| When a retina catches the light |
| from outside as an image, a crystalline |
| lens changes to a concave or to a |
| convex automatically by the function of |
| muscles. You have a myopia |
| (nearsightedness) if the lens is hard to |
| concave and a hyperopia |
| (farsightedness) or presbyopia |
| (farsightedness due to old age) if the |
| lens is hard to convex. |
| If there is something wrong with |
| your eyes, you have stiffness in the |
| temple and in both sides of the |
| posterior neck. |