Irrigation with phosphate-buffered saline causes corneal calcification during treatment of ocular burns.

Corneal calcification is a vision-threatening manifestation of calcium containing agents in ocular burn. As we previously reported, our interest was sparked by a particular discrepancy of a case: A patient treated for a non-calcium containing agent in eye burn from exposure to an alkaline mixture of NaOH and KOH, who unexpectedly developed corneal calcification. This current study aims to elucidate whether the 2min lasting irrigation with a phosphate-buffered saline itself, regardless of rinsing regimen, triggers corneal calcification. The Ex Vivo Eye Irritation Test (EVEIT) system was used on rabbit corneas to replicate the very same phosphate-buffered saline solution the patient was treated with. The rabbit corneas were first burned with 1 M NaOH, rinsed with 4.9% phosphate-buffered saline for 2 min, and were then moisturized with an artificial tear solution for 48 h. All corneas were fluorescein-stained for photo documentation, snap-frozen, lyophilizated, and the electrolyte content was analyzed by Energy-Dispersive X-ray spectroscopy (EDX). The EDX analysis revealed pathological phosphorous in corneal stroma after a single rinsing with phosphate-buffered saline. Ongoing application of artificial tears containing physiological 14.581 mmol Ca2+ /l led to macroscopically visible calcification, but only in areas of induced corneal erosion. Regardless of the rinsing protocol neither 2 or 15 min of eye rinsing with phosphate containing rinsing solutions, we have given proof that corneal calcification is a foreseeable effect of the phosphate-buffered saline rinsing of mechanically epithelial damaged and chemically burnt eyes. Thus, it is crucial to legally restrict the formulations of phosphate-buffered salines in the medical treatment of eye burns, corneal erosions or chemical splashes of the eye.

[Recommendations for acute treatment for chemical and thermal burns of eyes and lids]. / Empfehlungen zur Akutbehandlung von Verätzungen und Verbrennungen der Augen und Lider.

With these recommendations the authors want to improve the acute therapy of eye burns based on the literature and clinical experience. Due to the lack of studies with high evidential value we base these recommendations on the results of experimental work and reports of successfully treated eye burns. A development of this document by systematic research is necessary. Despite the limited knowledge, the collated facts are the current state of the art of treatment according to the knowledge and research of the authors. The most important clinical recommendation is to rinse a chemically or thermally burnt eye as soon and as extensively as possible. Any delay worsens the prognosis. Substances on the market for first aid have different levels of clinical evidence. Thus saline and amphoteric diphoterine have been evaluated in a prospective clinical study showing an advantage for the amphoter. Water, borate buffer, phosphate buffers and derivatives have never been proven to work in clinical applications. Nevertheless, they are recommended. Within experimental work in vitro we could show the value of polyvalent decontamination. Side-effects of phosphate buffers have been demonstrated in retrospective clinical and prospective experimental studies so that even in cases of beneficial effects on pH we cannot recommend these substances which propagate corneal calcification. Special types of burns, such as hydrofluoric acid need special treatment but as clinical studies are lacking only experimental data can offer suitable recommendations.

[Chemical and thermal eye burns. Conservatíve and surgical options of a stage-dependent therapy]. / Verätzungen und Verbrennungen des Auges. Konservative und chirurgische Optionen einer stadiengerechten Therapie.

The basic principles of first aid for chemical and thermal burns are discussed. In the acute phase the primary goal of all measurements is the prevention or limitation of tissue destruction. The further therapeutic care is focused on the modulation of the inflammatory response, the prevention of a bacterial infection and secondary glaucoma and the stimulation of wound healing. The individual concept of measures to be taken is recruited from the careful identification of necrotic tissue, the eye burn classification of severity and on the basis of all described medical and surgical therapy options. In the case of severe and very severe ocular burns a comprehensive surgical reconstruction is included. All outpatient departments and eye clinics taking part on the treatment have to ensure a standardized complete and scientifically valid therapy regime to restore vision.

[Eye irritation and chemical eye burns. Review of experimental and clinical studies]. / Augenirritation und Augenverätzung. Experimentelle und klinische Übersicht.

Chemical burns of the eye are becoming rare due to improvements in occupational protection. Effective decontamination is the foundation for good clinical results of this ophthalmological emergency. The toxicological aspect focuses on classifying the specific toxicity of a chemical substance by evaluating the degree of eye irritation and eye burns. Chemical substances are classified into defined risk levels by specific tests. The traditional ophthalmological approach is based on the clinical presentation of eye burns as a result of contact with a specific toxic substance. In an integral approach it is shown that substance-specific characteristics, such as concentration and specific reactivity as well as individual features, such as mode and duration of exposition have an influence on the clinical appearance of the tissue damage. The decontamination is dependent on the mode of action and the effectiveness of the decontamination solution. Amphoteric substances have the best effectiveness for decontamination of the eye due to their specific characteristics.

[Intravitreal bevacizumab for chronic central serous chorioretinopathy]. / Intravitreales Bevacizumab bei chronischer Retinopathia centralis serosa.

Central serous chorioretinopathy (CSCR) can lead to permanent visual loss in chronic cases. We report on a 57-year-old female patient with persistent findings over 6 months despite conservative therapy. A single intravitreal injection of bevacizumab led to a rapid morphologic and functional restitution without relapse or complication during the 19 weeks period after injection. Intravitreal injection of bevacizumab could be a therapeutic option for the treatment of chronic CSCR, however the results of appropriate studies must be awaited before it can be introduced into routine use.

Emergency treatment of eye burns: which rinsing solution should we choose?

BACKGROUND: In the treatment of eye burns few data on the comparative application of rinsing solutions exist. We present experiments in vitro and ex vivo on the pH changes that can be achieved in alkali eye burns with currently distributed and propagated rinsing fluids like water, saline solution, Cederroth Eye Wash Solution (including borate buffer), Diphoterine, Ringers lactate solution and phosphate buffer. METHODS: Titration curves in beakers are compared with ex vivo experiments on isolated rabbit eyes. We exposed eyes to burns from filter paper soaked in 2 mol NaOH, continuously measuring the anterior chamber pH by means of a micro pH electrode placed near the endothelium. In each experiment--repeated five times--the corneal burn of 20 s in 2 mol NaOH was followed by a period of 15 min of rinsing under a defined flow of 66 ml/min. RESULTS: We found highly significant differences in intracameral pH related to different types of rinsing solutions. The return of the intracameral pH to normal was not achieved by any of the rinsing fluids, but the best results were noted for of Cederroth Eye Wash Solution (Cederroth Industrial Products, Upplands Väasby, Sweden) and the Diphoterine- and Previn solutions (Prevor, Cologne, Germany). Water played an intermediate role whereas saline and phosphate buffer were not efficient at lowering intracameral pH after alkali burns. CONCLUSION: In alkali burns we recommend efficient buffering solutions. The tested isotonic phosphate buffer (PBS) was not effective at buffering the intraocular pH. Water was found to be much less efficient than Previn, Diphoterine or Cederroth Eye Wash solution in balancing intraocular pH.

Ascorbic acid reversibly inhibits proliferation of retinal pigment epithelial cells.

PURPOSE: Proliferation control in adult retinal pigment epithelial (ARPE) cells is an essential factor in the clinical management of proliferative vitreoretinopathy (PVR). Factors which inhibit PVR and which are without toxic potential are therefore of interest in controlling proliferation. The aim of the present study was to gain insight into a possible function of high intraocular ascorbic acid levels as a physiological modulator of proliferation. METHODS: Adult retinal pigment epithelial cells were incubated in vitro with increasing concentrations of ascorbic acid (0.5-4 mmol, pH 7.4). Cell proliferation was assayed by the bromide-deoxy-uridine (BrdU) assay. The culture medium (CM) containing ascorbic acid was replaced with normal CM and the recovery of proliferation was measured after 24 hours. In order to be able to distinguish between proliferation inhibition, apoptosis, necrosis and recovery of proliferation, we performed TUNEL assays and fluorescence analysis cell-counter (FAC) analysis. RESULTS: Ascorbic acid significantly inhibits ARPE cell proliferation if it is present in concentrations above 2 mmol. Proliferation resumed in all ARPE cell cultures after pre-incubation with ascorbic acid, indicating that direct toxicity of ascorbic acid is a negligible factor. The time-point and extent of recovery in proliferation was dependent on the initial ascorbic acid concentration. Fluorescence-labelled cell counts on apoptosis markers (FAC) data showed some induction of apoptosis and necrosis after incubation with 4 mmol ascorbic acid. CONCLUSIONS: Ascorbic acid has a dose-dependent influence on the proliferation of vital ARPE cells. This possibly reflects the role of ascorbic acid at a physiological level within the vitreous cavity in preventing proliferative vitreoretinopathy (PVR). These findings may stimulate the development of new strategies in the clinical treatment of PVR.

[Acute therapy for eye burns]. / Akuttherapie von Augenverätzungen.

BACKGROUND: Eye rinsing is the major therapeutic measure with a decisive impact on prognosis after chemical or thermal eye irritation. Several different major targets are addressed by this measure. AIM OF THE STUDY: Up to now emphasis in research was placed mostly on the neutralisation of chemical products. Newer experimental results on the basis of biological experiments interpreted against the background of basic chemical reactions may enhance clinical treatment by introducing new mechanisms of intervention. MATERIALS AND METHODS: Experiments on the modification of osmolarity, buffering capacity and solubility products show new possibilities of therapy in eye rinsing after eye irritation. These mechanisms are demonstrated by means of key experiments. RESULTS: The official recommendation of rinsing a burnt eye with water seems to be insufficient against the background of actual experimental data. Measurements of pH after eye burns indicate no buffering effects for water, or aqueous saline solution. There was weak buffering for phosphate buffer in alkali burns and a high capacity for neutralisation for diphoterine in alkali and acid burns. Ionic contents and osmolarities of the rinsing solutions have a decisive influence on the ionic composition and osmolarity of the burnt cornea after rinsing. Cellular damage is enhanced in unaffected healthy cell cultures by hyposomolar rinsing. CONCLUSION: We recommend buffered solutions with high buffer capacities for initial eye rinsing. The advantage or disadvantage of the elevated concentration of ions in the buffered rinsing solutions determining osmolarity cannot be confirmed or refuted up to now. It seems to us to be certain that osmolarity is a decisive future factor in initial rinsing.

The Aachen-keratoprosthesis--a flexible KPro that permits intraocular pressure measurement.

PURPOSE: Postoperative glaucoma is one of the major complications observed in patients with keratoprostheses (KPro). The optical components of the majority of KPros are rigid and inflexible, which prevents indirect tonometry by common methods. This study confirms that the Aachen-KPro allows measurements of intraocular pressure (IOP) due to its flexible optical part with a modified Schiotz tonometer. METHODS: The Aachen-KPro was placed in a special chamber where pressure can be generated and monitored by a transducer. Measurements were taken by common ophthalmologic methods. The results were compared to the initial pressure values in the chamber. RESULTS: With the Goldmann tonometer, the Tono-Pen and the topography system (Technomed), no significant pressure changes could be observed. The results of the Schiotz tonometer were promising. It was slightly modified and standard curves with different weights could be obtained. CONCLUSIONS: With a modified Schiotz tonometer, it is possible to detect elevated IOPs. Modifying this common instrument is inexpensive and can be easily performed. This advantage of the Aachen-KPro permits early management of postoperative high tension glaucoma.

Persistent indocyanine green (ICG) fluorescence 6 weeks after intraocular ICG administration for macular hole surgery.

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 epiretinal membranes and the ILM is an obstacle to successful surgery. Recently, indocyanine green (ICG) has been reported to be a helpful intraocular substance in identifying these membranes. METHODS: In a case of stage IV macular hole, epiretinal membranes and ILM were intraoperatively 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 membranes were peeled. Autologous thrombocytes were applied to the macular hole, and the eye was endotamponaded with 20% SF6 gas. Six weeks postoperatively, visual acuity was measured and fundus photographs and autofluorescence images, as well as a multifocal ERG, were obtained. RESULTS: Intraoperatively, the ILM could be nicely visualized by ICG, which allowed immediate peeling. Six weeks after surgery, the visual acuity had improved from 0.1 to 0.7 and the macular hole was closed. Autofluorescence imaging at 795 nm revealed a strong signal. Multifocal ERG recording showed regular amplitudes. CONCLUSION: ICG as an intraocular tool for staining of the ILM is helpful in macular hole surgery. We did not observe any negative effect on retinal function; however, we were surprised to identify traces of ICG in retinal fluorescein angiography images 6 weeks postoperatively.

Interactions between ocular surface fluid and cornea related to contact lenses.

PURPOSE: To improve the quantification of damage to the ocular surface, metabolite levels, electrolyte concentrations, and enzyme activities were assayed in corneal epithelium, stroma and tears. METHODS: In rabbits, rinsing or contact lenses were used to induce microtrauma. For more severe trauma, experimental injuries were induced with 1 N NaOH. Human accidents included epithelial lesions and mild chemical burns. Enzymatic test systems and electron dispersive X-ray analyses (EDXA) were employed. Corneal hydration was assessed by wet and dry weights. Interleukins were analysed with ELISA. RESULTS: In contrast to normal eyes, in ocular surface trauma the interaction between tear fluid and cornea played an important part. After wearing contact lenses or rinsing, glucose and lactate levels in the cornea and in tears increased, and ATP and glycogen in the cornea decreased. After epithelial lesions, N-acetylglucose aminidase (NAcGA, E.C.3.2.1.50) was released into the tears. Epithelial defects alone and--much more--rinsing the denuded stromal surface produced an increase of lactate and glucose in tears and a dramatic fall in Na, Cl, and S levels in the stroma. Rinsing with phosphate induced corneal calcification. IL-1 and IL-6 were increased in human corneal buttons from patients with trauma and inflammation. CONCLUSIONS: Biochemical analyses may be useful to quantify trauma to the ocular surface.

Phosphate buffer in alkali eye burns as an inducer of experimental corneal calcification.

Corneal calcification is a common problem in severe inflammation, chronic glaucoma, renal disorders and other diseases with disturbed calcium and phosphorus metabolism. The pathogenesis of corneal calcifications in ocular diseases is not yet completely understood. We present a model of an induced corneal calcification by local treatment. In a double-masked experiment 16 rabbits underwent eye burn of one cornea followed by immediate rinsing (160 ml) with isotonic phosphate buffer (n=8) or saline solution (n=8) three time a day for 16 days. Tissues were excised, shock frozen and cut into 10 microm slices, freeze dried and coated with evaporated carbon. In the phosphate buffer group an early onset of corneal opacification occurred resulting in completely white corneas after 16 days, combined with corneoscleral ulceration. The other group showed similar corneal erosion and a little corneal ulceration, but no opacifications. The opacifications of the phosphate buffer group could be identified as calcifications by direct measurements of calcium and phosphate (by energy dispersive X-ray analysis on corneal samples). In conclusion, inappropriate application of phosphate leads to uncontrolled calcifications of the cornea after severe burns to the eye. This reflects clinically observed calcifications after eye burns and possibly the adverse side effects of phosphate buffered eye drops being applied in ophthalmology.

Effects of ascorbic acid on retinal pigment epithelial cells.

PURPOSE: Evaluation of effects of ascorbic acid on cell characteristics of dedifferentiated porcine retinal pigment epithelial (pRPE) cells. METHODS: pRPE cells were incubated in vitro with increasing concentrations of ascorbic acid (0.25-1.5 mMol). Cell proliferation was assayed by measuring the incorporation of 5-bromo-2'-deoxy-uridine (BrdU) into cellular DNA. Migration and contraction properties were studied on a cell permissive porous membrane and collagen gels, respectively. Phenotypic changes in response to ascorbic acid and its derivative ascorbic acid 2-phophate were evaluated by microscopy and indirect immunofluorescence. RESULTS: Ascorbic acid significantly inhibits cell proliferation, migration, and contraction in concentrations of 1 mMol or more. Under the influence of at least 1 mMol ascorbic acid dedifferentiated pRPE cells exhibited a pigmented status within 24 hours. Addition of 500 U/ml catalase prevented the antiproliferative effect of ascorbic acid and the formation of pigment. Concentrations of 0.5 mMol ascorbic acid as well as 1 mMol ascorbic acid 2-phosphate promoted differentiation of cell phenotype. Furthermore, ascorbic acid 2-phosphate supported the formation of in vivo-like epithelial structures. CONCLUSIONS: Ascorbic acid has an influence on vital cell characteristics such as proliferation, migration, contraction and differentiation of pRPE cells. As dedifferentiation of these cells is an integral part in the development of proliferative vitreoretinopathy (PVR), ascorbic acid should be taken into consideration as a supplement in the clinical management of this disease.

Eye burns: an emergency and continuing problem.

Adequate treatment of eye burns is an essential task of rescue teams. Clinical and occupational medicine studies have shown that efficient emergency treatment can prevent severe eye damage, but therapy is frequently delayed or inadequate. When initial therapy has been delayed or missed, several treatment strategies, including surgery, are available that may improve the outcome of an injury with poor visual prognosis. Discussed in this review are common accident mechanisms, causative agents and biophysical/pathogenetic aspects of eye burns, together with emergency and long-term treatment strategies including surgical procedures, and factors influencing outcome.

Aachen keratoprosthesis as temporary implant for combined vitreoretinal surgery and keratoplasty: report on 10 clinical applications.

UNLABELLED: A new keratoprosthesis was used during pars plana vitrectomy in order to test the optical quality, watertightness, short-term biocompatibility and handling of the new device. The implantability was also tested, given that this keratoprosthesis might in future be left in place for several months. This Aachen keratoprosthesis (Aachen-KPro) is developed to be used as permanent implant to restore vision in corneal blind patients. PATIENT AND METHODS: The Aachen-KPro was used during pars plana vitrectomy in 10 patients with opaque corneas. In four cases, trauma precipitated the ocular disease. Eye burn was the cause of corneal and retinal disorders in another four cases. One patient had a history of congenital glaucoma with myopia, and one of uveitis with corneal dystrophy. After trephination of 6.5 mm in diameter, the Aachen-KPro, composed of soft silicone rubber, was temporarily placed in the trephination hole. After completion of the vitrectomy, the Aachen-KPro was replaced by a 7 mm corneal graft. RESULTS: Intraoperative use of the Aachen-KPro allowed uncomplicated intraoperative handling, smooth adaptation to the corneal rim in the trephination hole, and an undistorted view of the central and peripheral retina. Leakage, even during scleral depression, could be avoided by individual suturing of the scleral rim. After a follow-up period of 1-10 months, the retina was still attached in all cases. The corneal graft was clear after surgery in four eyes, and edema was found in three cases. Amnion or conjunctiva was placed over three patients' transplants. CONCLUSION: We report the first temporary implantations of a new keratoprosthesis in 10 patients. Its flexibility and good optical qualities allowed control of intraoperative procedures. The outcome and prognosis of the vitreoretinal surgery and keratoplasty were related to the primary diagnosis. The Aachen-KPro has shown advantages, especially in eyes where the anterior eye segment is severely damaged by eye burn or previous surgical interventions. In the future, prolonged use of the Aa-chen-KPro is planned for selected eyes.

Microbiopsy in healthy rabbit corneas. A long-term study.

PURPOSE: Corneal biopsies are important in diagnosing multiple corneal diseases. They were previously performed by way of keratectomy, a method that causes corneal opacity and topographic changes due to scarring. Microbiopsy is a new way to perform corneal biopsies. Before microbiopsy may be performed on human corneas, the safety of this procedure has to be proved concerning clinical development, histological changes and topographic changes after multiple biopsies. METHODS: The healthy right cornea of 24 rabbits was punctured. 12 microtrephinations in 4 different symmetric patterns were performed. The clinical development of the bioptic sites as well as the topographic changes were observed over 5 months. After enucleation, serial sections of the corneas were analysed histologically. RESULTS: Out of 294 performed biopsies, 291 samples could be collected. 4 perforations occurred. The initial epithelial defect closed within 3 days. A pale stromal scar remained. The histological analysis of these scars showed a facette underlined by a dense hypocellular fibrous layer and a typical star-shaped figure consisting of a loose hypercellular stromal tissue. Only dioptric power of corneas with circle-pattern showed a statistically significant decrease. CONCLUSION: Micropuncture is a safe and efficient bioptic procedure. Even 12 micropunctures do not lead to significant changes of dioptric power in most patterns. Further studies are necessary to evaluate the reproducibility of refractive changes by circle patterns and corrections of astigmatisms.

Functionally adapted surfaces on a silicone keratoprosthesis.

BACKGROUND: Silicone intraocular lenses as well as silicone sponges and encircling bands on the bulbar surface are widely used and are well tolerated. The aim of this project is a new one-piece silicone keratoprosthesis with enhanced cell adhesion in the haptic region to optimize the keratoprosthesis stability. These investigations show how enhanced profileration of conjunctival fibroblasts and, therefore, improved tissue compatibility can be achieved by hydrophilizing and by protein immobilisation on a hydrophobic silicone surface. This allows a combination of desired chemical and mechanical properties of the silicone bulk material with surfaces of improved tissue compatibility. METHODS: Silicone foils with surface modifications of different kinds were tested. Experiments were done using cell cultures with murine fibroblasts L-929 and human conjuctival fibroblasts. Cytotoxicity assays were carried out with cells grown on the material in direct contact, as well as in indirect contact, with extracts (EN 30993-5). Viability stains by means of fluoresceindiacetate and ethidiumbromide together with morphology analyses by hemalaun-staining were performed. RESULTS: For the unmodified and modified foils themselves and their extracts any negative influence on cell cultures of murine and human cells could be excluded. There was a gradual improvement of cell morphology, spreading and proliferation dependent on the degree of surface modification. Covalently immobilised fibronectin showed the best results in contrast to adsorptive binding. CONCLUSIONS: Silicone surfaces can be modified chemically with bioactive proteins. These modifications are cell compatible and do not result in toxic reactions. The degree and type of silicone hydrophilization results in improved development of cell morphology, spreading and proliferation. Even better results are obtained after covalent binding of bioactive proteins like fibronectin. Improved biocompatibility with enhanced cellular overgrowth has been demonstrated in vitro for the modified silicone of the haptic region. We believe that this type of modification will help in reducing extrusion problems observed with former keratoprostheses.

A new way of removing silicone oil from the surface of silicone intraocular lenses.

PURPOSE: This study was performed to ascertain the efficacy of Perfluorhexyl-octan, C14F13H17 (F6H8), in dissolving silicone oil from the surface of silicone intraocular lenses. So far F6H8 is the only solvent of silicone oil that is tolerated by intraocular tissues. MATERIALS AND METHODS: Intraocular silicone lenses (Domilens) were examined after application of small droplets of silicone oil of two different viscosities (AdatoSIL-OL 1000 and 5000) followed by rinsing with F6H8. To allow distinction between silicone oil and F6H8 the silicone oil was stained. Microscopic examination was carried out under video control. RESULTS: One hundred microliters of AdatoSIL-OL 1000 could be easily removed with about 800 microl of F6H8; 50 microl of AdatoSIL-OL 5000 also disappeared after 800 microl of F6H8. A larger drop of the latter oil could not be removed even after application of 2 ml of F6H8. CONCLUSION: Silicone oil 1000 can be easily dissolved by F6H8, whereas silicone oil 5000 is more difficult to remove because of its higher viscosity.