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Corneal Hydrops

 

Eyelid Abnormalities

Written by Dr's Dennis Hacker & Michael Zigler

Basic Anatomy and Function

The upper and lower eyelids have many functions. They protect the cornea [clear portion out front of the eye] and the eye itself from drying out, from insults and from trauma from the outside. They spread the tear film across the corneal surface. They produce portions of the tear film from glands along the eyelid margin and from cells in the folds of the eyelids. They determine the shape and size of the eyelid openings. They keep out the light. Finally they pump the tears out to the tear duct. Meanwhile, the third eyelid helps to spread the tear film and the third eyelid gland produces from 30 to 60% of the watery portion of the tears.

Neonatal Problems

The eyelids of dogs and cats open between 10 and 14 days of age. If the eyelids open too early, tear production is not present and signs of dry eye (keratoconjunctivitis sicca) will occur unless you apply antibiotic ointment 3-to-4 times daily until tear production begins.

Conjunctivitis Neonatorum

A condition known as conjunctivitis neonatorum occurs when bacteria or viruses enter the eye through the eyelids that are closed following birth. Corneal rupture and chronic scaring of the white of the eye (conjunctiva) will occur unless the eyelids are opened by a Veterinarian and the eyes are treated with appropriate medication. We now know that in kittens, conjunctivitis neonatorum is due to herpesvirus infection. These kittens will benefit from appropriate antiviral medication. Cortisone medication should not be used.

Eyelid Agenesis

A lack of portions of the eyelid occurs in cats and is known as eyelid agenesis or coloboma. This condition is seen in the lateral portion of the upper eyelid. This condition will lead to scarring and blood vessels occurring because tears are not spread normally and because hairs on the abnormally developed area will rub the cornea. Surgery is necessary to correct this condition.

Epibulbar Dermoid

An abnormality known as dermoids can occur along the conjunctiva (white of the eye) on the upper eyelid or along the lateral eyelid opening. Depending on the size and location, these growths may be left alone [if they are causing no problems] or removed in surgery.

Eyelash Abnormalities

Eyelash disease is actually a group of conditions that cause eye injury from hairs that irritate the eye. Trichiasis is a condition of normal hairs lying on or irritating the globe. Examples of this would be very long facial hairs in long haired dogs and nasal folds in the Pekingese. Also tiny hairs at the nose side of the eye can act as a wick and cause tear spilling in Miniature Poodles and Persian cats. Distichiasis is the condition of eyelashes coming out of an abnormal position such as the glands that are located along the eyelid edge. Districhiasis is more than 1 eyelash coming out of each of the gland openings. Ectopic cilia are abnormal hairs that exit a hair follicle on the inside of the eyelid. Ectopic cilia are very painful. The successful elimination of the offending hairs will require surgical treatment.

Lagophthalmos

Lagophthalmos means "rabbit eye" and is commonly seen in the Pekingese, Pug, Boston Terrier, Lhasa Apso, Japanese Chin, Dandy Dinmont and Shih Tzu, and the Persian and Himalayan cat. In animals with lagophthalmos, the ability to blink is impaired, and owners may notice the animal sleeping with the eyes partially open. Whilst these animals may not exhibit any signs of eye problems for years, increased pigmentation will start on the cornea at the nose side of the eye. An all too common presentation will be the patient that develops a corneal ulcer in the center of the eye. The ulceration occurs because the tearfilm is not distributed effectively over the corneal surface, due to the inability to blink properly. If corneal pathology is detected early enough, a surgical procedure called a medial canthoplasty may be done. This procedure shortens the eyelid fissure and improves the ability to blink and distribute the tearfilm.

Entropion and Ectropion

Entropion (rolling in of the eyelids) and ectropion (rolling out of the eyelids) are conditions caused by abnormal eyelid position in relation to the globe itself. If the patient has heavy facial features they will probably have ectropion. If it causes exposure problems, ectropion needs correction. If the eye size is relatively small for the size of the orbit, entropion will result. Entropion will often cause abrasions of the cornea and/or irritation of the conjunctiva. This is very painful and will require surgery to correct. Most cases of entropion and ectropion are heritable in so far as the conformation of the head, size of the orbit, size of the globe, and eyelid conformation is heritable. Entropion or ectropion may also occur due to scarring from previous injury or surgery.

Excessive facial folds are seen in the neonatal and young Shar Pei and Chow Chow. This may result in a combination of entropion and trichiasis The most common treatment in young pups is the use of "temporary tacking sutures or staples" to hold the eyelids away from the cornea to prevent damage. If the entropion persists beyond six months of age, a more convention entropion surgery is used to effect permanent correction.

Acquired Conditions

Eyelid Tumours

Most eyelid tumours in dogs are Meibomian Gland Adenomas, the remainder are Papillomas, and some are Squamous Cell Carcinomas, Melanomas, Histiocytomas, Mast Cell and Basal Cell Tumours. In dogs approximately 80% of eyelid tumours are benign. It is recommended that any eyelid tumour which is removed by examined by a pathologist to ensure that it is not malignant. If it is malignant, the pathologist will carefully examine all the margins of the submitted tissue to ensure that all of the tumour was removed.

In cats, Squamous Cell Carcinoma and Melanoma are the more common eyelid tumours. The rate of malignancy for these tumours is much higher than in dogs.

Chalazion

Chalazia are firm, swollen masses that are well localized in the eyelid. They are caused by an impaction of the meibomian glands along the eyelid margin. The gland becomes distended with secretion, and in many cases the gland ruptures releasing the secretion to the surrounding eyelid tissue. This may result in a localized tissue reaction called a granuloma. Chalazion often occur adjacent to an eyelid tumour when the tumour is blocking the normal drainage of the meibomian gland. In some cases chalazia are lanced and curetted, while in others they are removed surgically and sent for pathology to rule-out the possibility of tumour.

Eyelid Lacerations

Eyelid lacerations are injuries that should be sutured as soon as the patient's stability permits. Meticulous suturing is needed so that the eyelid anatomy is restored, and that sutures do not touch or irritate the cornea.

Facial nerve palsy

Facial nerve palsy (paralysis of eyelids) is commonly seen in patients with chronic ear infections and is more common in American Cocker Spaniels. Because of the paralysis of the muscle that circles the eye, the eyelids cannot blink and the cornea will dry out due to an uneven spreading of the tears. This drying can lead to ulcers, infection and even globe rupture. Early recognition of this disorder along with frequent application of lubricants to the eye should prevent complications.

Blepharitis

Eyelid inflammation is known as blepharitis. This is often seen as enlargements of the glands of the eyelids that will appear as small abscesses on the inner surface of the eyelid. Gland contents may be expressed by the ophthalmologist and the contents cultured. Treatment will involve broad-spectrum antibiotics given by mouth, topically applied antibiotics and warm, moist compresses.