Eye lashes do not always grow in the proper direction and in some individuals there may be several rows instead of just one. In rare cases there may be two or even three rows. A German ophthalmologist named Blatt in 1924 first described individuals with two rows of eyelashes.
A double row of eyelashes is known as distichiasis and is quite rare. The condition is not associated with other eye or systemic abnormalities. In most people the two rows are found in all four lids but sometimes only one or two. The lashes growing in the second row are often thinner, shorter, and less pigmented than the normal ones. Most of the time this is of little consequence but occasionally the extra lashes grow in the wrong direction and rub against the eye causing painful irritation or scratches of the cornea (the clear windshield of the eye). The offending lashes can be removed by your eye doctor but the majority of the time no treatment is needed.
Distichiasis is an autosomal dominant disorder which is passed from parent to child in sometimes for multiple generations.
It may be possible to see the extra lashes by looking into a mirror. However, your eye doctor can make the diagnosis and determine if any are misdirected and likely to cause problems. A simple office procedure called electrolysis can get rid of these if necessary. No other treatment is necessary.