It depends on your skincare concerns. Retinol is an over-the-counter anti-aging ingredient in eye creams that often helps treat under-eye wrinkles. It’s a strong exfoliant, but it can cause some irritation for sensitive skin and should typically be applied at night. Vitamin C, on the other hand, targets dark under-eye circles and signs of photoaging. It also stimulates collagen production to help with wrinkles and fine lines. Unlike retinol, products with vitamin C should generally be applied in the morning.