Reflecting on the Introductions of CO₂ Laser Resurfacing and Fractional Photothermolysis

The path from the early lasers of the 1980s to today’s devices has been anything but linear. Early adopters have pushed boundaries to advance the field, learning lessons along the way that have informed subsequent innovations. Modern Aesthetics March/April Guest Medical Editor Jill Waibel, MD, FACS, FAAD, sat down with 3 fellow pioneers in the field for an inspirational and reflective journey through the history of laser and light-based technology. This is the third excerpt from that conversation. (Editor’s note: This transcript has been lightly edited for clarity and conciseness).

CO₂ LASER RESURFACING

Dr. Waibel: Moving to our next era, the 1990s and early 2000s, what made CO₂ laser resurfacing both transformative and also feared?
Dr. Ross: What really made those lasers work was the pulse duration, or the dwell time, depending on whether you use the pulsed laser or the scanning version. They both would establish these fluences of 5 to 15 J/cm2, and the laser tissue interaction time was classically supposed to be less than a millisecond. That allowed for this very confined heating. It was a strange type of selective photothermolysis; it was selective by time more than target. You could treat people to a certain depth with a fairly predictable outcome and trajectory of healing, and a day-by-day scenario of re-epithelialization. For the first time, we could hold a workshop, and 4 days later, somebody who was skilled, safe, and cautious could get good results.

Dr. Waibel: What led to the swing from, “These are great,” to “We need to be careful”?
Dr. Geronemus: I was using the scanning device, and when we published our first paper on perioral lines, we were 

so excited by the dramatic results on wrinkles for those 47 patients.² After we published this paper, however, the patients started to come back 6 months later, and they were hypopigmented or depigmented. We ultimately had to publish another paper showing that, in fact, this was a delayed phenomenon—something we did not appreciate early on, and something that we generally do not see with today’s fractional lasers. It was that “Got milk” look on the upper lip, reminiscent of dermabrasion. These patients were walking around with white upper lips or a perioral area that was white relative to the normal skin. Even though we get persistent erythema now that may last a month or 2—maybe a little bit longer in some cases—the pigmentation generally comes back to normal with fractional lasers. It did not with these scanning devices and these pulse devices. That, along with scarring, really led to the demise of those devices. Interestingly, now, in 2026, they are making a little bit of a comeback, but with a lot more caution and probably better technology.

Dr. Ross: This problem led partly to the introduction of the Er:YAG laser. When it was first introduced, it had a fiber, but it was a weight guide, not a true fiber laser. We hit the ceiling and burned part of the ceiling with it the first time we used it. Eventually, a newer version was developed. The great thing about that laser was that the heat was so much less and the pain was so much less, but you still had to go to a certain depth to get results. It was positioned as being cooler and less painful than CO₂ lasers, but in the end, you can use either one. It was just nice to have another tool. The Er:YAG was not that much better non-fractionally than the CO₂. It might have been a bit safer if you were using it correctly. The big advantages were the lack of pain compared to the CO₂ and the lack of infection and other things that went along with thermal damage, but sometimes the results were not as good. One of the first patients I treated came back the next day looking as if nothing had happened. We had thought we were going pretty deep; we were using the Er:YAG like a CO₂ laser, so we thought this patient should look horrible. She healed so fast, and her results were not great, so it told us we had to go a lot deeper with Er:YAG to get the same results. It also told us how much faster the healing would be at certain depths with Er:YAG because there was little to no thermal damage. Still, there was a lot of bleeding sometimes. If a patient, for example, stopped taking aspirin and had a lot of telangiectasias and rosacea, when you got into their wrinkles with a non-fractional Er:YAG laser, it was a blood fest.

Dr. Waibel: Now, though, resurfacing is so great because I can do it on all ages, and I just turn it down for younger patients. I would treat patients in their early 40s like you treated that patient you did not recognize in your waiting room, but if I get a 75-year-old who has never done anything, I am driving 100 mph.

FRACTIONAL PHOTOTHERMOLYSIS

Dr. Waibel: In the next era, the mid-2000s, what did fractional photothermolysis solve that ablative resurfacing could not, and how did that change the risk-benefit equation?
Dr. Anderson: The era of non-fractional laser resurfacing was great. You use a CO₂ or erbium laser to blow away someone’s epidermis, which after enough sun exposure is mutated anyway. The trouble is that people get infections and they have a lot of downtime. A well-controlled burn comes with risks, and people overdid it—they got overconfident. There were some horrible burn scars from that era. Fractional laser was born of a desire to still “tickle” the skin to remodel itself. Skin is alive, and it needs a kickstart to repair damage such as sagging and aging-related changes. From selective photothermolysis, I knew the skin would tolerate microscopic hits. It’s amazing: if I take a scalpel and cut your skin, you always get a scar. If I take a little needle and poke your skin, you never get a scar. They are both pieces of steel, so what is the difference? It is the size of the wound. Fractional treatment was born of the need for something safer yet still effective, mostly for photoaging, but this wonderful doctor named Jill Waibel taught me fractional laser treatment was useful for scars. Mother Nature can be wonderful: using a laser to damage a scar at a microscopic scale improves tremendously. It is satisfying to treat hypertrophic burn scars, especially in children. The kid wants to grow, and the scar wants to contract. You can change that equation by relaxing the scar and letting the child grow the way Mother Nature intended. Fractional lasers come in various flavors: ablative ones that remove tissue; non-ablative ones that produce a bunch of little hits. Still, this is not selective—this is just carpet bombing. I think the next era is selective fractional. That is what we are working on now.

Dr. Waibel: That would be great, because with scars, the depth changes with every millimeter. The lasers you are developing do some of that—they have smart tools.

Dr. Anderson: What is different there is focusing into the dermis and producing a very deep and more profound injury. It is a cousin of early fractional lasers that made a long column of injury. There is so much to do. There are so many problems we have not solved yet. I get more excited not about the technology but about the unsolved problems worth working on.

Dr. Geronemus: The key to fractional lasers has been safety. The first fractional was the 1550 nm in 2004. It was relatively good for rejuvenating the skin and treating acne scars. The next was the fractional CO₂ in 2008, and then the fractional 1927 nm came in 2011. The safety profile was the key, and that is essentially why this technology was developed: to have non-invasive improvement and ultimately safer ablative treatments with the CO₂ laser that came out in 2008. Expanding the indications with both non-ablative and ultimately with ablative, particularly when it comes to laser-assisted drug delivery or scars, has been quite significant as well.

Dr. Ross: We had no way off the face. One patient was talking about a scar on her arm that had gotten worse, but her previous dermatologist did not have fractional lasers; I would have made it worse, too. Even for somebody who is very skilled, trying to treat a scar with a non-fractional laser off the face was almost impossible. The risk-to-benefit ratio was intolerably poor. The capabilities with skin of color and scars, the fast recovery, the lower risk of infection, and the lower levels of pain all make fractional lasers great. I always tell people the two things in my laser career that changed things more than anything else were the introduction of fractional lasers and the introduction of integrated skin cooling.

Dr. Waibel: Have we optimized fractional? We understand the physics. Do we need smaller spot sizes? Could we go faster? So many great companies have come out with great devices, but could fractional be even better than it is?

Dr. Ross:There is a point about the micro spot size; that has been considered. On surface-to-volume ratio arguments alone, you might argue a smaller spot is better for healing. Think about pixels on a screen: high definition has more tiny pixels, so, intuitively, high definition would be better, but the technology to accomplish that is harder. Certain companies were looking at nanofractional, with spots that are 50 µm or less. There is a diffraction limit for most of these wavelengths where you cannot go lower than 20 µm to 50 µm for your spot, or else your depth of field suffers, so you cannot keep that spot small over any kind of range vertically. So, there are some physics challenges there. Would it make things better if there was a higher-resolution grid? I don’t know without doing a study, but it would be worth pursuing.

Dr. Geronemus: Look at the speed with which these spots are delivered, particularly for the pediatric population. For those of us who are treating pediatric scars, it is particularly helpful that some of these faster delivery devices are slightly less painful. These are things that allow us to expand the population of patients we can treat.