Hypopigmentation is a lightening of the normal skin color. It can occur for many reasons and can be permanent. When seen after laser skin resurfacing, it is typically due to damage to the melanocytes (pigment producing cells) which do not grow back.
Fully ablative CO2 laser skin resurfacing of the face in the 1990's commonly caused hypopigmentation that left an obvious line of demarcation along the jawline. I published an article in the medical literature in 1996 describing this complication. It is because of this complication and others that led to the "fractionation" of laser beams now employed in modern lasers. So these days, it is very uncommon to see true hypopigmentation with Fractional Laser Resurfacing. However, it can still occur especially in cases in which too much energy was applied or too many passes were performed.
CO2 Laser Resurfacing: Recognizing and Minimizing Complications, Roberts, T.L., Lettieri, J.T., Ellis, L.B., Aesthetic Surgery Quarterly, 2:16, 142-8. 1996
Sadly, those of us in our 50's and beyond frequently did not use sunscreen. We enjoyed a "healthy-looking" tan and even used tanning accelerators! If you compare the skin on your breasts to the skin on your chest, it's the same age skin but the exposed, tanned chest skin is crepy, thin and blotchy. It's prematurely aged. To get back to the real skin you should have for your age (as much as possible) there are several treatments to consider.
To improve thinning/crepey skin, energy-based skin remodeling modalities should be used. Those include sub-lative or fractionated laser treatments such as Lumenis' ResurFX and MiXto CO2 laser, Ultherapy ultrasound treatments and radiofrequecy tissue remodeling treatments such as Inmode's Morpheus8.
For brown and red blotchy discolorations, Intense Pulsed Light (IPL) and vascular laser treatments work well.
Mature skin is often thinning, crepey, blotchy and lax. These issues are due to the aging process itself typically complicated by past sun damage and other forms of environmental damage that produce free radicals breaking down the tissue. Tanning and smoking produce the most damaging effects.
The best treatments are based on many considerations including location of the treatment area. For example: face vs neck, chest, arms, abdomen, legs...
In my practice, I often use a combination of treatments. For upper eyelids I use CO2 laser resurfacing. For very thin skin on the face I begin with a collagen building supplement and Ultherapy or a sublative laser treatment. For most other patients I treat with Morpheus8 Radiofrequency skin remodeling which can be applied to skin just about anywhere on the body with the exception of upper eyelids. I treat a lot of arms, thighs and abdomens with this modality.
And as with all energy-based tissue remodeling/resurfacing treatments, living a healthy life-style is a must for the best outcome and preservation of results. Eat a healthy diet, sleep well, drink water-at least 1/2 your ideal body weight in ounces every day. Manage stress and ensure you are getting enough micronutrients.
Crepey, saggy under eye skin is primarily due to loss of collagen and thinning of the skin related to aging and past sun damage. Correction involves promoting collagen production and tissue remodeling which is best achieved with energy-based treatments. There is no doubt that the current gold standard in tissue remodeling is radiofrequency microneedling. I often use a combination of CO2 laser resurfacing for the upper eyelid with Morpheus 8 RF microneedling for the lower lid. This give beautiful, enduring results that look natural.