The Eyelids

By | November 12, 2015

Developmental Abnormalities

Eyelid Agenesis. Eyelid agenesis is a congenital defect of the eyelid margin resulting in absence of varying segments of the eyelid margin, palpebral conjunctiva, and fornices. The agenesis may be unilateral or bilateral, affecting the kitten more often than the puppy. The lateral one third or two thirds of the upper eyelid margin is most frequently involved. Keratitis and ulceration result from direct contact of the cornea with facial hairs and from exposure secondary to imperfect eyelid closure. Small eyelid defects may be successfully managed with ophthalmic lubricant ointments applied three to four times a day to reduce ocular irritation or by performing an entropion procedure to evert the offending hairs. If one third of the eyelid or more is missing, a pedicle graft from the inferior temporal aspect of the lower eyelid can be transposed to the upper eyelid.

Distichiasis. Distichiasis is an extra row of eyelashes (cilia) that protrudes from the orifices of the meibomian glands onto the eyelid margin. The upper, lower, or both eyelids may be involved (). Congenital distichiasis often occurs in the English bulldog, toy poodle, miniature poodle, American cocker spaniel, golden retriever, Shetland sheepdog, Chesapeake Bay retriever, Lhasa apso, Shih Tzu, and Pekingese dog breeds. Distichiasis is uncommon in kittens but may occur in the Abyssinian. Canine distichiasis may be inherited as an autosomal dominant trait. Surgical treatment is performed on those puppies in which other causes of epiphora, blepharospasm, conjunctivitis, and keratitis have been ruled out. Manual epilation is temporarily effective, but cilia will regrow within 2 to 3 weeks. Electroepilation destroys the follicular tissue within the meibomian gland but is time consuming in puppies with numerous distichia and may require several applications before satisfactory results are obtained. Cryoepilation with application of liquid nitrogen or application of nitrous oxide cryoprobe also appears to be a safe and effective method of managing distichiasis. Tarsoconjunc-tival resection or lid-splitting is not usually recommended for young puppies due to the potential for postoperative scarring and secondary entropion.

Trichiasis. Trichiasis occurs when otherwise normal eyelashes or facial hairs deviate inward, contacting the surface of the eye (). The resulting irritation may lead to corneal vas-cularization, pigmentation, or ulceration if untreated. Management of the trichiasis should begin with correction of any primary condition that may be present, such as entropion, redundant facial folds, or eyelid agenesis. Electroepilation or cryoepilation will remove offending cilia. Ophthalmic corticosteroid preparations will reduce corneal vascularization and slow corneal melanosis and scarring in the absence of corneal ulceration.

Ectopic Cilia. Ectopic cilia are hairs that emerge from the meibomian glands through the palpebral conjunctiva of the eyelid, usually 2 to 6 mm from the eyelid margin (). The hair rubs against the corneal surface, often creating an ulcer. If an ulcer in the upper one third of the cornea fails to heal normally, close inspection of the palpebral surface of the upper eyelid is recommended. The ectopic hair frequently appears as a small dark spot at the base of the meibomian gland. En bloc excision of the palpebral conjunctiva and affected meibomian gland is usually curative.

Entropion. Entropion is a defect in which the eyelid margin turns toward the globe. Entropion occurs commonly in various breeds of dogs and infrequently in the cat (). The lower eyelid is more often affected; the tarsal plate of the lower eyelid is poorly formed while the inferior orbicularis oculi muscle segment contracts with greater force. It is likely that several genes that define the eyelid structure, globe-orbit relationship, and facial skin influence the degree of entropion. Entropion often occurs in the narrow palpebral fissure of the chow chow, the deeply set eye of the golden retriever, and the Chinese shar-pei’s redundant facial folds. Painful ocular disorders may also cause entropion, with inward deviation of the eyelid secondary to spasm of the orbicularis oculi muscle. Application of a topical ophthalmic anesthetic agent such as 0.5% proparacaine eliminates the spastic component and gives a more reliable representation of eyelid conformation.

Young animals with entropion but without keratopathy may be given palliative treatment with a high-viscosity ophthalmic lubricant ointment until they are 4 to 5 months of age before surgical intervention is attempted. Delaying surgery in the Chinese shar-pei may not be possible because of the severity of the breed’s entropion and its potential for causing corneal damage. Affected puppies may benefit from a temporary eyelid correction to forestall corneal vascularization, ulceration, and fibrosis. This “tacking” procedure may be performed with sedation or regional anesthesia in the 3- to 4-week-old puppy. A suture of 6-0 Vicryl is passed through the skin and muscle of the eyelid in a vertical mattress pattern, the base of which should be parallel to and 3 mm above the margin of the offending eyelid (). A permanent correction may then be performed at a later time. The conventional procedure for correction of entropion is the Hotz-Celsus procedure. An elliptical section of the eyelid skin is removed, and the skin margins are reapposed using 4-0 silk interrupted sutures. Best eversion is achieved when the incision nearer the eyelid margin is approximately 4 mm from the margin. The sutures may be removed 10 days after surgery.

In some dog breeds, such as the Chinese shar-pei and chow chow, the retractor anguli oculi muscle is poorly developed, allowing inward deviation of the temporal canthus. This may be corrected by performing a temporal canthoplasty. A crescent-shaped or arrowhead-shaped incision is made 3 to 4 mm from the canthal margin (). The incision is then closed with 4-0 silk interrupted sutures to evert the canthus.

Ectropion. The eyelid of the puppy affected with ectropion is everted away from the globe, exposing the underlying bulbar conjunctiva. As a consequence, the conjunctival cul-de-sacs accumulate debris, and the conjunctiva is mildly and chronically inflamed. Ectropion tends to occur with greater frequency in those dog breeds with laxity of the lower eyelids such as the cocker spaniel, bloodhound, basset hound, and Saint Bernard. Temporary relief of ocular signs may be attained with ophthalmic lubricant ointments. The repair of ectropion is usually an elective and cosmetic procedure. Shortening the lower eyelid by means of a wedge resection in its lateral aspect is perhaps the simplest means of correction. Minor forms of ectropion may also be treated surgically by employing the V to Y incision.

Acquired Abnormalities

Lacerations. Eyelid lacerations occur as those that parallel the eyelid margin and those that are perpendicular to the eyelid margin. Meticulous suturing after minimal debridement is indicated in most instances. The perpendicular laceration should be closed in two layers due to the force of the orbicularis muscle pulling the wound margins apart. A layer of absorbable suture in a continuous pattern is used to close the conjunctiva/tarsus, and a second layer of nonabsorbable material is placed in the skin (). The eyelid margin should be sutured precisely to avoid the obvious cosmetic and functional defects resulting from poor marginal apposition.

Immunologic Diseases. Allergic and immune-mediated skin diseases may also involve the eyelid and conjunctiva. Immediate hyper-sensitivity results in severe swelling of the eyelids and conjunctiva with varying amounts of epiphora and pruritus. Reactions to insect bites, food, or medication may initiate an IgE-mediated response that is manageable with antihistamine and/or corticosteroid therapy. Although uncommon in the young dog or cat, delayed hypersensitivity involving the eyelids may present as a component of atopy. The animal will display swelling and congestion of the conjunctiva and serous ocular discharge that becomes more mucoid as the condition progresses. Schirmer’s tear test values may be reduced in more advanced cases. Although topical antimicrobial and corticosteroid ophthalmic solutions may provide palliative or transient relief, allergy testing and desensitization are preferred for long-term control of ocular signs.

Bacterial Infections. Young puppies are commonly affected with staphylococcal folliculitis, which may involve the eyelids. Swelling of the eyelids, face, and muzzle, coupled with pustular dermatitis in young dogs, is most likely due to juvenile pyoderma. Topical ophthalmic and systemic antimicrobial agents are recommended. Corticosteroids are used in all cases at least initially and is started with the antimicrobial agents, continuing both for a minimum of 2 weeks. Warm compresses assist in establishing local drainage of eyelid pustules. Complete resolution of the juvenile pyoderma may take as long as 6 to 12 weeks.

Parasitic Infestations. Generalized or local infestation with a variety of ectoparasites may result in alopecia, erythema, and pruritus of the eyelids (). The more common parasites involved are Demodex cams, Notoedres cati, Otodectes cyanotis, and Sarcoptes scabiei. Serial skin scrapings of the affected areas with or without identification of the offending parasite(s) makes the diagnosis. Local treatment of the affected eyelids with a suitable insecticidal ointment is generally indicated. When an effective parasiticide is selected, the possibility of local irritation involving the conjunctiva or cornea should be considered.

 

Selections from the book: “Veterinary pediatrics: dogs and cats from birth to six months”. Johnny D. Hoskins. (2001)

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