Pies: Dogs have a third eyelid called a nictitating membrane, which helps to protect their eyes and keep them moist

Evidence: 75 • authority: 72

An eyelid ( EYE-lid) is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. "Palpebral" (and "blepharal") means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies. A set of specialized hairs known as lashes grow from the upper and lower eyelid margins to further protect the eye from dust and debr…

Evidence: 68 • authority: 72

Cherry eye is a disorder of the nictitating membrane (NM), also called the third eyelid, present in the eyes of dogs and cats. Cherry eye is most often seen in young dogs under the age of two. Common misnomers include adenitis, hyperplasia, adenoma of the gland of the third eyelid; however, cherry eye is not caused by hyperplasia, neoplasia, or primary inflammation. In many species, the third eyelid plays an essential role in vision by supplying oxygen and nutrients to the eye via tear production. Normally, the gland can turn inside-out without detachment. Cherry eye results from a defect in the retinaculum which is responsible for anchoring the gland to the periorbita. This defect causes t…

Evidence: 61 • authority: 72

The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. Most Anura (tailless amphibians), some reptiles, birds, and sharks, and some mammals (such as cats, beavers, polar bears, seals, sheep, and aardvarks) have full nictitating membranes; in many other mammals, a small, vestigial portion of the nictitating membrane remains in the corner of the eye. It is often informally called a third eyelid or haw; the scientific terms for it are the plica semilunaris, membrana nictitans, or palpebra tertia.

Evidence: 54 • authority: 72

The musculus retractor bulbi (Latin for "the muscle that retracts the eyeball") is an extraocular muscle found in the orbit of most mammals and some other vertebrates, but is notably absent in humans and other primates. Its primary function is to retract the eyeball deeper into the orbit, usually as part of an eye-protection reflex. This action also often aids in the movement of the nictitating membrane (third eyelid) across the cornea for additional protection. The retractor bulbi muscle is a muscle posterior to the eyeball. It generally originates from the orbital apex near the optic canal, often attaching to the periorbita. The base encloses a core of fat and the optic nerve. It surround…

Evidence: 47 • authority: 92

Stent‐Assisted Surgical Creation of a Ductal Drainage Tract in the Third Eyelid Gland for Treatment of Postoperative Lacrimal Cyst of the Nictitating Membrane in a Dog. ABSTRACT Objective To describe a surgical technique of stent‐assisted creation of a ductal drainage tract in the third eyelid gland, combined with mitomycin‐C application, for the treatment of recurrent lacrimal cyst of the nictitating membrane (LCNM) in a referred dog. Animal Studied A client‐owned 8‐month‐old castrated male Maltese dog (3.6 kg) with recurrent LCNM following conjunctival pocket technique for PNMG repair. Procedures Following two recurrences after surgical cyst drainage via intentional incision, stent‐assist…

Evidence: 47 • authority: 80

Surgical treatment of nictitans gland prolapse and cartilage eversion accompanying the nictitating membrane (third eyelid) rotation in cats

Evidence: 47 • authority: 92

Surgical and Conservative Management of Periorbital Tumors in Four Dogs.. Four client-owned dogs with histopathologically confirmed periorbital tumors were included in this retrospective case series: one spayed female, one intact male, and two neutered males. The dogs ranged in age from 6 to 8 years. The most common clinical signs were slowly progressive exophthalmos (4/4 dogs), epiphora (3/4 dogs), and prolapse of the nictitating membrane gland (2/4 dogs). Periorbital disease was initially suspected based on the clinical examination. Computed tomography (CT) was subsequently used to characterize the presence, location, and extent of the lesion and for surgical planning, whereas histopathol…

Evidence: 47 • authority: 92

Bilateral Blepharoplasty and Shortening of the Third Eyelid Cartilage as Treatment for Chronic Corneal Ulceration in a Giant Rabbit-A Case Report.. This case report describes the clinical presentation and successful surgical management of a combined dorsal entropion-ectropion macroblepharon with an elongated and folded nictitating membrane in a 2-year-old male giant rabbit. The rabbit initially presented with bilateral chronic, recurrent corneal erosions secondary to abnormal eyelid and third eyelid conformation. Surgical correction was performed via wedge excision of the upper eyelid and shortening of the third eyelid cartilage. Following the procedure, the corneal erosions resolved comple…

Evidence: 39 • authority: 92

Reassessing Antibiotic Use in Canine and Feline Eyelid and Third Eyelid Surgeries: An Observational Study Supporting Selective Prophylaxis.. Purpose This study aimed to evaluate postoperative outcomes in dogs and cats undergoing eyelid and third eyelid surgeries without routine prophylactic antibiotic use. Methods This observational study included 96 animals (71 dogs and 25 cats) that underwent 163 eyelid and third eyelid procedures between March 2024 and November 2025. Animals were divided into four groups: no antibiotics, topical only, systemic only, or both topical and systemic. Prophylactic antibiotics were administered only when predefined clinical criteria were met, including prolonge…

Evidence: 39 • authority: 80

Ipsilateral cerebellar lesions prevent learning of the classically conditioned nictitating membrane/eyelid response

Evidence: 39 • authority: 92

Bilateral Eyelid Agenesis With Multiple Congenital Ocular Anomalies in an Australian Labradoodle Puppy: Case Report and Surgical Management.. A 15-week-old Australian Labradoodle puppy was presented to The University of Queensland Small Animal Hospital for bilateral eyelid agenesis/coloboma and associated ocular complications. Enucleation of the left globe and repair of the right eyelid via a lip-to-lid transmucosal flap was performed. Given the subsequent development of prolapse of the gland of the nictitating membrane and a lack of vision of the right eye, enucleation of the right globe was then performed 2 months following the initial procedure. Both globes and a skin wedge from the righ…

Evidence: 39 • authority: 92

Complications Following Nictitating Membrane Resection in Horses: 92 Eyes (2015-2024).. Objective The goal of this retrospective study is to evaluate the complications following nictitating membrane resection in horses with the aim of providing valuable information on the risks of this surgical procedure. Animals 83 horses (92 eyes). Procedures Medical records for 83 horses that underwent nictitating membrane resection in 92 eyes between February 2015 and June 2024 were reviewed. Horses were included if they had at least 1 month of follow-up data available. Owners were contacted via telephone or email questionnaire to obtain follow-up information. Complications were recorded only when prese…