Changes in mineral composition of rabbit corneas after alkali burn.

BACKGROUND

Mineral balance is essential for maintaining corneal transparency. In preliminary investigations, we found alterations of mineral concentrations in the human cornea after chemical burns. In this prospective study the mineral content of the rabbit cornea was quantified after experimental alkali burns.

METHODS

Thirty-two eyes of rabbits were burnt for 30 s with 1 M NaOH. A short period of saline rinsing followed, but no further therapy was given. The eyes of 20 healthy rabbits served as a control. We measured the water content by weighing the cornea before and after drying. The mineral content of the cornea was determined in different stromal layers using energy-dispersive X-ray analysis in the scanning electron microscope. Groups of eight rabbits were examined on days 0, 1, 4 and 8 after the experimental burns.

RESULTS

After alkali burns the mineral composition of the corneal stroma changed considerably. Sodium was present in high concentrations immediately after burning, up to 708 mmol/kg dry weight, and returned to normal on day eight. Chlorine increased significantly throughout the whole period. Sulphur concentrations stayed almost normal, showing only a minute loss of ground substance after alkali burn. A considerable and increasing edema could be concluded from the water content.

CONCLUSIONS

Alkali burns resulted in a dramatic change of the corneal mineral content. Therapeutic intervention with appropriate solutions is required to restore and maintain the normal mineral composition of the denuded corneal stroma.