[Corneal epithelial biomechanics: Resistance to stress and role in healing and remodeling]. / Biomécanique de l'épithélium cornéen : résistance au stress et implications dans la cicatrisation et le remodelage.

The corneal epithelium is one of the first tissue barriers of the eye against the environment. In recent years, many studies provided better knowledge of its healing, its behavior and its essential role in the optical system of the eye. At the crossroads of basic science and clinical medicine, the study of the mechanical stresses applied to the cornea makes it possible to learn the behavior of epithelial cells and better understand ocular surface disease. We describe herein the current knowledge about the adhesion systems of the corneal epithelium and their resistance to mechanical stress. We will also describe the involvement of these mechanisms in corneal healing and their role in epithelial dynamics. Adhesion molecules of the epithelial cells, especially hemidesmosomes, allow the tissue cohesion required to maintain the integrity of the corneal epithelium against the shearing forces of the eyelids as well as external forces. Their regeneration after a corneal injury is mandatory for the restoration of a healthy epithelium. Mechanotransduction plays a significant role in regulating epithelial cell behavior, and the study of the epithelium's response to mechanical forces helps to better understand the evolution of epithelial profiles after refractive surgery. A better understanding of corneal epithelial biomechanics could also help improve future therapies, particularly in the field of tissue engineering.

[Regression and ablation profiles in corneal refractive surgery]. / Régression et profils d'ablation en chirurgie réfractive cornéenne.

Regression after corneal refractive surgery is a complex phenomenon which seems inevitable. The choice of surgical technique has very little influence on regression for low myopia or myopic astigmatism. However, LASIK and SMILE are the two techniques of choice in the correction of high myopia. LASIK is also better for the correction of hyperopia, hyperopic astigmatism and mixed astigmatism. Intraoperatively, the choice of a wide optical zone and adherence to a thick residual stromal bed provide stability. Regression may also be reduced by modulating anti-inflammatory therapy, treating dry eye, and using mitomycin C in PKR. In all cases, obtaining keratometry during patient follow-up helps to identify the cause of the regression. The objective of this review is to synthesize recent data from the literature on regression in refractive surgery as a function of the ablation profiles used.

An algorithm in ophthalmic emergencies to evaluate the necessity of physical consultation during COVID-19 lockdown in Paris: Experience of the first 100 patients.

PURPOSE: This study aimed to evaluate the ability of a freely accessible internet algorithm to correctly identify the need for emergency ophthalmologic consultation for correct diagnosis and management. METHOD: This retrospective observational cohort study was based on the first 100 patients who requested recommendations on the necessity of breaking the lockdown for emergency ophthalmology consultation during the period from March to May 2020. RESULTS: Ninety-one patients completed questionnaires. Forty-nine were directed to emergency consultation and 42 to differed scheduled visits or telemedicine visits. One patient sent for emergency consultation had an overestimated severity and could have been seen later, while two patients initially recommended for a scheduled visit were considered appropriate for emergency consultation. However, these patients' management did not suffer as a consequence of the delay. The sensitivity of the algorithm, defined as the number of emergency consultations suggested by the algorithm divided by the total number of emergency consultations deemed appropriate by the practitioner's final evaluation, was 96.0%. The specificity of the algorithm, defined as the number of patients recommended for delayed consultation by the algorithm divided by the number of patients deemed clinically appropriate for this approach, was 97.5%. The positive predictive value, defined as the number of appropriate emergency consultations divided by the total number of emergency consultations suggested by the algorithm, was 97.9%. Finally, the negative predictive value, defined as the number of appropriately deferred patients divided by the number of deferred patients recommended by the algorithm, was 95.2%. CONCLUSION: This study demonstrates the reliability of an algorithm based on patients' past medical history and symptoms to classify patients and direct them to either emergency consultation or to a more appropriate deferred, scheduled appointment. This algorithm might allow reduction of walk-in visits by half and thus help control patient flow into ophthalmologic emergency departments.

Excimer laser programming of refractive astigmatism vs. anterior corneal astigmatism in the case of ocular residual astigmatism (ORA).

PURPOSE: To determine whether manifest refractive astigmatism (RA) or anterior corneal astigmatism (CA) is the best value for excimer laser programming in cases of ocular residual astigmatism (ORA). PATIENTS AND METHODS: Patients who had undergone LASIK surgery with a disagreement between manifest refractive and corneal cylinder (ocular residual astigmatism ORA)>0.75 D were included retrospectively in this study. We calculated target induced astigmatism vector (TIA), surgically induced astigmatism vector (SIA), difference vector between the astigmatism correction programmed in the excimer laser and refractive astigmatism (DVRA), difference vector between the astigmatism correction programmed in the excimer laser and corneal astigmatism (DVCA) and difference vector between TIA and SIA (DV), by the Alpins method. Vectorial differences between DV and DVRA, and between DV and DVCA, were then calculated to determine whether RA or CA was closest to the ideal cylinder for laser programming. RESULTS: Of a total of 104 eyes undergoing LASIK, 22 eyes of 12 patients (21.1%) had an ORA>0.75 D and were included. Mean ORA was 0.9±0.2 D and mean postoperative subjective cylinder was 0.45 D. The DV-DVRA difference vector was 0.57±0.2 D, and the DV-DVCA difference vector was 0.86±0.4 D (P=0.02). RA was closer than CA to the ideal astigmatism correction. CONCLUSION: In cases of discrepancy between manifest astigmatism and corneal astigmatism, correction of manifest refractive astigmatism seems to give a better refractive result.

Corneal crosslinking in keratoconus management.

Since two decades, corneal crosslinking (CXL) has been proposed as the sole therapeutic option to halt progression of keratoconus or other ectatic diseases. CXL aims at stiffening the cornea using a combination of ultraviolet-A light and a chromophore (vitamin B2, riboflavin), and has been proposed in various indications, from progressive ectatic diseases to corneal infection. Despite being in clinical use for many years, many controversies and discrepancies exist towards CXL procedure and its exact role is still under debate. We report an up-to-date review of the state of the art of CXL and describe the basic principles, the different existing CXL techniques reporting basic and clinical evidence, as well as the new perspectives and the possible future developments of the procedure.

[SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018 (French translation of the article)]. / Quelle place pour le SMILE (Small Incision Lenticule Extraction) dans la chirurgie réfractive cornéenne en 2018.

Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (Small Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to disadvantages of the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia with LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding improvements in the technique.

SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018.

Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (SMall Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia related to LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding new improvements in the technique.

[Femtosecond laser-assisted cataract surgery]. / Chirurgie de la cataracte assistée par laser.

Femtosecond laser-assisted cataract surgery is a major technological innovation. The femtosecond laser, during a pretreatment step, helps to prepare the patient's eye for the surgery proper by creating corneal incisions, anterior capsulotomy and lens fragmentation in an automated fashion. Thus, these steps can be performed with precision and reproducibility, and lens fragmentation reduces the amount of ultrasound required during surgery. Drawbacks of this technology are a longer operating time, a more demanding surgical procedure and a much higher cost for patients and surgical centers. New models of organization in the operating room, patient flow, and financial systems have to be designed to adapt this procedure to our practice. The benefits of this technology should make it an essential tool in the future, provided that cataract surgery can be reconsidered logistically and economically.

Weight Loss Reversed Obesity-Induced HGF/c-Met Pathway and Basal-Like Breast Cancer Progression.

Epidemiologic studies demonstrate that obesity is associated with an aggressive subtype of breast cancer called basal-like breast cancer (BBC). Using the C3(1)-TAg murine model of BBC, we previously demonstrated that mice displayed an early onset of tumors when fed obesogenic diets in the adult window of susceptibility. Obesity was also shown to elevate mammary gland expression and activation of hepatocyte growth factor (HGF)/c-Met compared to lean controls, a pro-tumorigenic pathway associated with BBC in patients. Epidemiologic studies estimate that weight loss could prevent a large proportion of BBC. We sought to investigate whether weight loss in adulthood prior to tumor onset would protect mice from accelerated tumorigenesis observed in obese mice. Using a life-long model of obesity, C3(1)-TAg mice were weaned onto and maintained on an obesogenic high-fat diet. Obese mice displayed significant elevations in tumor progression, but not latency or burden. Tumor progression was significantly reversed when obese mice were induced to lose weight by switching to a control low-fat diet prior to tumor onset compared to mice maintained on obesogenic diet. We investigated the HGF/c-Met pathway known to regulate tumorigenesis. Importantly, HGF/c-Met expression in normal mammary glands and c-Met in tumors was elevated with obesity and was significantly reversed with weight loss. Changes in tumor growth could not be explained by measures of HGF action including phospho-AKT or phospho-S6. Other mediators associated with oncogenesis such as hyperinsulinemia and a high leptin:adiponectin ratio were elevated by obesity and reduced with weight loss. In sum, weight loss significantly blunted the obesity-responsive pro-tumorigenic HGF/c-Met pathway and improved several metabolic risk factors associated with BBC, which together may have contributed to the dramatic reversal of obesity-driven tumor progression. Future research aims to evaluate the role of obesity and the HGF/c-Met pathway in basal-like breast cancer progression.

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.

Corneal imaging of intrastromal femtosecond laser treatment for presbyopia (Intracor(®)).

PURPOSE: To evaluate anatomic appearance and corneal cellular modifications after monocular Intracor(®) procedure with two different anterior segment imaging techniques within the first postoperative year. PATIENTS AND METHODS: Four patients underwent an Intracor(®) procedure in one eye performed at Clinique de la vision, and corneal imaging was performed in Quinze-Vingts National Ophthalmology Hospital. Slit-lamp photography, confocal microscopy with Heidelberg retinal tomography (HRT) and anterior segment spectral-domain optical coherence tomography (OCT) were performed 2 days, and 1, 6, and 12 months after the procedure. RESULTS: Confocal microscopy showed strong cellular activation of keratocytes within the first postoperative month which diminished over time. The linear femtosecond incisions appeared as hyper-reflective regular lines and reflectivity decreased throughout the follow-up period. After 6 months, a fibrotic process with appearance of corneal scars was visible as small intrastromal hyper-reflective lines and thick hyper-reflective spicules around the incisions and remained stable over time. On spectral-domain OCT, the size and depth of the incisions decreased from the center to the periphery. Visibility of the corneal femtosecond incisions on OCT decreased from day 2 until they almost disappeared at 12 months. The incision angles seemed to curve progressively from the center to the periphery in their deep portion on the peripheral rings. CONCLUSION: Corneal cellular modifications found on HRT, anatomical features, and the sizes of the intrastromal rings, may provide valuable information on this new refractive technique.

Improving the diagnosis of pulmonary tuberculosis in HIV-infected individuals in Ho Chi Minh City, Viet Nam.

SETTING: District 6, An Hoa Clinic in Ho Chi Minh City (HCMC), Viet Nam. OBJECTIVE: To evaluate the performance of various algorithms in tuberculosis (TB) screening and diagnosis in a human immunodeficiency virus (HIV) infected population in HCMC, Viet Nam. DESIGN: A cross-sectional study of 397 consecutive HIV-infected patients seeking care at the An Hoa Clinic from August 2009 to June 2010. Data on participant demographics, clinical status, chest radiography (CXR) and laboratory results were collected. A multiple logistic regression model was developed to assess the association of covariates and pulmonary TB (PTB). RESULTS: The prevalence of sputum culture-confirmed PTB, acid-fast bacilli (AFB) positive TB, and multidrugresistant TB among the 397 HIV-infected patients was respectively 7%, 2%, and 0.3%. Adjusted odds ratios for low CD4+ cell count, positive sputum smear, and CXR to positive sputum culture were respectively 3.17, 32.04 and 4.28. Clinical findings alone had poor sensitivity, but combining CD4+ cell count, AFB sputum smear and CXR had a more accurate diagnostic performance. CONCLUSION: Results suggest that symptom screening had poor clinical performance, and support the routine use of sputum culture to improve the detection of TB disease in HIV-infected individuals in Viet Nam. However, when routine sputum culture is not available, an algorithm combining CD4+ cell count, AFB sputum smear and CXR is recommended for diagnosing PTB.

[Macular fold following retinal detachment surgery]. / Pli maculaire compliquant la chirurgie du décollement de rétine.

INTRODUCTION: The occurrence of a retinal fold after vitrectomy for retinal reattachment is not often described. In this case report, its treatment, prevention, and mechanism are discussed. CASE REPORT: A 45-year-old pseudophakic woman experienced a superotemporal retinal detachment with macula-on and numerous retinal tears. The treatment consisted of a vitrectomy, perfluorocarbon injection, cryotherapy, and a complete fluid/gas exchange. Postoperative examination disclosed a retinal fold centered by the fovea. The treatment of this macular fold included the creation of a new detachment of the posterior pole by means of an injection of balanced saline solution into the subretinal space through a 39-gauge cannula, the injection of perfluorocarbon liquid to move the fold superiorly, endolaser at the inferior limit of the fold, and silicone oil injection. At the postoperative examination, the macula was flattened and the fold was near the superior temporal arcade. DISCUSSION: The formation of a macular fold after vitrectomy was probably caused by the complete fluid/gas exchange, which displaced the subretinal fluid from the periphery to the posterior pole, detaching the macula. Tangential traction exerted by the presence of intravitreal gas and subretinal fluid might have stretched the retina and resulted in the formation of the fold. This mechanism is similar to the technique used in macular translocation surgery. To avoid this complication in macula-on retinal detachment, we suggest not using perfluorocarbon liquid systematically and replacing the complete fluid/gas exchange with a limited bubble of expansive gas combined with postoperative positioning.

Fibronectin regulates epithelial organization during myocardial migration in zebrafish.

Several genes have been implicated in heart tube formation, yet we know little about underlying cellular mechanisms. We analyzed the cellular architecture of the migrating myocardial precursors, and find that they form coherent epithelia that mature as they move medially. Mutant analyses indicate that the cardia bifida locus natter (nat) is required for the integrity of the myocardial epithelia. We positionally cloned nat and show that it encodes Fibronectin. During myocardial migration, Fibronectin is deposited at the midline between the endoderm and endocardial precursors, and laterally around the myocardial precursors. Further analyses show that Fibronectin deposition at the midline is required for the timely migration of myocardial precursors, but dispensable for the migration process itself. In the complete absence of Fibronectin, adherens junctions between myocardial precursors do not form properly, suggesting that cell-substratum interactions are required for epithelial organization. These data suggest that myocardial migration is dependent on epithelial integrity.

Recovery of mouse endostatin produced by Pichia pastoris using expanded bed adsorption.

Endostatin, a 20 KDa fragment of collagen XVIII, was shown to have an inhibitory effect on angiogenesis and can potentially be used as a tumor growth suppressor. To obtain the amount needed for testing, the protein was successfully cloned and expressed in Pichia pastoris. At the end of the fermentation process, the concentration of the endostatin in the culture was 50 mg per liter, accompanied by 400 gr per liter (wet weight) of biomass. Before the protein can be captured and purified on a packed bed of heparin-Sepharose, the biomass must be removed. Because of the high biomass concentration, conventional biomass removal techniques like centrifugation or filtration are inefficient and cumbersome. Therefore, the expanded-bed adsorption technique was chosen as an alternative approach. An efficient procedure for the initial recovery and purification of the endostatin was developed. The process utilized a cation- exchanger resin instead of a heparin-based affinity resin, because its dynamic capacity was higher, even though it was affected by the high linear flow on the expanded bed. After adjusting the conductivity, pH and biomass concentration, the complete broth was pumped directly on the expanded-bed matrix (Streamline SP XL). Though the yields of protein are similar, the expanded-bed approach is superior to the packed-bed method for several reasons. The expanded-bed process was shorter (only 8 hours compared to 16 hours for the packed bed), it is cheaper, and the product has higher specific activity (29% compared with 18%). Endostatin produced by the expanded-bed adsorption method showed the expected bioactivity and is currently being tested for its potential as a tumor suppressor.

Correction of the NMR structure of the ETS1/DNA complex.

The ETS family of transcription factors consists of a group of proteins that share a highly conserved 85 amino acid DNA-binding domain (DBD). This family recognizes a consensus sequence rich in purine bases with a central GGAA motif. A comparison of the published three-dimensional structures of the DBD/DNA complexes of ETS1 by NMR [Werner et al. (1995) Cell, 83, 761-771] and the related Pu.1 by X-ray crystallography [Kodandapani et al. (1996) Nature, 380, 456-460] reveals an apparent discrepancy in which the protein domains bind with opposite polarity to their target sequences. This surprising and highly unlikely result prompted us to reexamine our NMR structure. Additional NMR experiments now reveal an error in the original interpretation of the spectra defining the orientation of the ETS1-DBD on DNA. It was originally reported that the ETS1-DBD bound to DNA with a bipartite motif involving major groove recognition via a helix-turn-helix element and minor groove recognition via protein side-chain intercalation. The presence of intercalation was deduced on the basis of numerous NOEs between several amino acids in the protein and a resonance at 12.33 ppm originally assigned to a DNA imino proton. New NMR experiments now conclusively demonstrate that this resonance, which is located within the DNA imino proton region of the spectrum, arises from the hydroxyl proton of Tyr86. Realization of this error necessitated reanalysis of the intermolecular NOEs. This revealed that the orientation of the ETS1-DBD in the complex is opposite to that originally reported and that a tryptophan residue does not intercalate into the DNA. The calculation of a new ensemble of structures based on the corrected data indicates that the structure of the ETS1-DBD/DNA complex is indeed similar to the X-ray structure of the Pu.1-DBD/DNA complex.

The solution structure of the human ETS1-DNA complex reveals a novel mode of binding and true side chain intercalation.

The solution structure of a 24.4 kDa specific complex of the DNA-binding domain (DBD) of the human ETS1 (hETS1) oncoprotein with a 17-mer DNA has been solved by NMR. The interaction of the hETS1 DBD with DNA reveals a surprising twist on the general features of helix-turn-helix (HTH)-DNA interactions. Major groove recognition involves the C-terminal two thirds of the HTH recognition helix, while minor groove recognition occurs via true intercalation of the side chain of Trp-28, which extends from the minor to the major groove. This results in a sharp kink of approximately 60 degrees and a widening of the minor groove over one-half turn of the DNA. The orientation of the HTH element of the hETS1 DBD with respect to the major groove is significantly rotated relative to other HTH proteins. These observations establish the ETS family of DNA-binding proteins as a distinct family of HTH proteins.