Inferior Lacrimal Gland Removal From Rabbit Model: A Surgical Procedure to Remove the Larger Inferior Tear Gland From Rabbit Eye Orbit

Overview

In this video, we describe a surgical procedure to remove the large inferior lacrimal gland from a rabbit model to study the effect on tear production in the animal. 

Protocol

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

1. Resect the ILG

1. Allow at least 5 min for the local anesthetic to take effect in the rabbit.
2. Incise the skin, the depressor muscle of the inferior palpebra, the zygomaticolabial part of the zygomatic muscle, and orbicularis muscle with the Colorado microdissection needle and make the skin incisions along the surgical markings. Settings can vary based on clinical response and typically are between 10 to 15 units for both cut and coagulation.
3. Maintain hemostasis with the monopolar cautery.
4. As the incision is carried deeper through the skin marking, look for the sheen of a fascial plane over the zygomatic bone or superficial part of the masseter muscle. At this point, maintain the tissue plane and carry it superiorly toward the orbital rim using the Colorado needle for cutting (Figure 1A).
   NOTE: For the purpose of identifying the ILG, it is easiest to perform this part of the dissection over the head of the ILG which is typically inferior to the anterior limbus of the eye.
5. After identifying and incising the capsule surrounding the ILG, identify the tan tissue of the ILG. Only the anterior portion of the ILG head will be visible (Figure 1B). However, the head can be followed medially as it passes beneath the zygomatic arch and transitions into the tail (Figure 1C).
6. Use tenotomy scissors to cut the orbital septum along the inferior rim exposing the more posterior portion of the ILG tail. Once the tissue plane is identified, extend the dissection posteriorly along the entire incision line (Figure 1D).
   NOTE: The duct of the ILG passes through the lower fibrous connective tissues to enter the inferior conjunctival space in the temporal aspect of the lid. At the posterior rim, the tail of the ILG can have varying anatomic configurations. Sometimes it terminates inferior to the posterior (lateral) canthus, while in other dissections it extends more superiorly around the temporal orbit.
7. Use extreme care to prevent inadvertent damage to the blood supply, which the ILG receives from branches of the carotid artery. The blood supply can be seen during this part of the dissection (Figure 1E).
8. In cases where the tail terminates under the posterior (lateral) canthus, it may be necessary to bisect the temporal portion of the frontoscutular muscle to expose the tail of the ILG, which lies along the zygomatic bone.
9. After the entire ILG has been isolated and exposed, remove it. Due to its large size, it is often preferable to cut the gland in half with scissors and remove the head separately from the tail.
10. Proceed very cautiously when removing the head of the ILG as it lies immediately adjacent to a large venous sinus in the orbit. Although bleeding from this structure during surgical resections has not occurred, have ample hemostatic aids present to mitigate this risk.
11. After removal of all gland tissue, close the deep connective tissue plane with multiple interrupted 5-0 ethylene terephthalate sutures. Close the superficial muscles and skin with a running 6-0 polyglactin 910 suture (Figure 1F) using 0.3 tissue forceps and a needle driver.

Representative Results

Figure 1: Removal of the ILG. (A) The skin and superficial muscle are incised until the fascial plane overlying the zygomatic bone or superficial part of the masseter muscle is reached. The head of the ILG usually is clearly evident as a small bulge located under the anterior limbus. (B) The fibrous capsule of the ILG is incised with scissors exposing the ILG. Once the capsule is incised, the deeper portions of the gland can be easily removed. (C) The most external portion of the ILG head that lies on the zygomatic bone has been exposed and reflected anteriorly showing the underlying zygomatic bone. (D) Incision of the orbital septum along the inferior rim exposes the tail of the ILG. (E) A branch of the external carotid artery feeds the tail of the ILG (arrow). (F) Appearance following the closure of skin incisions after complete dacryoadenectomy.

Materials

Name	Company	Catalog Number	Comments
Acepromazine, Aceproinj	Henry Schein Animal Health, Dublin, OH	NDC11695-0079-8	0.1ml/kg subcutaneously injection for rabbit sedation
Anesthesia vaporizer	VetEquip, Pleasanton, CA	Item # 911103
Animal restraining bag	Henry Schein Animal Health, Dublin, OH	Jorvet J0170	Use appropriately sized bag
Cautery unit, high-temperature, battery-powered	Medline Industries Inc, Northfield, IL	REF ESCT001	Keep on hand in case of bleeding
Clipper, Wahl Mini Arco	Henry Schein Animal Health, Dublin, OH	No. 022573	Cordless shears for fur removal
Colorado needle	Stryker Craniomaxillofacial, Kalamazoo, MI	N103A	Use with electrosurgical unit to make incisions
Electrosurgical unit with monopolar cautery plate	Valleylab, Boulder, CO	Force FXc	Use with electrosurgical unit to make incisions
Forceps, curved dressing	Bausch and Lomb (Storz), Bridgewater, NJ	Storz E1406	delicate serrated dressing forceps
Forceps, 0.3	Bausch and Lomb (Storz), Bridgewater, NJ	ET6319	For removal of nictating membrane
Forceps, Bishop Harmon	Bausch and Lomb (Storz), Bridgewater, NJ	E1500-C	Use toothed forceps for dacryoadenectomy
Hair remover lotion, Nair	Widely available	Softening Baby oil	Dipilitory cream for sensitive skin
Isoflurane	Henry Schein Animal Health, Dublin, OH	29405	Possible alternative sedation
Laryngeal mask airway	Docsinnovent Ltd, London, UK	Vgel R3
Lid speculum, wire	Bausch and Lomb (Storz), Bridgewater, NJ	Barraquer SUH01	For removal of nictating membrane
Scissors, Vannas	McKesson Medical-Surgical, San Francisco, CA	Miltex 2-130	Capsulotomy scissors for dacryoadenectomy
Sedation gas mask	DRE Veterinary, Louisville, KY	#1381	Possible alternative sedation
Surgical marking pen	Medical Action Industries, Arden, ND	REF 115
Sutures, 5-0 Mersilene	Ethicon US, LLC		Ethylene terephthalate sutures, used for deep connective tissue closure
Rabbit, New Zealand White	Charles River Labs, Waltham, MA (NZW)	2-3 kg	Research animals
Sutures, Vicryl 6-0	Ethicon US, LLC		Polyglactin 910 sutures, used for superficial muscle and skin closure
Syringe, 1 cc	BD, Franklin Lakes, NJ	Ref 309659	For injection of lidocaine/ epinephrine
Tissue forceps, 0.8mm Graefe	Roboz Surgical Store, Gaithersburg, MD	RS-5150	Curved Weck forceps