[Experimental study about intra-ocular penetration of ammonia]

The seriousness of ocular alkali burn depends on low quick the alkali to enter the eye. We report the results of an experimental study on intra-ocular penetration of ammonia.

This study included 23 eyes of New Zealand albino rabbits, burned for 1 minute by 100 microl of a solution titrating 15.3% ammonia. An pH meter probe inserted into the anterior chamber measured pH every 5 seconds. Experiment were carried out within 1, 3, 5, 10 and 30 minutes. An anterior chamber puncture was performed at the end of experiments, after of 1, 3, 5, and 10 minutes, for measuring the ammonia concentration in the anterior chamber.

PH increased 1 to 3 minutes after applying of ammonia on the cornea, until a maxima 10, 5 to 6 minutes later, followed by an exponential decrease. After 30 minutes, pH was still higher than physiological pH, and the ammonia concentration was low. The penetration-ratio of ammonia through cornea was about 11%. Measured pH differed from pH calculated from the concentration of ammonia.

The difference between measured and calculated pH evidences chemical reactions. The two pH increases interspersed with a plateau prove the existence of 2 successive acido-basic chemical reactions between ammonia and 2 sorts of acid. Also, the density of protein uptake can be calculated from ammonia. This suggests an interesting avenue of research as protein density can be related in the eye with the pK of the base, and thus foresee the potential danger of a base to biological tissues.