Conditions of the eyelids are seen commonly in veterinary practice and are important since in many cases they can be treated surgically without the necessity of referral to a specialist centre. It is important to understand the anatomy of the lids before discussing techniques for ameliorating problems of lid conformation. Also it must be realised that many of these problems are inherent in the breed standards of several breeds such as the Bloodhound or predisposed to by the characteristic features of the dog such as skin folds in the Shar-Pei.
The eyelids are folds of tissue lined by skin anteriorly and palpebral conjunctiva posteriorly. The various glands include those of Zeiss and Moll on the outer eyelid surface producing aqueous and sebaceous secretions respectively and associated with the eyelashes. The Meibomian glands open along the eyelid margin and produce the lipid component of the tear film.
The structure of the eyelid is based on a tarsal plate of cartilage with muscles consisting of the orbicularis oculi contraction of which results in eyelid closure, the levator palpebrarum superioris which, as its name suggests lifts the upper eyelid and is innervated by the trigeminal nerve, specifically a sympathetic supply, this accounting for the ptosis (upper eyelid drooping) in Horner's syndrome. The eyelids play an important role in protection of the globe and also in the distribution and drainage of the tear film over the ocular surface.
In-turning of the eyelid may occur after eyelid injury but is most commonly seen as an inherited problem particularly in breeds such as Flat Coated and other retrievers, Cocker Spaniels.
Hotz-Celsus surgery is required to remove an oval of skin to out-turn the eyelid, closing the defect with 6/0 vicryl. The critical thing is to make the incision at the eyelid margin close to the eyelid edge (2–3 mm).
Estimate the amount of skin to be removed by pinching the skin up to out-turn the eyelid in the unsedated dog. A key feature of any surgery is to draw the eyelid conformation before sedation with an estimate of the amount of skin needing to be removed rather than just to guess the amount. Estimating the degree of anatomical entropion as differentiated from spastic entropion caused by corneal irritation can be facilitated by using topical anaesthetic.
Entropion may be caused by too long an eyelid margin. Here a full thickness wedge resection may be required.
Chows and Shar-Pei puppies have entropion associated with excess eyelid skin. Entropion may correct itself as the skull grows. The lids should be everted with temporary vertical mattress sutures rather than permanent surgery early in life.
Cocker Spaniels can develop a drooping of the upper eyelid with in-turning and trichiasis involving abrasion of the eyelashes on the cornea. This can best be remedied with the Stades procedure which removes the lashes and adjacent skin without suturing the defect completely closed.
Out-turning of the lid margin, generally caused by too long a lower lid margin.
While not generally causing the same problems that entropion does, ectropion can look disfiguring and may, if severe, result in exposure keratitis.
A wedge resection of excess lid cures the problem of simple ectropion. The Khunt-Szymanowski procedure, involving lid splitting can also be used.
Cicatricial ectropion is caused when scar tissue pulls the lid outwards. This is more difficult to remedy than familial ectropion but using the Wharton-Jones blepharoplasty a V-Y tissue-releasing incision, such lid defects can be cured.
Diamond Eye and associated combined defects
Diamond eye is part of the Bloodhound, Clumber Spaniel and St. Bernard breed standards. Here ectropion is combined with entropion of the sloping lid edges.
Complicated techniques to suture flaps of orbicularis oculi muscle (the Wyman lateral canthoplasty) or major periocular skin flap replacement may be used.
Often a combination of V-resection and Hotz-Celsus surgery can remedy the defects.
Again these ocular abnormalities are part of the breed standard in several breeds. Remedying the ocular problem while keeping the animal looking optimal for its breed can be difficult!
Problems Associated with Lid Hairs
The three problems associated with hairs causing irritation and sometimes overt corneal damage are distichiasis, ectopic cilia and trichiasis. Successful treatment of these depends on defining which of them is the true problem.
Distichia arise from the Meibomian gland orifices along the edge of the lid. Distichia occur commonly in breeds such as Pekinese, Cocker Spaniels, Bulldogs and miniature longhaired Dachshunds. Watch that these really are the cause of apparent ocular irritation. If they are seen in a young animal with irritation they probably are the reason for the noxious signs. But if an older animal develops ocular irritation and has fine distichia these hairs are probably not the sole cause of the irritation - the dog will have had them for years without any problems so look for another cause of the pain. Distichia can be removed by:
Epilation using simple plucking with a pair of distichiasis forceps.
Electrolysis using a thermocautery or electrocautery device.
Cryosurgical or sharp knife ablation of hair roots in the Meibomian glands.
The technique which should never be attempted is removal of the hairs by sharp knife surgery of the lid margin itself. This almost inevitably produces lid scarring and subsequent corneal pathology.
Ectopic cilia arise from true follicles in the conjunctiva normally of the eyelid but potentially from any site. Ectopics are particularly seen in specific breeds such as Flat Coated Retrievers and Pekinese. They require sharp knife removal of the entire follicle. The critical thing is to tell the owners that new ectopics may well grow. If you don't do this they will think that the recurrence they see is because of your poor surgical technique!
Trichiasis is hairs originating from a normal site but abnormally placed to impinge on the corneal surface. These may be from a nasal fold in a Pekinese, an upper lid droop in an ageing cocker spaniel or ingrowing medial canthal hairs in any brachycephalic dog.
The remedy for each of these will be different. Removal of the nasal folds works well although does tend to change the appearance of the dog somewhat. The upper eyelid droop often seen in Cocker Spaniels is best treated with the Stades procedure. Medial canthal hairs can be removed by sharp knife excision.