In general, I recommend sunscreen be applied to all incision sites (once they've healed) for a period of six-months after surgery. The rationale for this is that scars exposed to the sun have a tendency to get very tanned (hyper-pigment) initially and in some instances bleach-out/turn white (hypo-pigment) later on. This obviously draws attention to the scars and makes them extremely visible.
That being said, eyelids are a privileged site in the sense that the incision is well hidden and nearly always heals beautifully. Only in very rare circumstances do eyelid scars hyper- or hypo-pigment (increase or decrease in their darkness). The only times I've seen this is amongst patients who use tanning salons and do not use eye protection, or in patients who spend a lot of time sunbathing - both of which are bad ideas if you want to stay looking youthful and prevent skin cancer.
Bottom line, if you don't live in an extremely sunny climate and don't spend much time in the sun, then you can likely skip the sunscreen on your eyelids and wear eye-covering sunglasses. If you do live where it's really sunny, enjoy many outdoor activities, or simply want to keep your skin looking its best, then you should be using a skin moisturizer with sunscreen (Sun Protection Factor-SPF 30 or greater) that can also be applied to your eyelids - this will keep your skin looking young, help prevent skin cancer, and finally, keep your incisions looking inconspicuous.