Defining corneal chemical burns: A novel exact and adjustable ocular model.

INTRODUCTION: Live-animal-free ocular toxicity models and tests are a necessity in multiple branches of medicine, industry and science. Corneal models with adjustable ranges of injury severities do not exist. In this work, a novel and precise and dose - response method to induce and observe ex vivo corneal chemical burns has been established. METHODS: The EVEIT (Ex Vivo Eye Irritation Test) is based on an ex vivo corneal organ model for rabbit corneas from food industry. Further, a highly precise three - axis workstation has been employed to apply liquid corrosive, sodium hydroxide (NaOH), droplets in a nanolitre (nL) range onto the corneal surface. Optical Coherence Tomography (OCT) has been used to observe and quantify the elicited changes in the corneal layers. RESULTS: The speed and intervals of single nanodroplet application played a crucial role in the extent of the corneal changes. Similar total volumes applied at low frequencies elicited deep and extensive changes in the corneal layers whereas high application frequencies elicited comparatively superficial changes. Increasing NaOH concentrations effected measurably increasing corneal changes. Increasing the volume of applied NaOH also showed an increase in corneal changes. CONCLUSIONS: OCT imaging proved to be effective in observing, documenting and quantifying the changes in the corneal layers. The ex vivo model, in conjunction with the novel application method was able to induce and display distinctive and consistent correlations between NaOH volume, concentration and elicited corneal changes. This ex vivo ocular chemical burn model provides a consistent in vitro basis for pharmaceutical and toxicological experiments and investigations into corneal chemical burn mechanisms and treatment.

The Ex vivo Eye Irritation Test (EVEIT) model as a mean of improving venom ophthalmia understanding.

Snakes belonging to the genus Naja (Elapid family), also known as "spitting cobras", can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non-spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non-spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high-resolution optical coherence tomography (HR-OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non-spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia.

Intraocular silicone implant to treat chronic ocular hypotony-preliminary feasibility data.

PURPOSE: Ocular hypotony secondary to proliferative vitreoretinopathy-related retinal detachment, trauma or inflammation is difficult to treat. Besides endotamponades such as silicone oil, vitreous implants such as iris diaphragms or balloons have been developed to stabilize the eye and to prevent phthisis of the globe. Vitreous implants tested thus far exhibit a seam at the attachment site of the hemispheres, or micropores. This manuscript reports the development of a seamless silicone balloon implant without micropores, which can be filled with silicone oil and surface-modified to improve its biocompatibility. Developed for intraocular placement in the management of chronic hypotony and phthisis prevention, it may also be suitable for tamponading retinal detachments. METHODS: Silicone was used as the basic structure for the fabrication of a seamless balloon-shaped intraocular implant, which was coated by employing a six-arm star-shaped (sP) macromer of a copolymer of 80 % ethylene oxide (EO) and 20 % propylene oxide (PO) with conjugated functional terminal isocyanate groups, NCO-sP(EO-stat-PO), with and without heparin. Three variants of implants, which differ in their surfaces, were manufactured: uncoated silicone, NCO-sP (EO-stat-PO) coated silicone and heparin-NCO-sP (EO-stat-PO) coated silicone implants. To exert a tamponade effect, the implant was filled with silicone oil and its properties were studied. RESULTS: Seamless thin balloon implants made of silicone, which are considered biocompatible and intrinsically resistant to biological attacks in vivo, could be fabricated in different sizes. The silicone oil-filled implant can mimic the mechanism of buoyant force and high surface tension of silicone oil, which is the only long-term vitreous substitute currently available. The silicone oil-filled implant can also mimic the natural vitreous body by occupying the entire posterior segment. CONCLUSIONS: The intraocular silicone implant as an alternative long-term treatment of chronic ocular hypotony might offer a new option for clinical ophthalmological practice. In vivo studies need to be performed to collect more data on the implant's long-term mechanical and optical properties, as well as long-term biocompatibility.

The Ex Vivo Eye Irritation Test as an alternative test method for serious eye damage/eye irritation.

Ocular irritation testing is a common requirement for the classification, labelling and packaging of chemicals (substances and mixtures). The in vivo Draize rabbit eye test (OECD Test Guideline 405) is considered to be the regulatory reference method for the classification of chemicals according to their potential to induce eye injury. In the Draize test, chemicals are applied to rabbit eyes in vivo, and changes are monitored over time. If no damage is observed, the chemical is not categorised. Otherwise, the classification depends on the severity and reversibility of the damage. Alternative test methods have to be designed to match the classifications from the in vivo reference method. However, observation of damage reversibility is usually not possible in vitro. Within the present study, a new organotypic method based on rabbit corneas obtained from food production is demonstrated to close this gap. The Ex Vivo Eye Irritation Test (EVEIT) retains the full biochemical activity of the corneal epithelium, epithelial stem cells and endothelium. This permits the in-depth analysis of ocular chemical trauma beyond that achievable by using established in vitro methods. In particular, the EVEIT is the first test to permit the direct monitoring of recovery of all corneal layers after damage. To develop a prediction model for the EVEIT that is comparable to the GHS system, 37 reference chemicals were analysed. The experimental data were used to derive a three-level potency ranking of eye irritation and corrosion that best fits the GHS categorisation. In vivo data available in the literature were used for comparison. When compared with GHS classification predictions, the overall accuracy of the three-level potency ranking was 78%. The classification of chemicals as irritating versus non-irritating resulted in 96% sensitivity, 91% specificity and 95% accuracy.

[Postoperative care after cataract surgery]. / Die Staroperation Medikamentöse Prophylaxe und Therapie im Umfeld der Operation.

The postoperative treatment of cataract surgery is an important element for success of the surgery. The postoperative therapy primarily aims at the prevention of intraocular bacterial infection by administration of antibiotics. Anti-inflammatory drugs can suppress the operation-related inflammation. In addition to fundamental risks of topical eye drop application, this review article discusses the current therapeutic strategies for the prevention of postoperative bacterial infection and suppression of surgically induced inflammation.

Changing the composition of buffered eye-drops prevents undesired side effects.

PURPOSE: The Ex Vivo Eye Irritation Test (EVEIT) is used to analyse the clinical observations of corneal calcification attributed to the presence of phosphate within applied eye-drops used in treating glaucoma, Still-Chauffard syndrome, ocular burns and dry eyes. METHOD: Live corneas from abattoir rabbit eyes were cultured in order to study epithelial healing following mechanical abrasion of the corneal surface combined with repeated exposure to various eye-drops. RESULTS: Obvious corneal calcification of the wound area along with a complete epithelial healing covering the calcified area was observed following exposure to phosphate hyaluronate eye-drops. Epithelial healing without calcification was achieved using citrate hyaluronate eye-drops. CONCLUSION: Clinical observations show that topical use of artificial tears containing phosphate on injured eyes may lead to sight-threatening corneal complications. Simulation of such treatment conditions by the EVEIT convincingly demonstrates that changes in the composition of the pharmaceutically used treatments can prevent this undesired side effect. Although considerable healing was achieved during the repeated application of eye-drops, using either a phosphate or citrate buffer, only the drops containing citrate did not develop corneal calcification on the eye. The authors therefore recommend discontinuing the use of phosphate-buffered eye-drops, or other topically applied solutions, to avoid further injury to the patient.

Towards a new in vitro model of dry eye: the Ex Vivo Eye Irritation Test.

Understanding of dry eye syndrome (DES) today is driven by in vivo analysis of tear osmolarity, tear film break up time, impression cytology and description of symptoms. Existing in vivo models of DES need severe alterations of tear production or corneal integrity. For a more detailed analysis of DES under particular environmental and treatment conditions a considerable lack of in vitro methods exists. The main disadvantage of current in vitro models is the limited experimental time frame of only several hours and the impossibility to evaluate healing of epithelial defects. In the present study, evidence is given that these restrictions can be overcome by modifying the established Ex Vivo Eye Irritation Test (EVEIT) to realize a model system for DES. This test is based on abattoir rabbit eyes allowing an experimental time frame of up to 21 days using self-healing corneal cultures. In first experiments it is demonstrated that different severity levels of dry eye can be simulated in the EVEIT system. High-resolution optical coherence tomography (OCT) is applied to monitor the initial phase of DES under evaporative stress acting on the cornea. We observed changes in corneal layer thicknesses and in scattering properties of the stroma, which are sensitive indicators of environmental stress leading to irritation of the ocular surface under dry eye conditions. The combination of corneal culture under desiccating conditions and OCT monitoring offers a new perspective in understanding and treating of DES and is expected to allow for significant pharmacological screening tests.

Repeated exposure to benzalkonium chloride in the Ex Vivo Eye Irritation Test (EVEIT): observation of isolated corneal damage and healing.

The prediction of side-effects is a key issue in the REACH initiative on chemicals, in the production of cosmetics and in the preclinical testing of drugs. A new ex vivo test for repeated substance application is presented, that is able to identify corrosive and irritant effects on the eye by using crucial endpoints, such as cellular and morphological damage, and healing characteristics. The test is intended to replace the Draize eye test and to improve the preclinical testing of drugs and chemicals that are likely to come into direct contact with the cornea. The Ex Vivo Eye Irritation Test (EVEIT) is a self-healing system, involving living corneas obtained from abattoir rabbit eyes. The corneas are cultured in a similar way to the method used during the transplantation of corneal grafts. The corneas are exposed to multiple small, mechanical abrasions, and then test substances are repeatedly dropped onto the centres of the corneas. The test substances applied in this study were citrate-buffered hyaluronate eye drops and an artificial tear replacement, with increasing concentrations of up to 0.1% benzalkonium chloride. A dose-dependent inhibition of recovery and impairment of the lactate production mechanism in the cornea was observed with benzalkonium chloride treatment.

Analysis of hydrofluoric acid penetration and decontamination of the eye by means of time-resolved optical coherence tomography.

So far the study of chemical burns has lacked techniques to define penetration kinetics and the effects of decontamination within biological structures. In this study, we aim to demonstrate that high-resolution optical coherence tomography (HR-OCT) can close this gap. Rabbit corneas were exposed ex vivo to 2.5% hydrofluoric acid (HF) solution, and microstructural changes were monitored in the time domain by OCT imaging. HF application and penetration resulted in shrinkage of the corneal thickness, interpreted as a result of osmolar changes and of loss of water-binding capacity, and a substantial increase in OCT signal amplitudes. The effectiveness of different rinsing solutions on the chemical burn was also evaluated. With tap water and with 1% calcium gluconate, the deep corneal stroma remained clear until the end of the rinsing period but became opaque afterwards. With Hexafluorine, the cornea remained clear for 60 min after rinsing ceased. We conclude that HR-OCT can assist in the clinical evaluation of an ex vivo eye irritation test, and that decontamination of an HF burn using Hexafluorine is efficient.

Dynamic analysis of chemical eye burns using high-resolution optical coherence tomography.

The use of high-resolution optical coherence tomography (OCT) to visualize penetration kinetics during the initial phase of chemical eye burns is evaluated. The changes in scattering properties and thickness of rabbit cornea ex vivo were monitored after topical application of different corrosives by time-resolved OCT imaging. Eye burn causes changes in the corneal microstructure due to chemical interaction or change in the hydration state as a result of osmotic imbalance. These changes compromise the corneal transparency. The associated increase in light scattering within the cornea is observed with high spatial and temporal resolution. Parameters affecting the severity of pathophysiological damage associated with chemical eye burns like diffusion velocity and depth of penetration are obtained. We demonstrate the potential of high-resolution OCT for the visualization and direct noninvasive measurement of specific interaction of chemicals with the eye. This work opens new horizons in clinical evaluation of chemical eye burns, eye irritation testing, and product testing for chemical and pharmacological products.

Choroidal neovascularisation secondary to Best's disease in a 13-year-old boy treated by intravitreal bevacizumab.

BACKGROUND: To describe the effect of intravitreal bevacizumab for the treatment of choroidal neovascularisation secondary to vitelliform dystrophy of the macula (Best's disease). METHODS: A 13-year-old boy with confirmed Best's disease presented with visual acuity (VA) loss due to secondary choroidal neovascularisation (CNV). He was treated with a single injection of 1-mg bevacizumab. RESULTS: Best corrected VA (Snellen) fully recovered from 20/40 preoperatively to 20/20 over a period of 6 months. Optical coherence tomography (OCT) and angiography demonstrated regression of the CNV and resolution of the macular edema. CONCLUSIONS: A single intravitreal injection of bevacizumab may be effective to induce morphologic and functional improvement in a juvenile suffering from CNV secondary to Best's disease.

Efficacy of plasmin enzymes and chondroitinase ABC in creating posterior vitreous separation in the pig: a masked, placebo-controlled in vivo study.

BACKGROUND: Induction of posterior vitreous detachment (PVD) during vitrectomy helps to prevent proliferative complications, but can be traumatic to the retina, particularly in young patients. Adjunct enzymes have been proposed to facilitate PVD. We investigated the efficacy of enzymes in creating PVD as an adjunct to vitrectomy in the pig. METHODS: Five groups of 8 pigs received a masked intravitreal injection of chondroitinase (1 IU), human (0.4 or 1.3 activity units [AU]) or porcine plasmin (0.18 AU or 0.47 AU) into one eye, and osmolarity adjusted control into the other. After incubation, a core vitrectomy was performed on each eye at low suction, without vitreous peeling. The occurrence of spontaneous PVD and its extent were graded. Eyes were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Vitreous remnants on the retina were quantified in SEM. Data were analyzed using McNemar's test for paired observations and Wilcoxon paired signed rank test. RESULTS: Spontaneous PVD occurred more frequently in human plasmin-treated eyes (p<0.025) and all plasmin eyes (p<0.025) than in placebo controls. The extent of PVD appeared larger in human plasmin (p<0.025) and all plasmin-treated eyes (p<0.025). In plasmin-treated eyes, SEM morphometry showed a significant reduction in the vitreous-covered retina areas. Chondroitinase failed to produce an effect. CONCLUSIONS: Plasmin may prove a useful adjunct to conventional vitrectomy.

Translocation of iris pigment epithelium in patients with exudative age-related macular degeneration: long-term results.

PURPOSE: To report the practicability and efficacy of autologous iris pigment epithelium (IPE) translocation in exudative age-related macular degeneration (ARMD) over 1 year. METHODS: The consecutive interventional case series included 56 patients with exudative ARMD. During vitrectomy the submacular neovascular membrane (CNV) was removed and IPE cells, harvested from a peripheral iridectomy, were injected into the submacular space. Included were patients with subfoveal occult CNV (11 eyes), classic CNV (10 eyes), mixed CNV (17 eyes), CNV with a pigment epithelial detachment (13 eyes) or CNV with a hemorrhage (5 eyes). Outcome measures were visual acuity, foveal fixation, size of CNV and rate of recurrence based on fluorescence angiographic imaging. RESULTS: All patients underwent successful surgical removal of the CNV with consecutive subretinal IPE injection. Visual acuity was better than 20/100 in 19 patients preoperatively and in 18 patients postoperatively. A visual acuity of 20/100 or less was found in 37 patients preoperatively and in 38 patients postoperatively. Mean preoperative visual acuity (1.0+/-0.3 logMAR units) did not change significantly after 1 year (1.0+/-0.3 logMAR units). Ten eyes (18%) developed a recurrence. Fixation within the surgically denuded area could be demonstrated in 25 eyes (45%). CONCLUSIONS: Autologous IPE translocation for ARMD over one year can preserve foveal function on a low level, but cannot improve visual acuity. IPE translocation is technically feasible with a low rate of complications. Continued research seems justified to improve functional outcome.

Indocyanine-green-assisted internal limiting membrane peeling in macular hole surgery--a follow-up study.

BACKGROUND: Macular hole surgery including vitrectomy and peeling of epiretinal membranes and the internal limiting membrane (ILM) has become a standard procedure in retinal surgery. Poor visualization of the ILM is an obstacle for successful surgery. Recently, indocyanine green (ICG) has been reported to be a helpful intraocular substance in identifying these membranes. PATIENTS AND METHODS: Eighteen eyes with macular holes stages 2-4 were included. Intraoperatively, the ILM was stained with three drops of 1:9-diluted ICG. After 1 min incubation, the vitreous cavity was rinsed with Ringer's lactate solution, and the ILM was peeled. Autologous thrombocytes were applied to the macular hole and the eye was endotamponaded with 20% SF-6 gas. Preoperatively, 6 weeks postoperatively, and in 3-month intervals thereafter, visual acuity, fundus photographs, scanning laser ophthalmoscope imaging, and Humphrey 24-2 static perimetry was performed. RESULTS: Intraoperatively, the ILM could be nicely visualized by ICG, which allowed easier and less traumatic peeling. At 6 weeks follow-up, visual acuity had improved in 14 of 18 patients, and the macular hole was closed 6 weeks after surgery. Scanning laser imaging revealed a strong signal. During prolonged follow-up, visual acuity declined due to cataract formation. CONCLUSION: ICG as an intraocular tool for staining of the ILM is helpful in macular hole surgery. We observed no negative effects on retinal function, but patients should be followed.

[Treatment of Acute Central Retinal Artery Occlusion (CRAO) by Hyperbaric Oxygenation Therapy (HBO)--Pilot study with 21 patients]. / Behandlung akuter retinaler Zentralarterienverschlüsse (ZAV) mit der hyperbaren Sauerstofftherapie (HBO)--Pilotstudie an 21 Patienten.

BACKGROUND: Central retinal artery occlusion causes severe loss of vision. Treatment trials include massage of the globe, paracentesis, antiglaucomatous eye drops, haemodilution or lysis therapy, which in individual cases did improve the visual outcome, although in general the prognosis remains poor. In this study we applied hyperbaric oxygenation treatment additionally to haemodilution to overcome retinal ischaemia until spontaneous recanalisation of the central retinal artery occurs. PATIENTS AND METHODS: Patients with central retinal artery occlusion and onset of symptoms up to 12 h were included. Following initial ocular massage and application of antiglaucomatous eyedrops, hyperbaric oxygenation treatment was performed twice daily for up to three days. RESULTS: 21 patients could be included. The time lag between onset of symptoms and admission was between 4 and 12 h. Initial visual acuity ranged from light perception to 0.08. On discharge 19 patients reported on a subjective visual improvement which could be confirmed in 13 patients. In 9 patients an initial increase of visual acuity under hyperbaric oxygenation treatment could be observed which however was again reduced by at least one line on discharge. No patient experienced vision loss below admission vision. CONCLUSIONS: Hyperbaric oxygenation treatment seems to improve the visual outcome in central retinal artery occlusion. Major parameters for visual prognosis are the time lag from the onset of symptoms to the beginning of hyperbaric oxygenation treatment and the time lag until retinal reperfusion begins. Hyperbaric oxygenation treatment can compensate retinal ischaemia; however, the lack of glucose and accumulation of toxic metabolites is not addressed. A combination of hyperbaric oxygenation treatment with administration of glutamate antagonists or intravitreal glucose application might further improve the visual outcome.

Comparison of emergency eye-wash products in burned porcine eyes.

BACKGROUND: The long-term prognosis of patients with chemical eye burns depends on immediately rinsing the eye after the trauma. The chemical properties and tolerance of currently used rinsing solutions were examined. METHODS: NaCl 0.9%, Ringer lactate, balanced salt solution (Aqsia), phosphate buffer, tap water, and Previn were analyzed. The buffer capacities were determined by titration with HCl and NaOH. The osmolarity of the solutions and the osmolarity of 100 healthy and 100 alkali burned porcine corneas were determined by means of freezing point depression. 56 enucleated porcine eyes were burned and rinsed with NaCl solutions of different osmolarities (0-1200 mosmol/l), Previn, NaCl 0.9% or phosphate buffer, respectively. The different swelling behaviors were determined by pachymetric measurements, and the resulting corneal osmolarity after irrigation was assessed. The effect of Previn as a hyperosmolar solution in comparison with isoosmolar phosphate buffer was examined on 10 healthy human eyes. RESULTS: Only phosphate buffer and Previn show high buffer capacities. The osmolarity of the healthy/burned porcine corneas was 329+/-61/1203+/-289 mosmol/kg. Except for Previn (862+/-3 mosmol/l), all solutions are hypo- or almost isoosmolar in comparison with the healthy cornea. Rinsing of the burned corneas causes swelling in all groups in inverse proportion to the osmolarity of the solution. Thus, the lower the solution's osmolarity, the stronger the swelling reaction of the cornea. The resulting corneal osmolarity following rinsing behaves proportionally to the osmolarity of the rinsing solution. Therefore, a high osmolarity of the rinsing solution correlates with a high corneal osmolarity. No long-term effects in healthy eyes were observed after rinsing with Previn or phosphate buffer. CONCLUSION: Corneal thickness and osmolarity are significantly correlated to the osmolarity of the rinsing solution. Corneal edema dilutes the agent in the stroma. Therefore, we recommend solutions with low osmolarity (tap water) or high buffer capacity (Previn) for the initial post-trauma irrigation.

Use of perfluorohexyloctane as a long-term internal tamponade agent in complicated retinal detachment surgery.

PURPOSE: To report the use of perfluorohexyloctane, a liquid semifluorinated alkane that is heavier than water, as an internal tamponade agent in surgery for complicated retinal detachments. DESIGN: A consecutive interventional case series from three study centers. METHODS: In 23 consecutive eyes (23 patients, 19 men and four women, mean +/- standard deviation (SD) age of 58.5 years +/- 16.1) perfluorohexyloctane was used for long-term internal tamponade. Included were eyes with complicated retinal detachment involving the lower two quadrants of the fundus. Excluded were patients with diseases in the fellow eye or severe systemic disease. A pars plana vitrectomy was performed, including membrane peeling and retinotomy where necessary. RESULTS: The mean duration for perfluorohexyloctane being left in situ was 76 days (SD 37.64) (range, 35-202 days). Four weeks following the removal of perfluorohexyloctane 19 of the 23 patients had total reattachment of the retina; three eyes had a recurrence of retinal detachment. One patient was lost to follow-up. The mean follow-up after perfluorohexyloctane removal was 97 days (range, 48 to 169 days). Cataract formation or progression was noted in nine of the 10 eyes. There were two cases with high intraocular pressures. Dispersion into small droplets was observed as early as 3 days postoperatively in three of the 23 patients. At least 12 of the 23 patients had an obvious dispersion by the time of perfluorohexyloctane removal. There was no sign of optic atrophy, retinal necrosis, or retinal vascular occlusion. CONCLUSION: Perfluorohexyloctane was tolerated as a long-term internal tamponade agent without obvious signs of damage to the retina or optic disk. Of all the complications noted, the most common was that of dispersion of the perfluorohexyloctane bubble into droplets.