Figure 1

Figure 2
![Cystatin C concentration in various biological matrices in healthy individuals. Concentration of cystatin C in each biological fluid (mean ± standard deviation [s.d.]; n = 28 [n = 13 healthy controls ≤ 40 years old + n = 15 healthy controls 41–60 years old]), since Table 1 shows a significant increase in cystatin C concentrations in serum and intraocular fluid (IOF) in 61–80 year old healthy controls, and thus, this age group was not included; cerebral spinal fluid (CSF) was obtained from an additional and separate group of cancer-free neurosurgical patients (n = 8) for the determination of the cystatin C concentration as described in the Materials and methods section.
a Significant difference (p < 0.001) from mean values indicated with the same letter.
b Significant difference (p < 0.001) from mean values indicated with the same letter.
c Significant difference (p < 0.01) from mean values indicated with the same letter.
d Significant difference (p < 0.01) from mean values indicated with the same letter.
e Significant difference (p < 0.01) from the mean value indicated with the same letter.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647356294e662f30ba53aaf0/j_raon-2021-0049_fig_002.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251204%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251204T185237Z&X-Amz-Expires=3600&X-Amz-Signature=53a30ae2bd967bbe06f057ec7c749f846b421747e947dbb82a83715119916268&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 3
![Cystatin SN concentration in various biological matrices in healthy individuals. Concentration of cystatin SN in each biological fluid (mean ± standard deviation [s.d.]; n = 28 [n = 13 healthy controls ≤ 40 years old + n = 15 healthy controls 41–60 years old]), since Table 1 shows a significant increase in the cystatin SN concentration in the serum of 61–80 year old healthy controls, and thus, this age group was not included; cerebral spinal fluid (CSF) was obtained from an additional and separate group of cancer-free neurosurgical patients (n = 8) for the determination of the cystatin SN concentration as described in the Materials and methods section.
a Significant difference (p < 0.001) from the mean value indicated with the same letter.
b Significant difference (p < 0.05) from mean values indicated with the same letter.
c Significant difference (p < 0.001) from the mean value indicated with the same letter.
d Significant difference (p < 0.01) from the mean value indicated with the same letter.
e Significant difference (p < 0.001) from the mean value indicated with the same letter.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647356294e662f30ba53aaf0/j_raon-2021-0049_fig_003.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251204%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251204T185237Z&X-Amz-Expires=3600&X-Amz-Signature=f07925c05020a4485d2b8a422fb410cef7609a84d12964bb5ecc441bf5eaa6b0&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 4

Figure 5

Concentrations of cystatin C and cystatin SN in biological fluids of healthy individuals as a function of age (Mean ± s_d_)
| Groups | Inhibitor | Serum (ng/mL) | Tears (ng/mL) | IOF (ng/mL) |
|---|---|---|---|---|
| Healthy | Cystatin C | 561 ± 10.0 | 296 ± 11.1 | - |
| (≤ 40 years) [n = 13] | Cystatin SN | 2.24 ± 0.20 | 0.49 ± 0.30 | |
| Healthy | Cystatin C | 539 ± 111 | 256 ± 82.3 | 414 ± 28 |
| (41–60 years) [n = 15] | Cystatin SN | 2.96 ± 0.70 | 0.6 ± 0.35 | 2.7 ± 1.40 |
| Healthy | Cystatin C | a1,341 ± 177 | 382 ± 116 | a844 ± 113 |
| (61–80 years) [n = 9] | Cystatin SN | b4.77 ± 0.10 | 0.75 ± 0.14 | 2.18 ± 0.20 |