is not possible due to the hard texture of the lens nucleus so partial phacoemulsification is followed by enlargement of the corneal incision and extraction of the lens nucleus (Adamovicz et al. 2015). However, in the case of a sturgeon infected by intraocular digenean trematodes, complete phacoemulsification of the lens has been reported (Bakal et al. 2005). These trematodes can cause cataracts causing inflammation that can lead to softening of the lens (Adamovicz et al. 2015).
Enucleation
Enucleation is performed to alleviate pain associated with nonresolvable ocular lesions (Figure 5.13) (da Silva et al. 2010; Lair et al. 2014) or severe injury. A prosthetic eye can be placed (Nadelstein et al. 1997), but keeping the prosthesis in place long‐term may be problematic (Harms and Wildgoose 2001).
After performing a local block with lidocaine, dissect and transect periorbital tissue, conjunctiva and oculomotor muscles off the globe with fine curved scissors. Branches of the trigeminal and facial nerves running along the caudolateral border of the orbit should not be transected (Wildgoose 2007b). If a hemostat is placed on the retro‐orbital pedicle, minimize traction on the optic nerve to prevent damage to the optic chiasm, which will result in blindness in the contralateral eye. Transect the pedicle, remove the globe, and ligate the retro‐orbital vessels. Supplement hemostasis by applying digital pressure and a hemostatic agent (Gelfoam®, Pfizer, New York, NY). Suturing the periorbital tissue, with an H‐plasty if needed, enables one to close the orbit for esthetical purposes in some fish species such as cod (Gadus morhua) and saithe (Pollachius virens) (Figure 5.14). In fish where this is not possible, leave the orbit open to heal (Figure 5.15) and expect mild hemorrhagic discharge after recovery. Some authors recommended placing a waterproof paste containing pectin, gelatin, and methylcellulose (Orabase®, ConvaTec, Bridgewater Township, NJ) into the orbit over the next 24–72 hours (Harms and Wildgoose 2001).
Figure 5.13 Enucleation of a rockfish (Sebastes caurinus) with a retinal tumor.
Source: Photo courtesy: Aquarium du Québec.
Figure 5.14 Suture of the periorbital tissue after an enucleation in a saithe (Pollachius virens).
Source: Photo courtesy: Aquarium du Québec.
Figure 5.15 Enucleation of a sea horse (Hippocampus erectus) with a retro‐orbital abscess. The tube on the right of the image is used for anesthesia maintenance and Harmon–Bishop's forceps were used to elevate the globe from the orbit and allow section of the optic nerve and retro‐orbital pedicle. In this species, it is not possible to close the orbit after enucleation due to the dermal plates greatly reducing the elasticity of the skin.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Coelomic Surgery
The coelomic cavity may be approached ventrally or laterally. For a ventral approach, make either an incision caudal to the pelvic fins just cranial to the vent (Figure 5.16) or an incision from the pectoral to the pelvic fins. If wider access to the coelom is needed, section the pelvic girdle on midline. The pelvic bones are joined on midline by a fibrous junction in some younger fish which becomes ossified in older specimens (Harms and Wildgoose 2001). During the approach, take care to avoid damaging the digestive tract, especially if a coelomic mass is displacing the intestine near the ventral body wall (Weisse et al. 2002; Weber 2011b). Perform a lateral approach or an L‐shaped incision in the coelom to access dorsal organs such as the kidneys or the swim bladder (Harms and Wildgoose 2001). Make the craniocaudal incision just ventral to the lateral line of the fish, extending from the caudal edge of the pectoral fin to the level of the anus. Make the dorsoventral incision at the level of the anus and extend as needed for exposure; do not incise too close to the sphincter of the anus.
Coelomic adhesions are common in some species of fish including koi and are not necessarily an indication of coelomitis (Wildgoose 2000; Boone et al. 2008; Grosset et al. 2015). During the celiotomy, take care to limit traction on the coelomic wall as trauma to this delicate tissue can result in postoperative necrosis of the body wall. An assistant may gently retract the coelomic wall using a Farabeuf or Roux retractor or a self‐retaining retractor such as Heiss, Lone Star, or Gelpi retractors, or a Barraquer eyelid speculum may be used depending on the size of the fish (Harms and Wildgoose 2001).
Figure 5.16 Incision of the coelom between the pelvic fins and the digestive orifice in an anesthetized goldfish (Carassius auratus). A Lone Star retractor is placed on the coelomic cavity to facilitate visualization.
Source: Photo courtesy: Zoological Medicine Service, Université de Montréal.
Close the coelomic wall in two layers: muscle and skin (Harms and Wildgoose 2001). During closure, take care to close the pelvic girdle in accurate apposition if it has been sectioned. A subcuticular pattern rather than cutaneous suture is recommended in goldfish, as this induces less local reaction than simple interrupted sutures or interrupted horizontal mattress sutures (Nematollahi et al. 2010). Ideally, leave no additional air in the coelom during closure to avoid buoyancy problems. Also, consider the weight of suture materials and any prosthetics or surgical devices in very small patients (Britt et al. 2002).
Do not remove sutures before four weeks (Shin et al. 2011). Sutures may be removed after four to eight weeks in temperate species (Sladky and Clarke 2016). Months may be necessary for adequate healing before suture removal in cold‐water species. Carefully examine the wound margins to assess skin continuity prior to suture removal.
Swim Bladder Surgery
The swim bladder is important in maintaining neutral buoyancy. Abnormal buoyancy is a common presentation of ornamental fish (Wildgoose 2007a) with a number of etiologies that can be diagnosed using radiography or other imaging techniques. Positive buoyancy may be due to overinflating of the swim bladder (Figure
