Lipids from ocular meibum and tears may serve as biomarkers for depression and post-traumatic stress disorder.

BACKGROUND: There is a need to develop biomarkers for diagnosis and prediction of treatment responses in depression and post-traumatic stress disorder (PTSD). METHODS: Cross-sectional study examining correlations between tear inflammatory proteins, meibum and tear sphingolipids, and symptoms of depression and PTSD-associated anxiety. Ninety individuals filled depression (Patient Health Questionnaire 9, PHQ-9) and PTSD-associated anxiety (PTSD Checklist-Military Version, PCL-M) questionnaires. In 40 patients, a multiplex assay system was used to quantify 23 inflammatory proteins in tears. In a separate group of 50 individuals, liquid chromatography-mass spectrometry was performed on meibum and tears to quantify 34 species of sphingolipids, encompassing ceramides, monohexosyl ceramides and sphingomyelins. RESULTS: The mean age of the population was 59.4 ± 11.0 years; 89.0% self-identified as male, 34.4% as White, 64.4% as Black, and 16.7% as Hispanic. The mean PHQ-9 score was 11.1 ± 7.6, and the mean PCL-M score was 44.3 ± 19.1. Symptoms of depression and PTSD-associated anxiety were highly correlated (ρ =0.75, p < 0.001). Both PHQ9 and PCL-M scores negatively correlated with multiple sphingolipid species in meibum and tears. In multivariable models, meibum Monohexosyl Ceramide 26:0 (pmol), tear Ceramide 16:0 (mol%), meibum Monohexosyl Ceramide 16:0 (mol%), and tear Ceramide 26:1 (mol%) remained associated with depression and meibum Monohexosyl Ceramide 16:0 (mol%), meibum Monohexosyl Ceramide 26:0 (pmol), tear Sphingomyelin 20:0 (mol%), and tear Sphingosine-1-Phosphate (mol%) remained associated with PTSD-associated anxiety. CONCLUSIONS: Certain meibum and tear sphingolipid species were related to mental health indices. These interactions present opportunities for innovative diagnostic and therapeutic approaches for mental health disorders.

Prevalence and Impact of Neuropathic and Nonneuropathic Pain in Chronic Spinal Cord Injury.

OBJECTIVE: To compare prevalence, intensity ratings, and interference ratings of neuropathic pain (NeuP) and nociceptive pain in people with chronic spinal cord injury (SCI) DESIGN: Cross-sectional survey. SETTING: Six SCI Model System centers in the United States. PARTICIPANTS: Convenience sample of 391 individuals (N=391) with traumatic SCI, 18 years or older, 81% male, 57% White. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Survey based on the International Spinal Cord Injury Pain Basic Data Set and the Spinal Cord Injury Pain Instrument, including 0-10 numeric ratings of pain intensity and pain interference with daily activities, mood, and sleep RESULTS: A total of 80% of those surveyed reported having at least 1 pain problem; 58% reported 2 or more pain problems; 56% had probable NeuP; and 49% had non-NeuP. When comparing ratings for all pains (n=354 for NeuP, n=290 for non-NeuP) across participants, probable NeuPs were significantly more intense (6.9 vs 5.7) and interfered more with activities (5.2 vs 3.7), mood (4.9 vs 3.2), and sleep (5.4 vs 3.6) than non-NeuPs (all P<.001). However, when comparing ratings for probable NeuPs and non-NeuPs within participants, for the subgroup of 94 participants with both pain types, only ratings for sleep interference were found to be significantly different between the pain types. Additionally, we found significantly greater prevalence of NeuP and non-NeuP for women compared with men and of NeuP for those with paraplegia compared with those with tetraplegia. CONCLUSIONS: Independent assessment of the pain conditions experienced by an individual with SCI is useful in understanding the differential effect that pain type has on quality of life. This is particularly important regarding sleep interference and should be kept in mind when determining treatment strategies for meeting patient-centered outcome goals.

Physical Function Recovery Trajectories After Spinal Cord Injury.

OBJECTIVE: To explore trajectories of functional recovery that occur during the first 2 years after spinal cord injury (SCI). DESIGN: Observational cohort study. SETTING: Eight SCI Model System sites. PARTICIPANTS: A total of 479 adults with SCI completed 4 Spinal Cord Injury-Functional Index (SCI-FI) item banks within 4 months of injury and again at 2 weeks, 3, 6, 12, and 24 months after baseline assessment (N=479). INTERVENTION: None. MAIN OUTCOME MEASURES: SCI-FI Basic Mobility/Capacity (C), Fine Motor Function/C, Self-care/C, and Wheelchair Mobility/Assistive Technology (AT) item banks. RESULTS: Growth mixture modeling was used to identify groups with similar trajectory patterns. For the Basic Mobility/C and Wheelchair Mobility/AT domains, models specifying 2 trajectory groups were selected. For both domains, a majority class exhibited average functional levels and gradual improvement, primarily in the first 6 months. A smaller group of individuals made gradual improvements but had greater initial functional limitations. The Self Care/C domain exhibited a similar pattern; however, a third, small class emerged that exhibited substantial improvement in the first 6 months. Finally, for individuals with tetraplegia, trajectories of Fine Motor Function/C scores followed 2 patterns, with individuals reporting generally low initial scores and then making either modest or large improvements. In individual growth curve models, injury/demographic factors predicted initial functional levels but less so regarding rates of recovery. CONCLUSIONS: Trajectories of functional recovery followed a small number of change patterns, although variation around these patterns emerged. During the first 2 years after initial hospitalization, SCI-FI scores showed modest improvements; however, substantial improvements were noted for a small number of individuals with severe limitations in fine motor and self-care function. Future studies should further explore the personal, medical, and environmental characteristics that influence functional trajectories during these first 2 years and beyond.

Spinal Cord Injury-Functional Index/Capacity: Responsiveness to Change Over Time.

OBJECTIVE: To establish responsiveness of 3 Spinal Cord Injury-Functional Index/Capacity (SCI-FI/C) item banks in the first year after spinal cord injury (SCI). DESIGN: Longitudinal patient-reported outcomes assessment replicated through secondary analysis of an independent data set. SETTING: A total of 8 SCI Model Systems rehabilitation hospitals in the United States. PARTICIPANTS: Study 1 participants included 184 adults with recent (≤4 months) traumatic SCI and 221 community-dwelling adults (>1 year post injury) (N=405). Study 2 participants were 418 individuals with recent SCI (≤4 months) (N=418). INTERVENTIONS: In study 1, SCI-FI/C computer adaptive tests were presented in a standardized interview format either in person or by phone call at baseline and 6-month follow-up. Responsiveness was examined by comparing 6-month changes in SCI-FI scores within and across samples (recently injured vs community-dwelling) because only the recent injury sample was expected to exhibit change over time. Effect sizes were also computed. In study 2, the study 1 results were cross-validated in a second sample with recent SCI 1 year after baseline measurement. Study 2 also compared the SCI-FI/C measures' responsiveness to that of the Self-reported Functional Measure (SRFM) and stratified results by injury diagnosis and completeness. MAIN OUTCOME MEASURES: The SCI-FI Basic Mobility/C, Self-care/C and Fine Motor/C item banks (study 1 and study 2); Self-reported Functional Measure SRFM (study 2 only). RESULTS: In study 1, changes in SCI-FI/C scores between baseline and 6-month follow-up were statistically significant (P<.01) for recently injured individuals. SCI-FI Basic Mobility/C, Self-care/C, and Fine Motor/C item banks demonstrated small to medium effect sizes in the recently injured sample. In the community-dwelling sample, all SCI-FI/C effects were negligible (ie, effect size<0.08). Study 2 results were similar to study 1. As expected, SCI-FI Basic Mobility/C and Self-care/C were responsive to change for all individuals in study 2, whereas the SCI-FI Fine Motor/C was responsive only for individuals with tetraplegia and incomplete paraplegia. The SRFM demonstrated a medium effect size for responsiveness (effect size=0.65). CONCLUSIONS: The SCI-FI Basic Mobility/C and Self-care/C banks demonstrate adequate sensitivity to change at 6 months and 1 year for all individuals with SCI, while the SCI-FI/C Fine Motor item bank is sensitive to change in individuals with tetraplegia or incomplete paraplegia. All SCI-FI/C banks demonstrate stability in a sample not expected to change. Results provide support for the use of these measures for research or clinical use.

Treatments that are perceived to be helpful for non-neuropathic pain after traumatic spinal cord injury: a multicenter cross-sectional survey.

STUDY DESIGN: Cross-sectional survey. OBJECTIVES: The objective of the study was to identify the treatments that people with traumatic spinal cord injury (SCI) used for their non-neuropathic pains (nonNeuPs) and how they subjectively rated the helpfulness of those treatments. SETTING: Six centers from the Spinal Cord Injury Model Systems. METHODS: Three hundred ninety one individuals who were at least 1-year post-traumatic SCI were enrolled. A telephone survey was conducted for pharmacologic and non-pharmacologic treatments utilized in the last 12 months for each participant's three worst pains and the perceived helpfulness of each treatment for each pain. RESULTS: One hundred ninety (49%) participants reported at least one nonNeuP (Spinal Cord Injury Pain Instrument score < 2) in the previous 7 days. NSAIDs/aspirin, acetaminophen, opioids, and cannabinoids were the most commonly used and helpful pharmacologic treatments for overall nonNeuP locations (helpful in 77-89% of treated pains). Body position adjustment, passive exercise, massage, resistive exercise, and heat therapy were reported as the most commonly used non-pharmacological treatments for nonNeuPs. Heat therapy, aerobic exercise, massage, and body position adjustment were the most helpful non-pharmacological treatments for overall nonNeuP locations (helpful in 71-80% of treated pains). Perceived helpfulness of treatments varied by pain locations, which may be due to different mechanisms underlying pains in different locations. CONCLUSIONS: Results of the study may help guide clinicians in selecting pain-specific treatments for nonNeuPs. The self-reported helpfulness of heat therapy, exercise, and massage suggests a possible direction for clinical trials investigating these treatments of nonNeuP while limiting the side effects accompanying pharmacologic treatments.

Oral Gabapentinoids and Nerve Blocks for the Treatment of Chronic Ocular Pain.

PURPOSE: There is a recognition that nerve dysfunction can contribute to chronic ocular pain in some individuals. However, limited data are available on how to treat individuals with a presumed neuropathic component to their ocular pain. As such, the purpose of this study was to examine the efficacy of our treatment approaches to this entity. METHODS: A retrospective review of treatments and outcomes in individuals with chronic ocular pain that failed traditional therapies. RESULTS: We started eight patients on an oral gabapentinoid (gabapentin and/or pregabalin) as part of their pain regimen (mean age 46 years, 50% women). Two individuals reported complete ocular pain relief with a gabapentinoid, in conjunction with their topical and oral medication regimen. Three individuals noted significant improvements, one slight improvement, and two others no improvement in ocular pain with gabapentin or pregabalin. We performed periocular nerve blocks (4 mL of 0.5% bupivacaine mixed with 1 mL of 80 mg/mL methylprednisolone acetate) targeting the periocular nerves (supraorbital, supratrochlear, infratrochlear, and infraorbital) in 11 individuals (mean age 54 years, 36% women), 10 of whom had previously used a gabapentinoid without ocular pain improvement. Seven individuals experienced pain relief after nerve blocks that lasted from hours to months and four failed to benefit. Five of the individuals who experienced pain relief underwent repeat nerve blocks, weeks to months later. CONCLUSIONS: Approaches used to treat chronic pain outside the eye can be applied to ocular pain that is not responsive to traditional therapies.

Longitudinal Examination of Resilience After Traumatic Brain Injury: A Traumatic Brain Injury Model Systems Study.

OBJECTIVES: To evaluate (1) the trajectory of resilience during the first year after a moderate-severe traumatic brain injury (TBI); (2) factors associated with resilience at 3, 6, and 12 months postinjury; and (3) changing relationships over time between resilience and other factors. DESIGN: Longitudinal analysis of an observational cohort. SETTING: Five inpatient rehabilitation centers. PARTICIPANTS: Patients with TBI (N=195) enrolled in the resilience module of the TBI Model Systems study with data collected at 3-, 6-, and 12-month follow-up. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Connor-Davidson Resilience Scale. RESULTS: Initially, resilience levels appeared to be stable during the first year postinjury. Individual growth curve models were used to examine resilience over time in relation to demographic, psychosocial, and injury characteristics. After adjusting for these characteristics, resilience actually declined over time. Higher levels of resilience were related to nonminority status, absence of preinjury substance abuse, lower anxiety and disability level, and greater life satisfaction. CONCLUSIONS: Resilience is a construct that is relevant to understanding brain injury outcomes and has potential value in planning clinical interventions.

Obesity and Overweight Problems Among Individuals 1 to 25 Years Following Acute Rehabilitation for Traumatic Brain Injury: A NIDILRR Traumatic Brain Injury Model Systems Study.

OBJECTIVE: Examine the prevalence of weight classifications and factors related to obesity/overweight among persons 1 to 25 years following traumatic brain injury (TBI) using the Traumatic Brain Injury Model Systems national database. DESIGN: Multicenter, cross-sectional, observational design. SETTING: Traumatic Brain Injury Model Systems inpatient rehabilitation facilities. PARTICIPANTS: Persons (N = 7287) 1, 2, 5, 10, 15, 20, or 25 years after TBI who required inpatient acute rehabilitation. MAIN OUTCOME MEASURES: Body mass index, demographic characteristics, functional, health, satisfaction with life, and global outcomes. RESULTS: Overall postinjury weight prevalence rates were 23% obese, 36% overweight, 39% normal, and 3% underweight. Higher rates for obesity and overweight problems were associated with increasing time since injury. Younger (18-19 years) and older (80+ years) age, those in a vegetative state, and those reporting excellent health were less likely to be obese. Individuals with a history of hypertension, heart failure, or diabetes were more likely to be obese. CONCLUSIONS: Being obese or overweight presents a health risk in the years following rehabilitation for TBI. The findings support the need for longitudinal studies and highlight the advisability of monitoring weight and promoting healthy lifestyle behaviors over time in survivors of TBI.

Race/Ethnicity and Retention in Traumatic Brain Injury Outcomes Research: A Traumatic Brain Injury Model Systems National Database Study.

OBJECTIVE: To investigate the contribution of race/ethnicity to retention in traumatic brain injury (TBI) research at 1 to 2 years postinjury. SETTING: Community. PARTICIPANTS: With dates of injury between October 1, 2002, and March 31, 2013, 5548 whites, 1347 blacks, and 790 Hispanics enrolled in the Traumatic Brain Injury Model Systems National Database. DESIGN: Retrospective database analysis. MAIN MEASURE: Retention, defined as completion of at least 1 question on the follow-up interview by the person with TBI or a proxy. RESULTS: Retention rates 1 to 2 years post-TBI were significantly lower for Hispanic (85.2%) than for white (91.8%) or black participants (90.5%) and depended significantly on history of problem drug or alcohol use. Other variables associated with low retention included older age, lower education, violent cause of injury, and discharge to an institution versus private residence. CONCLUSIONS: The findings emphasize the importance of investigating retention rates separately for blacks and Hispanics rather than combining them or grouping either with other races or ethnicities. The results also suggest the need for implementing procedures to increase retention of Hispanics in longitudinal TBI research.

Epidemiology of Comorbid Conditions Among Adults 50 Years and Older With Traumatic Brain Injury.

OBJECTIVES: Aging individuals with traumatic brain injury (TBI) experience multiple comorbidities that can affect recovery from injury. The objective of this study was to describe the most commonly co-occurring comorbid conditions among adults 50 years and older with TBI. SETTING: Level I Trauma centers. PARTICIPANTS: Adults 50 years and older with moderate/severe TBI enrolled in the TBI-Model Systems (TBI-MS) from 2007 to 2014 (n = 2134). DESIGN: A TBI-MS prospective cohort study. MAIN MEASURES: International Classification of Disease-9th Revision codes collapsed into 45 comorbidity categories. Comorbidity prevalence estimates and trend analyses were conducted by age strata (50-54, 55-64, 65-74, 75-84, ≥85 years). A dimension reduction method, Treelet Transform, classified clusters of comorbidities that tended to co-occur. RESULTS: The 3 most commonly occurring comorbid categories were hypertensive disease (52.6/100 persons), other diseases of the respiratory system (51.8/100 persons), and fluid component imbalances (43.7/100 persons). Treelet Transform classified 3 clusters of comorbid codes, broadly classified as (1) acute medical diseases/infections, (2) chronic conditions, and (3) substance abuse disorders. CONCLUSION: This study provides valuable insight into comorbid conditions that co-occur among adults 50 years and older with TBI and provides a foundation for future studies to explore how specific comorbidities affect TBI recovery.

The Association of Dry Eye Symptom Severity and Comorbid Insomnia in US Veterans.

PURPOSE: To investigate the association between dry eye (DE) and insomnia symptom severity. METHODS: Cross-sectional study of 187 individuals seen in the Miami Veterans Affairs eye clinic. An evaluation was performed consisting of questionnaires regarding insomnia (insomnia severity index [ISI]) and DE symptoms, including ocular pain, followed by a comprehensive ocular surface examination. Using a two-step cluster analysis based on intensity ratings of ocular pain, the patient population was divided into two groups (high and low ocular pain groups: HOP and LOP). A control group was ascertained at the same time from the same clinic as defined by no symptoms of DE (Dry Eye Questionnaire 5 [DEQ5], <6). The main outcome measure was the frequency of moderate or greater insomnia in the DE groups. RESULTS: The mean age of the study sample was 63 years, and 93% were male. All insomnia complaints were rated higher in the HOP group compared with the LOP and control groups (P<0.0005). Most (61%) individuals in the HOP group experienced insomnia of at least moderate severity (ISI≥15) compared with the LOP (41%) and control groups (18%) (P<0.0005). Black race (odds ratio [OR], 2.7; 95% confidence interval [CI], 1.2-6.0; P=0.02), depression severity (OR, 1.2; 95% CI, 1.1-1.3; P<0.0005), and DE symptom severity (DEQ5; OR, 1.1; 95% CI, 1.01-1.2; P=0.03) were significantly associated with clinical insomnia (ISI≥15) after controlling for potential confounders. CONCLUSIONS: After adjusting for demographics and medical comorbidities, we show that DE symptom severity is positively associated with insomnia severity.

Evidence that Dry Eye Represents a Chronic Overlapping Pain Condition.

Abstract: Recent data suggest that corneal somatosensory dysfunction may be the underlying cause of severe dry eye symptoms in the absence of ocular surface pathology seen in a subset of patients diagnosed with "dry eye syndrome." This subset of patients tends to demonstrate a unique constellation of symptoms that are persistent, more severe, and generally respond poorly to current dry eye therapies targeting inadequate or dysfunctional tears. A growing body of literature suggests that symptoms in these patients may be better characterized as neuropathic ocular pain rather than dry eye. In these patients, dry eye symptoms are often associated with numerous comorbid pain conditions and evidence of central pain processing abnormalities, where eye pain is just one of multiple overlapping peripheral manifestations. In this review, we discuss the concept and potential mechanisms of chronic overlapping pain conditions as well as evidence for considering neuropathic ocular pain as one of these overlapping pain conditions.

Characteristics of Ocular Pain Complaints in Patients With Idiopathic Dry Eye Symptoms.

OBJECTIVE: The purpose of this study was to examine the severity and quality of ocular pain complaints in patients with dry eye symptoms. METHODS: Subjects with clinically relevant dry eye symptoms (dryness, discomfort, tearing) of unknown origin seen in the Miami Veterans Affairs eye clinic were administered questionnaires for dry eye symptoms and ocular pain and underwent a standardized ocular examination. Qualities and severity ratings of ocular pain in subjects with idiopathic dry eye were compared with similar measures from published data in other chronic pain populations. RESULTS: The study sample consisted of 154 subjects, of which 91% were men and ranged in age from 27 to 89 (mean age=61). Fifty-three percent of participants reported an average ocular pain of at least moderate intensity (numerical rating scale≥4), with specific characteristics (i.e., "burning" spontaneous pain) reported at frequencies comparable to prevalent chronic neuropathic pain syndromes as reported in the literature. Significant correlations were found between ocular pain metrics and dry eye symptom severity scores (r=0.57-0.66). Dry eye signs, however, did not generally correlate with ocular pain severity. CONCLUSIONS: A significant proportion of subjects with idiopathic dry eye symptoms reported moderate or greater ocular pain intensity, with most endorsing descriptors commonly used by patients with nonocular neuropathic pain conditions. Identifying subgroups of dry eye patients based on the presence and characteristics of ocular pain complaints may improve dry eye subclassification and better individualize treatment strategies.

Burning Eye Syndrome: Do Neuropathic Pain Mechanisms Underlie Chronic Dry Eye?

OBJECTIVE: Dry eye is a multi-factorial disorder that manifests with painful ocular symptoms and visual disturbances, which can only be partly attributed to tear dysfunction. This disorder may also involve neuroplasticity in response to neuronal injury. This review will emphasize the key characteristics of dry eye pain and its pathologic mechanisms, making the argument that a subset of dry eye represents a neuropathic pain disorder of the eye, more appropriately called "burning eye syndrome." METHODS: A literature review was conducted using a PubMed search focusing on dry eye, corneal nociception, and neuropathic pain. Articles were reviewed and those discussing clinical course, pathophysiology, and neuronal regulation of chronic ocular pain as related to dry eye were summarized. RESULTS: We found that there is a discordance between ocular pain and dryness on the ocular surface. Although tear dysfunction may be one of the initial insults, its persistence may be associated with repeated ocular sensory nerve injury leading to an acute-to-chronic pain transition associated with neuropathologic changes (peripheral and central sensitization), neuronal dysfunction, and spontaneous ocular pain. CONCLUSION: Dry eye is becoming a major health concern due to its increasing incidence, significant morbidity, and economic burden. Recent evidence suggests that a subset of dry eye may be better represented as a chronic neuropathic pain disorder due to its features of dysesthesia, spontaneous pain, allodynia, and hyperalgesia. Future therapies targeted at the underlying neuroplasticity may yield improved efficacy for patients with this subset of dry eye, which we term "burning eye syndrome."

Resilience Following Traumatic Brain Injury: A Traumatic Brain Injury Model Systems Study.

OBJECTIVE: To examine resilience at 3 months after traumatic brain injury (TBI). DESIGN: Cross-sectional analysis of an ongoing observational cohort. SETTING: Five inpatient rehabilitation centers, with 3-month follow-up conducted primarily by telephone. PARTICIPANTS: Persons with TBI (N=160) enrolled in the resilience module of the TBI Model System study with 3-month follow-up completed. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Connor-Davidson Resilience Scale. RESULTS: Resilience scores were lower than those of the general population. A multivariable regression model, adjusting for other predictors, showed that higher education, absence of preinjury substance abuse, and less anxiety at follow-up were significantly related to greater resilience. CONCLUSIONS: Analysis suggests that lack of resilience may be an issue for some individuals after moderate to severe TBI. Identifying persons most likely at risk for low resilience may be useful in planning clinical interventions.

Chronic dry eye symptoms after LASIK: parallels and lessons to be learned from other persistent post-operative pain disorders.

Laser in-situ keratomileusis (LASIK) is a commonly performed surgical procedure used to correct refractive error. LASIK surgery involves cutting a corneal flap and ablating the stroma underneath, with known damage to corneal nerves. Despite this, the epidemiology of persistent pain and other long-term outcomes after LASIK surgery are not well understood. Available data suggest that approximately 20-55% of patients report persistent eye symptoms (generally regarded as at least 6 months post-operation) after LASIK surgery. While it was initially believed that these symptoms were caused by ocular surface dryness, and referred to as "dry eye," it is now increasingly understood that corneal nerve damage produced by LASIK surgery resembles the pathologic neuroplasticity associated with other forms of persistent post-operative pain. In susceptible patients, these neuropathological changes, including peripheral sensitization, central sensitization, and altered descending modulation, may underlie certain persistent dry eye symptoms after LASIK surgery. This review will focus on the known epidemiology of symptoms after LASIK and discuss mechanisms of persistent post-op pain due to nerve injury that may be relevant to these patients. Potential preventative and treatment options based on approaches used for other forms of persistent post-op pain and their application to LASIK patients are also discussed. Finally, the concept of genetic susceptibility to post-LASIK ocular surface pain is presented.

Human Tear Serotonin Levels Correlate with Symptoms and Signs of Dry Eye.

PURPOSE: Serotonin, a neurotransmitter known to be involved in nociceptor sensitization, is present in human tears. The purpose of this study was to correlate tear serotonin levels, as a marker of nociceptor sensitization, to facets of dry eye (DE), including symptoms and signs. DESIGN: Cross-sectional study. PARTICIPANTS: A total of 62 patients with normal eyelid and corneal anatomy were prospectively recruited from a Veterans Administration Ophthalmology Clinic over 11 months. METHODS: Dry eye symptoms (Ocular Surface Disease Index [OSDI]), signs (tear break-up time [TBUT], corneal staining, and Schirmer's score), and clinical descriptors of neuropathic ocular pain (NOP) (sensitivity to light or sensitivity to wind) were assessed. For tear analysis, each patient's tears were collected after instilling 50 µl of sterile saline to the lower cul-de-sac of each eye and using capillary action microcaps to collect the ocular wash. Tear serotonin levels were measured using enzyme-linked immunosorbent assay. MAIN OUTCOME MEASURES: Correlations between tear serotonin concentrations and DE symptoms and signs. RESULTS: The mean age of the population was 61±14 years, and 84% (n = 52) of the patients were male. Serotonin concentrations negatively correlated with Schirmer's scores (r = -0.28; P = 0.02) but did not correlate with other DE parameters, such as OSDI scores, sensitivity to light or wind, TBUT, and staining. According to our hypothesis, we divided patients into groups based on both DE symptoms and aqueous tear production; serotonin concentrations were significantly higher in DE group 1 (OSDI ≥6 and Schirmer's <8) compared with both DE group 2 (OSDI ≥6 and Schirmer's ≥8) and controls (OSDI <6 and Schirmer's ≥8). Patients in DE group 2 more frequently reported sensitivity to light (64%) and wind (67%) compared with DE group 1 (40% and 60%, respectively) and controls (8% and 17%, respectively). CONCLUSIONS: Patients with DE symptoms and aqueous tear deficiency had higher tear serotonin levels compared with those with DE symptoms but normal tear production and those without DE symptoms.

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 (ß = -0.26, p = 0.02) and only the corneal nerve fiber area remained significantly related to corneal sensation (ß = 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.