The timing of the effects of your treatment will be dependent on many factors, including your specific skincare goals (e.g. reducing the appearance of fine lines and wrinkles, helping prevent wrinkles, reducing redness, etc.), how severe yoursymptoms are, how well you tolerate the treatment, and others. It is also important to understand that for certain treatments, your skin may get worse before it gets better. Depending on the treatment you are prescribed, you will receive detailed information on the formulation and what to expect.
Using an eye cream won't banish dark circles, but a select few creams really work, mostly by using high-tech ingredients to constrict blood vessels (which cause dark shadows), diffuse light, and brighten pigmented areas for a noticeable improvement in their appearance.