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Enucleation is a common ocular surgery performed by general practitioners. It is indicated for patients with a painful or nonvisual eye that is nonresponsive to medical therapy. Removing an eye may not only be therapeutic but may also serve as a diagnostic measure when intraocular neoplasia (primary or metastatic) or infectious, primary, or secondary glaucoma cannot be defined clinically.

Potential complications
The most common problem encountered with this surgery is an inability to accurately distinguish all secretory tissues and completely excise them, depending on the surgical approach chosen. The secretory tissues often left behind are the conjunctiva and the nictitating membrane. These tissues will continue to secrete, causing cyst formation. In our experience, this complication is most common when the transconjunctival technique is used.
The second most common complication encountered during surgery is exerting excessive force and traction on the globe before cutting the optic nerve, causing displacement of and traction on the optic chiasm, which can lead to permanent blindness in the remaining eye. This complication is more likely to occur when you are treating brachycephalic

Surgery approaches
There are two approaches for enucleation surgery: transconjunctival (also referred to as subconjunctival) and transpalpebral.

The transconjunctival approach involves an initial incision around the bulbar conjunctiva and has the advantages of reduced orbital tissue loss and subsequent orbital sinking with time, less hemorrhaging intraoperatively, and a faster procedure time. This approach should not be used in a patient with a suspected or known intraocular infection. It is important to identify and remove all conjunctival tissue and nictitating membrane with glands to avoid the postoperative complications mentioned above.

The transpalpebral approach is recommended for any indication when removing an eye. With this approach, an elliptical incision is made around the eyelids, and the globe and all secretory tissues (eyelids, conjunctiva, nictitating membrane) are removed within the conjunctival sac.

It is recommended that you learn one method and commit to performing that approach so you are comfortable trouble-shooting when unexpected intraoperative complications arise. Because the transpalpebral approach is the more versatile of the two, it is the recommended approach for performing enucleation surgery.

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Initial patient preparation and positioning
After induction and maintenance of general anesthesia, clip to the midline, taking care not to traumatize the delicate and thin skin around the eye. Trim the patient’s upper eyelashes by using fine scissors, but first apply ointment to the scissor blades to prevent the hair from falling onto the globe. Apply tape directly to the skin to remove fine short hairs.

Prepare the periocular skin, conjunctival fornix, and corneal surface by wiping with a 1:50 povidone-iodine solution. (Please note that this solution is not the scrub that is commonly used for aseptic surgical skin preparation.) Despite the fact the eye is being prepared for removal, it is recommended that you use a nondetergent-based iodine solution when preparing the eye to completely avoid the possibility of accidental application to the healthy eye and drainage into the remaining eye, which results in severe corneal damage if a detergent-based iodine is used.

Optimal head positioning is important and can be achieved with a patient positioning device (e.g. Olympic Vac-Pac—Natus Medical Inc., Hug-U-Vac—Hug-U-Vac Inc.) or towels. Place the patient in a semidorsal or lateral recumbency, and align the palpebral fissures parallel to the floor (Figure 1). This alignment may require flexing the patient’s head downward, which can compromise the endotracheal tube aperture. Reinforced endotracheal tubes are highly recommended with any ocular surgery to avoid anesthetic complications.

Figure 1

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Step 1

If the globe is infected, suture the eyelids closed. If the globe is not infected, you may skip this step. Any suture material can be used to close the eyelids. Start at one end of the eyelid fissure and suture in a simple continuous pattern, staying close to the eyelid margin or close to meibomian gland openings (Figure 2).

Figure 2

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Step 2

Using a No. 15 scalpel blade, make elliptical full-thickness incisions about 5 mm away from the eyelid margins, and join the incisions at the medial and lateral canthus (Figure 3A; different patient than in 3B and 3C).

Figure 3A

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Step 2 cont'd

Using Allis tissue forceps or towel clamps, grasp the incised eyelid margins (Figure 3B). Start blunt dissection by using curved Metzenbaum scissors, alternating sides until you approach the sclera.

Figure 3B

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Step 2 cont'd

If the conjunctiva is accidently cut and the cornea is visible, you can close the hole created with Allis tissue forceps and proceed with the dissection. Avoid the angularis oculi vein at the dorsomedial aspect of the orbital rim (Figure 3C). If hemorrhage occurs, ligate the vein immediately.

Figure 3C

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Step 3

As the blunt dissection deepens into the orbit, it is difficult to release the globe until the medial and lateral canthal ligaments are transected. To locate the medial broad ligament, run your finger along the medial aspect of the orbital rim while placing upward tension on the lids by using Allis tissue forceps. Direct a perpendicular No. 15 blade halfway between the eyelid incision and orbital rim and cut downward with slow, controlled tension (Figure 4A).

Figure 4A

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Step 3 cont'd

Repeat the same procedure above for the lateral canthal ligament which is less broad and easier to transect (Figure 4B).

Figure 4B

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Step 4

Identify the orbital rim (Figure 5A).

Figure 5A

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Step 4 cont'd

Using Metzenbaum scissors, create a plane of dissection to release the globe from the remaining tissues that are attaching it to the orbital rim (Figure 5B).

Traction on the extraocular muscles stimulates a vagal reflex. Do not use excessive force, twisting, or traction because these actions can damage the optic chiasm. Clamping or ligating the optic nerve and surrounding blood vessels (short and long posterior ciliary arteries) before dissection is optional and often unnecessary. Sever the optic nerve and posterior ciliary arteries by using curved Metzebaum scissors.

Submitting the globe for histologic examination is strongly encouraged not only as a diagnostic confirmation but also as a follow-up for further life-threatening systemic disease. After removing the globe, carefully dissect the periocular tissue from the sclera before placing it in fixative.

Figure 5B

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Step 5

Once the globe is removed, pack the orbit with gauze, and apply pressure for at least five minutes. If excessive bleeding is noted from a vessel, ligate the vessel. Minor capillary bleeding will achieve hemostasis once closure is started. Synthetic hemostasis products can be applied (Gelfoam—Pfizer, Surgicel—Ethicon) if you are unable to identify the source of bleeding.

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Step 6

Place a sterile silicone orbital prosthesis in the orbit. If not placing the optional prosthesis (i.e. leaving the scar tissue to fill the orbit), skip to step 7.

Silicone prostheses ranging from 22 to 24 mm fit most dogs. To flatten a portion of the spherical ball, cut the prosthesis, and then trim it to eliminate any sharp edges. This flattening will result in less tension on the incision line if the prosthesis is trimmed flush to the orbital rim. The risk of complications from the prosthesis is low (< 10%); however, if it occurs, a second surgery is necessary to remove the prosthesis. Prostheses are not recommended for patients that have a history or suspicion of neoplasia or infection.

Step 7

Close the orbit with a minimum of three layers. To minimize orbital depression, start along the periosteum of the anterior orbital rim with bites 3 to 4 mm apart in a taut simple continuous pattern using 3-0 or 4-0 monofilament polyglyconate synthetic absorbable suture to create a periosteal mesh. This mesh closure incorporates the tissue around the periorbital rim; you should be able to see the suture pattern spanning across the orbital rim and lift the head with this layer (Figure 6A; different patient than in 6B). Note that the tissue around the rim will not come together.

Figure 6A

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Step 7 cont'd

Suture the next two or three layers (subcutaneous and subcuticular) in a simple continuous pattern by using 3-0 absorbable braided or monofilament sutures. To decrease the risk of swelling and dehiscence, the tissue should come in contact without gaps, and the suture lines spanning across should not be visible.

A subcuticular or intradermal layer can be placed for better apposition and cosmesis (Figure 6B).

Place skin sutures by using 4-0 monofilament synthetic nonabsorbable sutures (nylon) in a cruciate or simple interrupted pattern.

Figure 6B

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Postoperative care
Place an ice pack on the surgical site until the patient wakes up or for no more than 10 to 15 minutes. Icing the site is typically not necessary throughout the postoperative recovery period.

If the globe or periocular skin was infected or an orbital silicone prosthesis was placed, an oral broad-spectrum antibiotic should be prescribed for 10 to 14 days.

For analgesia, an oral synthetic opioid (tramadol) or nonsteroidal anti-inflammatory drug is recommended for about two or three days, or longer if needed. Usually the first 24 to 48 hours after surgery is when patients exhibit the highest pain level. However, I frequently encounter patients that are more comfortable after surgery than before it because the source of pain has been removed. If the surgery and recovery were uneventful, the patient can be discharged the same day.

An Elizabethan collar is recommended if the patient is contacting the surgical site. Skin sutures should be removed in 10 to 14 days.

Acknowledgements
The authors wish to thank Kim Sherman, CVT.

REFERENCE
1. Stiles J, Buyukmihci NC, Hacker DV, et al. Blindness from damage to optic chiasm. J Am Vet Med Assoc 1993;202(8):1192.

SUGGESTED READING
1. Gelatt KN. Diseases and surgery of the canine orbit. In: Veterinary ophthalmology. 4th ed. Pg. 551-555 Baltimore, Md.: Blackwell Publishing, 2007;551-555.
2. Gelatt KN. Surgery of the orbit. In: Veterinary ophthalmic surgery. Philadelphia, Pa: Elsevier Saunders, 2011;60-67.