Do cataracts have to develop or ripen before they can be operated on?

No. Not all cataracts require surgery. If best vision is worse than 20/40 or glare is significantly affecting VA, most surgeons prefer to do surgery sooner but depends on pt's sx, risk factors, preferences; also, though no guarantees with any surgery, many patients are less dependent on or free of glasses after surgery; clear lens removal also possible in some pts; info:
See below. Insurances and medicare will not pay for cataract surgery until they reach a certain level. This is usually based on ones visual acuity but there are other factors that contribute. However, the natural lens can be removed at any time. This is called refractive lens exchange and is usually done for people wanting to avoid glasses. This is an out-of-pocket expense.
Visual significance. Cataract surgery is one when the cataract is visually significant. Meaning, that it interferes with our vision, difficulty driving a nights, difficulty reading....
No. Cataracts should be removed when they adversely affect your vision despite how ripe or dense they become. The risk is low but not zero so the decision is made when the quality of life is reduced by visial impairment. Waiting too long can make the surgery more challenging.