Entropion is when the eyelashes turn inwards and rub against the cornea of the eye. Usually this involves the upper lid and can be present as a young puppy or develop later in life. In some instances, when the puppy is going through extreme growth changes 4 months to 18 months, the entropion may resolve itself. It is advisable to not do the surgery on puppies under 12 months of age, however if left untreated damage to the cornea can occur. It is important to discuss this with your breeder and your veterinarian.

Ectropion is when the eyelid rolls out away from the eye resulting in abnormal exposure to the eyeball itself.  This is often confused with the revealing haw which is preferred in both the bloodhound and neapolitan mastiff.  Any treatment should be discussed with your breeder. 

Further Research:

"Entropion and The Neapolitan Mastiff" by Dr. Scalia  published in the Summer 08 Neogram