My over thirty years of experience in treating acne scars has taught me that since most people with acne scars have a variety of different kinds of scars (atrophic–indented–scars, pit scars, rolling scars and boxcar scars), their treatment(s) need to be tailored and individualized for best effect. A one size fits all approach seldom works.
For example when extensive acne scarring of the face leads to a more sunken look to the cheeks, the mid-face and cheeks may be plumped, lifted and stretched (and the scarred skin secondarily smoothed) with a technique that uses volumizing fillers, known as The Nonsurgical 3D Vectoring Facelift.
Following this, subcision can be used to further lift and smooth remaining depressed, atrophic scars. In general I would additionally inject a a biostimulatory volumizing agent, such as Radiesse combined with Perlane L (in my Upper East Side Manhattan office and Radiesse combined with Restylane SQ in my Israel satellite facility where a far greater number of regulatory agency approved injectable fillers and volumizers are available). The addition of the volumizer not only yields immediate cosmetic improvement, but promotes new native collagen synthesis (neocollagenesis).
Pit scars may respond well to the CROSS Technique, which uses high concentration trichloroacetic acid placed deep down the depth of the pits in order to close them off and shrink them.
Following the above, medical microneedling (aka fractional microneedle resurfacing or needle dermabrasion) may be appropriate. Depending upon the extent of the scars and their depths, medical microneedling may be performed manually with dermal rollers or electrically with electrically driven automated devices that possess the flexibility to be adjusted for rates of perforation and for varying scar depths. Deeper acne scars best respond in my opinion to microneedle treatment with the Dermapen electrically driven device, using a 2.5 needle length and a rapid speed setting, and at least two aggressive passes per area per treatment session. For patient comfort, these treatments may be performed using local anesthesia.