Is it possible to replace eyelashes that you have lost for a unknown reason? I have a visible space in my left eyelashes (Photo)

I suggest PRP and steroid injections if this was lost rapidly.  Latisse everyday should help if this is not an alopecia from autoimmune conditions.  Best, Dr. Emer.

Latisse or Revitalash will only work if the follicles are still alive. If the follicles are "dead and gone" from accidents/trauma, surgery, scars, styes, or eyelash extension damage, you may be a candidate for eyelash transplants. What is an eyelash transplant? The eyelash implant procedure provides a comfortable, permanent restoration of living and growing hair follicles to the eyelid where the eyelash gap exists. Eyelash transplantation is a common procedure I have performed at Bauman Medical for over 15 yrs and my proven techniques are detailed in the top textbooks on Hair Transplantation.  Eyelash implants take several hours to perform, but there is little activity restriction during the cosmetic healing phase which takes about a week.
The main "downside" is that you will have to trim the eyelashes, grooming them to the desired length because the implanted follicles come from the back of the scalp. 

If the hair follicle hasn't been badly damaged, latisse could help the hair to grow back. It's certainly worth a try. You will need to use it regularly for 3-4 months to see. If, at that point, you don't have results, you could look into a hair transplant or if you could always just have individual false lashes applied to the area. However, they will need to be replaced every time they fall off. Hope this helps, Dr. Nazarian

Per manufacturer's information, there is a chance latisse can reactivate an old hair follicle, so as long as that follicle hasn't been severely damaged, there's a chance you could see it regrow.  Please allow 16 weeks to achieve the full results, and make sure to purchase genuine latisse from a board certified practitioner--this is not something you want to buy online.  Best of luck!

I am sorry that you are having concerns about your appearance
and thanks for sharing your question. I can appreciate your
concern.
The gap of your eyelid could be treated in several ways:

1.hair transplant. The only problem is that the
hair will grow like a regular hair, making it painful to trim it to keep it in length.2.Cutting the gap out and approximating the edges.3.Use latisse. This should make your surrounding eyelashes
thicker and possibly disguising the gap.
Finally, make sure that you have a
consultation with a board certified plastic surgeon that specializes in after
weight loss surgery.



Wishing you the best in your journey

Although, there are surgical procedures to either cut out the gap between the eyelashes or transplant eyelashes, I would suggest trying Lattise, first.  The cost would be less and the results may be just as good as the surgical results.  Best wishes, Dr. Lepore.