Katsu Nakamori

Blinking Is Controlled Primarily by Ocular Surface Conditions

PURPOSE To investigate the relation between blinking and ocular surface conditions and to introduce and examine a new index, the maximum blink interval. METHODS In a prospective study, the blink rate of subjects under relaxed conditions was determined from a video recording taken by a hidden observer. The maximum blink interval was defined as the longest time subjects can avoid blinking without feeling uncomfortable. RESULTS Significant changes in the blink rate and maximum blink interval were induced by factors that directly or indirectly affect the ocular surface: topical anesthesia, changing exposed ocular surface area, and wind. Moreover, the blink rate and maximum blink interval were significantly different in dry eye patients compared with healthy volunteers, with the values of the former approaching the values of the latter after use of artificial tears. The maximum blink interval was decreased by the same factors that increased the blink rate, and there was a significant inverse correlation between blink rate and maximum blink interval. Use of video display terminals was associated with decreased maximum blink interval and, hence, the development of dry eye symptoms. CONCLUSIONS There was an important association among blink rate, maximum blink interval, and ocular surface conditions. The blink rate and our newly introduced measurement, the maximum blink interval, should prove useful in assessing factors that cause dry eye. This prospective study should contribute to the understanding and treatment of dry eyes.

THE REACTIVITY OF TAURINE WITH HYPOCHLOROUS ACID AND ITS APPLICATION FOR EYE DROPS

The ability of taurine to protect biomembranes attacked by HOCl was examined using canine erythrocytes which had been pre-treated with HOCl. Of the amino acids tested, taurine was the most effective in inhibiting attack by HOCl, followed by glycine, alpha-alanine and beta-alanine. During the incubation of HOCl-treated erythrocytes with taurine, an appreciable amount of monochlorotaurine (TauNHCl) was detected in the supernatant. This suggests that taurine may remove the oxidized chlorine from HOCl-treated erythrocytes, resulting in the production of TauNHCl. The effect of taurine on the removal of Cl+ moiety was examined using Sepharose gel with amino groups. Taurine removed Cl+ from HOCl-treated Sepharose gel. The yield of TauNHCl depended on the concentration of taurine. The effectiveness of taurine in preventing ocular surface damage caused by HOCl was investigated in albino rabbits. The activity of lactate dehydrogenase (LDH) released from ocular tissues into tears during eye irritation was used as an index of ocular surface damage. Taurine effectively protected ocular surface tissues from damage induced by HOCl, and arrested the progression of tissue damage that had already been initiated by HOCl. These finding suggest that taurine may be clinically useful in the treatment of ocular surface damage caused by oxidants such as HOCl.