FIG. 9.

Doxycycline ameliorated the increase in corneal thickness (measured by pachymetry) induced by SM exposure. Corneal thickness was read at 5 areas in each cornea (left, right, top, bottom, and center). Values were averaged to obtain the mean thickness for each cornea. (A) Preexposure, the average of the 64 corneas was 353.5 ± 19.3 μm (standard deviation). Mean values of exposed eye corneal thickness at indicated times postexposure without taking into account each cornea's preexposure thickness. When damage is severe, pachymetery cannot be read. Therefore, 5 readings were not possible in the 1 and 3 days postexposure samples. The value for the 1 day postexposure thickness for the SM + dox corneas (indicated by “ + ”) was calculated from 4 readings from 1 animal, 3 readings from the second, and 5 readings from the third; the SM + hydrogel containing dox (HG dox) value (indicated by “ + + ”) was averaged from 5 readings from the first animal, 4 from the second, and 4 from the third. The value for the 3 days postexposure thickness for the SM-exposed corneas (indicated by *) was calculated from 1 reading from the first animal, 0 readings from the second, and 4 readings from the third; the value for the thickness of SM + dox corneas (indicated by **) was calculated from 1 reading from the first animal, 4 readings from the second, and 1 readings from the third; the SM + HG dox value (indicated by ***) was averaged from 1 reading from the first animal, 1 from the second, and 2 from the third. (B) Mean corneal thickness index for each group, shown in histogram form, correcting for the initial thickness of corneas before exposure. The equation for this calculation is “right eye postexposure” minus “right eye preexposure” divided by “right eye preexposure” for individual corneas. Next, the mean of the 3 corneas in the group was determined. This removes bias in the postexposure thickness that might be due to individual variations in the thickness of the preexposed corneas. At day 3 the damage was severe, and thickness due to edema could be reliably determined for only 1 cornea in the SM group and 1 cornea in the SM + dox group, and thus these histograms have no error bars. The 3 days SM + HG dox group had edema measurable in 2 corneas; therefore, an error bar is shown. The P values from statistical analysis (analysis of variance) of all groups were 0.0049 for 1 day, 0.1029 for 3 days, <0.0001 for 7 days, and 0.1053 for 28 days. The 3-day value includes all corneas in the group, that is, those that were of larger than preexposure thickness from edema, and those thinner from other SM damage. With a Tukey analysis, there was a significant difference between SM-challenged groups at 7 days: the corneal thickness index in the SM group was significantly greater than that for the SM + dox group (difference = 0.81, P value = 0.0015) and the SM + HG dox group (difference = 0.57, P value = 0.0156). A P value of <0.05 was considered significant.