Patients who are perfectly comfortable in the beginning can become uncomfortable after a period of time. There are several conditions of which can cause these discomfort.
 

Rough-Build Up of Dry Mucous on the eye
Some patient’s eyelids do not close completely over their prosthesis during sleep will have partially dried film of “matter” on the front of the eye when they wake up in the morning.

Sometimes this can be cleared off without removing the eye by rubbing it with rolled up tip of good quality facial tissue moistened with warm water. Never use any kind of cloth for the reasons already given in that it can dull the surfaces of the eye.

Those with eyelids that close completely can have a very slow build-up of matter which can start as a thin film that can hardly be seen.

This can make the surface of the eye just rough enough to irritate the underside of the eyelids as they blink. One should think of the possible presence of such a film if the eye socket is irritated with scratching, burning or itching sensation.

The Prosthetic eye should be removed and carefully, but thoroughly, cleaned in such instances; in the manner describe earlier.

Foreign Bodies Under The Eyelids
 An eyelash can come loose or be broken off and be carried into the socket while replacing the eye. Dust or larger particles can blow into the eye socket. All can cause discomfort requiring removal and cleaning.

Loss Of Surface Polish Or Deeper Scratches On the Prosthesis
 Dust in the air can get into the tear film and the scrubbing action of the eyelids during blinking can reduce the polish of the surface of the plastic. Accidental scratching of the front surface, even while the eyes are in the socket, has happened to many persons. Dropping the eye onto hard, rough surfaces can also causes rather deep scratches. Both these flaws can cause irritation to the underside of the eyelids.The eyes must be re-polished to correct the problem. We recommend that prosthesis be polished once a year or twice for some to maintain comfort to the eye socket tissues and reduce any discharge, if present.

Discomfort Accompanying Common Colds
With any common cold there may be discomfort, mattering and discharge from the socket of the artificial eye while the companion eye does not seem to be affected.   

Some persons have reported that removing the eye and washing it once each day during the period of the cold reduce the discomfort and discharge.

Bacterial and Viral Infections
You must remember that the socket tissues around the prosthetic eye can become infected at least as easily as the companion eye. Discomfort and yellow-greenish discharge might indicate infection. Your tear duct (drainage) may be closed. Your ophthalmologist must be consulted in such instances.

Allergic Reaction to Various Substances

Many persons have mild allergies in the surface tissues of their living eyes without being aware of any discomfort. Allergies in the eye can be to such things as house dust, animal hair, plant pollens, and foods.

In our experience, no one has been allergic to a completely cured plastic eye which has been fabricated of pure, medical grade acrylic. (On the other hand, incompletely cured plastic eyes and eyes made of “cold-cure” acrylic can very definitely cause trouble in the socket.) While we can not guarantee that one person in many hundred thousand and thoroughly cured plastic eye, we can assure you that the chance is extremely remote.

Therefore, if an allergy of some king is suspected, your ophthalmologist and possibly an allergist should be consulted.

Empty Space Where “Stale” Tears Can Collect
The eye sockets of most persons change in contour slowly over a long period of time. Probably due to the effects of the Enucleation, ageing and fat atrophies from the depths of the orbit. This increases the depth of the eye socket and pulls the back surface into new shapes which no longer fit the contours of the previously well fitted prosthesis. This causes pockets of space between the eye and the tissues. These can fill with tears which can lie there and become “stale”. Salts leach out of the tears and irritate the tissues which, in turn, produce mucoid material. In extreme cases, where the spaces are large, tears and mucous can spill out suddenly over the eyelid onto the face, resulting in an embarrassing occurrence.
 

Probable Toxic Substances Within An “Old” Prosthetic Eye; A Development After A long Period Of Time
Acrylic plastic (METHYL METHACRYLATE RESIN) has intermolecular spaces large enough for the passage of water molecules. While the plastic eye is being bathed in the tear film, it takes up water very slowly. The water moves continually through the plastic carrying with it minute quantities of substances with small enough molecules to pass through the spaces. Very probably viruses and some bacteria can get into the eye. Very good evidence indicates that proteins collect in the plastic and that these cause irritation in the eye socket. For some persons, polishing or even refitting will not make such eyes comfortable.

The correction of this problem is simply to fit a new eye made of new plastic.