Entropion in the dog and cat

The term entropion means an anomalous position of an eyelid, characterized by inversion of its free margin. As a result of this defect, the hairs present near the margin of the lower eyelid or the eyelashes on the border of the upper eyelid come into contact with the conjunctiva and cornea initially causing irritation and then secondary complications (erosions and ulcers) (Fig. 1).

The defect may be unilateral or bilateral and may involve part (medial, lateral or centro-lateral) or the whole of the eyelid. Depending on the amount of eyelid involved and the angle of inversion, the abnormality can be classified as mild, moderate or severe. Entropion of the lower eyelid is more common than that of the upper eyelid and entropion is more frequent in dogs than in cats.

AETIOLOGY

It is thought that entropion has an underlying hereditary basis in numerous dog breeds although the mode of genetic transmission has not yet been well defined. According to some theories, there may be a polygenic background, although dominant transmission with incomplete penetrance or a recessive gene cannot be excluded. In these subjects the entropion may be congenital or may form during development (Table 1).

Table 1. Main breeds of dogs affected by entropion of the upper and/or lower eyelid.

Entropion may also be secondary to microphthalmus and phthisis bulbi because of the loss of corneal support of the eyelid. In some cases it may be iatrogenic as a result of incorrect surgery or secondary to trauma such as burns or contact with caustic substances including acids and alkalis. A so-called spastic entropion may develop in the case of strong ocular pain and consequent enophthalmus due to excessive contraction of the orbicularis oculi muscle in response to the pain stimulus. In cats entropion often follows scar retraction secondary to conjunctival herpetic lesions (Fig. 2).

SIGNS

The contact between eyelids, conjunctiva and cornea can cause blepharospasm, photophobia, pain and secondary enophthalmos associated with prolapse of the third eyelid; the severity of these conditions depends on the degree of malposition of the eyelids. The animal may rub the affected eye and cause itself further harm. In mild cases the only sign may be an increase in blinking. Usually the eyelid edge in contact with the ocular surface is damp and may show an accumulation of mucous or mucopurulent material. If only the conjunctiva is involved, the signs are hyperaemia and a serous, sero-mucous, or purulent ocular discharge if there is a bacterial superinfection. If the cornea is involved, there may be localised oedema and neovascularisation near the surface of contact; often there are superficial epithelial erosions or corneal ulcers which may become deep when there are secondary bacterial complications. Neovascularisation in chronic cases may have the characteristics of granulation tissue. In the stage of scarring the cornea may develop whitish opacities of variable degree depending on the severity of the lesions created (nubeculae, leukomas), or pigmentation.

In some breeds of dogs affected by what is commonly called euryblepharon or macroblepharon (enlargement of the palpebral fissure) there is often the contemporaneous presence of entropion and ectropion. This is very probably due to the coexistence of several predisposing factors including instability of the lateral canthus and excessive length of the palpebral fissure. This disorder typically occurs together with ectropion of the lower eyelid centrally and entropion of the upper and lower eyelids laterally.

DIAGNOSIS

The diagnosis of entropion is based mainly on the clinical appearance. In mild forms it is very important to assess the animal in a stimulus-free environment because if distracted the animal can open its eyelids wider thus tending to minimise the disturbances related to the defect. No restraint should be used, particularly at the level of the head, in order not to stretch the eyelids. Anatomical and spastic entropion can be differentiated with the help of a local application of an oxybuprocaine anaesthetic collyrium.

TREATMENT

The treatment of entropion is essentially surgery. Medical therapy, including local and systemic antibiotics, is prescribed in association with the surgery. Possible antibiotics for topical use are tobramycin, quinolones, tetracyclines, chloramphenicol and gentamicin; the products should be applied at least three or four times a day. Systemic treatments include the combination of amoxicillin and clavulanic acid (8.75-25 mg/kg every 8-12 hours, per os, subcutaneously or intramuscularly), doxycycline (10 mg/kg every 24 hours per os) and cephalosporins.

There are numerous surgical techniques for the management of entropion. The choice of which to use depends not only on the type and severity of the defect, but also on the preferences and experience of the surgeon. The main corrective techniques are described below, with a brief discussion on those most frequently used.

Temporary suture (“tacking” suture or “stay” suture)

A tacking suture (Fig. 3a and 3b) is used specifically in very young animals in order to avoid general anaesthesia and at the same time allow the most appropriate, definitive surgery to be performed once the animal’s growth has been completed. In some cases, a subsequent operation may not be necessary when the animal has reached maturity. This technique can also be used in adult subjects in order to evaluate the exact contribution of spastic entropion present in relation to anatomical entropion. The operation is performed by placing a series of simple “mattress” sutures perpendicular to the edge of the eyelid extremely close to the margin involved. It is recommended that a non-absorbable thread from 2/0 to 5/0 is used, depending on the size of the animal. Some authors have also suggested using metal staples instead of traditional surgical thread. After the operation the animal should wear an Elizabethan collar for a few days and an antibiotic eye ointment should be applied for several days.

Techniques for correcting infero-lateral palpebral entropion

• Hotz-Celsus technique

This technique consists in making a first incision parallel to the edge of the eyelid immediately next to the hairless rim (Fig. 4) and a second incision parallel to the first one at a distance considered sufficient to correct the anatomical defect. The incisions can be made with a N. 15 Bard-Parker_^® or N. 64 Beaver_^® scalpel blade. The cut to remove the skin and part of the underlying orbicularis oculi muscle is completed with curved tenotomy scissors. The wound is then sutured with simple interrupted stitches using 3/0 to 6/0 thread depending on the size of the animal. Usually the first stitch is put at the centre of the incision with subsequent stitches placed in such a way as to halve the remaining defect each time. The suture thread may be absorbable or non-absorbable depending on the choice and preference of the surgeon. Post-operative management includes the use of an Elizabethan collar, systemic administration of antibiotics (amoxicillin and clavulanic acid) for about 5-7 days and topical application of antibiotic ointments (tobramycin, tetracycline) three to four times a day for 7-10 days. If considered necessary for anti-inflammatory and analgesic purposes, non-steroidal anti-inflammatory drugs can be used (carprofen 4 mg/kg/die intravenously or subcutaneously). When non-absorbable sutures are used, these must be removed after about 7-10 days.

• “Wedge” resection associated or not with the Hotz-Celsus procedure

This technique, suitable for cases of mild entropion,  involves the removal of the whole thickness of a wedge of eyelid near to the lateral canthus (Fig. 5). The cut must be made with a scalpel aided with a Jager spatula, or with simple tenotomy scissors. The eyelid defect is closed with two overlying layers: the conjunctiva is sutured with a running stitch with absorbable 6/0-7/0 thread, while a “figure-of-eight” stitch is used to realign the eyelid margin; the skin suture is completed with simple interrupted stitches with 3/0-6/0 absorbable or non-absorbable thread according to the size of the animal. As described for the Hotz-Celsus procedure, also in this case topical and systemic antibiotic therapy is used. In some animals, the wedge resection can be combined with a Hotz-Celsus procedure at the central part of the eyelid to be corrected.

• “ Y ” to “ V ” plasty

This procedure involves an initial "Y "incision of the palpebral skin and underlying orbicularis oculi muscle. The oblique arms of the "Y" must start about 2 mm from the margin of the eyelid, while the length of the vertical arm is proportional to the entity of the defect to correct. Subsequently a triangle of skin and orbicularis oris muscle is dissected from the underlying tarsal plate with tenotomy scissors. The first stitch joins the apex of the triangular section to the most distal point of the vertical arm of the “Y” in order to transform the "Y" into a "V" thus inverting and correcting the eyelid margin. The rest of the surgical wound is sutured with simple interrupted stitches. The type of thread and the post-operative management are the same as those for the above-described surgical procedures.

Techniques for correcting infero-medial palpebral entropion

• Classical Hotz-Celsus technique
• Modified Hotz-Celsus technique
• Medial canthoplasty

Techniques for correcting lateral palpebral entropion

• Classical Hotz-Celsus technique
• Modified arrowhead Hotz-Celsus technique

This technique is used to stretch the lateral canthus and the lateral parts of the upper and lower eyelids. The procedure involves asportation of a section of skin the shape of an arrowhead from the lateral part of the eyelid; the skin section is removed using blunt scissors after the incision has been made with a N. 64 Beaver_^® scalpel blade (Fig. 6). The amount of tissue removed is proportional to the defect to be corrected. The surgical wound is then sutured with simple interrupted stitches. The type of thread and the post-operative management are the same as those for the above-described surgical procedures.

• Wyman’s lateral canthoplasty

In the first stage of this procedure, a lozenge- or “Y”-shaped area of skin of 3-5 mm is removed from the lateral canthus with the two arms of the “Y” extending slightly superiorly and inferiorly  for about 5-10 mm. Two thin pedicles of orbicularis oculi muscle are then created, leaving their bases anchored to the lateral canthus. The two pedicles are sutured with 4/0-5/0 non-absorbable thread to the periosteum of the zygomatic arch with the purpose of exerting traction on the lateral canthus. The surgical wound is then sutured with simple interrupted stitches.

• Robertson’s tendonectomy‏

This technique is used particularly in giant breeds with the aim of releasing, through resection of the lateral canthus tendon, the tension exerted by this anatomical structure on the external part of the eyelid. Through decreased mobility of the lateral commissure, the tendon makes the margin of the most external part of the eyelid more likely to undergo inversion, thus causing repeated corneal erosions, blepharospasm and enophthalmos. The access route requires dissection of the palpebral conjunctiva from the tarsal plate at the level of the lateral canthus using tenotomy scissors and incision of the tendon that joins the lateral canthus to the zygomatic arch.

• The Gutbrod and Tietz procedure

Techniques for correcting euryblepharon (macroblepharon):  entropion + ectropion

• Wyman’s lateral canthoplasty
  • Permanent lateral tarsorraphy
    • Bigelbach technique
    • Stades technique
    • Bedford technique
    • Grussendorf technique
  • “Wedge” resection

COMPLICATIONS OF SURGICAL CORRECTION OF ENTROPION

The possible complications of surgery for entropion include infection of the wound with consequent dehiscence of the stitches, stitches pulled out by the animal or lost because of incorrect choice of the diameter of the thread used, over- or under-correction of the defect, the development of excessive scarring (keloid) and contact of the stitches with the corneal and conjunctival surfaces.

Suggested readings

1. Gelatt KN e Gelatt JP: Surgery of the eyelids. In Gelatt KN e Gelatt JP (eds) Handbook of Small Animal Ophthalmic Surgery. Vol 1: Extraocular procedures. Tarrytown, Elsevier Science Hamsterdam 1994, 69-124.
2. Gelatt KN: Veterinary Ophthalmology, 4^rd ed. Blackwell publishing vol 2 2007,574-583.
3. Hamilton HL, Whitley RD et al: Basic Blepharoplasty techniques. Comp Cont Educ Pract Vet 1999; 21: 946-952.
4. Lackner PA: Techniques for surgical correction of adnexal disease. Clinical techniques in Small Anim Pract, 2001; (16)1:40-50.
5. Leanarduzzi R: Management of eyelid problems in Chinese Shar-pei puppies. Vet Med Small Anim Clin 1983; 78:548.
6. Wyman M: Ophthalmic surgery for the practitioner. Vet Clin North Am Small Anim Pract