What secondary complication might arise from proptosis?

Proptosis, which is the forward displacement of the eye from the orbit, can lead to several complications due to the exposure of the cornea and other structures. One of the most significant secondary complications that may arise is corneal ulceration. When the eye is proptosed, it often becomes exposed to the external environment, which can cause drying of the corneal surface and make it vulnerable to abrasions and infections. This lack of protection can result in the development of corneal ulcers, which are painful and can lead to serious vision problems or even loss of the eye if not treated appropriately.

In contrast, the other options indicate positive or neutral outcomes that are generally not associated with proptosis. Normal eye function and increased vision would not occur as a result of proptosis, and orbital bone healing typically concerns different clinical conditions rather than being a complication stemming from proptosis itself. Thus, among the options provided, corneal ulceration is the most relevant and likely secondary complication of proptosis.