Chemical and thermal injuries of the eyes. Surgical and medical treatment based on clinical and pathophysiological findings.

Light burns heal well within a few days. Severe chemical and thermal injuries of the eyes destroy surface epithelia and cause ischemic necroses of conjunctiva, cornea, sclera, iris, ciliary body, and lids. An inflammatory response follows with leucocyte infiltration and release of inflammatory mediators. Prostaglandins, lipoxygenase products, cytokines, superoxide radicals and Iysosomal enzymes are known to be active in eye burn disease. Their activities result in corneal, scleral and conjunctival ulceration, tissue proliferation and scarification, which develop within weeks, months and even years after the accident. Pathophysiological events produce defined clinical pictures. Some agents take special actions, e.g. alkali penetrates within seconds into the anterior chamber, sulfuric acid burns as well as quick lime burns forming slaked lime produce considerable heat. Hydrofluoric acid is highly toxic and induces early necroses. Heat causes deep ischemic necroses and lateron strongly shrinking scars. Onset and intensity of first aid decided on the outcome. Immediate rinsing is essential. Cool water, saline, Ringers lactate solution and BSS are good rinsing media. For first aid, buffered Previn seems suitable. Major chemical and thermal injuries need a variety of medical and surgical treatments: Necroses must be excised surgically. Tenon plasty is performed to reconstruct conjunctiva. Amnion-, limbus- and early keratoplasty or artificial epithelium are applied, initially to save the cornea from melting, and later to restore vision. Conjunctical, lid and intraocular surgery may be necessary. The aim of medical treatment is to suppress the inflammatory response and to prevent infection. Corticosteroids, antibiotics, ascorbate and inhibitors of proteolytic enzymes are used. Secondary glaucoma must not be forgotten. Extensive therapy is sometimes rewarding, results are presented.

[Effect of serum and osmotically active substances on metabolism in 262 tissue cultures of pig's corneas--improved preservation of donor tissue for keratoplasty]. / Einfluss von Serum und osmotisch wirksamen Substanzen auf den Stoffwechsel in 262 Organkulturen der Kornea von Schweineaugen--Ein Beitrag zur Verbesserung des Spendermaterials zur Keratoplastik.

BACKGROUND: The storage time of corneal organ cultures in limited in the closed system mainly used in European eye banks. In addition, swelling during storage reduces the quality of the donor material for keratoplasty. Therefore, dextrane was added in concentrations of 2.5%, 5%, 7.5% and 10% to the culture medium, and the energy producing metabolism was investigated. MATERIALS AND METHODS: The experiments were carried out with 262 pig corneas. MEM with some supplements was used at 31 degrees C. No serum was added, because glucose consumption, lactate production and ATP levels proved to be the same or better than with serum supplement. After 6 and 12 days, the corneas from organ cultures were extracted with perchloric acid. The levels of glucose and lactate in the stroma and of ATP and ADP in the epithelium were analysed with enzymatic-optical tests. RESULTS: Dextrane inhibited glycolysis and the production of ATP in corneal organ cultures during twelve days. With 7.5% and 10% dextrane in the medium, lactate levels in the cornea decreased from 6.09 to 4.5 and 4.6 microM/g H2O instead of increasing. At the same time, glucose increased paradoxical from 1.3 to 3.4 and 2.2 microM/g H2O, respectively. With 5% dextrane, glycolysis operated sufficiently producing an increase of lactate levels from 6.0 to 8.8 microM/g H2O and consuming glucose from levels of 1.27 down to 0.57 microM/g H2O. After 12 days with 7.5% and 10.0% dextrane, ATP levels were reduced, from 4.54 to 0.98 and 0.49 microM/g dry weight, and ATP/ADP ratios from 1.9 to 1.1 and 0.7 respectively. With 2.5% dextrane, the ATP was diminished from 4.5 to 2.2 microM/g dry weight. When 5% dextrane were added to the culture medium, the hydration was at optimum by 4.1, and ATP levels were reduced only from 4.5 to 2.6 microM/g dry weight. Moreover, the ATP/ADP ratios were at 2.1 as good as without dextrane. CONCLUSIONS: From the results it was concluded, that serum free medium may be used, and that permanent dewelling proved to be beneficial for the energy producing metabolism of the cornea in organ culture. Such conditions may improve morphological and metabolic quality of donor material. From previous publications, it was recommended, to use instead of toxic dextran the well tolerated HES (hydroxyethyl starch) and to apply a storage temperature of 21 degrees C, which slowed down glucose consumption without impairing the energy producing metabolism.

The corneal stroma: an inhomogeneous structure.

PURPOSE: This study was conducted to determine the elemental composition of the human cornea. Special attention was paid to corneal stroma inhomogeneity. METHODS: Seventy human corneas were examined by means of energy-dispersive X-ray analysis. Epithelium, subepithelium, middle stroma, sub-Descemet layer, Descemet's membrane and endothelium were subjected to repeated measurements. RESULTS: In the cellular layers the phosphorus concentrations were high [0.35 mol/kg dry weight (dw) in the epithelium and 0.403 mol/kg dw in the endothelium]. Similar concentrations were found for sulphur (0.38 mol/kg dw in the epithelium). Stromal layers showed high contents of sulphur: 0.26 mol/kg dw. The phosphorus concentration was found to be higher in the subepithelium than in the middle stroma. Sulphur concentrations were highest in Descemet's membrane, followed by the subepithelium and the middle stroma. DISCUSSION: Nucleic acids and energy-containing phosphates explain the high levels of phosphorus in the cellular layers. The high sulphur concentrations may be related to the phosphoadenosinphosphosulfate and protein turnover in the epithelium. We interpret the inhomogeneous distribution of phosphorus in the stroma as a function of the density of keratocytes. An evaluation of all known sulphur-containing biochemical components of the stroma (0.217 mol sulphur/kg dw) corresponds to our measurements. In contrast to former results we find the corneal stroma to be an inhomogeneous structure.

[Energy metabolism of the human cornea in various culture systems]. / Untersuchungen zum Energiestoffwechsel der humanen Hornhaut in verschiedenen Kultursystemen.

BACKGROUND: There are two well known systems to culture human corneas prior to transplantation. First, corneal storage at 4 degrees C especially in Optisol medium. Second, organ-culture at physiological temperatures in a modified minimal essential medium (MEM). In the cold storage system the number of endothelial cells after storage might be overestimated because the damaged cells are not able to leave the monolayer. It has been supposed that the lack in energy recruitment is the main reason for that, but has not been proven yet. It was the purpose of this study to describe the energy status of the human cornea after storage in both systems. MATERIALS AND METHODS: 32 human corneas were investigated. They were stored for 7 days in Optisol, and for 7 days in MEM plus 1 day in MEM supplemented with 5% dextran 500 and 12 days in modified MEM plus 1 day in MEM supplemented with 5% dextran 500. The endothelial cell density (ECD) as well as the hydration were determined. Glucose, lactate, ATP, ADP and AMP were measured to reflect the energy status. RESULTS: Hydration was comparable in all three groups. ECD was slightly higher in Optisol stored corneas, although the amount of damaged cells was much higher. Optisol stored corneas showed a severe anaerobic situation, especially lacate concentrations were increased. In contrast ATP and ADP concentrations were twice as high in MEM than in Optisol stored corneas. DISCUSSION: The severe anaerobic situation in Optisol stored corneas leads to a lack in energy recruitment. This reduces the ability of cell function (mitosis) and the function of the monolayer (migration, elimination). Whether these changes are reversible after transplantation has to be determined in future.

Does the human cornea contain silicon?

BACKGROUND: Our study investigated the presence, type and quantity of silicon in the human cornea. We report the results of silicon measurements in the corneas of silicotic individuals, bricklayers and apparently normal human individuals and offer a hypothesis for the mechanism of silicon deposition in the human cornea. METHODS: We examined corneas from 13 decreased subjects who suffered from silicosis, 2 bricklayers and 6 apparently healthy subjects. Cornea samples were examined by energy-dispersive x-ray analysis (EDXA) under calibrated conditions in a scanning electron microscope (SEM). The EDXA detector was a silicon-free germanium crystal. Five distinct layers (epithelium, Bowman's membrane, central stroma. Descemet's membrane and endothelium) were analyzed in each cornea. The method allows simultaneous semiquantitative analysis of, among other elements, silicon, calcium and oxygen. We measured amorphous silicon and visible particles of silicon. RESULTS: We found amorphous silicon in low concentrations in 38% of the silicotic corneas and in very low concentrations in 29% of the healthy corneas. Bricklayers showed high concentrations of amorphous silicon. These accumulations of silicon were predominantly located in Descemet's membrane. Silicotic corneas showed significantly more silicon-containing particles than corneas of healthy controls (chi 2-test, P < 0.01). CONCLUSION: Normal corneas contain very low amounts of silicon. Longterm exposure to inhalative silicon dusts results in only very slightly increased levels of amorphous silicon in the cornea. However, silicon-containing particles accumulate in the cornea of silicotic individuals. Bricklayers incorporate more amorphous silicon into the cornea.

[Autologous transplantation of nasal mucosa after severe chemical and thermal eye burns]. / Autologe Nasenschleimhauttransplantation nach schwersten Verätzungen und Verbrennungen.

BACKGROUND: Extensive conjunctival scarring is common after severe chemical and thermal eye burns. There is often not enough healthy conjunctiva from the other eye available to correct the symblepharons, therefore other autologous tissues have to be transplanted. PATIENTS AND METHODS: From February 1992 until March 1993 13 patients were treated with free nasal mucosal grafts from the inferior turbinates for reconstruction of the fornices. The newly created deep fornices were secured by a silicone band. In 3 patients an Illig plastic shell was used additionally. The surgical treatment was supplemented with an intensive treatment with topical corticosteroids to decrease the inflammatory reaction. RESULTS: The patients were followed for an average of 7-18 months. The interval between the accident and the transplantation ranged from 2-26 months. In 10 patients a reconstruction of the fornices was achieved. In all patients, however, some slight scars could be observed. Postoperative Schirmertest was markedly improved. These results encourage us to plan a penetrating keratoplasty in 7 cases. 3 patients showed a recurrence of the symblepharon 2 months after the transplantation. CONCLUSION: The nasal mucosa graft material is best suited for repair of extensive symblepharon. The advantages of this tissue are the availability of large pieces of mucosa and the transplantation of intraepithelial goblet-cells. Long-term effects are the improvement and stabilisation of the tear film.

A simple empirical calibration of energy dispersive X-ray analysis (EDXA) on the cornea.

Monitoring of the corneal electrolyte content is important for the study of chemical eye burns. This paper describes quantitative measurements on gelatin standards, corneas and a cornea homogenate with an energy dispersive X-ray analyzer (EDX) in the scanning electron microscope (SEM). Ten micrometers thick cryosections were freeze-dried and mounted on solid carbon supports. The applied quantification procedure was a local peak background analysis with a specifically designed computer program. Similar chemical and physical properties of gelatin, cornea homogenate, and cornea were proven by EDX-analysis and wet chemical analysis. Gelatin standards with known concentrations of different added salts showed linear correlations with a correlation coefficient higher than 0.95 for all considered elements. The local background generation on carbon supports was the same for gelatin standards and corneal tissue. The results demonstrate that quantitative EDX analysis of semi-thin samples, mounted on neutral carbon supports, can be reliably used for the assessment of the corneal mineral composition.

[Silver nitrate burn after Credé's preventive treatment. A roentgen analytic and scanning electron microscopy study]. / Silbernitratverätzung nach Credéscher Prophylaxe. Eine röntgenanalytische und rasterelektronenmikroskopische Untersuchung.

Following Credé's prophylaxis with silver-nitrate, the cornea of a newborn presented greyish-brown, lime-like plaques on the nasal part of the right eye. A paracentral ulcerating stromal opacification undermined these appositions, when the patient was admitted to the eye-clinic at Aachen. In the material taken in a lamellar keratectomy scanning electron microscopical examination was able to prove the existence of granules, previously described in light-microscopy. These granules measured 100 to 300 nm in diameter and were placed up to 110 microns deep into the corneal stroma of the specimen. An earlier chemical analysis of necrotic material showed no silver specific reaction. By means of EDX-Analysis these granules could be identified as silver-containing. This was once reassured by a newly developed modification of van-Kossa's-staining-method. The fact that the granular deposits contained mainly silver proves that the onset of a sodium-chloride-irrigation did not promote an intended therapeutic silver-chloride-precipitation and therefore had no effects on the silver-nitrate's penetration abilities. Injuries by silver-nitrate-solutions used for Credé's prophylaxis are seldom but still reported. The mechanism of injury in this case of a child, born by sectio remains unknown. Neither the use of an unusual silvernitrate solution, that was taken from a disposable ampoule (Mova-Nitrat) was reported, nor any corneal injury during sectio mentioned.(ABSTRACT TRUNCATED AT 250 WORDS)

[The metabolism of organ cultures of cornea in TC 199 with added dextran 500 or hydroxyethyl starch 450]. / Uber den Stoffwechsel von Organkulturen der Cornea in TC 199 mit Zusatz von Dextran 500 oder HAES 450.

Pig corneas were stored at room temperature for 20 days in TC 199 culture medium supplemented with 10% pig blood serum, antibiotics, and to reduce swelling with 10% Dextran 500 or 10% hydroxyethyl starch HAES 450. The high molecular weight of these additions, 500,000 and 450,000 Daltons respectively, prohibited swelling by their osmotic pressure. The water content of the cultured corneas was 80.6 +/- 0.5% with HAES 450 and 76.4 +/- 2.0% with Dextran 500. The epithelial cells of the cultured cornea rounded and desquamated after 12 to 16 days of culture. The endothelium showed vacuoles. The metabolism of the cultured corneas was measured by glucose and lactate levels in the epithelium, the stroma, and the medium as well as by the glycogen, ATP, and ADP content in the corneal epithelium. The cultured corneas consumed reasonable amounts of glucose and produced lactate. The glycogen content and the ATP levels decreased slightly, but the ATP/ADP ratio showed a good energy state. In the cultures containing HAES 450 the entire system was flooded with glucose released from hydroxyethyl starch. The Dextran 500 culture system could prove suitable for culturing human donor material without swelling.