| Grade | State of wrinkles |
| 0 | Wrinkles are absent |
| 1 | Only a few unclear shallow wrinkles are observed |
| 2 | A few clear shallow wrinkles are observed |
| 3 | Clear shallow wrinkles are observed |
| 4 | A few slightly deep wrinkles are observed among clear shallow wrinkles |
| 5 | Slightly deep wrinkles are observed |
| 6 | Clear deep wrinkles are observed |
| 7 | Markedly deep wrinkles are observed |