Drooping Left Eyelid Really Bothers Me and Wondering if It Can Hurt Vision if It Starts Covering the Pupil, Even So Slightly.

Significant ptosis, covering the pupil, can affect the vision permanently ONLY if you are a child (less than 8 years old) when the brain visual pathways are developing, resulting in amblyopia.  You are well passed that stage and your ptosis is very mild.  If it is something that really bothers you, you can have your eyelid lifted.  Consult an oculoplastic surgeon.

Mehryar Taban, MD

Your ptosis does seem significant and will not affect your vision.  When and if ever it does, you can consider surgical correction.  Stop worrying!

Ramtin Kassir, MD NY/NJ Facial Plastic Surgeon

You do not have visually significant ptosis- if you wanted any lid surgery it would be cosmetic in nature. Having a droopy lid in adulthood does not cause permanent vision loss and is correctable. If you're very concerned seek consultation with an oculoplastics surgeon.

Stratus,

If your eyelid position does not change during the day, then your ptosis appears very mild in your photo.  You are not at any risk of permanent vision loss due to your eyelid position.  Any correction would be cosmetic in nature, and not covered by insurance.

Most adult onset ptotic (drooping) eyelids result from stretching of the levator muscle or its connecting fibers. Correction envolves outpatient surgery to shorten or repair these structures.You probably do not have enough to bother with at this time and it may be that it will be many years if ever before you will need surgery.The only effect on vision has to do with mechanical blockage; there is no efffect on the eye itself. 

Your ptosis is extremely mild and should not cause any visual problems. If it seems to worsen in future years you can always have an upper lid blepharoplasty or endoscopic browlift at a later date however this is not indicated at this time. You are fine and should mark this off of your list of concerns and enjoy life! Best regards!