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Ocular neuropathic pain (ONP) has various etiologies, and patients have various symptoms. The clinical management of patients with ONP has been debated. We aimed to evaluate the effect of repeated greater occipital nerve block (GONB) on ONP based on convergence in the trigeminocervical complex. In this single-center retrospective study, the medical records of 204 patients who were referred to the pain clinic by the ophthalmology department of our hospital and subsequently underwent repeated GONB for chronic ONP between January 2008 and February 2022 were analyzed. They received GONB every two weeks, up to 10 times. Symptoms of ONP were divided into five categories: eye pain, dysesthesias/allodynia, non-eye pain, visual disturbance, and tearing. The primary outcome of this study was the pain relief scale (PRS) score after repeated injections. The differences and magnitude of decrease in the overall pain relief scale score were statistically significant (estimate = -0.55, p < 0.001). There were two patients who had recurrence of ONP and seven patients who had adverse events. According to our study, repeated GONB can reduce symptom severity in patients with ONP. Therefore, it appears that GONB can be considered a multimodal management method for ONP.

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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.

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BACKGROUND: Purpose of the present systematic review is to investigate preclinical evidence in favor of the working hypothesis of efficacy of cannabinoids in ocular pain treatment. METHODS: Literature search includes the most relevant repositories for medical scientific literature from inception until November, 24 2021. Data collection and selection of retrieved records adhere to PRISMA criteria. RESULTS: In agreement with a priori established protocol the search retrieved 2471 records leaving 479 results after duplicates removal. Eleven records result from title and abstract screening to meet the inclusion criteria; only 4 results are eligible for inclusion in the qualitative synthesis impeding meta-analysis. The qualitative analysis highlights the antinociceptive and anti-inflammatory efficacy of Δ8-tetrahydrocannabinol, cannabidiol and its derivative HU-308 and of new racemic CB1 allosteric ligand GAT211 and its enantiomers GAT228 and GAT229. Moreover, CB2R agonists RO6871304 and RO6871085 and CB2R ligand HU910 provide evidence of anti-inflammatory efficacy. CB2 agonist HU308 reduces of 241% uveitis-induced leukocyte adhesion and changes lipidome profile. Methodological and design issues raise concern of risk of bias and the amount of studies is too small for generalization. Furthermore, the ocular pain model used can resemble only inflammatory but not neuropathic pain. CONCLUSIONS: The role of the endocannabinoid system in ocular pain is underinvestigated, since only two studies assessing the effects of cannabinoid receptors modulators on pain behavior and other two on pain-related inflammatory processes are found. Preclinical studies investigating the efficacy of cannabinoids in ocular inflammatory and neuropathic pain models are needed to pave the way for clinical translation.

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INTRODUCTION: Transient dry eye symptoms have been reported following laser in situ keratomileusis (LASIK). Very rarely, patients may present with debilitating symptoms of dry eye syndrome (DES) with limited or no evidence of ocular surface disease. These patients are diagnosed with a form of DES known as neuropathic corneal pain (NCP). PATIENTS AND METHODS: This study is a retrospective medical record review of a case series of 18 patients who developed NCP post-LASIK over the years 1996-2021. All patients who developed severe ocular pain following LASIK consistent with NCP were included. Patients with severe ocular pain who had evidence of severe ocular surface disease or other ophthalmic etiology to explain their debilitating symptoms were not included. RESULTS: The average age of patients in our study was 39.5 years. The majority of our patients were female (72.2%) and of Caucasian ancestry (83.3%). The average onset of symptoms was 9.6 months post-LASIK. Patients had past medical histories significant for neuropsychiatric conditions (50%), functional pain syndromes (22.2%), autoimmune diseases (33.3%), and hypothyroidism (27.8%), and the occurrence of these was higher than the national prevalence of these diseases. Symptoms were consistent with the severity and characteristics defining NCP. Treatment was multimodal, involved topical and systemic therapies, and was unique to each patient. Overall, the majority of patients had clinical improvement in symptoms following treatment with regular follow-up. CONCLUSION: Although rare, the 26-year prevalence of NCP post-LASIK in our study was roughly 1 in 900 cases. The mean time to onset after surgery was delayed at 9.6 months. Certain risk factors such as neuropsychiatric conditions, history of functional pain syndromes, history of autoimmune conditions, and hypothyroidism may predispose patients to the development of this condition. Patients benefited from proper diagnosis and a multimodal approach to treatment.

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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.

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PURPOSE: Pain is a frequently reported symptom in dry eye disease (DED). We examine the factors associated with ocular pain severity and patient-reported improvement in ocular pain to commonly used dry eye and pain treatments. METHODS: Cross-sectional study of patients presenting for dry eye management. Demographics, ocular and medical history, OSDI, numeric pain scale, pain descriptors, and subjective response to tried eye drop, systemic, and non-pharmacologic treatments were collected. Statistical analysis was performed to identify differential treatment response in patients with various pain levels using the non-parametric test for trend. RESULTS: 144 patients were categorized into 4 groups according to reported pain severity. Increasing pain was significantly associated with younger age, history of refractive surgery, higher OSDI score, and less likelihood of corneal staining. Patients with higher pain intensity were more likely to report a history of fibromyalgia, depression, anxiety, and migraine. Patients with greater pain severity were less responsive to treatment with artificial tears (p < 0.001), lubricating ointment (p = 0.002), steroid eye drops (p = 0.03), cyclosporine 0.05% (p = 0.03), 20% autologous serum tears (p = 0.01), hot compresses (p = 0.04), lid hygiene (p = 0.002) and punctal occlusion (p = 0.03). CONCLUSIONS: Dry eye patients with severe ocular pain often have associated psychological and systemic pain conditions. Treating the underlying DED is beneficial in reducing ocular pain, however the low rate of a satisfactory response highlights the need for further investigation of effective therapies. Cross-sectional studies can provide guidance in the treatment of patients with dry eye-related ocular pain and guide future prospective studies on potentially effective therapies.

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