Human tear responses to alkali.

With the use of a closed-chamber microelectrode system, the buffering capacities of over 100 tear samples were measured in response to alkali challenge of several strengths. Although distinctive variations were found among the seven subjects studied, a substantially greater buffer capacity was consistently noted in all their tear responses to pH conditions of near 10 and above. These results are consistent with the early observations of Friedenwald, who demonstrated the buffering capacity of corneal tissue when challenged in this higher pH range, and may here be due to the onset of protein denaturation in the tears.