third eyelid


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pli·ca sem·i·lu·na·'ris of con·junc·ti·'va

[TA]
1. the semilunar fold formed by the palpebral conjunctiva at the medial angle of the eye;
2. a fold of the conjunctival mucous membrane found in many animals; normally partially hidden in the medial canthus of the eye when at rest, it may be extended to cover part or all of the cornea in a winklike action to clean the cornea, as in birds. Synonym(s): membrana nictitans, nictitating membrane, palpebra III, palpebra tertia, third eyelid

third eyelid

third eyelid


third eyelid eversion
the free margin of the third eyelid is rolled outwards because of a curvature of the cartilage. More prevalent in large breeds of dogs and may be an inherited defect in St. Bernards and German shorthaired pointers.
Enlarge picture
Eversion of the third eyelid in a dog. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991
third eyelid protrusion syndrome
References in periodicals archive ?
Normally, the third eyelid is held back by the position of the eyeball, so anything that makes the eyeball shrink slightly or sink back into the head will allow the membrane to slip up.
Sometimes cats may have a prominent third eyelid for no apparent reason.
At surgical resection, the mass grossly appeared to infiltrate the third eyelid with some involvement of the sclera.
Most of the time, when the animal is awake, the third eyelid is not visible, being tucked out of sight in the corner of the eye, however, it can sometimes be seen if the animal is tired.
Q MY cat is two years old and both his third eyelids (the inner membranes some animals have for protection) have closed over.
Dehydration and anaemia, worms or other parasites can cause the third eyelid to be more prominent and also if your cat has mild depression.
Bilaterally, no movement was detected in the lower eyelids; however, the third eyelid range of motion was normal and maintained a normal blinking rate.
Normally the third eyelid is held back by the position of the eyeball, so anything that makes the eyeball shrink slightly or sink back into the head will allow the membrane to slip up, eg, if a cat loses weight, due to the shrinking of the fat pad behind the eye.
But with the eyelid test, all that's needed is a small sample of lymph tissue snipped from a special membrane covering the sheep's eye, called the third eyelid.
It could also just be that his third eyelid is more visible than usual, but you would normally see them in both eyes in their inner corners.
O'Rourke discovered that prions collect in pockets of lymphoid tissue in a sheep's nictitating membrane, or third eyelid.