Comparison of tear proteomic and neuromediator profiles changes between small incision lenticule extraction (SMILE) and femtosecond laser-assisted in-situ keratomileusis (LASIK)

Neuropathic Corneal Pain: Tear Proteomic and Neuromediator Profiles, Imaging Features, and Clinical Manifestations

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.

Topical and oral peroxisome proliferator-activated receptor-α agonist ameliorates diabetic corneal neuropathy

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.

Dry Eye Disease: An Update on Changing Perspectives on Causes, Diagnosis, and Management

Dry eye disease is a common clinical problem encountered by ophthalmologists worldwide. Interest in this entity has increased in recent years due to the consequences it has on the ocular surface after any surface procedure. With changing times, several new factors have come to light that can influence this disease. The effect of the COVID-19 pandemic has also been greatly felt, with a range of causes, starting from increased screen work to inflammatory processes, exacerbating the condition in many. With changes in the concepts of the etiopathogenesis of the disease, a paradigm shift has taken place in the approaches to treatment. More researchers are in favor of a new tear film-oriented approach that tries to localize the disease to a single component in the tear film. Innovation of newer techniques for the treatment of meibomian gland disease has also made its foray into clinical ophthalmology. Newer drug formulations and molecules are underway to better treat the inflammatory component of the disease. Many other receptors and targets for the treatment of dry eyes are being researched. This review hopes to provide a succinct, narrative summary of the relevant research on dry eye disease to date to increase awareness about the nature and future course of this disease and its management.

Applications of artificial intelligence and bioinformatics methodologies in the analysis of ocular biofluid markers: a scoping review

PURPOSE

This scoping review summarizes the applications of artificial intelligence (AI) and bioinformatics methodologies in analysis of ocular biofluid markers. The secondary objective was to explore supervised and unsupervised AI techniques and their predictive accuracies. We also evaluate the integration of bioinformatics with AI tools.

METHODS

This scoping review was conducted across five electronic databases including EMBASE, Medline, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Web of Science from inception to July 14, 2021. Studies pertaining to biofluid marker analysis using AI or bioinformatics were included.

RESULTS

A total of 10,262 articles were retrieved from all databases and 177 studies met the inclusion criteria. The most commonly studied ocular diseases were diabetic eye diseases, with 50 papers (28%), while glaucoma was explored in 25 studies (14%), age-related macular degeneration in 20 (11%), dry eye disease in 10 (6%), and uveitis in 9 (5%). Supervised learning was used in 91 papers (51%), unsupervised AI in 83 (46%), and bioinformatics in 85 (48%). Ninety-eight papers (55%) used more than one class of AI (e.g. > 1 of supervised, unsupervised, bioinformatics, or statistical techniques), while 79 (45%) used only one. Supervised learning techniques were often used to predict disease status or prognosis, and demonstrated strong accuracy. Unsupervised AI algorithms were used to bolster the accuracy of other algorithms, identify molecularly distinct subgroups, or cluster cases into distinct subgroups that are useful for prediction of the disease course. Finally, bioinformatic tools were used to translate complex biomarker profiles or findings into interpretable data.

CONCLUSION

AI analysis of biofluid markers displayed diagnostic accuracy, provided insight into mechanisms of molecular etiologies, and had the ability to provide individualized targeted therapeutic treatment for patients. Given the progression of AI towards use in both research and the clinic, ophthalmologists should be broadly aware of the commonly used algorithms and their applications. Future research may be aimed at validating algorithms and integrating them in clinical practice.

Comparison of early changes in tear film protein profiles after small incision lenticule extraction (SMILE) and femtosecond LASIK (FS-LASIK) surgery

BACKGROUND

Small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK) are widely used surgical methods to correct myopia with comparable efficacy, predictability, and safety. We examined and compared the early changes of tear protein profiles after SMILE and FS-LASIK surgery in order to find possible differences in the initial corneal healing process.

METHODS

SMILE operations for 26 eyes were made with Visumax femtosecond laser. In FS-LASIK surgery for 30 eyes, the flaps were made with Ziemer FEMTO LDV Z6 femtosecond laser and stromal ablation with Wavelight EX500 excimer laser. Tear samples were collected preoperatively, and 1.5 h and 1 month postoperatively using glass microcapillary tubes. Tear protein identification and quantification were performed with sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS).

RESULTS

Immediately (1.5 h) after we found differences in 89 proteins after SMILE and in 123 after FS-LASIK operation compared to preoperative protein levels. Of these differentially expressed proteins, 48 proteins were common for both surgery types. There were, however, quantitative differences between SMILE and FS-LASIK. Upregulated proteins were mostly connected to inflammatory response and migration of the cells connected to immune system. One month after the operation protein expressions levels were returned to baseline levels with both surgical methods.

CONCLUSIONS

Our study showed that immediate changes in protein profiles after SMILE and FS-LASIK surgeries and differences between the methods are connected to inflammatory process, and the protein levels quickly return to the baseline within 1 month. The differences in protein profiles between the methods are probably associated with the different size of the epithelial wound induced.

Neuropathic Corneal Pain after Coronavirus Disease 2019 (COVID-19) Infection

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.

Differences in change of post-operative antioxidant levels between laser-assisted lenticule extraction and femtosecond laser in situ keratomileusis

To evaluate the change of total antioxidant capacity (TAC) and ascorbic acid (AA) between femtosecond laser in situ keratomileusis (FS-LASIK) and laser-assisted lenticule extraction (LALEX). A prospective non-randomized study was conducted, and 33 and 75 eyes that had undergone FS-LASIK or LALEX surgeries were enrolled, respectively. The tear films near corneal incisions were collected, and the concentrations of TAC and AA were determined. The generalized linear mixed model was adopted to calculate the adjusted odds ratio (aOR) with 95% confidence interval (CI) of TAC and AA between the two groups. The AA reduction was significant 1 month after the LALEX and FS-LASIK procedures (both p < 0.05), and the decrement in AA level was significantly larger in the FS-LASIK group compared to the LALEX group (p = 0.0002). In the subgroup analysis, the LALEX group demonstrated a lower decrement in TAC level in the individuals with dry eye disease (DED) than the FS-LASIK group (p = 0.0424), and the LALEX group demonstrated a significantly lower AA decrement in the participants with high myopia (p = 0.0165) and DED (p = 0.0043). The LALEX surgery causes lesser AA decrement compared to FS-LASIK surgery especially for the patients with DED.

Using machine learning model explanations to identify proteins related to severity of meibomian gland dysfunction

Meibomian gland dysfunction is the most common cause of dry eye disease and leads to significantly reduced quality of life and social burdens. Because meibomian gland dysfunction results in impaired function of the tear film lipid layer, studying the expression of tear proteins might increase the understanding of the etiology of the condition. Machine learning is able to detect patterns in complex data. This study applied machine learning to classify levels of meibomian gland dysfunction from tear proteins. The aim was to investigate proteomic changes between groups with different severity levels of meibomian gland dysfunction, as opposed to only separating patients with and without this condition. An established feature importance method was used to identify the most important proteins for the resulting models. Moreover, a new method that can take the uncertainty of the models into account when creating explanations was proposed. By examining the identified proteins, potential biomarkers for meibomian gland dysfunction were discovered. The overall findings are largely confirmatory, indicating that the presented machine learning approaches are promising for detecting clinically relevant proteins. While this study provides valuable insights into proteomic changes associated with varying severity levels of meibomian gland dysfunction, it should be noted that it was conducted without a healthy control group. Future research could benefit from including such a comparison to further validate and extend the findings presented here.

Impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction and LASIK

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.

Impact of Dry Eye Disease on the Uncorrected Distance Visual Acuity after Small Incision Lenticule Extraction

The aim of this study was to explore the impact of dry eye disease (DED) on the uncorrected distance visual acuity (UDVA) and refractive status after small incision lenticule extraction (SMILE). This prospective cohort study enrolled 29 patients (DED group, 11 eyes; non-DED group, 18 eyes) who underwent SMILE in our center from July to September 2022. The examinations on DED, refractive status and UDVA were performed before surgery, and on day 7 and 20 after surgery. The results showed that on day 20 after SMILE, subjects in the non-DED group reported greater changes of ocular surface disease index value increase and tear-film breakup time reduction compared to baseline than those in the DED group (p < 0.001 and p = 0.048, respectively). Compared to preoperative status, DED patients had greater improvements of UDVA and better optometric outcomes on day 20 after surgery than non-DED subjects (p = 0.008 and 0.026, respectively). Multiple linear regression analysis showed age, contact lens daily wearing time, and tear meniscus height before surgery were of the highest value to predict UDVA on day 20 after SMILE in contact lens wearers (p = 0.006, 0.010 and 0.043, respectively). In conclusion, preoperative tear function could affect UDVA after SMILE. The impact of DED on UDVA and refraction should be taken into consideration before surgery.

Chronic Kidney Disease Has No Impact on Tear Film Substance P Concentration in Type 2 Diabetes

PURPOSE

The study aimed to ascertain the potential effects of chronic kidney disease (CKD) on substance P concentration in the tear film of people with type 2 diabetes.

METHODS

Participants were classified into two groups: type 2 diabetes with concurrent chronic kidney disease (T2DM-CKD (n = 25)) and type 2 diabetes without chronic kidney disease (T2DM-no CKD (n = 25)). Ocular surface discomfort assessment, flush tear collection, in-vivo corneal confocal microscopy, and peripheral neuropathy assessment were conducted. Enzyme-linked immunosorbent assays were utilized to ascertain the levels of tear film substance P in collected flush tears. Correlation analysis, hierarchical multiple linear regression analysis, and t-tests or Mann-Whitney U tests were used in the analysis of data for two-group comparisons.

RESULTS

There was no substantial difference between the T2DM-CKD and T2DM-no CKD groups for tear film substance P concentration (4.4 (0.2-50.4) and 5.9 (0.2-47.2) ng/mL, respectively; p = 0.54). No difference was observed in tear film substance P concentration between the low-severity peripheral neuropathy and high-severity peripheral neuropathy groups (4.4 (0.2-50.4) and 3.3 (0.3-40.7) ng/mL, respectively; p = 0.80). Corneal nerve fiber length (9.8 ± 4.6 and 12.4 ± 3.8 mm/mm2, respectively; p = 0.04) and corneal nerve fiber density (14.7 ± 8.5 and 21.1 ± 7.0 no/mm2, respectively; p < 0.01) were reduced significantly in the T2DM-CKD group compared to the T2DM-no CKD group. There were significant differences in corneal nerve fiber density (21.0 ± 8.1 and 15.8 ± 7.7 no/mm2, respectively; p = 0.04) and corneal nerve fiber length (12.9 ± 4.2 and 9.7 ± 3.8 mm/mm2, respectively; p = 0.03) between the low- and high-severity peripheral neuropathy groups.

CONCLUSION

In conclusion, no significant difference in tear film substance P concentration was observed between type 2 diabetes with and without CKD. Corneal nerve loss, however, was more significant in type 2 diabetes with chronic kidney disease compared to type 2 diabetes alone, indicating that corneal nerve morphological measures could serve greater utility as a tool to detect neuropathy and nephropathy-related corneal nerve changes.

Tear proteomic analysis of young glasses, orthokeratology, and soft contact lens wearers

Contact lens-related ocular surface complications occur more often in teenagers and young adults. The purpose of this study was to determine changes in tear proteome of young patients wearing glasses (GL), orthokeratology lenses (OK), and soft contact lenses (SCL). Twenty-two young subjects (10-26 years of age) who were established GL, OK, and SCL wearers were recruited. Proteomic data were collected using a data-independent acquisition-parallel accumulation serial fragmentation workflow. In total, 3406 protein groups were identified, the highest number of proteins identified in Schirmer strip tears to date. Eight protein groups showed higher abundance, and 11 protein groups showed lower abundance in the SCL group compared to the OK group. In addition, the abundance of 82 proteins significantly differed in children compared to young adult GL wearers, among which 67 proteins were higher, and 15 proteins were lower in children. These 82 proteins were involved in inflammation, immune, and glycoprotein metabolic biological processes. In summary, this work identified over 3000 proteins in Schirmer Strip tears. The results indicated that tear proteomes were altered by orthokeratology and soft contact wear and age, which warrants further larger-scale study on the ocular surface responses of teenagers and young adults separately to contact lens wear. SIGNIFICANCE: In this work, we examined the tear proteomes of young patients wearing glasses, orthokeratology lenses, and soft contact lenses using a data-independent acquisition-parallel accumulation serial fragmentation (diaPASEF) workflow and identified 3406 protein groups in Schirmer strip tears. Nineteen protein groups showed significant abundance changes between orthokeratology and soft contact lens wearers. Moreover, eighty-two protein groups significantly differed in abundance in children and young adult glasses wearers. As a pilot study, this work provides a deep coverage of tear proteome and suggests the need to investigate ocular responses to contact lens wear separately for children and young adults.

Postoperative efficacy, safety, predictability, and visual quality of implantable collamer lens implantation versus small incision lenticule extraction in myopic eyes: a Meta-analysis

AIM

To compare the postoperative efficacy, safety, predictability, and visual quality of implantable collamer lens (ICL) implantation versus small incision lenticule extraction (SMILE) in myopia eyes.

METHODS

PubMed, EMBASE, Web of Science, Cochrane Library and several Chinese databases were searched at May 2021 to select relevant studies in comparison of clinical outcomes between ICL implantation and SMILE for myopia. The primary outcomes were efficacy, safety, and predictability. And the secondary outcomes were postoperative higher-order ocular aberrations (HOAs), modulation transfer function cutoff frequency (MTF), objective scatter index (OSI), contrast sensitivity and a quality of vision (QoV) questionnaire.

RESULTS

A total of 1036 eyes from 10 studies, of which 503 eyes underwent ICL implantation and 533 eyes underwent SMILE, were enrolled in this Meta-analysis. Pooled results revealed that ICL group had a better safety index and post-corrected distance visual acuity (CDVA) (P=0.007, <0.00001, respectively), and a lower percentage of eyes with a postoperative CDVA lost 1 line (P=0.007) than the SMILE group. No significant differences were found in comparison of the other primary outcomes. In the long-term follow-up (>6mo), ICL group had a lower total HOA, coma, and spherical aberration than SMILE group (P=0.003, <0.00001, 0.04). Yet higher trefoil was found in ICL group at 6mo after surgery (P=0.003). Additionally, ICL group also had a higher MTF value (P=0.02), and a higher contrast sensitivity score for spatial frequencies of 1.5, 6, and 12 cpds (P=0.02, 0.005, 0.02, respectively). And it also had a lower score of bothersome in QoV questionnaire than SMILE group (P=0.003).

CONCLUSION

ICL implantation and SMILE have similar and comparable outcomes in term of the efficacy and predictability for correcting high myopia. However, ICL group is relatively safer and also has better visual quality in comparison of SMILE group.

Diabetic corneal neuropathy as a surrogate marker for diabetic peripheral neuropathy

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.

Modulating the tachykinin: Role of substance P and neurokinin receptor expression in ocular surface disorders

Substance P (SP) is a tachykinin expressed by various cells in the nervous and immune systems. SP is predominantly released by neurons and exerts its biological and immunological effects through the neurokinin receptors, primarily the neurokinin-1 receptor (NK1R). SP is essential for maintaining ocular surface homeostasis, and its reduced levels in disorders like diabetic neuropathy disrupt the corneal tissue. It also plays an essential role in promoting corneal wound healing by promoting the migration of keratocytes. In this review, we briefly discuss the structure, expression, and function of SP and its principal receptor NK1R. In addition, SP induces pro-inflammatory effects through autocrine or paracrine action on the immune cells in various ocular surface pathologies, including dry eye disease, herpes simplex virus keratitis, and Pseudomonas keratitis. We provide an in-depth review of the pathogenic role of SP in various ocular surface diseases and several new approaches developed to counter the immune-mediated effects of SP either through modulating its production or blocking its target receptor.

Associations Between Disordered Microbial Metabolites and Changes of Neurotransmitters in Depressed Mice

Backgrounds

Many pieces of evidence demonstrated that there were close relationships between gut microbiota and depression. However, the specific molecular mechanisms were still unknown. Here, using targeted metabolomics, this study was conducted to explore the relationships between microbial metabolites in feces and neurotransmitters in prefrontal cortex of depressed mice.

Methods

Chronic unpredictable mild stress (CUMS) model of depression was built in this study. Targeted liquid chromatography-mass spectrometry analysis was used to detect the microbial metabolites in feces and neurotransmitters in prefrontal cortex of mice. Both univariate and multivariate statistical analyses were applied to identify the differential microbial metabolites and neurotransmitters and explore relationships between them.

Results

Ninety-eight differential microbial metabolites (mainly belonged to amino acids, fatty acids, and bile acids) and 11 differential neurotransmitters (belonged to tryptophan pathway, GABAergic pathway, and catecholaminergic pathway) were identified. Five affected amino acid-related metabolic pathways were found in depressed mice. The 19 differential microbial metabolites and 10 differential neurotransmitters were found to be significantly correlated with depressive-like behaviors. The two differential neurotransmitters (tyrosine and glutamate) and differential microbial metabolites belonged to amino acids had greater contributions to the overall correlations between microbial metabolites and neurotransmitters. In addition, the significantly decreased L-tyrosine as microbial metabolites and tyrosine as neurotransmitter had the significantly positive correlation (r = 0.681, p = 0.0009).

Conclusions

These results indicated that CUMS-induced disturbances of microbial metabolites (especially amino acids) might affect the levels of neurotransmitters in prefrontal cortex and then caused the onset of depression. Our findings could broaden the understanding of how gut microbiota was involved in the onset of depression.

Aqueous Lumican Correlates with Central Retinal Thickness in Patients with Idiopathic Epiretinal Membrane: A Proteome Study

Idiopathic epiretinal membrane (iERM) is a pathological fibrocellular change in the vitreoretinal junction over the macular area; however, possible pathogenic mechanisms remain unclear. Changes in the differential protein composition of the aqueous humor (AH) may represent potential molecular changes associated with iERM. To gain new insights into the molecular mechanisms of iERM pathology, a sensitive label-free proteomics analysis was performed to compare AH protein expressions in patients with cataracts with or without iERM. This study employed nanoflow ultra-high-performance liquid chromatography-tandem mass spectrometry to investigate protein compositions of the AH obtained from individual human cataract eyes from 10 patients with iERM and 10 age-matched controls without iERM. Eight proteins were differentially expressed between the iERM and control samples, among which six proteins were upregulated and two were downregulated. A gene ontology (GO) analysis revealed that iERM was closely associated with several biological processes, such as immunity interactions, cell proliferation, and extracellular matrix remodeling. Additionally, multiple proteins, including lumican, cyclin-dependent kinase 13, and collagen alpha-3(VI) chain, were correlated with the central retinal thickness, indicating a multifactorial response in the pathogenic process of iERM. Changes in the AH level of lumican between iERM and control samples were also confirmed by an enzyme-linked immunosorbent assay. In conclusion, several pathological pathways involved in iERM were identified in the AH by a proteomic analysis, including immune reactions, cell proliferation, and remodeling of the extracellular matrix. Lumican is a potential aqueous biomarker for predicting iERM development and monitoring its progression. More clinical parameters also need to be identified to complete the analysis, and those could provide additional targets for treating and preventing iERM.

In Vivo Confocal Microscopy Evaluation in Patients with Keratoconus

Keratoconus is the most common primary corneal ectasia characterized by progressive focal thinning. Patients experience increased irregular astigmatism, decreased visual acuity and corneal sensitivity. Corneal collagen crosslinking (CXL), a minimally invasive procedure, is effective in halting disease progression. Historically, keratoconus research was confined to ex vivo settings. In vivo confocal microscopy (IVCM) has been used to examine the corneal microstructure clinically. In this review, we discuss keratoconus cellular changes evaluated by IVCM before and after CXL. Cellular changes before CXL include decreased keratocyte and nerve densities, disorganized subbasal nerves with thickening, increased nerve tortuosity and shortened nerve fibre length. Repopulation of keratocytes occurs up to 1 year post procedure. IVCM also correlates corneal nerve status to functional corneal sensitivity. Immediately after CXL, there is reduced nerve density and keratocyte absence due to mechanical removal of the epithelium and CXL effect. Nerve regeneration begins after 1 month, with nerve fibre densities recovering to pre-operative levels between 6 months to 1 year and remains stable up to 5 years. Nerves remain tortuous and nerve densities are reduced. Corneal sensitivity is reduced immediately postoperatively but recovers with nerve regeneration. Our article provides comprehensive review on the use of IVCM imaging in keratoconus patients.

Looking deeper into ocular surface health: an introduction to clinical tear proteomics analysis

Ocular surface diseases are becoming more prevalent worldwide. Reasons for this include the ongoing population ageing and increasing use of digital displays, although ophthalmologists have a wide selection of tools, which can be implemented in the evaluation of the ocular surface health, methods, which enable the in-depth study of biological functions are gaining more interest. These new approaches are needed, since the individual responses to ocular surface diseases and treatments can vary from person to person, and the correlations between clinical signs and symptoms are often low. Modern mass spectrometry (MS) methods can produce information on hundreds of tear proteins, which in turn can provide valuable information on the biological effects occurring on the ocular surface. In this review article, we will provide an overview of the different aspects, which are part of a successful tear proteomics study design and equip readers with a better understanding of the methods most suited for their MS-based tear proteomics study in the field of ophthalmology and ocular surface.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide. In laser refractive surgery, Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy. Following laser refractive surgery, the corneal nerves, epithelial and stromal cells release neuromediators, including neurotrophins, neuropeptides and neurotransmitters. Notably, nerve growth factor, substance P, calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration. Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced. In this review, we will discuss the (1) Functions of neuromediators and their physiological and clinical significance; (2) Changes in the neuromediators following various laser refractive surgeries; (3) Correlation between neuromediators, ocular surface health and corneal nerve status; and (4) Future directions, including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery, and as adjuncts to aid in corneal regeneration after laser refractive surgery.

Tear Neuromediator and Corneal Denervation Following SMILE

PURPOSE

To investigate the changes in tear neuromediators and corneal subbasal nerve plexus following small incision lenticule extraction (SMILE) and to study its association with different refractive power of corrections.

METHODS

Thirty patients were included for tear neuromediator analysis (40 eyes) and corneal nerve analysis using in vivo confocal microscopy scans (20 eyes). Tear samples were collected preoperatively and 1 week and 1, 3, 6, and 12 months postoperatively and analyzed for the substance P, calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF) concentrations using the enzyme-linked immunosor-bent assay (ELISA).

RESULTS

Corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), and corneal nerve branch density (CNBD) decreased significantly postoperatively, then gradually increased from 3 months onward, but did not recover to the baseline levels at 12 months. Tear substance P and CGRP levels remained stable over 12 months. Tear NGF levels demonstrated a small peak at 1 week before decreasing significantly compared to preoperative levels at 6 months (P = .03) and 12 months (P = .007). The 1-month reduction in CNFL, tear substance P, and CGRP concentrations were significantly correlated with the corrected spherical equivalent (SE) (r = 0.71 for CNFL; r = -0.33 to -0.52 at different time points for substance P and CGRP, respectively, all P < .05). Compared to the low to moderate myopia group, the high myopia group (corrected SE greater than -6.00 diopters) had a significantly greater decrease in CNFD, significantly higher tear substance P concentrations at 1 week, 1 month, and 6 months, and significantly higher tear CGRP concentrations at 1 and 6 months.

CONCLUSIONS

These results provide new insight into the neurobiological responses and their potential implications in corneal nerve damage and recovery after SMILE. High myopia treatment was associated with greater corneal denervation and neuroinflammation. [J Refract Surg. 2021;37(8):516-523.].

Advances in refractive corneal lenticule extraction

Refractive errors are the leading cause of reversible visual impairment worldwide. In addition to the desired spectacle independence, refractive procedures can improve quality of life, working ability, and daily working performance. Refractive corneal lenticule extraction (RCLE) is a relatively new technique, dependent only on a femtosecond laser (FS). This leads to potential benefits over laser-assisted in situ keratomileusis (LASIK) including a quicker recovery of dry eye disease, a larger functional optical zone, and no flap-related complications. SMILE, available with the VisuMax FS (Carl Zeiss Meditec AG, Jena, Germany), is the most established RCLE application, offering visual and refractive outcomes comparable to LASIK. SmartSight (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany) and CLEAR (Ziemer Ophthalmic Systems AG, Port, Switzerland) are two new RCLE applications that received Conformité Européenne (CE) approval in 2020. In this article, we review refractive and visual outcomes, advantages, and disadvantages of RCLE and also report on the latest advances in RCLE systems.