NICTITATING MEMBRANE (THIRD EYELID)

Protrusion, elevation or prominence of the nictitating membrane occurs in many conditions such as:

1-     Congenital microphthalmia and enophthalmia.

2-     Diseases accompanied by loss of weight and dehydration (decreased amount of periorbital fat).

3-     Encephalitis due to rabies, tetanus or canine distemper and meningitis.

4-     Postorbital space occupying lesion such as; abscesses, cysts, tumors and hematomas.

5-     Swelling or symblepharon of the nictitating membrane.

6-     Horner’s syndrome  in dogs. It is a partial or complete loss of sympathetic innervation of the eye. The condition manifests itself clinically by miosis of pupil, protrusion of the third eyelid, ptosis, enophthalmia, small palpebral fissure and changes in intraocular pressure mainly occur in dog.

Fig.6:  Protrusion of the third eyelid in a cat.

Treatment:

The specific cause is treated