Fig. 6.14  Exposure of L929 cells to osmolar stable solutions with variation of pH from 11.3 to 9.5 for

64 min

Fig. 6.15  Exposure of L929 cells to osmolar stable solutions with variation of pH from 5 to 2 for 64 min

of the pH in the anterior chamber of the eye is much more harmful than the elevation above 9.

6.5  High End Decontamination

6.5.1  Peroxides and Radicals

Decontamination

We have found in some preliminary experiments that the decontamination of peroxides is insufficient with buffers, due to missing action on these substrates.

Therefore, we have examined drugs known for peroxide decontamination such as Dimercaprol, Vitamin C, and Tocopherol. Similar experiments were made with Diphoterine®. Our investigation aims to the restoration of the glutathione equilibrium in the exposed corneal tissue without any regeneration capacity of the tissue itself. These experiments were performed on homogenates of porcine corneas that were exposed to hydrogen peroxide and nitric acid and then treated with the different drugs. The results, given in Fig. 6.16, show a clear restoration when using Diphoterine®.

The measurements of glutathione reflect the total capacity of decontamination of oxidative stress within the cornea. The glutathione system gives the outer

Fig. 6.17  The glutathione system

limits of oxidation and reduction by supplying the glutathione peroxidase with a redox potential [18] (Fig. 6.17).

All decontaminations of radicals within the body are operated by means of structural changes of ascorbate, b-carotin, or tocopherol. Those reactive partners known as the antioxidative system are all regenerated by the glutathione system. Therefore, this system gives a good overview on the oxidative state of a tissue (Fig. 6.18).

The reversal of the glutathione is not achieved by all substances and a considerable loss is produced by the agents.

The ratio of glutathione to reduced glutathione is reestablished only by Dimercaprol and Diphoterine® (Fig. 6.19).

The above-presented charts give a clear indication that none of the commercially available drugs or medical devices is able to protect the cornea from changes due to strong reducing agents or oxidants. Except this, the restoration of an equilibrium of reduced glutathione (GSH) and oxidized glutathione (GSSG) provides source of peroxidic decontamination for the tissue.

Thus with Diphoterine® and Dimercaprol, there is a considerable improvement of the physiological capacity of chemical decontamination. By this, the use of polyvalent solutions in first aid offers a considerable advantage as the best currently available treatments.

With the concept of Diphoterine®, even the restoration of glutathione contents in the burnt cornea can be achieved without any action of the regenerating tissues. This is a major value. Dimercaprol has similar effects and might be an opportune alternative, but this drug does not act on alkali and acids as well as the buffers and amphoteric substances do.

6.5.2  Hydrofluoric Acid Decontamination

In recent work, we could give proof of different decontamination strategies from conventional water rinsing over calcium gluconate to the rinsing with the specific fluoride decontaminating rinsing solution Hexa­ fluorine®. The specific complexation due to HF action on tissue results in the total loss of calcium within seconds as shown in cell cultures in Chap. 5 (Sect. 5.1.4, Fig. 5.9a and b). By means of photography in the ex vivo eye irritation assay and by means of Optical coherence tomography, we could give clear indication of the efficiency of the decontamination with Hexa­ fluorine® (Fig. 6.20).

Fig. 6.18  Glutathione reduced content after treatment of corneal homogenate with hydrogen peroxide or HNO3

Fig. 6.19  Ratio of glutathione/reduced glutathione