Correlation between the neuropeptide levels and ocular surface evaluation tests/central corneal SBNFL in the study groups
| Study variables | SP (ng/mL) | NGF (pg/mL) | CGRP (ng/mL) | VIP (ng/mL) | NPY (ng/mL) |
| Ocular surface evaluation tests | |||||
| Group I (antiglaucoma with BAK) (n=82 eyes) | |||||
| Mean TBUT (s) | −0.05 (0.62) | −0.08 (0.46) | −0.06 (0.56) | 0.04 (0.67) | −0.07 (0.51) |
| Mean Schirmer’s test | −0.00 (0.92) | −0.01 (0.92) | −0.08 (0.47) | −0.11 (0.34) | −0.04 (0.70) |
| Mean corneal staining score | 0.03 (0.73) | 0.09 (0.43) | −0.10 (0.37) | 0.10 (0.37) | 0.10 (0.38) |
| Mean conjunctival staining | 0.09 (0.42) | −0.01 (0.91) | 0.11 (0.32) | 0.20 (0.86) | −0.14 (0.20) |
| Group II (antiglaucoma without BAK) (n=71 eyes) | |||||
| Mean TBUT (s) | −0.02 (0.83) | −0.17 (0.18) | −0.09 (0.48) | 0.04 (0.72) | 0.16 (0.21) |
| Mean Schirmer’s test | 0.11 (0.38) | 0.02 (0.83) | −0.06 (0.62) | 0.04 (0.71) | 0.21 (0.09) |
| Mean corneal staining score | −0.28 (0.02) | 0.05 (0.67) | −0.10 (0.42) | 0.33 (0.007) | −0.10 (0.43) |
| Mean conjunctival staining | −0.14 (0.27) | 0.08 (0.49) | −0.18 (0.15) | 0.24 (0.05) | 0.02 (0.84) |
| Control eyes (n=30) | |||||
| Mean TBUT | 0.05 (0.78) | 0.20 (0.26) | −0.04 (0.80) | 0.21 (0.24) | −0.06 (0.72) |
| Mean Schirmer’s I test | −0.00 (0.99) | 0.02 (0.89) | −0.09 (0.61) | 0.03 (0.87) | −0.02 (0.89) |
| Central corneal SBNFL | |||||
| Group I (antiglaucoma with BAK) (n=82 eyes) | |||||
| Mean SBNFL density | 0.02 (0.84) | 0.04 (0.77) | 0.14 (0.33) | 0.06 (0.67) | −0.16 (0.25) |
| N length | 0.07 (0.62) | 0.01 (0.91) | 0.07 (0.59) | 0.09 (0.49) | −0.10 (0.47) |
| N number | 0.01 (0.91) | 0.05 (0.71) | 0.08 (0.58) | 0.07 (0.59) | −0.25 (0.07) |
| Group II (antiglaucoma without BAK) (n=71 eyes) | |||||
| Mean SBNFL density | −0.22 (0.11) | 0.10 (0.45) | 0.12 (0.37) | −0.29 (0.03) | −0.15 (0.26) |
| N length | −0.12 (0.39) | 0.10 (0.45) | 0.05 (0.68) | −0.24 (0.08) | −0.12 (0.37) |
| N number | 0.00 (0.98) | 0.08 (0.54) | 0.20 (0.15) | −0.28 (0.04) | −0.06 (0.67) |
Correlation coefficient (*p value) (*Spearman correlation test)
BAK, benzalkonium chloride; CGRP, calcitonin gene-related peptide; NGF, nerve growth factor; NPY, neuropeptide Y; SBNFL, subbasal nerve fibre layer; SP, substance P; TBUT, tear breakup time; VIP, vasoactive intestinal peptide.