Intraocular penetration of toxic substances

PURPOSE: The seriousness of ocular alkali burns has been linked to the rapidity with which the alkali enters the eye. The authors report the results of an experimental study on intraocular ammonia penetration. MATERIALS AND METHODS: 23 eyes of New Zealand albino rabbits were burned by applying for one minute 100 ul of a solution titrating 15.3 percent of ammonia. A pH meter probe was inserted into the anterior chamber beforehand to permit pH measurements every 5 seconds. Experiments were carried out after 1,3,5,10 and 30 minutes. The ammonia concentration was measured at the end of the experiment by puncturing the anterior chamber. RESULTS: The pH increased 1 to 3 minutes after applying ammonia on the cornea, reaching a maximum (mean) of 10 five to six minutes later, before an exponential decrease. After 30 minutes, the pH was always more than the physiological pH. The penetration ratio of ammonia through the cornea is about 11 percent. At 30 minutes, the concentration of ammonia is low. The pH observed differs from the calculated pH. DISCUSSION: The difference between observed and calculated pH indicates increases with an intervening plateau, showing the existence of two successive acid-base chemical reactions between ammonia and two types of acid. In addition, the amount of protein destroyed by ammonia can be calculated. CONCLUSIONS: These data show for the time the possibility of calculating the density of proteins destroyed in vivo by a base penetrating the anterior chamber. This opens the possibilty of interesting research work, because it is possible to relate the density of proteins destroyed in the eye to the pK of this base, and to forecast the potential danger of a base of biological tissues.(AU)

Ocular ammonia burns: treatment

PURPOSE: The authors present the results of an experimental study to support the proposal for a delay in ocular bathing in the treatment of severe ocular burns due to ammonia. This study compares two solution of ocular wash: physiological serum and Diphoterine. MATERIALS AND METHODS: 23 eyes of New Zealand albino rabbits were burned for one minute by 100 ul of a solution containing 15.3 percent ammonia. Then, each eye was washed by an ocular wash of 250 ml of physiological serum, or of 250 ml of Diphoterine, after a delay of 1,3,5,10 and 30 minutes. The effects were appraised by measuring the anterior chamber, the concentration of ammonia in the anterior chamber, and by the cytopathological analysis of these burned corneas. RESULTS: An ocular wash with Diphoterine in the first few minutes following an ocular burn induces an inflexion of the pH graph, contrary to an ocular wash with physiological serum. On the other hand, there is no inflexion of the pH graph at 30 minutes, and the concentration of ammonia in the anterior chamber is low at that time. The cytopathological analysis shows stromal oedema with the ocular wash by physiological serum, but not when Diphoterine ocular wash is used. DISCUSSION AND CONCLUSIONS: This study proves the importance of ocular bathing in the first minutes following an ocular burn by ammonia. The efficacy of an external ocular wash by Diphoterine features; the importanve of sequelae has been linked to the initial stromal oedema.(AU)

Ocular alkali burns: limbal autograft

The authors present five patients treated with limbal autograft for serious recent ocular alkali burns, in four of whom it has permitted healing of recurrent corneal ulcers or the reduction in the period of conjunctival recovery. Functional amelioration is also important and this intervention has permitted a useful visual acuity. One case was complicated by bacterial keratitis, but our experience has confirmed the efficacy of the technique for managing surface ocular disorders. However there have been few reports hitherto of the use of limbal autografts for serious ocular burns, and our study has demonstrated its usefulness in this setting and the appropriate timing. VIDEOTAPES(U-Matic or VHS): The authors report their surgical technique of limbal autograft use in recent and severe ocular burn, a modification of Kenyon and Tseng's technique. The physical signs used as indicators for surgery, the selection of the limbal region and methods of following the graft, are presented.(AU)