Effect of different irrigating solutions on aqueous humour pH changes, intraocular pressure and histological findings after induced alkali burns.

PURPOSE: To evaluate the effects of hypo-osmolar tap water and isotonic saline solution on the intracameral pH, intraocular pressure and histological changes in alkali burned rabbit eyes.

METHODS: Four groups of four rabbit corneas each were burned with 2 N sodium hydroxide, and then rinsed with 0.5 l or 1.5 l of saline solution or tap water, respectively. Changes in pH were monitored with an intracameral microelectrode. Intraocular pressure (IOP) was monitored by a transducer placed in the vitreous cavity. After enucleation, histology was performed.

RESULTS: The pH increased after 1.5 min following alkali application. Irrigation with different solutions affected the maximum pH levels reached. Following the tap water rinse, the maximum rise was significantly lower than after the saline solution rinse. The maximum rise following rinsing with 1.5 l of tap water showed a significant delay. The increase in IOP was 23 +/- 10 mmHg without differences between the groups; the original pressure was recovered after 18 +/- 9 min. Histology of the eyes revealed a significant oedema in all corneas. Other ocular structures appeared unchanged.

CONCLUSIONS: The hypo-osmolarity of tap water led to remarkable corneal oedema. Enlargement of the diffusion barrier and intracorneal dilution inhibit elevated intracameral pH levels. The difference in maximum pH levels reached may influence the degree of subsequent intraocular structure injury. Therefore, the use of iso-osmolar saline solution proves to be less efficacious than tap water as an irrigation agent for ocular burns.