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Liu C, Lin MTY, Lee IXY, Wong JHF, Lu D, Lam TC, Zhou L, Mehta JS, Ong HS, Ang M, Tong L, Liu YC. Neuropathic Corneal Pain: Tear Proteomic and Neuromediator Profiles, Imaging Features, and Clinical Manifestations. Am J Ophthalmol 2024; 265:6-20. [PMID: 38521157 DOI: 10.1016/j.ajo.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 01/05/2024] [Accepted: 03/15/2024] [Indexed: 03/25/2024]
Abstract
PURPOSE To investigate the tear proteomic and neuromediator profiles, in vivo confocal microscopy (IVCM) imaging features, and clinical manifestations in neuropathic corneal pain (NCP) patients. DESIGN Cross-sectional study. METHODS A total of 20 NCP patients and 20 age-matched controls were recruited. All subjects were evaluated by corneal sensitivity, Schirmer test, tear break-up time, and corneal and ocular surface staining, Ocular Surface Disease Index and Ocular Pain Assessment Survey questionnaires were administered, as well as IVCM examinations for corneal nerves, microneruomas, and epithelial and dendritic cells. Tears were collected for neuromediator and proteomic analysis using enzyme-linked immunosorbent assay and data-independent acquisition mass spectrometry. RESULTS Burning and sensitivity to light were the 2 most common symptoms in NCP. A total of 188 significantly dysregulated proteins, such as elevated metallothionein-2, creatine kinases B-type, vesicle-associated membrane protein 2, neurofilament light polypeptide, and myelin basic protein, were identified in the NCP patients. The top 10 dysregulated biological pathways in NCP include neurotoxicity, axonal signaling, wound healing, neutrophil degradation, apoptosis, thrombin signaling mitochondrial dysfunction, and RHOGDI and P70S6K signaling pathways. Compared to controls, the NCP cohort presented with significantly decreased corneal sensitivity (P < .001), decreased corneal nerve fiber length (P = .003), corneal nerve fiber density (P = .006), and nerve fiber fractal dimension (P = .033), as well as increased corneal nerve fiber width (P = .002), increased length, total area and perimeter of microneuromas (P < .001, P < .001, P = .019), smaller corneal epithelial size (P = .017), and higher nerve growth factor level in tears (P = .006). CONCLUSIONS These clinical manifestations, imaging features, and molecular characterizations would contribute to the diagnostics and potential therapeutic targets for NCP.
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Affiliation(s)
- Chang Liu
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Cornea and Refractive Surgery Group (C.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore
| | - Molly Tzu-Yu Lin
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore
| | - Isabelle Xin Yu Lee
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore
| | - Jipson Hon Fai Wong
- Clinical Research Platform (J.H.F.W.), Singapore Eye Research Institute, Singapore
| | - Daqian Lu
- Centre for Myopia Research (D.L., T.C.L.), School of Optometry, Hong Kong Polytechnic University, Hong Kong
| | - Thomas Chuen Lam
- Centre for Myopia Research (D.L., T.C.L.), School of Optometry, Hong Kong Polytechnic University, Hong Kong; Centre for Eye and Vision Research (CEVR) (T.C.L.), Hong Kong
| | - Lei Zhou
- School of Optometry (L.Z.), Department of Applied Biology and Chemical Technology, Research Centre for SHARP Vision (RCSV); The Hong Kong Polytechnic University, Hong Kong
| | - Jodhbir S Mehta
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Cornea and Refractive Surgery Group (C.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Department of Cornea and External Eye Disease (J.S.M., H.S.O., M.A., L.T., Y.-C.L.), Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program (J.S.M., H.S.O., M.A., Y.-C.L.), Duke-NUS Medical School, Singapore
| | - Hon Shing Ong
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Cornea and Refractive Surgery Group (C.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Department of Cornea and External Eye Disease (J.S.M., H.S.O., M.A., L.T., Y.-C.L.), Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program (J.S.M., H.S.O., M.A., Y.-C.L.), Duke-NUS Medical School, Singapore
| | - Marcus Ang
- Department of Cornea and External Eye Disease (J.S.M., H.S.O., M.A., L.T., Y.-C.L.), Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program (J.S.M., H.S.O., M.A., Y.-C.L.), Duke-NUS Medical School, Singapore
| | - Louis Tong
- Department of Cornea and External Eye Disease (J.S.M., H.S.O., M.A., L.T., Y.-C.L.), Singapore National Eye Centre, Singapore; Ocular Surface Research Group (L.T.), Singapore Eye Research Institute, Singapore; Eye Academic Clinical Program (L.T.), Duke-NUS Medical School, Singapore; Department of Ophthalmology (L.T.), Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Yu-Chi Liu
- From Tissue Engineering and Cell Therapy Group (C.L., M.T.-Y.L., I.X.Y.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Cornea and Refractive Surgery Group (C.L., J.S.M., H.S.O., Y.-C.L.), Singapore Eye Research Institute, Singapore; Department of Cornea and External Eye Disease (J.S.M., H.S.O., M.A., L.T., Y.-C.L.), Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program (J.S.M., H.S.O., M.A., Y.-C.L.), Duke-NUS Medical School, Singapore; Department of Ophthalmology (Y.-C.L.), National Taiwan University, Taiwan.
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Chow BJ, Lee IXY, Liu C, Liu YC. Potential therapeutic effects of peroxisome proliferator-activated receptors on corneal diseases. Exp Biol Med (Maywood) 2024; 249:10142. [PMID: 38993197 PMCID: PMC11238193 DOI: 10.3389/ebm.2024.10142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Accepted: 06/12/2024] [Indexed: 07/13/2024] Open
Abstract
The cornea is an avascular tissue in the eye that has multiple functions in the eye to maintain clear vision which can significantly impair one's vision when subjected to damage. Peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptor proteins comprising three different peroxisome proliferator-activated receptor (PPAR) isoforms, namely, PPAR alpha (α), PPAR gamma (γ), and PPAR delta (δ), have emerged as potential therapeutic targets for treating corneal diseases. In this review, we summarised the current literature on the therapeutic effects of PPAR agents on corneal diseases. We discussed the role of PPARs in the modulation of corneal wound healing, suppression of corneal inflammation, neovascularisation, fibrosis, stimulation of corneal nerve regeneration, and amelioration of dry eye by inhibiting oxidative stress within the cornea. We also discussed the underlying mechanisms of these therapeutic effects. Future clinical trials are warranted to further attest to the clinical therapeutic efficacy.
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Affiliation(s)
- Bing Jie Chow
- Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Isabelle Xin Yu Lee
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Chang Liu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Yu-Chi Liu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore (NUS) Medical School, Singapore, Singapore
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Mansoor H, Lee IXY, Lin MTY, Ang HP, Xue YC, Krishaa L, Patil M, Koh SK, Tan HC, Zhou L, Liu YC. Topical and oral peroxisome proliferator-activated receptor-α agonist ameliorates diabetic corneal neuropathy. Sci Rep 2024; 14:13435. [PMID: 38862650 PMCID: PMC11167005 DOI: 10.1038/s41598-024-64451-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 06/10/2024] [Indexed: 06/13/2024] Open
Abstract
Diabetic corneal neuropathy (DCN) is a common diabetic ocular complication with limited treatment options. In this study, we investigated the effects of topical and oral fenofibrate, a peroxisome proliferator-activated receptor-α agonist, on the amelioration of DCN using diabetic mice (n = 120). Ocular surface assessments, corneal nerve and cell imaging analysis, tear proteomics and its associated biological pathways, immuno-histochemistry and western blot on PPARα expression, were studied before and 12 weeks after treatment. At 12 weeks, PPARα expression markedly restored after topical and oral fenofibrate. Topical fenofibrate significantly improved corneal nerve fibre density (CNFD) and tortuosity coefficient. Likewise, oral fenofibrate significantly improved CNFD. Both topical and oral forms significantly improved corneal sensitivity. Additionally, topical and oral fenofibrate significantly alleviated diabetic keratopathy, with fenofibrate eye drops demonstrating earlier therapeutic effects. Both topical and oral fenofibrate significantly increased corneal β-III tubulin expression. Topical fenofibrate reduced neuroinflammation by significantly increasing the levels of nerve growth factor and substance P. It also significantly increased β-III-tubulin and reduced CDC42 mRNA expression in trigeminal ganglions. Proteomic analysis showed that neurotrophin signalling and anti-inflammation reactions were significantly up-regulated after fenofibrate treatment, whether applied topically or orally. This study concluded that both topical and oral fenofibrate ameliorate DCN, while topical fenofibrate significantly reduces neuroinflammation.
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Affiliation(s)
| | - Isabelle Xin Yu Lee
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - Molly Tzu-Yu Lin
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - Heng Pei Ang
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - Yao Cong Xue
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - L Krishaa
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - Moushmi Patil
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore
| | - Siew-Kwan Koh
- Ocular Proteomic Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Hong Chang Tan
- Department of Endocrinology, Singapore General Hospital, Singapore, Singapore
| | - Lei Zhou
- Department of Applied Biology and Chemical Technology, School of Optometry, Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hung Hom, Hong Kong
- Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Pak Shek Kok, Hong Kong
| | - Yu-Chi Liu
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, 11 Third Hospital Ave, Singapore, 168751, Singapore.
- Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore, Singapore.
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore, Singapore.
- Eye-Academic Clinical Program, Singapore Graduate Medical School, Duke-National University, Singapore, Singapore.
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.
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Gong Q, Huang K, Li K, Tong Y, Zhao J, Wang H, Xu Z, Lin M, Lu F, Hu L. Structural and functional changes of binocular corneal innervation and ocular surface function after unilateral SMILE and tPRK. Br J Ophthalmol 2024:bjo-2023-324358. [PMID: 38527771 DOI: 10.1136/bjo-2023-324358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 02/18/2024] [Indexed: 03/27/2024]
Abstract
AIMS To evaluate the bilateral changes in the sub-basal nerve plexus of the cornea and ocular surface function after unilateral small incision lenticule extraction (SMILE) and transepithelial photorefractive keratectomy (tPRK) procedures. METHODS 34 patients were enrolled in the study and underwent unilateral SMILE (21 of 34 patients) or unilateral tPRK (13 of 34 patients). Complete ophthalmic examinations, tear film function tests and Cochet-Bonnet esthesiometry were conducted to assess the effects of the surgeries on the corneal nerves and tear function. Morphological changes were assessed using in vivo confocal microscopy to evaluate the corneal sub-basal nerve plexus and dendritic cells. ELISA was used to measure the tear neuromediators. Clinical and morphological data at each follow-up point were compared with preoperative baseline values. RESULTS All patients who underwent unilateral SMILE or tPRK procedures exhibited bilateral corneal nerve degenerative changes, decreased corneal sensitivity, worsening of dry eye symptoms and changes in bilateral tear neuromediators. In the SMILE group, bilateral corneal sensitivity was positively correlated with corneal nerve fibre length and negatively correlated with dendritic cell area. The dry eye severity was negatively correlated with corneal sensitivity. Tear levels of substance P and nerve growth factor were positively correlated with mean dendritic cell area and dry eye severity, but negatively correlated with corneal sensitivity. In the tPRK group, bilateral corneal sensitivity was positively correlated with corneal nerve fibre density. CONCLUSIONS Unilateral refractive surgery may bilaterally affect the morphology and function of corneal nerves and ocular surface status postoperatively.
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Affiliation(s)
- Qianwen Gong
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Kaiyan Huang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Kexin Li
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yixuan Tong
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jian Zhao
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Hui Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhiqiang Xu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Meng Lin
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Fan Lu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Liang Hu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
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Chin JY, Liu C, Lee IXY, Lin MTY, Cheng CY, Wong JHF, Teo CL, Mehta JS, Liu YC. Impact of Age on the Characteristics of Corneal Nerves and Corneal Epithelial Cells in Healthy Adults. Cornea 2024; 43:409-418. [PMID: 37643477 PMCID: PMC10906190 DOI: 10.1097/ico.0000000000003363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 05/26/2023] [Accepted: 07/02/2023] [Indexed: 08/31/2023]
Abstract
PURPOSE The aim of this study was to investigate age-related changes in corneal nerves and corneal epithelial cell parameters and to establish age-adjusted reference values. METHODS A total of 7025 corneal nerve images and 4215 corneal epithelial images obtained using in vivo confocal microscopy from 281 eyes of 143 healthy participants were included. Seven corneal nerve parameters and 3 corneal epithelial cell parameters were quantified using 2 automatic analytic software and analyzed across 6 age groups ranging from 21 to 80 years. RESULTS There was a declining trend in all 7 nerve parameters with advancing age. In particular, corneal nerve fiber length and corneal nerve fiber density demonstrated a significant decrease in subjects aged 65 years or older compared with subjects younger than 65 years (10.8 ± 2.6 mm/mm 2 vs. 9.9 ± 2.0 mm/mm 2 , P = 0.011 in corneal nerve fiber length; 15.8 ± 5.2 fibers/mm 2 vs. 14.4 ± 4.3 fibers/mm 2 , P = 0.046 in corneal nerve fiber density), whereas corneal nerve fractal dimension demonstrated a borderline significant decrease ( P = 0.057). Similarly, there was a general declining trend in all epithelial cell parameters with advancing age. Corneal epithelial cell circularity was significantly lower in subjects aged 65 years and older as compared to subjects younger than 65 years (0.722 ± 0.021 μm 2 vs. 0.714 ± 0.021 μm 2 ; P = 0.011). CONCLUSIONS Advancing age results in reduced corneal nerve metrics and alteration of corneal cell morphology. Aging effects should be considered when evaluating patients with corneal neuropathy.
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Affiliation(s)
- Jia Ying Chin
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Chang Liu
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Isabelle Xin Yu Lee
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Molly Tzu Yu Lin
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Ching-Yu Cheng
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
- Epidemiology Group, Singapore Eye Research Institute, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore
| | - Jipson Hon Fai Wong
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Cong Ling Teo
- Epidemiology Group, Singapore Eye Research Institute, Singapore
| | - Jodhbir S. Mehta
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore; and
| | - Yu-Chi Liu
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore; and
- Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan
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Wong NSQ, Liu C, Lin MTY, Lee IXY, Tong L, Liu YC. Neuropathic Corneal Pain after Coronavirus Disease 2019 (COVID-19) Infection. Diseases 2024; 12:37. [PMID: 38391784 PMCID: PMC10887979 DOI: 10.3390/diseases12020037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 02/01/2024] [Accepted: 02/05/2024] [Indexed: 02/24/2024] Open
Abstract
INTRODUCTION This is a case report of a patient with neuropathic corneal pain after coronavirus disease 2019 (COVID-19) infection. METHODS A previously healthy 27-year-old female presented with bilateral eye pain accompanied by increased light sensitivity 5 months after COVID-19 infection. She was diagnosed with neuropathic corneal pain based on clear corneas without fluorescein staining, alongside the presence of microneuromas, dendritic cells, and activated stromal keratocytes identified bilaterally on in vivo confocal microscopy. RESULTS The patient's tear nerve growth factor, substance P, and calcitonin gene-related peptide levels were 5.9 pg/mL, 2978.7 pg/mL, and 1.1 ng/mL, respectively, for the right eye and 23.1 pg/mL, 4798.7 pg/mL, and 1.2 ng/mL, respectively, for the left eye, suggesting corneal neuroinflammatory status. After 6 weeks of topical 0.1% flurometholone treatment, decreased microneuroma size, less extensive dendritic cells, and reduced tear nerve growth factor and substance P levels were observed. The scores on the Ocular Pain Assessment Survey showed an improvement in burning sensation and light sensitivity, decreasing from 80% and 70% to 50% for both. CONCLUSIONS Neuropathic corneal pain is a potential post-COVID-19 complication that warrants ophthalmologists' and neurologists' attention.
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Affiliation(s)
- Natalie Shi Qi Wong
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
| | - Chang Liu
- Singapore Eye Research Institute, Singapore 169856, Singapore
| | | | | | - Louis Tong
- Singapore Eye Research Institute, Singapore 169856, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore 168751, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore 169857, Singapore
| | - Yu-Chi Liu
- Singapore Eye Research Institute, Singapore 169856, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore 168751, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore 169857, Singapore
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Toh CJL, Liu C, Lee IXY, Lin MTY, Tong L, Liu YC. Clinical associations of corneal neuromas with ocular surface diseases. Neural Regen Res 2024; 19:140-147. [PMID: 37488855 PMCID: PMC10479835 DOI: 10.4103/1673-5374.375308] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/04/2023] [Accepted: 04/06/2023] [Indexed: 07/26/2023] Open
Abstract
Corneal neuromas, also termed microneuromas, refer to microscopic, irregularly-shaped enlargements of terminal subbasal nerve endings at sites of nerve damage or injury. The formation of corneal neuromas results from damage to corneal nerves, such as following corneal pathology or corneal or intraocular surgeries. Initially, denervated areas of sensory nerve fibers become invaded by sprouts of intact sensory nerve fibers, and later injured axons regenerate and new sprouts called neuromas develop. In recent years, analysis of corneal nerve abnormalities including corneal neuromas which can be identified using in vivo confocal microscopy, a non-invasive imaging technique with microscopic resolution, has been used to evaluate corneal neuropathy and ocular surface dysfunction. Corneal neuromas have been shown to be associated with clinical symptoms of discomfort and dryness of eyes, and are a promising surrogate biomarker for ocular surface diseases, such as neuropathic corneal pain, dry eye disease, diabetic corneal neuropathy, neurotrophic keratopathy, Sjögren's syndrome, bullous keratopathy, post-refractive surgery, and others. In this review, we have summarized the current literature on the association between these ocular surface diseases and the presentation of corneal microneuromas, as well as elaborated on their pathogenesis, visualization via in vivo confocal microscopy, and utility in monitoring treatment efficacy. As current quantitative analysis on neuromas mainly relies on manual annotation and quantification, which is user-dependent and labor-intensive, future direction includes the development of artificial intelligence software to identify and quantify these potential imaging biomarkers in a more automated and sensitive manner, allowing it to be applied in clinical settings more efficiently. Combining imaging and molecular biomarkers may also help elucidate the associations between corneal neuromas and ocular surface diseases.
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Affiliation(s)
| | - Chang Liu
- Singapore Eye Research Institute, Singapore
| | | | | | - Louis Tong
- Singapore Eye Research Institute, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
| | - Yu-Chi Liu
- Singapore Eye Research Institute, Singapore
- Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
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Liu C, Lin MTY, Lee IXY, Mehta JS, Liu YC. Impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction and LASIK. J Cataract Refract Surg 2023; 49:1106-1113. [PMID: 37867284 PMCID: PMC10583913 DOI: 10.1097/j.jcrs.0000000000001278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/27/2023] [Accepted: 07/28/2023] [Indexed: 10/24/2023]
Abstract
PURPOSE To evaluate the impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). SETTING Singapore National Eye Center, Singapore. DESIGN Prospective study. METHODS 88 eyes undergoing SMILE or LASIK were divided into low-moderate (manifest refractive spherical equivalent [MRSE] <-6.0 diopters [D]) and high myopic (MRSE ≥-6.0 D) groups. In vivo confocal microscopy and clinical assessments were performed preoperatively and at 1 month, 3 months, 6 months, and 12 months postoperatively. RESULTS In SMILE, high myopic treatment presented with significantly greater reduction in the corneal nerve fiber area (CNFA) and nerve fiber fractal dimension (CFracDim) compared with low-moderate myopic treatment (both P < .05). There was a significant and negative correlation between the corrected MRSE and the reduction in corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length, CNFA, and CFracDim after SMILE (r = -0.38 to -0.66, all P < .05). In LASIK, a significant correlation between the MRSE and the changes in CNBD, corneal nerve fiber total branch density, CNFA (r = -0.37 to -0.41), and corneal nerve fiber width (r = 0.43) was observed (all P < .05). Compared with SMILE, LASIK had greater reduction in CNBD and CNFA for every diopter increase in the corrected MRSE. High myopic SMILE, compared with low-moderate myopic SMILE, resulted in significantly lower tear break-up time at 1 and 6 months (both P < .05). The changes in CNFA and CFracDim were significantly associated with Schirmer test values (both P < .001). CONCLUSIONS Postoperative corneal denervation was related to corrected refractive power in both SMILE and LASIK. With the same refractive correction, LASIK led to more prominent corneal denervation.
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Affiliation(s)
- Chang Liu
- From the Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore (C. Liu, Lin, Lee, Mehta, Y.-C. Liu); Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore (C. Liu, Mehta); Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore (Mehta, Y.-C. Liu); Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore (Mehta, Y.-C. Liu); Department of Ophthalmology, National Taiwan University, Taiwan (Y.-C. Liu)
| | - Molly Tzu-Yu Lin
- From the Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore (C. Liu, Lin, Lee, Mehta, Y.-C. Liu); Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore (C. Liu, Mehta); Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore (Mehta, Y.-C. Liu); Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore (Mehta, Y.-C. Liu); Department of Ophthalmology, National Taiwan University, Taiwan (Y.-C. Liu)
| | - Isabelle Xin Yu Lee
- From the Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore (C. Liu, Lin, Lee, Mehta, Y.-C. Liu); Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore (C. Liu, Mehta); Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore (Mehta, Y.-C. Liu); Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore (Mehta, Y.-C. Liu); Department of Ophthalmology, National Taiwan University, Taiwan (Y.-C. Liu)
| | - Jodhbir S. Mehta
- From the Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore (C. Liu, Lin, Lee, Mehta, Y.-C. Liu); Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore (C. Liu, Mehta); Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore (Mehta, Y.-C. Liu); Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore (Mehta, Y.-C. Liu); Department of Ophthalmology, National Taiwan University, Taiwan (Y.-C. Liu)
| | - Yu-Chi Liu
- From the Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore (C. Liu, Lin, Lee, Mehta, Y.-C. Liu); Cornea and Refractive Surgery Group, Singapore Eye Research Institute, Singapore (C. Liu, Mehta); Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore (Mehta, Y.-C. Liu); Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore (Mehta, Y.-C. Liu); Department of Ophthalmology, National Taiwan University, Taiwan (Y.-C. Liu)
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So WZ, Qi Wong NS, Tan HC, Yu Lin MT, Yu Lee IX, Mehta JS, Liu YC. Diabetic corneal neuropathy as a surrogate marker for diabetic peripheral neuropathy. Neural Regen Res 2022; 17:2172-2178. [PMID: 35259825 PMCID: PMC9083173 DOI: 10.4103/1673-5374.327364] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Diabetic neuropathy is a prevalent microvascular complication of diabetes mellitus, affecting nerves in all parts of the body including corneal nerves and peripheral nervous system, leading to diabetic corneal neuropathy and diabetic peripheral neuropathy, respectively. Diabetic peripheral neuropathy is diagnosed in clinical practice using electrophysiological nerve conduction studies, clinical scoring, and skin biopsies. However, these diagnostic methods have limited sensitivity in detecting small-fiber disease, hence they do not accurately reflect the status of diabetic neuropathy. More recently, analysis of alterations in the corneal nerves has emerged as a promising surrogate marker for diabetic peripheral neuropathy. In this review, we will discuss the relationship between diabetic corneal neuropathy and diabetic peripheral neuropathy, elaborating on the foundational aspects of each: pathogenesis, clinical presentation, evaluation, and management. We will further discuss the relevance of diabetic corneal neuropathy in detecting the presence of diabetic peripheral neuropathy, particularly early diabetic peripheral neuropathy; the correlation between the severity of diabetic corneal neuropathy and that of diabetic peripheral neuropathy; and the role of diabetic corneal neuropathy in the stratification of complications of diabetic peripheral neuropathy.
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Affiliation(s)
- Wei Zheng So
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore; Singapore Eye Research Institute, Singapore, Singapore
| | - Natalie Shi Qi Wong
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore; Singapore Eye Research Institute, Singapore, Singapore
| | - Hong Chang Tan
- Department of Endocrinology, Singapore General Hospital, Singapore, Singapore
| | | | | | - Jodhbir S Mehta
- Singapore Eye Research Institute; Department of Cornea and External Eye Disease, Singapore National Eye Centre; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
| | - Yu-Chi Liu
- Singapore Eye Research Institute; Department of Cornea and External Eye Disease, Singapore National Eye Centre; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
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Changes of Subjective Symptoms and Tear Film Biomarkers following Femto-LASIK. Int J Mol Sci 2022; 23:ijms23147512. [PMID: 35886858 PMCID: PMC9320097 DOI: 10.3390/ijms23147512] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 06/26/2022] [Accepted: 07/04/2022] [Indexed: 02/01/2023] Open
Abstract
Femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) represents a common treatment modality in refractive surgery and shows excellent results in terms of safety, efficacy, predictability, and long-term stability. However, patients may be affected by dry eye symptoms. The aim of this study was to identify a potential association between subjective dry eye symptoms, objective dry eye markers, and possible changes in the tear film, which could be a target for future therapy development. Therefore, clinical (dry eye) examinations (OSDI, Schirmer test, lissamine green and fluorescein staining, BUT, visual acuity) were carried out before LASIK as well as 5 and 90 days post-OP. The dry eye marker MMP-9, cytokines (IL-1β, IL-8), and pain markers (NGF, CGRP) were quantified in tear samples with immunoassays. In addition, correlation analyses were performed. Clinical examinations revealed an upregulated OSDI score 5 days post-OP and an increased lissamine green staining score 90 days post-OP. Downregulated CGRP levels were noted 5 days post-OP, while other protein markers were not significantly altered after Femto-LASIK. Hence, Femto-LASIK surgery induced subjective symptoms like that of dry eye which could objectively rather be classified as Femto-LASIK-related discomfort. In the future, this could possibly be better detected and treated using pain markers such as CGRP.
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Wang W, Yang X, Yao Q, Xu Q, Liu W, Liu J. Corneal confocal microscopic characteristics of acute angle-closure crisis. BMC Ophthalmol 2022; 22:21. [PMID: 35016625 PMCID: PMC8753899 DOI: 10.1186/s12886-022-02253-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 01/07/2022] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
To investigate characteristics of the acute angle-closure crisis (AACC) and fellow eyes using confocal microscopy.
Methods
Unilateral AACC patients hospitalized at the Xi’an People’s Hospital from October 2017 to October 2020 were recruited in this cross-sectional study. Age-matched participants scheduled for cataract surgery were enrolled as a healthy control group. Corneal epithelial cells, subepithelial nerve fiber plexus, stromal cells, and endothelial cells were examined by confocal and specular microscopy.
Results
This study enrolled 41 unilateral AACC patients (82 eyes) and 20 healthy controls (40 eyes). Confocal microscopy revealed that the corneal nerve fiber density, corneal nerve branch density and corneal nerve fiber length were reduced significantly in AACC eyes. The stromal cells were swollen and the size of the endothelial cells was uneven with the deposition of punctate high-reflective keratic precipitate on the surface. In severe cases, the cell volume was enlarged, deformed, and fused. The corneal subepithelial nerve fiber, stromal layer, and endothelial layer were unremarkable in the fellow eyes, and the density of the endothelial cells was 2601 ± 529 cells/mm2, which was higher than 1654 ± 999 cells/mm2 in AACC eyes (P < 0.001). Corneal edema prevented the examination of 17 eyes using specular microscopy and in only four eyes using confocal microscopy. There were no significant differences in endothelial cell density between confocal and specular microscopy in the AACC eyes (P = 0.674) and fellow eyes (P = 0.247). The hexagonal cell ratio reduced significantly (P < 0.001), and average cell size and coefficient of variation of the endothelial cells increased significantly compared with fellow eyes (P < 0.001, P = 0.008).
Conclusions
AACC eye showed decreased density and length of corneal subepithelial nerve fiber plexus, activation of stromal cells, increased endothelial cell polymorphism, and decreased density.
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