Abstract

A captive-born 34-year-old multiparous female western lowland gorilla (Gorilla gorilla gorilla) was diagnosed with retinal detachment and mature cataract development of the right eye in September 1997, presumably caused by previous trauma and secondary intraocular inflammation. The gorilla had exhibited behaviors indicating impaired vision for several years including holding food items close to her “good” eye for inspection before eating, and bending over to place her face close to the ground to forage for food. The left eye had no visible pathology until September 2003 when a central cataract was noted to be developing, and her vision appeared to be getting worse.

Following a complete physical and ophthalmic exam, surgical intervention to restore vision to her left eye was performed in October 2004. Biometric measurements of the fundus revealed a severely myopic left eye with an axial length measurement of 30 mm. The retina was intact and appeared normal (ultrasound evaluation) and the cataract was not completely mature. The cataract was removed using phacoemulsification and aspiration via a standard approach used in human medicine. A foldable intraocular lens implant (4.0 diopter, MA6OMA, AcrySof, Alcon Laboratories, Inc.) was inserted, and the lens capsule and limbal incisions were closed with 9-0 absorbable suture. Postoperative treatment included subconjunctival antibiotics and steroids, as well as prophylactic oral antibiotics and nonsteroidal anti-inflammatory medication. Recovery was uneventful, and marked vision improvement was evident within 24 hours. No postoperative complications were observed, and the gorilla was integrated back into its family group within 10 days, with noticeable improvement in social interactions and foraging behaviors.

Three months after the surgical procedure, keepers noted an abrupt change in the gorilla’s behavior and vision. She moved very slowly and cautiously, feeling around blindly for food items on the ground, not responding to visual training cues, and again, putting her face to the floor to try to see or find food items. A presumptive diagnosis of detached retina was made, and an exam was performed within 3 days. Fundic exam revealed a significantly detached retina of the left eye, involving the macula region, which is important for fine detail vision. No other pathology was evident, and the intraocular lens implant was still in place. Repair of the retinal detachment was performed 4 days later (7 days after the acute blindness) was noted. The procedure consisted of a vitrectomy, followed by an injection of 8 ml silicone oil into the posterior chamber after repositioning the retina. The retina was then tacked into place using pan-retinal spot laser treatments. Postoperative treatment included cage rest for 3 weeks, and oral antibiotics and nonsteroidal anti-inflammatory medication. The retina was rechecked under general anesthesia 17 days after the repair procedure was performed and was found to be intact and healing well. Additional spot laser treatments were done as a precaution at that time. These procedures have successfully restored the vision of this animal, which continues to improve as evidenced by better social interactions and foraging abilities.

Several publications exist on the topic of cataract surgery.^1-4 Further reading on this topic is encouraged.

Acknowledgments

Many thanks to the team of specialists who provided technical and surgical assistance to this animal, improving her quality of life, including Dr. Kathleen Karol, Dr. Greg Rosenthal and staff, Jim Ensminger, Rob Heornschemeyer, and many others.

Literature Cited

1.  De Faber, J.T.H.N. 2004. Cataract surgery with foldable intraocular lens implants in captive lowland gorillas (Gorilla gorilla gorilla). J. Zoo Wildl. Med. 35: 520–524.

2.  Dow, S., J. Sherwin, A. Gray, and S. Redrobe. 2003. Behavioral changes following remedial cataract surgery in a gorilla. Proc. Annu. Conf. Univ. Fed. Anim. Welfare.

3.  Pena,T., M. Badia, J. Fernandez, and M. Leiua. 2002. Cataract surgery considerations in a gorilla (abstr.). Vet. Ophthamol. 5: 285–286.

4.  Scott, I.U., H.W. Flynn, M. Lai, S. Chang, and S.P. Azen. 2002. First operation anatomic success and other predictors of postoperative vision after complex retinal detachment repair with vitrectomy and silicone oil tamponade. Am. J. Ophthamol. 130: 745–750.