Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Severe swelling, marked pain, or sudden loss of vision requires emergency assessment.
Arrange an urgent assessment if you notice a white or grey pupil, a repeated white reflection in photographs, or a missing red reflection in one eye.
These signs do not prove that a child has a cataract, but they need prompt examination because several eye conditions can cause them.
Prompt medical advice is also appropriate if a baby:
After cataract surgery, follow the eye team's instructions about urgent contact.
Seek urgent care for increasing redness, swelling, discharge, apparent eye pain, persistent vomiting, a sudden change in visual behaviour, or an eye injury.
Routine follow-up is different from urgent care.
Keep planned appointments for vision testing, glasses or contact lens checks, patching review, and eye-pressure measurement, even when there are no new symptoms.
Every sign above is quoted from the sofidex article on Congenital cataract. If you are not sure, err upward — it is always reasonable to be checked.