Surgical Treatment of Acute Lens Rupture by Phacoemulsification in a Patas Monkey (Erythrocebus patas)
A 22-year-old female captive Patas monkey (Erythrocebus patas) (6.08 kg) presented with an acute onset of unilateral, left-sided, bluish ocular lens discoloration. After 6 days of observation, the clinical signs progressed into a hypermature cataract, vomiting, ocular discomfort and abnormal head movement. The monkey would place the left side of its face against the wall or floor and apply pressure onto it by tipping its body forward.
The monkey was anesthetized with a ketamine (KetaVed, Phoenix Scientific Inc., St. Joseph, MO, USA) medetomidine (Domitor, Pfizer Animal Health, Exton, PA, USA) combination and maintained on isoflurane (IsoSol, Vedco Inc., St. Joseph, MO, USA, 2–3%). The monkey was diagnosed with spontaneous equatorial lens rupture of the left eye. Diagnostic techniques included measuring the intraocular pressure with a Tono-Pen tonometer and dilating the pupil to observe the lens with a slit lamp and a binocular indirect ophthalmoscope. Due to expulsion of lens protein, the left eye developed secondary cataract, glaucoma, and uveitis. The monkey’s right ocular lens contained a few small, microscopic opaque lesions, but these were insignificant findings. Temporary relief was given by applying dorzolamide hydrochloride (Trusopt, Merck Sharp & Dohme, Whitehouse Station, NJ, USA; 2% solution, 1–2 drops into left eye, BID).
The following day the monkey was treated with a standard phacoemulsification procedure,1 as blood samples and radiographs were negative for other systemic disorders. The lens capsule was left in place, as it would not decrease vision. The monkey was given meloxicam (Metacam, Boehringer & Ingelheim, St. Joseph, MO, USA; 0.1 mg/kg PO, SID) injected into grapes for 2 days for presurgical pain removal. During anesthesia, the monkey was given lactated Ringer’s solution (Lactated Ringer, Hospira Inc., Lake Forest, IL, USA) and ampicillin (Ampicillin, American Pharmaceutical Partners Inc., Schaumburg, IL, USA; 19.9 mg/kg IV, SID), as a tracheal lesion was made by the endotracheal tube. As the monkey is not trained to receive injections, the monkey was continued on topical neomycin polymyxin B sulphate (Bausch & Lomb Incorporation, Tampa, FL, USA; 2 drops topically, BID), and amoxicillin trihydrate (Amoxicillin, Ranbaxy Pharmaceuticals Inc., Jacksonville, FL, USA; 11 mg/kg, PO, BID). Both were given for 7 days. The monkey stayed 4 weeks in postoperative solitary confinement to prevent traumatization of the eye and ocular wound. As previous signs of discomfort disappeared, the meloxicam treatment (which had begun 2 days before surgery) was discontinued on day 22 post surgery. Treatment considerations included age (geriatric monkey), recovery time, and additional postoperative treatment. Enucleation was not chosen, as it would not have allowed her to regain her left eye’s function, thereby decreasing the monkey’s comfort level within its group. Future complications include intractable glaucoma and retinal detachment.
The author would like to thank the Simonyi Foundation for his scholarship at Woodland Park Zoo, Dr. Tom Sullivan for his support of Woodland Park Zoo, and Dr. Darin Collins and Kelly Helmick for knowledge and guidance on the subject matter.
1. Gelatt, K.N. 1991. Veterinary Ophthalmology. Lea & Febiger, Philadelphia, PA.