RNA-seq transcriptomic profiling of TGF-ß2-exposed human trabecular meshwork explants: Advancing insights beyond conventional cell culture models.

Primary open-angle glaucoma (POAG), a leading cause of irreversible vision loss, is closely linked to increased intraocular pressure (IOP), with the trabecular meshwork (TM) playing a critical role in its regulation. The TM, located at the iridocorneal angle, acts as a sieve, filtering the aqueous humor from the eye into the collecting ducts, thus maintaining proper IOP levels. The transforming growth factor-beta 2 (TGF-ß2) signaling pathway has been implicated in the pathophysiology of primary open-angle glaucoma POAG particularly, in the dysfunction of the TM. This study utilizes human TM explants to closely mimic in vivo conditions, thereby minimizing transcriptional changes that could arise from cell culture enabling an exploration of the transcriptomic impacts of TGF-ß2. Through bulk RNA sequencing and immunohistological analysis, we identified distinct gene expression patterns and morphological changes induced by TGF-ß2 exposure (5 ng/ml for 48 h). Bulk RNA sequencing identified significant upregulation in genes linked to extracellular matrix (ECM) regulation and fibrotic signaling. Immunohistological analysis further elucidated the morphological alterations, including cytoskeletal rearrangements and ECM deposition, providing a visual confirmation of the transcriptomic data. Notably, the enrichment analysis unveils TGF-ß2's influence on both bone morphogenic protein (BMP) and Wnt signaling pathways, suggesting a complex interplay of molecular mechanisms contributing to TM dysfunction in glaucoma. This characterization of the transcriptomic modifications on an explant model of TM obtained under the effect of this profibrotic cytokine involved in glaucoma is crucial in order to develop and test new molecules that can block their signaling pathways.

[Glaucomatous trabeculum: An inflammatory trabeculopathy? [French translation]]. / Trabéculum glaucomateux : une trabéculopathie inflammatoire ?

Glaucoma is an optic neuropathy in which the primary risk factor is increased intraocular pressure (IOP), attributed to increased resistance to trabecular outflow of aqueous humor (AH). This resistance is believed to result from trabecular degeneration secondary to chronic oxidative stress and cellular senescence but may also involve inflammatory mechanisms whose roles are little known. In fact, inflammatory processes play a major role in the pathophysiology of glaucoma to varying degrees, affecting all structures of the eye, including the ocular surface, the anterior and posterior segments, and even the visual pathways of the brain. These processes are thought to result from dysfunction of a regulatory, protective para-inflammation, becoming chronic and harmful in glaucoma. While the mechanisms of the retinal inflammation which accelerates the degeneration of retinal ganglion cells (RGC) as well as the inflammation of the ocular surface aggravated by long-term use of preserved glaucoma eye drops have been described for several years, very little is known about the pathophysiology of trabecular inflammation in glaucoma. The objective of this literature review is to provide a synthesis of knowledge on the roles and mechanisms of inflammation in both the healthy and glaucomatous trabecular meshwork, as well as its role in the pathophysiology of glaucoma. Therefore, after a review of the mechanisms of cellular senescence and oxidative stress - sources of trabecular inflammation, we will approach the study of the expression and roles of the main inflammatory mediators within the trabecular meshwork. Finally, we will discuss current knowledge on the toxicity of glaucoma eye drops and their preservatives on the ocular surface and trabecular meshwork as well as their role in trabecular inflammation.

The trabecular meshwork in glaucoma: An inflammatory trabeculopathy?

Glaucoma is an optic neuropathy in which the primary risk factor is increased intraocular pressure (IOP), attributed to increased resistance to trabecular outflow of aqueous humor (AH). This resistance is believed to result from trabecular degeneration secondary to chronic oxidative stress and cellular senescence but may also involve inflammatory mechanisms whose roles are little known. In fact, inflammatory processes play a major role in the pathophysiology of glaucoma to varying degrees, affecting all structures of the eye, including the ocular surface, the anterior and posterior segments, and even the visual pathways of the brain. These processes are thought to result from dysfunction of a regulatory, protective para-inflammation, becoming chronic and harmful in glaucoma. While the mechanisms of the retinal inflammation which accelerates the degeneration of retinal ganglion cells (RGCs) as well as the inflammation of the ocular surface aggravated by long-term use of preserved glaucoma eye drops have been described for several years, very little is known about the pathophysiology of trabecular inflammation in glaucoma. The objective of this literature review is to provide a synthesis of knowledge on the roles and mechanisms of inflammation in both the healthy and glaucomatous trabecular meshwork, as well as its role in the pathophysiology of glaucoma. Therefore, after a review of the mechanisms of cellular senescence and oxidative stress - sources of trabecular inflammation, we will approach the study of the expression and roles of the main inflammatory mediators within the trabecular meshwork. Finally, we will discuss current knowledge on the toxicity of glaucoma eye drops and their preservatives on the ocular surface and trabecular meshwork as well as their role in trabecular inflammation.

[The trabecular meshwork: Structure, function and clinical implications. A review of the littérature (French translation of the article)]. / Le trabéculum : structure, fonction et implications cliniques. Une revue de la littérature.

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

The trabecular meshwork: Structure, function and clinical implications. A review of the literature.

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

IgE Ratio in Tears: A Predictive Tool of Ocular Allergic Inflammation.

PURPOSE: To demonstrate the tear IgE (measured/exuded) ratio (R) as a useful biological marker of ocular allergy in order to distinguish severe from less severe inflammatory status. METHODS: Tear samples and sera from 78 ocular allergy patients and 19 control subjects were analyzed. Total IgE and albumin were measured for calculating the tear IgE-R defining two subgroups (SG) of samples: R ≥ 4-SG and R < 4-SG. Eosinophil cationic protein, Th1 and Th2 cytokines (IFN-γ, IL-4, -5, -6, -8 and -10) and protein electrophoretic profiles were also investigated in tears. RESULTS: The R < 4-SG compared to the R ≥ 4-SG shows higher levels of tear albumin, eosinophil cationic protein, and Th1 and Th2 cytokines. Moreover, each subgroup presents a specific protein profile. CONCLUSION: This study showed that an IgE-R lower than four must be carefully interpreted as a warning sign of a severe inflammatory context and should be also associated with an exploration of immunological profile.

Correlation of clinical symptoms and signs with conjunctival gene expression in primary Sjögren syndrome dry eye patients.

PURPOSE: The aim of this study was to characterize the expression of inflammation-related genes on the ocular surface of Sjögren syndrome (SS) patients and to evaluate their correlations with clinical symptoms and signs. METHODS: The study enrolled 30 patients with SS dry eye and 15 healthy controls. Symptoms were evaluated using OSDI questionnaire. The clinical signs were investigated using corneal fluorescein staining (CFS), tear breakup time (TBUT), Schirmer test and tear osmolarity measurement. Conjunctival superficial cells were collected using conjunctival impression cytology and total RNAs were extracted for analysis using the NanoString® nCounter technology. The Mann-Whitney nonparametric statistical test and Spearman correlations were used to explore the correlations between the up/downregulated genes and the clinical signs and symptoms. RESULTS: Twenty-seven genes were upregulated and 13 were downregulated with statistically significant fold changes ranging from 1.5 to 16.7 and 0.3 to 0.8, respectively. OSDI and CFS were the most significantly correlated parameters with 21 and 19 inflammatory genes, respectively. Among all the upregulated genes, 14 were positively correlated with both OSDI and CFS. Two downregulated genes (GNGT1, HSPB2) were negatively correlated with OSDI and CFS. IL1RN was the only gene positively correlated with the Schirmer test. CONCLUSIONS: These results highlight the differentially expressed genes in primary Sjögren syndrome and their relationships between the inflammatory genes expressed and the patient symptom score and corneal damage. The inflammatory genes implicated in SS-associated dry eye could be important tools to determine the pathophysiological profiles of SS and potentially useable as specific signatures.

In vivo confocal microscopy and optical coherence tomography as innovative tools for the diagnosis of limbal stem cell deficiency.

The limbus is the anatomical and functional barrier between the corneal and conjunctival epithelia. It is characterized by the presence of the limbal stem cell niche, which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, and subepithelial fibrosis. Spectral domain optical coherence tomography of the central cornea and limbus, with scans in variable orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective subepithelial fibrosis. The limbus is the anatomical and functional barrier between the corneal and conjunctival epithelia. It is characterized by the presence of the limbal stem cell niche, which allows corneal homeostasis to be maintained. Limbal stem cell deficiency (LSCD) is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation.

[In vivo confocal microscopy and optical coherence tomography as innovative tools for the diagnosis of limbal stem cell deficiency (French translation of the article)]. / Progrès dans les méthodes diagnostiques du déficit en cellules souches limbiques. Apport de la microscopie confocale et de la tomographie en cohérence optique.

The limbus is the anatomical and functional barrier between corneal and conjunctival epithelia. It is characterized by presence of the limbal stem cell niche which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views, parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, even with sub-epithelial fibrosis. Optical coherence tomography in central cornea and at the limbus, with scans in different orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective sub-epithelial fibrosis.

[Hyperosmolarity: Intracellular effects and implication in dry eye disease]. / Hyperosmolarité : effets intracellulaires et implication dans la sécheresse oculaire.

Dry eye disease is a multifactorial disease affecting the lacrimal functional unit and which has a significant impact on the quality of life of patients. This pathology works as a vicious circle at the ocular surface in which hyperosmolarity of the tear film plays a key role. This review intends to describe the different reported intracellular effects induced by hyperosmolarity in cells: alteration of cytoskeleton, cell cycle slowdown, adaptation mechanisms triggered as restoration of cell volume and accumulation of compatible osmolytes, the crucial role of the osmoprotectant factor Nuclear Factor of the Activated T cells-5 (NFAT5), apoptosis, as well as oxidative stress and inflammatory responses caused by this particular condition. Reported effects of hyperosmolarity in the experimental studies specific of dry eye disease concerning ocular surface cells will be described in parallel. Indeed, these data allow to understand a part of the pathophysiology of the disease, and specially the links between tear hyperosmolarity and inflammation of the ocular surface, the second key of the pathology phenomenon.

[Mesenchymal stem cell therapy, a new hope for eye disease]. / Thérapie cellulaire par cellules souches mésenchymateuses, un nouvel espoir pour les pathologies oculaires.

Mesenchymal stem cells (MSC) are adult stem cells, first identified in skeletal tissues and then found in the entire body. MSC are able to not only differentiate into specialized cells within skeletal tissue - chondrocytes, osteocytes, adipocytes and fibroblasts - but also secrete a large range of soluble mediators defining their secretome and allowing their interaction with a number of cell protagonists. Thus, in a general sense, MSC are involved in tissue homeostasis through their secretome and are specifically responsible for cell turn-over in skeletal tissues. For a decade and a half, safety and efficiency of MSC has led to the development of many clinical trials in various fields. However, results were often disappointing, probably because of difficulties in methods and evaluation. At a time when the first clinical trials using MSC are emerging in ophthalmology, the goal of this literature review is to gather and put into perspective preclinical and clinical results in order to better predict the future of this innovative therapeutic pathway.

Femtosecond and excimer laser-assisted endothelial keratoplasty (FELEK): a new technique of endothelial transplantation.

PURPOSE: To describe a new technique of endothelial keratoplasty (EK) that improves the quality of lamellar dissection of donor cornea. METHODS: We compared four techniques of donor cornea preparation for lamellar dissection on 8 donor corneas: mechanical dissection with a microkeratome, a single femtosecond laser lamellar cut, a double femtosecond laser lamellar cut and combined femtosecond laser lamellar dissection with excimer laser surface photoablation. The quality of the donor cornea interface was assessed and compared using scanning electron microscopy (SEM), and the most satisfactory technique was employed for EK on three patients. The postoperative anatomic results were analyzed with anterior segment spectral-domain optical coherence tomography (SD-OCT) and in vivo confocal microscopy (IVCM). RESULTS: The smoothest stromal interface was observed on SEM with the combined use of femtosecond laser dissection and excimer photoablation. The surgical procedures performed with donor cornea prepared by a combination of femtosecond and excimer lasers resulted in clear corneas after 1 month. SD-OCT showed good attachment of the endothelial graft and a hyperreflective interface. On IVCM, subepithelial haze, honeycomb-like activated keratocytes and needle-shaped particles were visible in the recipient corneal stroma as well as numerous hyperreflective particles on the donor-recipient interface. CONCLUSION: A new technique, femtosecond and excimer laser-assisted endothelial keratoplasty (FELEK), which refines the current limitations observed in Descemet-stripping automated endothelial keratoplasty (DSAEK), is described. Femtosecond laser dissection provides a thin and reproducible endothelial graft cut with a high level of safety and accuracy, while excimer photoablation yields a smooth, high-quality interface.

Comparison of preservative-free ketotifen fumarate and preserved olopatadine hydrochloride eye drops in the treatment of moderate to severe seasonal allergic conjunctivitis.

PURPOSE: To compare preservative-free ketotifen 0.025% ophthalmic solution to olopatadine 0.1% ophthalmic solution in with the treatment of seasonal allergic conjunctivitis (SAC) in clinical practice. METHODS: This was a comparative, randomised, investigator-masked, pilot clinical study in adult patients with documented history of SAC and presenting with moderate to severe itching and conjunctival hyperemia. Eligible patients initiated either ketotifen or olopatadine treatment at a dose of one drop twice daily for 28days. The resolution of ocular signs and symptoms was assessed on day 7 and day 28. Itching was also assessed within 15minutes following the first instillation (day 0). Conjunctival impression cytology was performed at each visit to assess the evolution of ICAM-1 expression (day 0, 7 and 28). RESULTS: Seventy-five patients were randomised (ketotifen: 38 patients; olopatadine: 37 patients). At day 28, the composite score for primary criteria (itching, tearing, and conjunctival hyperemia) improved from 6.8±1.2 to 0.9±1.0 in the Ketotifen group, without statistically significant difference between treatment groups (P=0.67). There was no relevant difference between treatment groups in other efficacy parameters, except a trend for a more rapid resolution of conjunctival hyperemia in the Ketotifen group. Both drugs were well tolerated, with a trend for a better tolerability reported by patients on ketotifen compared to those on olopatadine at day 7 (P=0.054). CONCLUSIONS: A rapid and comparable improvement in SAC was achieved after 28days of treatment with both preservative-free ketotifen and preserved olopatadine ophthalmic solutions, with a slightly better ocular tolerance with unpreserved ketotifen 0.025% eye drops.

RGTA-based matrix therapy in severe experimental corneal lesions: safety and efficacy studies.

Corneal alteration potentially leading to ulceration remains a major health concern in ocular surface diseases. A treatment that would improve both the quality and speed of healing and control the inflammation would be of great interest. Regenerating agents (RGTAs) have been shown to stimulate wound healing and modulate undesired fibrosis in various in vivo systems. We investigated the effects of RGTA-OTR4120(®) in a rabbit corneal model in order to assess its potential use in ocular surface diseases. First, we assessed its safety for 7 and 28 days using the Draize test criteria in healthy rabbit eyes; then, we investigated the effect of a single dose (50µl, 5µg) in an alkali-burned cornea model. Daily follow-up of clinical signs of healing was scored, and histology was performed at D7. RGTA was well tolerated; no signs of ocular irritation were observed. In the corneal alkali-burn model, non-RGTA-treated eyes showed inflammatory clinical signs, and histology confirmed a loss of superficial corneal layers with epithelial disorganization, neovascularization and infiltration of inflammatory cells. When compared to NaCl control, RGTA treatment appeared effective in reducing clinical signs of inflammation, enhancing re-epithelialization, and improving histological patterns: edema, fibrosis, neovascularization and inflammation. Three to four layers of epithelial cells were already organized, stroma was virtually unvascularized and keratocytes well implanted in parallel collagen fibers with an overall reorganization similar to normal cornea. RGTA appears to be a promising agent for controlling ocular surface inflammation and promoting corneal healing and was well tolerated. This study offers preclinical information and supports the findings of other (compassionate or pilot) studies conducted in patients with various ocular surface diseases.

CX3CL1 expression in the conjunctiva is involved in immune cell trafficking during toxic ocular surface inflammation.

Inappropriate expression of the chemokine CX3CL1 is reportedly known to act on inflammatory conditions in extraocular immune diseases. We studied the expression and effects of CX3CL1 in human patients, cultured human conjunctival cells, and transgenic mice exposed to benzalkonium chloride (BAC), a commonly used preservative in ophthalmic medications despite its proinflammatory properties, to determine whether CX3CL1 is involved in conjunctival inflammation. We report that CX3CL1 expression is increased in the conjunctiva of patients receiving BAC-containing medication, and correlates with clinical inflammation. BAC enhances the production of CX3CL1 in a conjunctival epithelial cell line, through the tumor-necrosis factor-α pathway, which attracts specific leukocyte subsets. In vivo, BAC-induced macrophage infiltration and subsequent inflammation of the conjunctiva is decreased in CX3CR1-deficient mice as compared with CX3CR1(+/+) controls. This translational study opens new avenue to investigate ocular surface disorders by focusing on chemokine-related inflammation and immune cell trafficking in the ocular conjunctival mucosa.

[Efficacy assessment of Nutrilarm®, a per os omega-3 and omega-6 polyunsaturated essential fatty acid dietary formulation versus placebo in patients with bilateral treated moderate dry eye syndrome]. / Évaluation de l'efficacité du Nutrilarm®, complément nutritionnel à base d'acides gras essentiels polyinsaturés oméga 3 et oméga 6, versus placebo chez des patients atteints de sécheresse oculaire bilatérale modérée et traitée.

INTRODUCTION: Inflammation is one of the main mechanisms common to all forms of dry eye. Since polyunsaturated acids are known to show biological anti-inflammatory properties, the aim of this study was to evaluate the efficacy of dietary n-6 and n-3 fatty acids in patients suffering from ocular dryness. PATIENTS AND METHODS: One hundred and eighty-one patients diagnosed with bilateral moderate dry eye who were already treated with lachrymal substitutes were randomized in a double-blind international study to receive placebo or Nutrilarm(®) capsules (combination of omega-3 and omega-6), twice a day for 6 months. In all subjects, dryness feeling, overall subjective comfort, and ocular symptoms (burning, stinging, sandy and/or gritty sensation, light sensitivity, reflex tearing, and ocular fatigue) were evaluated at each visit. Furthermore, fluorescein tests (break-uptime and Oxford scheme) and lissamine green test were performed at each visit. The Schirmer test was performed at inclusion and after 6 months of treatment. RESULTS: After 6 months of supplementation with Nutrilarm(®), both the BUT scores and ocular fatigue were significantly improved when compared with placebo (P=0.036 and P=0.044, respectively). There was a trend in favor of Nutrilarm(®) in terms of the efficacy evaluated by the investigator (P=0.061). Fewer patients experienced a feeling of severe dryness with Nutrilarm(®) compared with placebo after 6 months of treatment (2.5 and 9.3%, respectively), but the difference was not statistically significant. CONCLUSION: Oral administration of a double supplementation dietary n-6 and n-3 fatty acids present an additional therapeutic advantage in patients suffering from ocular dryness who were already treated with lachrymal substitutes.

Multiple endpoint analysis of BAC-preserved and unpreserved antiallergic eye drops on a 3D-reconstituted corneal epithelial model.

PURPOSE: To compare the effects of benzalkonium chloride (BAC)-preserved and unpreserved antiallergic eye drops on the human 3D-reconstituted corneal epithelial model (3D-HCE). METHODS: 3D-HCE were treated for 24 h followed or not by a 24 h post-incubation recovery period (24 h+24 h) with phosphate-buffered saline (PBS), 0.01% BAC, unpreserved formulations of ketotifen, N Acetyl-Aspartyl Glutamic Acid (NAAGA), cromoglycate, or BAC-preserved commercial formulations of ketotifen, olopatadine, epinastine, and levocabastine. The 3D-HCE viability was evaluated using the 3-(4,5-Dimethylthiazol-2-yl) -2,5-Diphenyltetrazolium Bromide (MTT) test at 24 h and 24 h+24 h. At 24 h, the numbers of Cluster of Differentiation 54 (CD54)- and Ki67-immunopositive cells as well as the number of apoptotic deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells were evaluated on 3D-HCE frozen sections. The expression of the tight junction-associated protein occludin was also assessed using fluorescence confocal microscopy on flat-mounted 3D-HCE epithelia. RESULTS: The MTT and the TUNEL tests revealed a significant decrease of cell viability and an increased apoptosis in the superficial layers of the 3D-HCE only when treated with BAC-containing formulations and in a BAC concentration-dependent manner. The expression of CD54 and Ki67 in the basal layers was also increased in this group. A concentration-dependent disorganization of occludin distribution in the epithelium treated with BAC-containing solutions was also observed. The unpreserved formulations induced effects comparable to the control. CONCLUSIONS: BAC-preserved solutions decreased cell viability and induced apoptosis in a concentration-dependent manner. Moreover, they induced CD54 expression, proliferation in the basal layers, and changes in the distribution of occludin, which is consistent with a disorganization of the tight-junctions and suggests the loss of the epithelial barrier function. On the contrary, the unpreserved solutions did not impair cell structures and viability, suggesting a better tolerance for the ocular surface. As allergic patients often exhibit impaired and inflammatory ocular surface, BAC-free compounds should be the first choice when treating allergic conjunctivitis.

[Preservatives in eye drops: toward awareness of their toxicity]. / Les conservateurs des collyres : vers une prise de conscience de leur toxicité.

Preservatives are present in numerous multidose eyedrops and provide the sterility of the solution against bacteria and fungi. However, numerous studies have shown their toxicity for the ocular surface, particularly in long-term treatments. The most widely used preservative in eyedrops is benzalkonium chloride. This quaternary ammonium acts as a detergent, antiseptic, disinfectant, fungicide, bactericide, and spermicide. Its use on the ocular surface therefore has significant consequences. Indeed, the preservatives are pro-apoptotic, pro-inflammatory and they cause the dissolution of the lachrymal film. The prolonged administration of one or several eye drops containing preservatives induces changes in the superficial structures (conjunctiva, cornea) as well as in deeper structures (trabecula, lens). The least severe symptoms are irritation and discomfort, including sensation of a foreign body, itching, or burning sensations. However, more severe side effects have been described, such as chronic inflammation of variable intensity or the progressive development of fibrosis with higher risk of failure after glaucoma filtering surgery. Ideally, preservative-free eyedrops should be recommended, or at least a reduction of the number of instilled preserved eyedrops should be considered. All these strategies could increase patient comfort, quality of life, and compliance, with better outcome at the time of filtering surgery.