fish tank. get a 5? gallon fishtank and maybe some neon or xray tetras... or other fish he thinks are beautiful put a light in the tank so that the water stays warm and let him stare away the light will disperse through the water and make xray and neon colored fish even more stunning.

Find a light you feel comfortable him staring out and set a visual timer letting him know he has 2 minutes to stare now and will get more time later. Then when the timer is up and he has to stop, let him do another high preference activity and let him know how proud you are of him stopping when the timer went off.

You might want to check with your doctor because if your son has any kind of nuerological disorder staring at lights could be a problem.

There are so many toys with lights for bedtime. Stuffed cuddle toys that reflect light on the ceiling, glowing face dolls, and mobiles and lighted screens that attached to the crib or bed... Perhaps, making his bedroom a place to go to relax and regroup. Your kiddo has a strategy for self soothing. I would modify rather than eliminate this behavior.

You could also satisfy his need for looking at lights by buying a children's projection toy that moves lights around his room...or a toy disc, light. Allow him to go into his darkened room and watch the lights, when he feels the urge...but it should be used to reinforce times when he did NOT stare at bright lights. (Ex: "Wow! Good job at seeing the light and not staring into it. That's not safe for your eyes! Would you like to go watch your colorful lights in your room?" Good luck. (Replace the negative behavior...with a behavior that is equally pleasing...yet impossible to replicate at the same time. Meaning: He can't have a bright light AND watch the color lights around the room.)