A child has got a congenital cataract involving the visual axis which was detected by the parents right at birth. This child should be operated –
Congenital unilateral cataract involving visual axis requires urgent surgery, as early as possible, i.e. within days.
However, you should keep in mind that surgery is inadvisable after 16 weeks (4 months) of age as the amblyopia is refractory

Congenital bilateral cataract

Dense :- Early surgery by 4-6 weeks of age.
Partial :- Regular follow-up.

Congenital unilateral cataract

Dense or involving visual axis :- Urgent surgery within days.
Partial:- Observation.
Immediately
At 2 months of age
At 1 year of age when the globe becomes normal sized
After 4 years when entire ocular and orbital growth becomes normal