Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Sudden severe eye pain with reduced vision, or vision loss after an injury or chemical exposure, requires emergency care.
These are not typical symptoms of uncomplicated astigmatism.
Return sooner if vision is no longer clear with current correction, headaches or eye strain continue, or contact lenses become uncomfortable.
Arrange prompt eye care for a sudden change in vision, new double vision, eye pain, pronounced redness, or strong light sensitivity.
Contact lens wearers with these symptoms should remove the lenses and seek advice promptly.
Flashes of light, many new floaters, or a dark curtain or shadow across the vision require urgent assessment because they can be signs of a retinal problem.
Routine follow-up depends on age, symptoms, eye health, contact lens use, and how stable the prescription is.
An eye care professional can recommend an appropriate schedule.
Children with significant astigmatism may need closer follow-up to confirm that glasses are worn as advised and that vision is developing evenly in both eyes.
People with keratoconus or another corneal condition may need repeat corneal mapping to look for progression.
Every sign above is quoted from the sofidex article on Astigmatism. If you are not sure, err upward — it is always reasonable to be checked.