Cataract treatment does not require an emergency surgery in most cases.
At the same time, you don’t have to wait for the cataract to “ripe” before going for the surgery. The concept of a “ripe” cataract is based on older surgery techniques. Phaco surgery is possible when the cataract has increased to such an extent that the normal vision is impaired, even though the cataract might not have matured completely. If the cataract has hardened beyond a point, Phaco surgery may not be possible though, and the conventional surgery may have to be resorted to.