 3.2 vs. 4.3 ± 2.7 vs. 3.5 ± 2.7; p = 0.02). Eyelid laxity was also more severe in the group with diabetes mellitus and end-organ complications (0.69 ± 0.64 vs. 0.73 ± 0.72 vs. 1.08 ± 0.77; p = 0.004) compared to the two other groups. The diabetic dry eye disease phenotype is driven by signs more so than by symptoms, with anatomic eyelid abnormalities being more frequent in individuals with diabetes mellitus and end-organ complications. Given this, ocular surface abnormalities in individuals with DM may be missed if screened by symptoms alone. As such, individuals with DM should undergo a slit lamp examination for signs of ocular surface disease, including anatomic abnormalities.

Evaluation of ocular neuropathic pain

AIM

To identify and assess the quality of current validated questionnaires that could be used to evaluate ocular neuropathic pain and its associated aetiologies.

METHODS

A literature search was performed on MEDLINE, PubMed, EMBASE, PsycINFO and The Cochrane Library. Articles evaluating questionnaires for ocular neuropathic pain and its associated aetiologies were included. Data on psychometric properties, validity, and reliability of the questionnaires was extracted and analysed using a set of quality criteria. Clinical and demographical associations with ocular neuropathic pain were also reviewed.

RESULTS

The search generated 1738 results with 61 publications meeting the inclusion criteria. The 61 publications covered 28 questionnaires including 3 ocular pain, 12 dry eye disease, 2 blepharitis, 2 refractive surgery, 3 contact lens wear, 3 Sjogren's Syndrome, and 3 that were non-disease-specific. Only 57 publications provided enough data on psychometric properties and validity of the questionnaire to be included for quality assessment. The Contact Lens Discomfort Index (CLDI) had the highest rated psychometric properties, whereas the English version of the Ocular Comfort Index (OCI) provided the most data on psychometric properties (9 out of 10 criteria). Most ocular pain and disease-specific questionnaires contained appropriate items to assess ocular pain in specific populations. However, non-disease-specific ophthalmic questionnaires demonstrated poor reliability and validity when evaluating ocular pain.

CONCLUSION

Ocular pain questionnaires can potentially diagnose ocular neuropathic pain. Disease-specific questionnaires were limited to their target populations, and non-disease-specific ophthalmic questionnaires were unreliable. Further studies are required to determine the most appropriate questionnaire to evaluate ocular neuropathic pain.

Ocular surface itch and pain: key differences and similarities between the two sensations

PURPOSE OF REVIEW

To review the pathophysiology and treatment of ocular itch and pain, encompassing nociceptive and neuropathic categories.

RECENT FINDINGS

Ocular itch and pain are sensations that arise from activation of ocular surface polymodal nerves. Nociceptive itch, commonly comorbid with ocular pain complaints, is mainly driven by a histamine-mediated type 1 hypersensitivity reaction. Beyond topical therapy, novel drug delivery systems are being explored to improve ocular residence time of nonsteroidal anti-inflammatory drugs (NSAIDs) and antihistamines. Nociceptive ocular pain can be driven by a variety of factors. Treatment focuses on addressing the causative sources of pain. Neuropathic ocular itch and pain are driven by nerve damage and dysfunction and as such, topical and oral neuromodulation have been explored as treatments. Oral neuromodulators include alpha 2 delta ligands, tricyclic antidepressants (TCAs), and low dose naltrexone. Novel therapies are being evaluated for both modalities such as difelikefalin (κ-opioid receptor agonist) for neuropathic itch and libvatrep (transient receptor potential vanilloid 1 antagonist) for neuropathic pain.

SUMMARY

Both ocular itch and pain can be driven by nociceptive and/or neuropathic mechanisms. Identifying contributors to abnormal ocular sensations is vital for precise medical care. Novel therapeutics for these conditions aim to improve patient outcomes and quality of life.

The environment and dry eye-manifestations, mechanisms, and more

Dry eye disease (DED) is a multifactorial condition that often presents with chronic symptoms of pain (that can be characterized as "dryness," "burning," and "irritation," to name a few) and/or fluctuating or poor-quality vision. Given its multifactorial nature, several pathophysiologic mechanisms have been identified that can underlie symptoms, including tear film, ocular surface, and/or corneal somatosensory nerve abnormalities. Research has focused on understanding how environmental exposures can increase the risk for DED flares and negatively impact the tear film, the ocular surface, and/or nerve health. Given that DED is a common condition that negatively impacts physical and mental functioning, managing DED requires multiple strategies. These can include both medical approaches and modulating adverse environmental conditions, the latter of which may be a cost-effective way to avoid DED flares. Thus, an understanding of how environmental exposures relate to disease is important. This Review summarizes research on the relationships between environmental exposures and DED, in the hope that this information will engage healthcare professionals and patients to consider environmental manipulations in their management of DED.

Clinical Characteristics and Tear Film Biomarkers in Patients With Chronic Dry Eye Disease After Femtosecond Laser-Assisted Laser in Situ Keratomileusis

PURPOSE

To investigate clinical characteristics and tear film biomarkers of patients with chronic dry eye disease (DED) following femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).

METHODS

Patients were divided into the chronic DED after FS-LASIK (n = 36), DED without FS-LASIK (n = 39), and normal control (without FS-LASIK; n = 34) groups. Dry eye, pain, and psychological-related symptoms were evaluated using the Ocular Surface Disease Index (OSDI), Numerical Rating Scale (NRS), Neuropathic Pain Symptom Inventory Modified for the Eye (NPSI-Eye), and Hamilton Anxiety Rating Scale (HAMA) questionnaires. Ocular surface parameters, tear cytokines, and neuropeptide concentrations were evaluated with specific tests.

RESULTS

The DED after FS-LASIK group showed higher corneal fluorescein staining scores, but lower OSDI and NPSI-Eye scores than the DED without FS-LASIK group (all P < .05). Corneal sensitivity and nerve density decreased in the DED after FS-LASIK group (all P < .01). Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-17A, IL-23, alpha-melanocyte stimulating hormone (α-MSH), oxytocin, and substance P levels were highest in the DED after FS-LASIK group, followed by the DED without FS-LASIK and normal control groups (all P < .05). Interferon-γ and neurotensin levels were only significantly higher in the DED after FS-LASIK group (all P < .05).

CONCLUSIONS

Patients with chronic DED after FS-LASIK showed milder ocular symptoms, greater epithelial damage, and higher levels of tear inflammatory cytokines and neuropeptides than patients with DED without FS-LASIK, indicating that the nervous and immune systems may play significant roles in FS-LASIK-related chronic DED development. [J Refract Surg. 2023;39(8):556-563.].

Ocular Pain after Refractive Surgery: Interim Analysis of Frequency and Risk Factors

PURPOSE

To examine the frequency and risk factors for ocular pain after laser assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).

DESIGN

Prospective study of individuals undergoing refractive surgery at 2 different centers.

PARTICIPANTS

One hundred nine individuals undergoing refractive surgery: 87% LASIK and 13% PRK.

METHODS

Participants rated ocular pain on a numerical rating scale (NRS) of 0 to 10 before surgery and 1 day, 3 months, and 6 months after surgery. A clinical examination focused on ocular surface health was performed 3 and 6 months after surgery. Persistent ocular pain was defined as an NRS score of 3 or more at both 3 and 6 months after surgery (patients), and this group was compared with individuals with NRS scores of < 3 at both time points (control participants).

MAIN OUTCOME MEASURES

Individuals with persistent ocular pain after refractive surgery.

RESULTS

The 109 patients who underwent refractive surgery were followed up for 6 months after surgery. Mean age was 34 ± 8 years (range, 23-57 years); 62% self-identified as female, 81% as White, and 33% as Hispanic. Eight patients (7%) reported ocular pain (NRS score ≥ 3) before surgery, with the frequency of ocular pain increasing after surgery to 23% (n = 25) at 3 months and 24% (n = 26) at 6 months. Twelve patients (11%) reported an NRS score of 3 or more at both time points and constituted the persistent pain group. Factors that predicted persistent pain after surgery in a multivariable analysis were (1) ocular pain before surgery predicated persistent pain after surgery (odds ratio [OR], 1.87; 95% confidence interval [CI], 1.06-3.31), (2) symptom report of depression before surgery (Patient Health Questionnaire-9: OR, 1.3; 95% CI, 1.1-1.6; P = 0.01), (3) use of an oral antiallergy medication before surgery (OR, 13.6; 95% CI, 2.1-89.3; P = 0.007), and (4) pain intensity day 1 after surgery (OR, 1.6; 95% CI, 1.2-2.2; P = 0.005). There were no significant associations between ocular surface signs of tear dysfunction and ocular pain, P > 0.05 for all ocular surface signs. Most individuals (> 90%) were completely or somewhat satisfied with their vision at 3 and 6 months.

CONCLUSIONS

Eleven percent of individuals reported persistent ocular pain after refractive surgery, with several preoperative and perioperative factors predicting pain after surgery.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Reliability and validity of the Japanese version of the Ocular pain assessment survey (OPAS-J)

This study aimed to determine the reliability and validity of the Japanese version of the Ocular Pain Assessment Survey (OPAS-J) to measure ocular pain and quality of life. A multi-institutional cross-sectional study was conducted on participants with and without ocular pain. The Wong-Baker FACES® Pain Rating Scale served as the gold standard for measuring the intensity of ocular pain. Sixty-four participants who visited two clinics located in Japan between May 2019 and October 2019 were included in the study. The OPAS was translated and culturally adapted to Japanese. The internal consistency of the OPAS-J was assessed using Cronbach's alpha coefficient. Twenty-four (37.5%) and 40 (62.5%) participants were classified as having ocular pain and no ocular pain, respectively. All dimensions of the OPAS-J had good reliability, with a Cronbach's alpha coefficient of 0.870 for ocular pain intensity over the past 24 h and 0.874, 0.899, 0.874, 0.871, and 0.876 for ocular pain intensity over the past 2 weeks, non-ocular pain, interference with quality of life, aggravating factors, and associated factors, respectively. The OPAS-J is a reliable and responsive tool that can be used to quantify ocular pain intensity.

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.

TFOS Lifestyle: Impact of lifestyle challenges on the ocular surface

Many factors in the domains of mental, physical, and social health have been associated with various ocular surface diseases, with most of the focus centered on aspects of dry eye disease (DED). Regarding mental health factors, several cross-sectional studies have noted associations between depression and anxiety, and medications used to treat these disorders, and DED symptoms. Sleep disorders (both involving quality and quantity of sleep) have also been associated with DED symptoms. Under the domain of physical health, several factors have been linked to meibomian gland abnormalities, including obesity and face mask wear. Cross-sectional studies have also linked chronic pain conditions, specifically migraine, chronic pain syndrome and fibromyalgia, to DED, principally focusing on DED symptoms. A systematic review and meta-analysis reviewed available data and concluded that various chronic pain conditions increased the risk of DED (variably defined), with odds ratios ranging from 1.60 to 2.16. However, heterogeneity was noted, highlighting the need for additional studies examining the impact of chronic pain on DED signs and subtype (evaporative versus aqueous deficient). With respect to societal factors, tobacco use has been most closely linked to tear instability, cocaine to decreased corneal sensitivity, and alcohol to tear film disturbances and DED symptoms.

Pyridostigmine Bromide Pills and Pesticides Exposure as Risk Factors for Eye Disease in Gulf War Veterans

To examine associations between the pyridostigmine bromide (PB) pill and/or pesticide exposure during the 1990-1991 Gulf War (GW) and eye findings years after deployment. A cross-sectional study of South Florida veterans who were deployed on active duty during the GW Era (GWE). Information on GW exposures and ocular surface symptoms were collected via standardized questionnaires and an ocular surface examination was performed. Participants underwent spectral domain-ocular coherence tomography (SD-OCT) imaging that included retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and macular maps. We examined for differences in eye findings between individuals exposed versus not exposed to PB pills or pesticides during service. A total of 40.7% (n = 44) of individuals reported exposure to PB pills and 41.7% (n = 45) to pesticides; additionally, 24 reported exposure to both in the GW arena. Demographics were comparable across groups. Individuals exposed to PB pills reported higher dry eye (DE) symptoms scores (the 5-Item Dry Eye Questionnaire, DEQ-5: 9.3 ± 5.3 vs. 7.3 ± 4.7, p = 0.04) and more intense ocular pain (average over the last week: 2.4 ± 2.6 vs. 1.5 ± 1.8, p = 0.03; Neuropathic Pain Symptom Inventory modified for the Eye (NPSI-E): 18.2 ± 20.0 vs. 10.8 ± 13.8, p = 0.03) compared to their non-exposed counterparts. DE signs were comparable between the groups. Individuals exposed to PB pills also had thicker OCT measurements, with the largest difference in the outer temporal segment of the macula (268.5 ± 22.2 μm vs. 260.6 ± 14.5 μm, p = 0.03) compared to non-exposed individuals. These differences remained significant when examined in multivariable models that included demographics and deployment history. Individuals exposed to pesticides had higher neuropathic ocular pain scores (NPSI-E: 17.1 ± 21.1 vs. 11.6 ± 12.9, p = 0.049), but this difference did not remain significant in a multivariable model. Individuals exposed to PB pills during the GWE reported more severe ocular surface symptoms and had thicker OCT measures years after deployment compared to their non-exposed counterparts.

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.

Neuropathic Pain Symptom Inventory (NPSI) Questionnaire-Persian Version Can Differentiate Neuropathic from Non-Neuropathic Pain

BACKGROUND

Neuropathic pain (NP) is a common condition that impacts life negatively. This type of pain responds poorly to treatment. Neuropathic Pain Symptom Inventory (NPSI) is a common instrument used for the assessment of NP response to the treatment.

AIM

The current study aims to validate the Persian version of NPSI (PV-NPSI).

METHODS

The current study has been conducted on 162 patients experiencing pain from neuropathic ornon-neuropathic origin. The Persian version of NPSI was proposed through standard protocol and responded to by patients twice: at baseline within an interval of 3 hours and then again within 1 month. Its correlation with the patient global impression of change (PGIC) and the clinical global impression of change (CGIC) was assessed. In addition, the validity and reliability of the PV-NPSI was evaluated.

RESULTS

The reliability Cronbach's alpha of PV-NPSI was 0.834 and test-retest intraclass-coefficient was calculated as 0.983 (95% confidence interval [CI]: 0.977-0.988; p < .001). In addition, the measured coefficient sensitivity to change based on PGIC and CGIC was 0.859 for both. Receiver operating characteristic (ROC) curve for the diagnosis of NP revealed area under curve (AUC) of 0.936 (p < .001; 95%CI: 0.894-0.978).

CONCLUSIONS

Based on the current study's findings, the PV-NPSI is a reliable and valid means for the differentiation of NP from the other types of pain in patients with several musculoskeletal pain complaints, but we cannot determine a cutoff point for it. Also, this questionnaire can be efficiently used for the assessment of response to NP treatment.

Clinical Neuroimaging of Photophobia in Individuals With Chronic Ocular Surface Pain

PURPOSE

To examine neural mechanisms underlying photophobia in individuals with chronic ocular surface pain by using functional magnetic resonance imaging (fMRI).

DESIGN

Cross-sectional case/control analysis.

METHODS

A total of 16 individuals from the Miami Veterans Affairs eye clinic underwent comprehensive ocular surface evaluations and were surveyed for ocular surface symptoms. Case patients included patients who reported chronic ocular surface pain symptoms and light sensitivity at least most of the time over 1 week. Controls included persons without chronic ocular surface pain who reported no or minimal light sensitivity. All patients viewed light stimuli during 2 fMRI scans, one before and one after topical anesthetic instillation, and rated their level of pain intensity to the stimulus at the end of each scan. Areas of brain activation in response to light stimuli presentation were correlated with pain responses and examined post- vs pre-anesthesia.

RESULTS

Case patients (n = 8) reported higher pain intensity ratings than controls (n = 8) in response to light stimuli during fMRI. Case patient ratings correlated more with light-evoked activation in pain-related areas within the trigeminal brainstem, primary somatosensory cortex (S1), anterior mid-cingulate cortex (aMCC), and insula than in controls. Topical anesthesia led to varying responses in pain ratings among case patients as well as decreased light-evoked activation in S1 and aMCC.

CONCLUSIONS

The trigeminal nociceptive system may contribute to photophobia in individuals with chronic ocular surface pain. We demonstrate modulation of cortical structures in this pathway with topically applied anesthetic to the eyes. Further understanding of modulatory interactions that govern ocular surface pain and photophobia is critical for developing effective, precision-based therapies.

Impact of Tumor Necrosis Factor Receptor 1 (TNFR1) Polymorphism on Dry Eye Disease

The goal of the study was to examine whether a genetic polymorphism in tumor necrosis factor receptor 1 (TNFR1) gene impacted the dry eye disease (DED) phenotype and response to anti-inflammatory therapy. The prospective study included 328 individuals with various dry eye (DE) symptoms and signs recruited from the Miami Veterans Hospital eye clinic between October 2013 and October 2017. The population underwent genetic profiling for a polymorphism within the TNFR1 gene (rs1800693 [TT, TC, CC]). The study examined the genotype distribution and relationships between the genotype, phenotype, and response to anti-inflammatory therapy. The mean age of the population was 61.7 ± 9.8 years. Here, 92% self-identified as male, 44% as White, and 21% as Hispanic; 13% (n = 42) of individuals had a CC genotype. DED symptoms and signs were similar across the three genotype groups. Thirty individuals (four with CC) were subsequently treated with an anti-inflammatory agent. There was a non-significant trend for individuals with CC genotype to have a partial or complete symptomatic response to treatment compared with the other two groups (100% for CC vs. 40% for TT and 36.4% for TC, p = 0.22). In conclusion, the presence of homozygosity of minor allele C (CC genotype) in a single nucleotide polymorphism (SNP) within TNFR1 was noted in a minority of individuals with various aspects of DED, but did not impact the DED phenotype. Our findings suggest that the current phenotyping strategies for DED are insufficient to identify underlying disease contributors, including potential genetic contributors.

Factors affecting the prevalence, severity, and characteristics of ocular surface pain

Introduction

Ocular surface pain has been traditionally lumped under the umbrella term "dry eye" (DE) but is now understood as its own entity and can occur in the absence or presence of tear dysfunction. Identifying patients at risk for the development of chronic ocular surface pain, and factors contributing to its severity are important in providing precision medicine to patients.

Areas covered

In this review, we discuss factors linked to the presence and severity of ocular surface pain, including eye related features, systemic characteristics, and environmental findings. We discuss corneal nerves, whose anatomic and functional integrity can be characterized through in vivo confocal microscopy images and testing of corneal sensitivity. We review systemic diseases that are co-morbid with ocular surface pain, including physical and mental health diagnoses. Finally, we identify environmental contributors, including air pollution, previous surgeries, and medications, associated with ocular surface pain.

Expert opinion

Intrinsic and extrinsic factors contribute to ocular surface pain and must be considered when evaluating an individual patient. These factors can inform the suspected etiology of the pain, and guide management decisions such as tear replacement or medications targeting nerve pain.

Understanding chronic ocular surface pain: An unmet need for targeted drug therapy

Chronic ocular surface pain (COSP) may be defined as a feeling of pain, perceived as originating from the ocular surface, that persists for >3 months. COSP is a complex multifactorial condition associated with several risk factors that may significantly interfere with an individual's daily activities, resulting in poor quality of life (QoL). COSP is also likely to have a high burden on patients with substantial implications on global healthcare costs. While patients may use varied terminology to describe symptoms of COSP, any ocular surface damage in the ocular sensory apparatus (nociceptive, neuropathic, inflammatory, or combination thereof) resulting in low tear production, chronic inflammation, or nerve abnormalities (functional and/or morphological), is typically associated with COSP. Considering the heterogeneity of this condition, it is highly recommended that advanced multimodal diagnostic tools are utilized to help discern the nociceptive and neuropathic pain pathways in order to provide targeted treatment and effective clinical management. The current article provides an overview of COSP, including its multifactorial pathophysiology, etiology, prevalence, clinical presentation, impact on QoL, diagnosis, current management, and unmet medical needs.

Neuropathic ocular surface pain: Emerging drug targets and therapeutic implications

INTRODUCTION

Dysfunction at various levels of the somatosensory system can lead to ocular surface pain with a neuropathic component. Compared to nociceptive pain (due to noxious stimuli at the ocular surface), neuropathic pain tends to be chronic and refractory to therapies, making it an important source of morbidity in the population. An understanding of the options available for neuropathic ocular surface pain, including new and emerging therapies, is thus an important topic.

AREAS COVERED

This review will examine studies focusing on ocular surface pain, emphasizing those examining patients with a neuropathic component. Attention will be placed toward recent (after 2017) studies that have examined new and emerging therapies for neuropathic ocular surface pain.

EXPERT OPINION

Several therapies have been studied thus far, and continued research is needed to identify which individuals would benefit from specific therapies. Gaps in our understanding exist, especially with availability of in-clinic diagnostics for neuropathic pain. A focus on improving diagnostic capabilities and researching gene-modulating therapies could help us to provide more specific mechanism-based therapies for patients. In the meantime, continuing to uncover new modalities and examining which are likely to work depending on pain phenotype remains an important short-term goal.

Dry Eye Symptoms and Signs in US Veterans With Gulf War Illness

PURPOSE

To examine dry eye (DE) symptoms and signs in individuals with vs without Gulf War illness (GWI).

DESIGN

Prospective cross-sectional study.

METHODS

We performed a prospective, cross-sectional study of South Florida veterans who were active duty during the Gulf War era (GWE; 1990-1991) and seen at an eye clinic between October 1, 2020, and March 13, 2021. Veterans were split into 2 groups: those who met Kansas criteria for GWI (cases, n = 30) and those who did not (controls, n = 41). DE symptoms were assessed via standardized questionnaires whereas DE signs were assessed using a series of ocular surface parameters. Differences between groups were assessed via Mann-Whitney U test. Linear regression analyses were used to examine which GWI symptoms most closely aligned with DE symptoms.

RESULTS

Veterans with GWI had higher DE symptoms scores compared to controls (Ocular Surface Disease Index [OSDI] scores: mean 41.20±22.92 vs 27.99±24.03, P = .01). In addition, veterans with GWI had higher eye pain scores compared with controls (average eye pain over past week: 2.63±2.72 vs 1.22±1.50, P = .03), including on neuropathic ocular pain questionnaires (Neuropathic Pain Symptom Inventory modified for the Eye [NPSI-E]: 17.33±17.20 vs 9.63±12.64, P = .03). DE signs were mostly similar between the groups. GWI symptoms "nausea or upset stomach" (β=14.58, SE = 3.02, P < .001) and "headache" (β=7.90, SE = 2.91, P = .011) correlated with higher OSDI scores.

CONCLUSION

Individuals with GWI have more severe DE symptoms and ocular pain scores but similar tear and ocular surface parameters compared to controls without GWI. This finding suggests that mechanisms beyond tear dysfunction drive eye symptoms in GWI.

Corneal sub-basal nerve plexus microneuromas in individuals with and without dry eye

BACKGROUND/AIM

An objective marker is needed to detect when corneal nerve abnormalities underlie neuropathic corneal pain (NCP), as symptoms often overlap with those of dry eye (DE). This study evaluated microneuroma (MN) frequency in various populations and investigated relationships between MN presence and DE clinical features in individuals with DE symptoms but without a history of refractive surgery, in order to eliminate refractive surgery as a potential confounder of nerve abnormalities.

METHODS

This was a retrospective study that included individuals with and without DE symptoms who underwent a clinical evaluation for DE (symptom surveys and ocular surface evaluation) and in vivo confocal microscopy imaging. DE clinical features (including those suggestive of neuropathic pain) were compared based on MN presence using t-tests, χ2 analyses and Pearson's correlation coefficients with 0.05 alpha level.

RESULTS

MN frequencies did not significantly differ between individuals with DE symptoms (Dry Eye Questionnaire 5 score ≥6) and a history of refractive surgery (n=1/16, 6%), individuals with DE symptoms without a history of refractive surgery (n=26/119, 22%) and individuals without DE symptoms (n=2/18, 11%, p=0.22). Among individuals with DE symptoms without a history of refractive surgery, DE clinical features, including those indicative of NCP (burning sensation and sensitivity to light, wind and extreme temperatures), did not significantly differ based on MN presence (p>0.05).

CONCLUSION

MN frequencies did not significantly differ between individuals with and without DE symptoms. Their presence alone could not distinguish between DE subtypes, including features of NCP in our study population.

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.

Topical Therapeutic Options in Corneal Neuropathic Pain

Purpose of Review: Corneal neuropathic pain can be difficult to treat, particularly due to its lack of response to standard dry eye therapies. We describe a variety of topical therapeutic options that are available to treat corneal neuropathic pain with a significant or primary peripheral component. We also describe possible mechanisms of action for such topical therapies.

Recent Findings: Topical corticosteroids and blood-derived tear preparations can be helpful. Newer therapies, including topical lacosamide and low-dose naltrexone are emerging therapeutic options that may also be considered.

Summary: Corneal neuropathic pain with a significant peripheral component may be managed with a variety of topical therapeutic options.

How Should Corneal Nerves be Incorporated Into the Diagnosis and Management of Dry Eye?

Purpose

a)Confocal microscopy and aethesiometry have allowed clinicians to assess the structural and functional integrity of corneal nerves in health and disease. This review summarizes literature on nerves in dry eye disease (DED) and discusses how this data can be applied to DED diagnosis and treatment.

Recent findings

b)Subjects with DED have a heterogenous symptom and sign profile along with variability in nerve structure and function. Most studies have reported lower nerve density and sensitivity in aqueous tear deficiency, while findings are more inconsistent for other DED subtypes. Examining nerve status, along with profiling symptoms and signs of disease, can help categorize subjects into disease phenotypes (structural and functional patterns) that exist under the umbrella of DED. This, in turn, can guide therapeutic decision-making.

Summary

c)Due to the heterogeneity in symptoms and signs of DED, corneal nerve evaluations can be valuable for categorizing individuals into disease sub-types and for guiding clinical decision making.

Ocular Pain Symptoms in Individuals With and Without a History of Refractive Surgery: Results From a Cross-Sectional Survey

PURPOSE

This study characterized ocular pain symptoms in individuals with and without a history of refractive surgery (RS) using a cross-sectional survey of individuals with ocular pain.

METHODS

A link to an anonymous survey was posted on a corneal neuralgia Facebook group that included individuals with ocular pain from any etiology and sent to individuals seen in our clinic with ocular pain. The survey asked about medical history, ocular pain symptoms (using standardized questionnaires), and treatment responses. Respondents were split into 2 groups based on a history of RS.

RESULTS

One hundred one individuals responded to the survey. The mean age for all respondents was 41.6 ± 15.6 years, and 50% reported a history of RS. A total of 46% of individuals with a history of RS reported that their ocular pain started within 1 month of surgery, with median pain duration of 36 (interquartile range 22-84) months. The median Dry Eye Questionnaire-5 (range 0-22) scores were 16 and 15 for the RS and no-RS groups, respectively. Most individuals in both groups characterized their pain as burning (score ≥1: RS, 86%; no-RS, 80%) and reported evoked pain to wind, light, or temperature (score ≥1: RS, 97%; no-RS, 85%). Fifty-nine of 101 individuals responded to treatment questions. Individuals in both groups reported >30% improvement in pain symptoms with some topical and systemic approaches.

CONCLUSIONS

Individuals with a history of RS developed ocular pain soon after surgery, which persisted for years. Symptom profiles were similar between those with and without RS. Topical and systemic approaches can treat pain in both groups.

Relationships between activated dendritic cells and dry eye symptoms and signs

PURPOSE

To examine whether "activated" dendritic cells (aDCs) could serve as a biomarker of systemic immune disorders in individuals with dry eye (DE) symptoms. Secondarily, to examine the impact of a topical anti-inflammatory agent on aDC number.

METHODS

Retrospective analysis was conducted to identify individuals with DE symptoms who had in-vivo confocal microscopy (IVCM) imaging between October 2018 and July 2020 at the Miami Veterans Hospital. aDCs were manually quantified based on morphology. Receiver operating curve (ROC) analysis examined relationships between aDC number and systemic immune disease status. Individuals were then grouped by aDC number (≥2 versus <2) and demographics and DE parameters were examined. Paired t-test was performed to evaluated aDC number pre-vs post-initiation of an anti-inflammatory agent.

RESULTS

128 individuals were included. Their mean age was 57.1 ± 15.0 years; 71.1% were male, 53.1% self-identified as White and 24.2% as Hispanic. The mean number of aDCs in the central cornea was 1.28 ± 2.16 cells/image. The presence of ≥2 aDCs had a sensitivity of 60% and specificity of 77% for the diagnosis of a systemic immune disorder. Individuals with ≥2 aDCs were more likely to self-identify as Black, have Secondary Sjögren's, and have higher nerve fiber area and fractal dimension. In 12 individuals, aDC number decreased from 2.69 ± 2.36 to 0.58 ± 0.73 cells/image after initiation of an anti-inflammatory agent, p = 0.01.

CONCLUSIONS

The presence of ≥2 aDCs in the central cornea suggests a systemic immune disorder in individuals with DE symptoms. Topical anti-inflammatory therapy can reduce the number of aDCs in the central cornea.

Validation of a Novel Confocal Microscopy Imaging Protocol With Assessment of Reproducibility and Comparison of Nerve Metrics in Dry Eye Disease Compared With Controls

PURPOSE

The purposes of this study were to assess the reproducibility of a novel standardized technique for capturing corneal subbasal nerve plexus images with in vivo corneal confocal microscopy and to compare nerve metrics captured with this method in participants with dry eye and control participants.

METHODS

Cases and controls were recruited based on their International Statistical Classification of Diseases and Related Health Problems (ICD-10) diagnoses. Participants completed the following 3 ocular symptom questionnaires: the Ocular Surface Disease Index, Neuropathic Pain Symptom Inventory, and Dry Eye Questionnaire 5. A novel eye fixation-grid system was used to capture 30 standardized confocal microscopy images of the central cornea. Each participant was imaged twice by different operators. Seven quantitative nerve metrics were analyzed using automated software (ACCmetrics, Manchester, United Kingdom) for all 30 images and a 6-image subset.

RESULTS

Forty-seven participants were recruited (25 classified as dry eye and 22 controls). The most reproducible nerve metrics were corneal nerve fiber length [intraclass correlation (ICC) = 0.86], corneal nerve fiber area (ICC = 0.86), and fractal dimension (ICC = 0.90). Although differences were not statistically significant, all mean nerve metrics were lower in those with dry eye compared with controls. Questionnaire scores did not significantly correlate with nerve metrics. Reproducibility of nerve metrics was similar when comparing the entire 30-image montage to a central 6-image subset.

CONCLUSIONS

A standardized confocal imaging technique coupled with quantitative assessment of corneal nerves produced reproducible corneal nerve metrics even with different operators. No statistically significant differences in in vivo corneal confocal microscopy nerve metrics were observed between participants with dry eye and control participants.

Exploring the Link Between Dry Eye and Migraine: From Eye to Brain

Dry eye and migraine are common diseases with large societal and economic burdens that have recently been associated in the literature. This review outlines the link between dry eye and migraine, which may have implications for reducing their respective burdens. We highlight possible shared pathophysiology, including peripheral and central sensitization, as the potential link between dry eye and migraine. Finally, therapies targeting similar pathophysiological mechanisms between dry eye and migraine are discussed.

Pain sensitivity and autonomic nervous system parameters as predictors of dry eye symptoms after LASIK

PURPOSE

Differences in pain processing and autonomic function among patients have been implicated in the development of chronic pain after surgery. This study was designed to evaluate whether pain and autonomic metrics predict severity of chronic dry eye (DE) symptoms after LASIK, as there is increasing evidence that DE symptoms may be manifestations of persistent post-operative ocular pain.

METHODS

Secondary analysis of prospective randomized clinical trial. Patients were treated with either pregabalin or placebo. As no significant differences in DE symptoms were detected by treatment allocation at six months, all participants were grouped together for the present analyses. Subjects were evaluated pre-LASIK with regard to evoked pain sensitivity (utilizing quantitative sensory testing), autonomic metrics and DE and ocular pain symptoms (via validated questionnaires). Measures of DE and ocular pain were assessed post-LASIK, and the Dry Eye Questionnaire 5 (DEQ5) score 6-months after surgery was the primary outcome of interest.

RESULTS

43 individuals were randomized to pregabalin (n = 21) or placebo (n = 22). 42 completed the 6-month visit. Several baseline autonomic metrics correlated with 6-month post-operative DEQ5 scores, including lower systolic (r -0.37, p = 0.02) and diastolic blood pressure (r -0.32, p = 0.04). Ocular pain at 6 months was also negatively correlated with blood pressure (r -0.31, p = 0.047). The presence of painful aftersensations was a significant predictor of chronic DE symptoms at 6 months (mean DEQ5 scores: 8.0 ± 1.9 versus 5.0 ± 5.0, p = 0.009).

CONCLUSIONS

Heightened parasympathetic tone and prolonged pain sensitivity measured prior to surgery predicted greater DE symptom severity 6 months after LASIK.

TRIAL REGISTRATION

NCT02701764.

Clinical characteristics of dry eye with ocular neuropathic pain features: comparison according to the types of sensitization based on the Ocular Pain Assessment Survey

BACKGROUND

To compare the clinical characteristics of dry eye patients with ocular neuropathic pain features according to the types of sensitization based on the Ocular Pain Assessment Survey (OPAS).

METHODS

Cross-sectional study of 33 patients with dry eye and ocular neuropathic pain features. All patients had a comprehensive ophthalmic assessment including detailed history, the intensity and duration of ocular pain, the tear film, ocular surface, and Meibomian gland examination, and OPAS. Patients with < 50% improvement in pain intensity after proparacaine challenge test were assigned to the central-dominant sensitization group (central group) and those with ≥50% improvement were assigned to the peripheral-dominant sensitization group (peripheral group). All variables were compared between the two groups.

RESULTS

No significant differences were observed in age, sex, underlying diseases, history of ocular surgery, duration of ocular pain, tear film, ocular surface and Meibomian gland parameters (all p > 0.05). Ocular pain and non-ocular pain severity and the percentage of time spent thinking about non-ocular pain were significantly higher in the central group than in the peripheral group (all p < 0.05). Central group complained more commonly of a burning sensation than did the peripheral group (p = 0.01).

CONCLUSIONS

Patients with central-dominant sensitization may experience more intense ocular and non-ocular pain than the others and burning sensation may be a key symptom in those patients.

Corneal Nerve Abnormalities in Ocular and Systemic Diseases

The trigeminal nerve gives rise to the corneal subbasal nerve system, which plays a crucial role in sensations of touch, pain, and temperature and in ocular healing processes. Technological advancements in instruments, in particular in vivo confocal microscopy and aethesiometry, have allowed for the structural and functional evaluation of corneal nerves in health and disease. Through application of these technologies in humans and animal models, structural and functional abnormalities have been detected in several ocular and systemic disorders, including dry eye disease (DED), glaucoma, migraine, and fibromyalgia. However, studies across a number of conditions have found that structural abnormalities do not always relate to functional abnormalities. This review will discuss instruments used to evaluate corneal nerves and summarize data on nerve abnormalities in a number of ocular and systemic conditions. Furthermore, it will discuss potential treatments that can alleviate the main manifestations of nerve dysfunction, namely ocular surface pain and persistent epithelial defects.

Ocular Surface Pain: A Narrative Review

Ocular surface pain is a frequent cause of visits to an eye care provider and has a substantial impact on healthcare cost, yet a complete understanding of its causative factors and tools for diagnostic workup are notably missing in many eye clinics. The cornea has the densest sensory innervation in the human body and has the potential to be a powerful producer of pain. Pain can manifest as a result of a noxious stimulus or disruption in the ocular surface anatomy (nociceptive pain), or it can result from abnormalities in the ocular surface neurosensory apparatus itself (neuropathic pain). Novel advances in neurobiology have sought to differentiate the two entities, particularly to identify when chronic dry eye symptomatology is driven by neuropathic ocular pain. In this review, we seek to provide an overview of the prevalence, physiologic factors, and management of ocular surface pain complaints.

Genomic analysis of 21 patients with corneal neuralgia after refractive surgery

Background

Refractive surgery, specifically laser-assisted in situ keratomileusis and photorefractive keratectomy, are widely applied procedures to treat myopia, hyperopia, and astigmatism. After surgery, a subgroup of cases suffers from persistent and intractable pain of obscure etiology, thought to be neuropathic. We aimed to investigate the contribution of genomic factors in the pathogenesis of these patients with corneal neuralgia.

Methods

We enrolled 21 cases (6 males and 15 females) from 20 unrelated families, who reported persistent pain (>3 months), after refractive surgery (20 laser-assisted in situ keratomileusis and 1 photorefractive keratectomy patients). Whole-exome sequencing and gene-based association test were performed.

Results

Whole-exome sequencing demonstrated low-frequency variants (allele frequency < 0.05) in electrogenisome-related ion channels and cornea-expressed collagens, most frequently in SCN10A (5 cases), SCN9A (4 cases), TRPV1 (4 cases), CACNA1H and CACNA2D2 (5 cases each), COL5A1 (6 cases), COL6A3 (5 cases), and COL4A2 (4 cases). Two variants, p.K655R of SCN9A and p.Q85R of TRPV1, were previously characterized as gain-of-function. Gene-based association test assessing "damaging" missense variants against gnomAD exome database (non-Finnish European or global), identified a gene, SLC9A3R1, with statistically significant effect (odds ratio = 17.09 or 17.04; Bonferroni-corrected P-value < 0.05).

Conclusion

These findings in a small patient cohort did not identify a common gene/variant among most of these cases, as found in other disorders, for example small-fiber neuropathy. Further studies of these candidate genes/variants might enhance understanding of the role of genetic factors in the pathogenesis of corneal neuralgia.

The correlation of cytokines and sensory hypersensitivity in mild dry eye patients characterized by symptoms outweighing signs

PURPOSE

To explore the correlation of tear and conjunctival cytokines and sensory hypersensitivity in mild dry eye (MDE) patients characterized by symptoms outweighing signs (DESOS).

METHODS

The subjects comprised 39 patients with MDE characterized by DESOS, 18 patients with common MDE (CMDE), and 15 healthy controls. The patients with DESOS were randomly subdivided into two groups; the C-DESOS group received artificial tears only, and the G-DESOS group received artificial tears and 0.1% fluorometholone eye drops three times a day. Symptoms were assessed using the Ocular Surface Disease Index (OSDI) and the Neuropathic Pain Symptoms Inventory modified for Eye (NPSI-E) questionnaire. Ocular examinations and in vivo confocal microscopy (IVCM) were also employed. Tear and conjunctival cytokines were measured using Multiplex or RT-PCR on Days 0, 7, and 30. The correlation between the expression of cytokines and hypersensitivity status was analyzed.

RESULTS

Compared with the CMDE and control groups, the DESOS groups showed a significant increase in symptom scores and in the ratio of symptoms versus signs. IL-1 β, IL-2, IL-6, and TNF-α in tears and conjunctiva increased in the DESOS groups compared to the CMDE and control groups, indicating a high correlation with hypersensitivity status in the DESOS groups. Glucocorticoid treatment significantly decreased the level of cytokines in tears and conjunctiva in the G-DESOS group and subsequently ameliorated the symptoms.

CONCLUSIONS

Tear and conjunctival cytokines, including IL-1 β, IL-2, IL-6, and TNF-α, were correlated with sensory hypersensitivity status in the DESOS groups, suggesting they play an important role in the discordance of symptoms outweighing signs.