from cells: Calcein with Ca2+ loaded (green) and calcein depleted from Ca2+ (red) are shown. Calcein or fluorescein complex is used as indicator of complexion for calcium ion with EDTA. Exposure of fibroblasts in cell culture toward a 0.0002% HF solution is shown in Fig. 5.9a and b. Excitation and emission wavelengths are 495/515 nm. Fluorometric possibilities are shown on orange color crystals. The green cells turn to red by complete depletion of free calcium from the cellular body.

This is similar to the highly selective action of oxygen removal from Fe++ by means of CO (carbon monoxide) or the intoxication of the metabolic breathing by CN– (cyanide ion). All these specific types of intoxications systemically result in ceasing of local metabolic activity with consecutive cellular necrosis.

Glutathione in reduced (GSH) and oxidized form (GSSG) ratios given within the cornea before and after exposure to oxidative stress is shown in Fig. 5.10.

A real confirmation that chemical reaction dependent on proteinic pKa is a real mechanism that takes place during the time course of eye burn has been presented by Gerard et al. [4]. They found a time-depen- dent and stepwise increase of the pH within the cornea after eye burn with ammonia.

This indicates the probability of levels of reactions because of the different pKa of ammonia and the presence in the cornea of substances producing a stepwise reaction from lower to higher pKa.

Cornea treated

Fig. 5.10  GHS/GSSG ration before and after oxidative stress

5.1.5  Limits between Irritation and Burn

Our body is used to repair small accidents of mechanical or chemical origin. These accidents of biological origin are due to stinging by nettles or insects on eye and skin. Further, there are mechanical damages that are used to be repaired within a short time – as seen in the ex vivo eye irritation test (EVEIT) – such as the healing of mechanical damage ex vivo within a short period of 3 days observed on the isolated rabbit cornea (Fig. 5.11a and b).

The damage is healed by highly regenerative cellular structures on surfaces that are sustained by depots of stem cells that react by reproducing the required cells by means of increased dividing rate and metabolic