Effects of triamcinolone acetonide on vessels of the posterior segment of the eye

PURPOSE: This study investigates the effects of triamcinolone acetonide (TA) on retinal endothelial cells in vitro and explores the potential vascular toxic effect of TA injected into the vitreous cavity of rats in vivo. METHODS: Subconfluent endothelial cells were treated with either 0.1 mg/ml or 1 mg/ml TA in 1% ethanol. Control cells were either untreated or exposed to 1% ethanol. Cell viability was evaluated at 24 h, 72 h, and five days using the tetrazolium 3-(4,5-dimethylthiazol-2-yl)-2,5 phenyltetrazolium bromide test (MTT) and lactate dehydrogenase (LDH) assays. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) test. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL assay), annexin-binding, and caspase 3 activation. Caspase-independent cell deaths were investigated by immunohistochemistry using antibodies against apoptosis inducing factor (AIF), cytochrome C, microtubule-associated protein (MAP)-light chain 3 (MAP-LC3), and Leukocyte Elastase Inhibitor/Leukocyte Elastase Inhibitor-derived DNase II (LEI/L-DNase II). In vivo, semithin and ultrathin structure analysis and vascular casts were performed to examine TA-induced changes of the choroidal vasculature. In addition, outer segments phagocytosis assay on primary retinal pigment epithelium (RPE) cells was performed to assess cyclooxygenase (COX-2) and vascular endothelial growth factor (VEGF) mRNAs upregulation with or without TA. RESULTS: The inhibitory effect of TA on cell proliferation could not explain the significant reduction in cell viability. Indeed, TA induced a time-dependent reduction of bovine retinal endothelial cells viability. Annexin-binding positive cells were observed. Cytochrome C was not released from mitochondria. L-DNase II was found translocated to the nucleus, meaning that LEI was changed into L-DNase II. AIF was found nuclearized in some cells. LC3 labeling showed the absence of autophagic vesicles. No autophagy or caspase dependent apoptosis was identified. At 1 mg/ml TA induced necrosis while exposure to lower concentrations for 3 to 5 days induced caspase independent apoptosis involving AIF and LEI/L-DNase II. In vivo, semithin and ultrathin structure analysis and vascular casts revealed that TA mostly affected the choroidal vasculature with a reduction of choroidal thickness and increased the avascular areas of the choriocapillaries. Experiments performed on primary RPE cells showed that TA downregulates the basal expression of COX-2 and VEGF and inhibits the outer segments (OS)-dependent COX-2 induction but not the OS-dependent VEGF induction. CONCLUSIONS: This study demonstrates for the first time that glucocorticoids exert direct toxic effect on endothelial cells through caspase-independent cell death mechanisms. The choroidal changes observed after TA intravitreous injection may have important implications regarding the safety profile of TA use in human eyes

Self-focusing and spherical aberrations in corneal tissue during photodisruption by femtosecond laser

International audienceThe use of ultrashort pulse lasers is current in refractive surgery and has recently been extended to corneal grafting (keratoplasty). When performing keratoplasty, however, permanent degradation of the optical properties of the patient's cornea compromises the penetration depth of the laser and the quality of the incisions, therefore causing unwanted secondary effects. Additionally, corneal grafting needs considerably higher penetration depths than refractive surgery. Little data are available about the interaction processes of the femtosecond pulses in the volume of pathological corneas—i.e., in the presence of spherical aberrations and optical scattering. We investigate the influence of the focusing numerical aperture on the laser–tissue interaction. We point out that at low numerical apertures (NAs), tissue damage is produced below and above the focal region. We attribute this phenomenon to nonlinear self-focusing effects. On the other hand, at high NAs, spherical aberrations become significant when focusing at high depths for posterior surgeries, which also limit the cutting efficiency. As high NAs are advisable for reducing unwanted nonlinear effects and ensure accurate cutting, particular attention should be paid to aberration management when developing clinical femtosecond lasers

Keratoprosthesis With Biocolonizable Microporous Fluorocarbon Haptic: Preliminary Results in a 24-Patient Study

BACKGROUND: Most complications of a keratoprosthesis occur at the tissue-to-implant interface. The ideal prosthesis would eliminate this interface by having the tissue actually grow into the supporting material. We present a prospective clinical human study of a novel biocolonizable keratoprosthesis in 24 eyes of 24 patients. DESIGN: To promote implant stability, the 9-mm—diameter haptic was fashioned using a custom-made microporous fluorocarbon with a 4-mm—diameter, 2.67-mm—long, central optic made of medical grade polymethylmethacrylate, giving a global visual field of 110° to 130°. Only bilaterally blind patients with untreatable corneal diseases were included in the study. The haptic was inserted into a lamellar pocket delaminated in the stroma, and the optic was positioned through a hole trephined in the central cornea. RESULTS: The average follow-up was 15.7 months (range, 4 to 28 months). The host corneal fibroblasts penetrated and proliferated into the peripheral microporous fluorocarbon and provided anchorage between the cornea and prosthesis. Seventeen patients (70.8%) had visual acuity improvements. Mean corrected final visual acuity was 20/100 (range, 20/30 to 20/400). Five anatomic failures occurred in the first 6 months (three extrusions, one dislocation of the optic, and one endophthalmitis). We had one case (4.1%) of treatable glaucoma. We successfully removed four of five retroprosthetic membranes that had occurred. No retinal detachment occurred. CONCLUSION: The biocompatible inert microporous polymer did not eliminate all mechanical complications associated with a keratoprosthesis

Laser parameters, focusing optics, and side effects in femtosecond laser corneal surgery

International audienceNowadays, femtosecond lasers are routinely used in refractive eye surgery. Until recently, commercialised clinical systems were exclusively based on ytterbium or neodymium-doped solid state lasers emitting sub-picosecond pulses at a wavelength of about 1 µm and repetition rates of a few 10 kHz. These systems use pulse energies in the µJ range and focussing optics of NA = 0.3 to 0.5. Recent developments have provided a variety of alternative and equally viable approaches: systems are now available using nJ pulses at high numerical apertures and MHz repetition rates - an approach so far only used for femtosecond cell surgery - and fibre laser technology is now being used for femtosecond laser corneal surgery. Recent research has also provided more insight in side effects occurring in present systems: self focusing phenomena and so far unexplained periodical structures have been observed even at high numerical apertures (NA >> 0.5) and moderate pulse energies. The interaction of femtosecond laser pulses with strongly scattering tissue has been studied in view of extending the application of femtosecond lasers to keratoplasty for opaque corneas and to glaucoma surgery. The use of new laser wavelengths and adaptive optics has been proposed. Despite the reputation of femtosecond surgical systems for their precision, repeatability and the absence of secondary effects or complications, a closer examination reveals the presence of subtle phenomena which merit further investigation. We present three of these phenomena: the influence of optical aberration on the quality of the incision, the occurrence of filamentation effects, and the deposit of microscopic glass fragments when performing penetrating incisions

Imagerie cornéenne par laser femtoseconde

International audienceLes auteurs présentent une nouvelle méthode d'utiliser l'émission optique non linéaire engendrée dans le tissu cornéen par laser femtoseconde chirurgical pour des fins d'imagerie et de contrôle de l'intervention in situ

Relating Nanostructural Properties of the Cornea, its Macroscopic Transparency and Compressibility

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Study of Scattering vs. Transparency for Corneal Graft Optimization

International audiencePurpose: Femtosecond laser corneal surgery is currently limited in depth for transfixing cuts in oedematous cornea. We perform spectral characterization measurements on corneal tissue over a wide spectral range in order to develop optimized laser sources and to gain new insight in tissue optics. We propose a new and simple optical device to evaluate corneal graft quality. Methods: Human corneas have been exposed to a spatially coherent white light system and used in confocal geometry to perform the ballistic transmission spectrum through the cornea, furthermore the total transmission spectrum has been obtained using an integrating sphere. In parallel, monochromatic light emitting diodes (LED) have been used for imaging a star target through human corneas to obtain its modulation transfer function (MFT) after a numerical analysis. Results: Ballistic and total transmission spectra of the corneas have been obtained, and from those the scattering cross section has been evaluated. Human corneas present a similar absorption spectrum as water. The scattering cross section is significantly lowered at longer wavelengths. The absorption losses which are present in this spectral range are compensated by reduced scattering. Therefore it is possible to perform efficient transfixing cuts in the depth of the cornea using mid-infrared wavelength (around 1.6 µm). The simplified star target system allows an efficient and objective evaluation of the corneal quality of individual donor grafts. Conclusions: Our findings suggest that future improved systems for keratoplasty may obtain optimized performance by using laser sources emitting at longer infrared wavelengths.The optical quality of individual donor corneas may be evaluated using our simplified, standardized optical measurement device

Impact of Operator Medical Specialty on Endotracheal Intubation Rates in Prehospital Emergency Medicine — A Retrospective Cohort Study

Prehospital endotracheal intubation (ETI) can be challenging, and the risk of complications is higher than in the operating room. The goal of this study was to compare prehospital ETI rates between anaesthesiologists and non-anaesthesiologists. This retrospective cohort study compared prehospital interventions performed by either physicians from the anaesthesiology department (ADP) or physicians from another department (NADP, for non-anaesthesiology department physicians). The primary outcome was the prehospital ETI rate. Overall, 42,190 interventions were included in the analysis, of whom 68.5% were performed by NADP. Intubation was attempted on 2797 (6.6%) patients, without any difference between NADPs and ADPs (6.5 versus 6.7%, p = 0.555). However, ADPs were more likely to proceed to an intubation when patients were not in cardiac arrest (3.4 versus 3.0%, p = 0.026), whereas no difference was found regarding cardiac arrest patients (65.2 versus 67.7%, p = 0.243) (p for homogeneity = 0.005). In a prehospital physician-staffed emergency medical service, overall ETI rates did not depend on the frontline operator’s medical specialty background. ADPs were, however, more likely to proceed with ETI than NADPs when patients were not in cardiac arrest. Further studies should help to understand the reasons for this difference.</p

Study of corneal scattering for the optimization of femtosecond keratoplasty

International audienceThe specular transmittance spectrum of human corneas is studied using a confocal geometry set-up. The comparison of the obtained spectrum with the total transmittance spectrum permits the determination of the stromal scattering spectrum of pathological corneas. The dependence of the scattering cross section on wavelength dependence is analyzed

Wavelength optimization in femtosecond laser corneal surgery: experimental results

International audienceFemtosecond laser surgery in the volume of corneal tissue is difficult in the case of oedematous or pathological corneas: in those corneas, the propagation of the laser beam is perturbed by the optical scattering. This phenomenon can be greatly reduced by using a better suited laser wavelength. A series of ex vivo surgical experiments has been conducted at wavelengths around 1600 nm. The results have been compared to experiments performed at 800 nm and 1000 nm. We have compared penetration depth and incision quality as a function of wavelength and energy