3.1 Comparison of visual acuity, IOP, BUT and of Schirmer I test value at 1 day, 1 month and 3 months after injury in each group.
Visual acuity, IOP, BUT and Schirmer I tests of patients were performed in the observation group at 1 day, 1 month and 3 months after injury, respectively. The same tests were performed in the control group on the first day of enrollment. And the results were shown as follows (Table 1).
Visual acuity: Compared with the control group, the visual acuity of patients with ocular acid burn in group I-IV significantly decreased 1 day after injury (all p < 0.05). 3 months after injury, there was no significant difference in visual acuity between patients in group I-III and those in the control group (all p > 0.05). And the visual acuity of patients in group IV was still significantly lower than those in the control group 3 months after injury (p < 0.05). Compared with 1 day after injury in the same group, the visual acuity of patients with ocular acid burn in group I-III was significantly improved 3 months after injury (all p < 0.05) whereas the visual acuity of patients in group IV didn’t significantly improve 3 months after injury(p > 0.05).
IOP: Compared with the control group, IOP of patients with ocular acid burn in group I-IV was significantly increased 1 day after injury (all p < 0.05). Although IOP in group I-III increased, it was still within the normal range while the IOP in group IV exceeded the upper limit of normal value. There was no significant difference in IOP between I-IV group and control group 3 months after injury (all p > 0.05), indicating that IOP in the four groups returned to the daily level three months later. Compared with 1 day after the injury in the same group, IOP of patients with ocular acid burn in group II-IV decreased significantly 3 months after the injury (all p < 0.05). However, there was no significant decrease in IOP of patients in group I, which may be due to the mild degree of injury and the difference in IOP between 3 months after recovery and 1 day after injury was too small to be statistically significant.
BUT: Compared with the control group, patients with ocular acid burn in groups I-IV had significantly shorter BUT 3 months after injury (all p < 0.05). 1 day after injury, however, BUT in groups II and III was longer than that in the control group (both p < 0.05) while BUT in groups I and IV was not significantly different from that in the control group (both p > 0.05). These results suggest that there was no regular difference in BUT between group I-IV and the control group 1 day after acid burn injury, which may be due to the high degree of corneal edema 1 day after injury that affected the timing of tear film rupture. When compared with 1 day after injury in the same group, BUT was significantly shorter at 1 and 3 months after injury in the I-IV group (all p < 0.05).
Schirmer I test: Compared with the control group, the values of Schirmer I test were significantly higher in patients with ocular acid burn in groups II-IV 1 day after injury; while the values of Schirmer I test significantly decreased in patients with ocular acid burn in groups I-IV 3 months after injury (all p < 0.05). When compared with 1 day after injury in the same group, Schirmer I test values of patients with ocular acid burn in the I-IV group were significantly shorter at 1 and 3 months after injury (all p < 0.05).
Table 1. Comparison of biological parameters at different times in each group
Group
Parameter
|
Visual acuity
|
IOP
|
BUT
|
Schirmer I test
|
Group I
(Grade I)
|
1 day
|
0.70±0.06*
|
18.38±1.00*
|
13.50±0.87
|
13.75±0.98
|
1 month
|
0.85±0.05
|
16.63±0.65
|
10.00±0.76#
|
8.50±0.42#
|
3 month
|
0.95±0.03#
|
16.50±0.68
|
8.75±0.70*#
|
9.25±0.37*#
|
Group II
(Grade II)
|
1 day
|
0.58±0.03*
|
19.25±0.88*
|
15.00±0.76
|
15.75±1.00*
|
1 month
|
0.80±0.05
|
16.50±0.82
|
10.00±0.27#
|
10.63±0.53#
|
3 month
|
0.88±0.05#
|
16.00±0.82#
|
8.75±0.65*#
|
8.88±0.61*#
|
Group III
(Grade III)
|
1 day
|
0.29±0.03*
|
19.88±0.58*
|
13.63±0.57
|
18.88±0.72*
|
1 month
|
0.65±0.07
|
16.13±0.51
|
8.50±0.63#
|
11.13±0.30#
|
3 month
|
0.83±0.06#
|
16.25±0.37#
|
6.88±0.58*#
|
9.00±0.38*#
|
Group IV
(Grade IV & V)
|
1 day
|
0.06±0.02*
|
22.33±1.45*
|
14.00±1.16
|
20.33±0.88*
|
1 month
|
0.10±0.02*
|
17.67±1.76
|
10.67±1.33#
|
11.67±0.88#
|
3 month
|
0.12±0.01*
|
17.67±0.88#
|
6.67±0.67*#
|
7.00±0.58*#
|
Control group
|
0.93±0.04
|
15.88±0.52
|
11.25±0.73
|
12.38±0.78
|
Note: a. Compared with the control group, *p<0.05; b. Compared with 1 day after injury in the same group, #p<0.05.
3.2 Comparison of corneal thickness at 1 day, 1 month and 3 months after injury in each group.
The comparison of corneal thickness at different time points in each group and OCT images of corneal thickness of a patient in group III were shown in Figure 1. The corneal thickness of the control group was (537.00±2.59) µm. 1 day after injury, the corneal thickness of patients with ocular acid burn in the I-IV group was (540.50±4.50) µm, (553.75±3.10) µm, (571.00±3.36) µm, (605.33±8.11) µm, respectively. The corneal thickness of patients with ocular acid burn in the II-IV group 1 day after injury was significantly thicker than that in the control group (all p < 0.05).
1 month after injury, the corneal thickness of patients with ocular acid burn in the I-IV group were (530.50±4.12) µm, (544.50±2.44) µm, (553.00±2.10) µm, (564.00±4.62) µm, respectively. The corneal thickness of patients with ocular acid burn in II-IV group at 1 month after injury was significantly thinner than that at 1 day after injury (all p < 0.05).
3 months after injury, the corneal thickness of patients with ocular acid burn in the II-IV group were (529.50±4.21) µm, (540.25±2.52) µm, (546.00±2.51) µm, (541.33±3.53) µm, respectively. The corneal thickness of patients with ocular acid burn in II-IV group 3 months after injury was significantly thinner than that 1 day after injury (all p < 0.05).
3.2 Comparison of tear meniscus height (TMH) at 1 day, 1 month and 3 months after injury in each group.
The comparison of tear meniscus height (TMH) at different time points in each group and OCT images of corneal thickness of a patient in group III were shown in Figure 2. The TMH of the control group was (228.00±6.93) µm. 1 day after injury, the TMH of patients with ocular acid burn in the I-IV group was (241.25±7.70) µm, (268.50±4.31) µm, (313.50±11.90)µm, (552.00±77.25) µm, respectively. 1 month after injury, the TMH of patients with ocular acid burn in the I-IV group were (216.00±5.24) µm, (217.00±6.67) µm, (198.50±6.97) µm, (214.67±16.38) µm, respectively. 3 months after injury, the TMH of patients with ocular acid burn in II-IV group were (199.00±5.39) µm, (199.50±8.80) µm, (188.50±7.61) µm, (176.00±6.11) µm, respectively. Compared with the control group, the TMH of patients with ocular acid burn in II-IV group significantly increased 1 day after injury (all p < 0.05), and patients with ocular acid burn in I-IV group had significantly lower TMH 3 months after injury (all p < 0.05). When comparing the TMH of patients with ocular acid burn in the same group, the TMH of patients in the I-IV group at 1 month after injury was significantly lower than that at 1 day after injury, and the TMH of patients in the I-IV group at 3 months after injury was significantly lower than that at 1 month after injury (all p < 0.05). (Figure 2)
3.3 Expression of CXCR3 and CCR5 of patients in each group at 1 day, 1 month and 3 months after injury.
The protein expression levels of CXC-chemokine receptor 3 (CXCR3) and CC-chemokine receptor 5 (CCR5) in tears of patients with ocular acid burn in each observation group were detected by ELISA at 1 day, 1 month and 3 months after injury. And the protein expression levels of CXCR3 and CCR5 in tears of patients in the control group were detected after they were recruited. The results are as follows. (figure 3)
The protein levels of CXCR3 in tears of patients in each group were compared at different times after injury. Compared with the control group, CXCR3 protein level in tears of patients with ocular acid burn in group II-IV was significantly increased 3 months after injury (all p < 0.05), and no significant change was found in the protein level of CXCR3 in tears of patients in group I 3 months after injury (p > 0.05). There was no significant difference in protein levels of CXCR3 in tears between the group I-IV and the control group 1 day and 1 month after injury (all p > 0.05). When compared with 1 day after injury in the same group, the protein levels of CXCR3 in tears of patients with ocular acid burn in group II-IV significantly increased 3 months after injury, but no significant change was observed in group I 3 months after injury (p > 0.05). And there was no significant difference in protein levels of CXCR3 of tears in group I-IV between 1 day and 1 month after injury (all p > 0.05). (figure 3A)
The protein levels of CCR5 in tears of patients in each group were compared at different times after injury. The protein levels of CCR5 in tears of patients with ocular acid burn in group I-IV was significantly higher than that in the control group at 1 month and 3 months after injury (all p < 0.05). The protein levels of CCR5 in tears of patients in group IV was significantly higher than that in the control group at 1 day after injury (p > 0.05). And there was no significant difference in the protein levels of CCR5 in tears between the group II-IV and the control group 1 day after injury (all p > 0.05). When compared with 1 day after injury in the same group, the protein levels of CCR5 in tears of patients with ocular acid burn in the I-IV group significantly increased 3 months after injury (all p < 0.05), and no significant change was found in the protein level of CCR5 in tears of patients in group I-IV 1 month after injury (all p > 0.05). (figure 3B)
3.4 Correlation analysis of CXCR3 and CCR5 protein expression levels with ocular biological parameters.
The protein expressions of CXCR3 and CCR5 in tears of acid burn patients in each group at different time points after injury were analyzed by Pearson correlation with their ocular biological parameters. The GraphPad Prism 8 software was used to make correlation images. The expression of CXCR3 in tears of patients with ocular acid burn was significantly negatively correlated with BUT (R=-0.4710, P<0.0001, Figure 4A), and the expression of CXCR3 in tears of patients with ocular acid burn was also significantly negatively correlated with values of Schirmer I test (R=-0.4864, P<0.0001, Figure 4B). The expression of CCR5 in tears of patients with ocular acid burn was significantly negatively correlated with BUT (R=-0.4173, P<0.0001, Figure 4C), the expression of CCR5 in tears of patients with ocular acid burn was also significantly negatively correlated with Schirmer I test (R=-0.3650, P=0.0004, Figure 4D), and CXCR3 and CCR5 in tears of patients with ocular acid burn were not significantly correlated with other indicators.