Eyes may suddenly develop astigmatism. If a sudden and dramatic change in astigmatism is detected and the tendency is to worsen, a corneal topography examination must be done to rule out the possibility of a cone cornea. Astigmatism may change over the course of a person’s life, and is generally relatively stable in the younger age group. In contrast, the middle-aged and elderly population has crystalline astigmatism due to a decrease in lens elasticity and uncoordinated ciliary muscle contraction. Therefore, middle-aged and elderly patients usually have an increase in astigmatism from year to year, with a predominantly retrograde pattern. The sudden increase in astigmatism may also be related to other pathological factors that cause corneal scarring, such as corneal lacerations after trauma, keratitis and corneal ulcers after infection, and corneal scarring after treatment. In addition, pterygium, incomplete dislocation of the lens or eye surgery can also lead to irregular astigmatism.