A 16-yr-old intact male, captive-born Black Water Monitor, Varanus salvator macromaculatus, was presented for evaluation of bilateral lens opacities. Examination showed bilateral cataracts, with blepharospasm, uveitis, and absence of vision in the left eye. Phacoemulsification was successfully performed on the left eye, and at six weeks postoperative, the animal was found to be visual in that eye and had complete healing of the surgical site. The right eye had phacoemulsification performed seven months later with similar results. The monitor made a full recovery and continues to have normal ocular examinations.

The black water monitor (Varanus salvator komaini) was first described in 1987 as a separate water monitor subspecies, with a range that included the small islands and areas near the coastline of southwestern Thailand. It is distinguished from its closest relative, Varanus salvator, by its shorter adult length, black coloration throughout the body (no spots or bands), and a grayish-purple tongue (Nutphand, 1987). The status of black water monitor has been contested by several authorities, with some considering this species to be a color morph of Varanus salvator salvator (Gaulke and Horn, 2004). In the most recent taxonomic revision, black water monitor was no longer considered to be a distinct subspecies and was instead synonymized with Varanus salvator macromaculatus (Koch et al., 2007). This species has seldom been maintained in zoological or private collections, and details on successful captive reproduction have only been published by Dwyer and Perez (2007). Although not commonly found in captivity, husbandry, nutrition, and diseases described in most other varanids are applicable to black water monitors.

A 16-yr-old intact male, captive-bred black water monitor was referred to the MedVet Medical and Cancer Centers for Pets (Worthington, OH) for evaluation of cloudy eyes. The monitor was housed alone at the Columbus Zoo and Aquarium (Powell, OH) in a 457-cm (179.9-in.) × 160-cm (63.0-in.) × 244-cm (96.0-in.) enclosure with a 70–80% relative humidity gradient, ambient temperature gradient of 27.2–31.7°C (81–89°F), and basking temperature of 31.7°C (89°F). The floor of the enclosure was heated and contained a pool measuring 122 cm (48 in.) × 152 cm (59.8 in.) × 20 cm (7.9 in.). Four light sources were mounted 244 cm (96.0 in.) above the exhibit floor and used ultraviolet B (UVB) bulbs (Mega-Ray®, Hubert, NC) to provide light 12 h per day. In addition to the radiant floor heat, two heat lamps (250 watt infrared, Sylvannia, St. Mary's, PA) were mounted 244 cm (96.0 in.) above the exhibit floor and provided heat for 24 h per day.

Caretakers had noted slow, progressive cloudiness to both eyes (OU) over a six month period of time, and at times questioned the monitor's vision because he no longer tracked food that was offered and appeared to be startled by items placed near him. Physical examination was unremarkable with the exception of the bilateral ocular opacities; otherwise, the monitor was in good physical condition. A complete blood count (CBC) and plasma biochemical analysis were performed and the results were within the reported reference range for varanid species. A gross ocular examination revealed mild blepharospasm of the left eye (OS). The adnexal structures were normal OU. The patient appeared blind OS with absent tracking, although ocular motility was normal. Ocular examination with a slit lamp biomicroscope (SL-15 portable Slit-lamp Biomicroscope, Kowa Col, Ltd., Tokyo, Japan) showed diffuse 1+ (scale of 1–4 with 4 being most severe) corneal edema, 2+ aqueous flare, and a shallow anterior chamber OS. An immature cataract was observed in the right eye (OD), and a mature, intumescent cataract was observed OS (Fig. 1). Lenticular opacities prevented clear visualization of the posterior segments OU (Keeler All Pupil, Keeler Ltd., Windsor, Canada). A diagnosis of cataracts OU was made with secondary phacolytic uveitis OS. The monitor was treated with 4.0 mg/kg carprofen (Novox 100mg/tab, IMPAX Laboratories Inc., Hayward, CA) orally (PO) q 24 h for 14 days and Neomycin/Polymyxin B/Dexamethasone ophthalmic suspension (Bausch and Lomb, Inc., Tampa, FL) topically OS q 6 h for 14 days. Given the ocular examination findings, phacoemulsification was recommended OU. It was also recommended to perform the surgeries at different times to assess the response to the first eye before proceeding with the second. An ocular ultrasound with a 20 mHz probe was performed preoperatively (E-technologies, Inc., Bettendorf, IA), and no posterior segment abnormalities were noted.

Figure 1.

Mature cataract in the left eye. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Figure 1.

Mature cataract in the left eye. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Close modal

The monitor was transported to the surgical center, and moderate sedation was achieved with 0.05 mg/kg hydromorphone hydrochloride (Hydromorphone, 2.0 mg/ml; Baxter Healthcare Corporation, Deerfield, IL) and 0.2 mg/kg midazolam hydrochloride (Midazolam, 5 mg/ml, Bedford Laboratories, Bedford, OH) administered intramuscularly (IM) as a single injection. Thirty minutes after administering the sedatives, an intravenous (IV) catheter was placed in the ventral coccygeal vein to provide direct vascular access for fluid and drug administration. Anesthetic induction was achieved with 8 mg/kg propofol IV (PropoFlo, 10 mg/ml, Abbott Laboratories, North Chicago, IL). The patient was intubated, and anesthesia was maintained on isoflurane (IsoSol, Vedco Inc., St. Joseph, MO) to effect; 0.9% NaCl (Braun Medical, Inc., Irvine, CA) fluids were administered at 7 ml/kg through the IV catheter. The OS was surgically prepped and rinsed with 1:60 dilute betadine (Vetadine, Vedco Inc.) solution. The patient was positioned in dorsolateral recumbency and the OS was draped for surgery.

A barraquer wire eyelid speculum was placed to increase exposure to the eye, and 1:10,000 dilute epinephrine (WestWard Pharmaceutical Corp., Eatontown, NJ) was applied for conjunctival vasoconstriction and hemostasis. Steven's tenotomy scissors were used to perform a lateral canthotomy for greater exposure. A #64 Beaver blade was used to create a 75% thickness corneal groove, approximately 4 mm in length in the dorsonasal region. A #63 Beaver blade was then used to make a stab incision to enter the anterior chamber. Dilute epinephrine (1:10,000 dilution) was injected intracamerally for hemostasis. Sodium hyaluronate (Hylartin V, Pharmacia and Upjohn Co., New York, NY) was injected into the anterior chamber to reinflate the chamber and dilate the pupil. Vannas scissors were used to create an anterior lens capsulotomy, and utrata forceps were used to complete a continuous curvilinear anterior capsulorhexis. The tip of the phacofragmentation handpiece (Accurus, Alcon Laboratories, Inc., Fort Worth, TX) was inserted through the corneal and anterior lens openings. The lens was fragmented and aspirated. The viscoelastic material was removed from the anterior chamber, and the corneal incision was closed in a double continuous pattern using 9-0 Vicryl (Ethicon, Inc., Guaynabo, Puerto Rico). The anterior chamber was re-inflated using balanced salt solution. The lateral canthoplasty was closed using a buried subcutaneous continuous pattern using 6-0 Vicryl (Ethicon, Inc.). At the conclusion of the surgery, the monitor received 3.33 mg/kg carprofen (Rimadyl, 50 mg/ml, Pfizer Animal Health, New York, NY) subcutaneously (SC), and 5 mg/kg enrofloxacin (Baytril, 22.7 mg/ml, Bayer HealthCare LLC, Animal Health Division, Shawnee Mission, KS) SC.

After the surgery, the monitor was transported back to the zoo and had a prolonged but uneventful recovery in the enclosure. Systemic antibiotics were initiated the next day at 5 mg/kg enrofloxacin (Baytril, 68 mg/tab and 22.7 mg/tab, Bayer HealthCare LLC) PO every 48 h for 28 days and anti-inflammatory therapy at 4 mg/kg carprofen PO every 24 h for 14 days. He also received Neomycin/Polymyxin B/Dexamethasone ophthalmic solution topically OS q 6 h for 14 days.

One week post-phacoemulsification OS, a gross ocular examination revealed severe blepharospasm OS. The lateral canthoplasty sutures were still in place, and there was moderate periocular swelling. The patient tracked with both eyes equally. Slit lamp examination showed intact sutures at the clear corneal incision, and a clear aqueous media OS. There was mild dyscoria present. Indirect ophthalmoscopy was attempted OU, but the patient's disposition did not allow for complete posterior segment evaluation, although the vitreal humor was clear, and limited views of the retina were normal. The cause of blepharospasm was likely lateral canthal suture reaction because the ocular exam was unremarkable. The OD was unchanged since the previous examination (Fig. 2). Neomycin/PolymyxinB/Dexamethasone ophthalmic solution was decreased to every 12 h. Intraocular pressures were not evaluated because of the patient's demeanor. CBC and biochemical analysis were repeated one month postoperative, and were still within the normal reference range. Six weeks post-phacoemulsification OS, the patient was comfortable and tracked equally OU. The clear corneal incision had healed, and the aqueous and vitreous humors were clear. All medications were discontinued.

Figure 2.

Immature cataract in the right eye. Photo credit Terah Webb, DVM, DACVO.

Figure 2.

Immature cataract in the right eye. Photo credit Terah Webb, DVM, DACVO.

Close modal

Seven months later, phacoemulsification was scheduled for the right eye. CBC and biochemical analysis was again performed, and the results were within the acceptable reference range for monitors. Sedation was again achieved with hydromorphone and midazolam IM as previously described. Propofol was also used to induce the monitor but at a lower dose (6 mg/kg IV). Fluids and injectable antibiotics and anti-inflammatory drugs were again administered as reported in the first surgery. The right eye was surgically approached without a lateral canthoplasty to improve the speed of postoperative healing and patient recovery. Surgery was performed as described previously for OS, and no complications were experienced. Because of the prolonged recovery noted after the first procedure, 0.007 mg/kg flumazenil (Flumazenil, 0.1 mg/ml, Sandoz Inc., Princeton, NJ) was administered IV at the conclusion of the surgery to reverse the effects of the midazolam. The monitor recovered from anesthesia prior to leaving the referral center and appeared normal when placed back in the exhibit at the zoo. Postoperative parenteral antibiotic, non-steroidal anti-inflammatory, and topical ophthalmic therapies were administered as described after the first surgery. Two days postoperatively, the patient was comfortable with no periocular swelling and was able to track equally OU. Complete ocular examination was unchanged OS, and OD showed intact corneal sutures, mild dyscoria, and clear aqueous and vitreous humors. CBC and biochemical analysis performed 30 days postoperatively were found to be unremarkable. By six weeks postoperatively, the corneal incision had healed, and all medications were discontinued (Figs. 3 and 4). The monitor continued to track equally OU and appeared to recognize objects and motion.

Figure 3.

Left eye four months postoperative. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Figure 3.

Left eye four months postoperative. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Close modal
Figure 4.

Right eye 18 months postoperative. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Figure 4.

Right eye 18 months postoperative. Photo credit Grahm Jones, Columbus Zoo and Aquarium.

Close modal

Cataracts in all species are generally classified by age of onset (congenital, juvenile, senile), amount of lens involvement (incipient, immature, mature, hypermature), anatomic location within the lens, and cause (hereditary or acquired). Most cataracts result in impaired or complete loss of vision. Although well-described in mammalian and avian species (Brooks, 1997), there is little reported in regards to cataract formation and treatment in reptiles. Juvenile cataracts have been reported in young varanids (Frye, 1991), and although genetics and nutrition have both been suggested as possible etiologies, the cause remains unknown. Cataracts in tortoises (Testudo spp.) have been associated with freezing episodes (Lawton, 1989; Lawton and Stoakes, 1989). Chelonian lenses are extremely soft and almost fluidlike in consistency, and it is hypothesized that they are particularly prone to damage from low temperatures (Duke-Elder, 1958; Lawton, 2000). Cataract formation in this monitor was presumed to be senile in etiology based on the slow progression; age of this patient; lack of support for a nutritional deficiency; excellent husbandry; no metabolic abnormalities identified on examination, CBC, or biochemical analysis; and no evidence of primary uveitis. At his current age (19 yr old), this animal is among the oldest on record for a water monitor in captivity (Slavens and Slavens, 2000).

Surgical removal of cataracts has a high success rate and is the only definitive therapy for resolution described in other species. Phacoemulsification is considered the gold standard for removal of cataracts regardless of species, using high frequency ultrasound waves to fragment the lens and allow for aspiration of the fragments through a 3.2-mm incision (Glover and Constantinescu, 1997; Gilger, 1998). Surgical removal of cataracts in non-mammalian species has been sparsely reported (Whitaker et al., 2001; Colitz et al., 2002; Kelly et al., 2002; Lawton, 2006). This case report suggests that phacoemulsification can be used to successfully restore vision in reptilian species affected by blinding cataracts.

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