PCOS (Polycystic Ovary Syndrome) is not the disease of the "Cysts". What appear as "cysts", are actually the follicles (the sacs containing the eggs inside) which have not grown larger.
In a woman, there are follicles in the ovaries. In one month only one can enlarge and rupture, releasing the eggs ("Ovulation"). However, in PCOS, thus ovulation cannot happen properly.
Therefore, there is no actual "Cysts". Ovarian Cyst is a different disease, which is actually a type of tumour, that can be treated by surgery. In PCOS, there is no such tumour. So, we cannot take out the "Cysts" and cure it.
In fact, PCOS is NOT CURABLE. It's a hormonal problem but can be kept under control. It's a chronic disease like Diabetes, Hypertension, Thyroid disease etc, which are not curable but can be controlled. If you find "less" or "no" cysts, that does not mean that your PCOS is cured. So, there is nothing called "mild PCOS" or "severe PCOS".
Please remember, PCOS and "Polycystic Ovaries" are not synonymous. Many women can have "Polycystic Ovaries" in ultrasound scan without PCOS. To stamp them as "PCOS", they must have irregular periods or features of excess testosterone (male hormone) like excessive hair growth. So, if a lady is having regular periods, no features of excess testosterone but is having "Polycystic Ovaries" in ultrasound, she is NOT having PCOS.
In PCOS infertility, "Ovulation Induction" (OI) works well. It means giving medicines to help the eggs grow and ovulate. But if you are taking these medicines, it's extremely important to check if your ovaries are responding to the medicine. This can be done by TVS Follicular scan. Otherwise, taking medicines for months after months, is simply the waste of time, money and energy.