I started slowly working this into my evening routine. I rotated applying this under my eyes, smile lines, and forehead creases. I first applied it as the last step over my moisturizer and then worked towards applying it over an oil and under my moisturizer.

Somewhere in the phase of applying it over the oil, I started noticing a lot of pressure on my eyes and headaches at the end of the day. It built up for a few days until I pieced together that it was because I had serious eye sensitivity to light. I stopped using the retinal and eventually recovered after a week.

Unfortunately, I won't continue using it. I looked it up and it seems like eye light sensitivity is a not very common but a possible side effect for some people when using retinal/retinol. Mostly leaving this review to let people know in case anyone experiences the same thing.