This letter is in regards to Fukuda et al.1 We thank the authors for their informative contribution. The use of rabbit specimens was relevant to this study as previously alluded to by Wilhelmus, who concluded from his research that rabbit eyes were more susceptible to irritants than human eyes.2The BAK additive could have influenced the results; however the authors did an excellent job of obtaining a more suitable measurement of the corneal damage by developing an apparatus to measure it.1 It would have been ideal if the authors had mentioned the details of the “apparatus,” so as to give the readers a little more information about how objectively the corneal damage was measured.The study was of a high quality, with an informative conclusion indicating that if HCO-40 was combined with BAK, it induced micellar BAK and reduced corneal injuries.