Experimental study about intra-ocular penetration of ammonia

Purpose : The seriousness of ocular alkali burn depends on low quick the al kali to enter the eye. We report the results of an experimental study on in tra-ocular penetration of ammonia. Materials and methods: This study included 23 eyes of New Zealand albino ra bbits, burned for 1 minute by 100 mu l of a solution titrating 15.3 % ammon ia. An pHmeter 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 o f 1, 3, 5, and 10 minutes, for measuring the ammonia concentration in the a nterior chamber. Results: PH increased 1 to 3 minutes after applying of ammonia on the corne a, until a maxima 10, 5 to 6 minutes later, followed by an exponential decr ease. After 30 minutes, pH was still higher than physiological pH, and the ammonia concentration was low. The penetration-ratio of ammonia through cor nea was about 11 %. Measured pH differed from pH calculated from the concen tration of ammonia. Conclusions: The difference between measured and calculated pH evidences ch emical reactions. The two pH increases interspersed with a plateau prove th e 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 de nsity can be related in the eye with the pK of the base, and thus foressee the potential danger of a base to biological tissues.