Did the treatment not work if I didn't experience any MEND's? (Photo)

Thank you for your question!  At this point, you may still develop some MEND's (which stands for microscopic epidermal necrotic debris) as you are still relatively early.  The clearance of this debris is what makes the Halo such a wonderful treatment, and helps you to heal in a shorter period of time.  Also, with a lower setting (which is very appropriate with your melasma), the MENDs may not be quite as dramatic as with a more aggressive setting.  Be sure to follow up with your dermatologist as regularly scheduled and share your concerns with him/her.  The fact that your melasma is getting darker is good sign that it is responding to treatment.I hope that this helps!-David Gilpin  

You may still develop MENDS - most of my patients do get them by day 2-4 and then tend to slough on day 5-6, but your doctor was entirely correct to use lighter settings due to your melasma and if you're moisturizing a lot (as you should be), you may not notice them.