Grading of pterygium
| Grade | |
| 1 | The maximum length of the invasion is less than one third of the corneal radius |
| 2 | The maximum length of the invasion is one third of the corneal radius or more |
| 3 | The invasion reaches the pupillary area |
| 4 | The invasion covers the whole pupillary area |
| 5 | The invasion transverse the cornea |