Abstract
Cataracts are commonly reported in captive seals2-4 and cataract removal has been attempted previously in pinnipeds1. The predominant problem encountered when attempting surgical extraction of the lens in seals is achieving successful mydriasis of the pupil.1,4 This paper reports effective pupillary dilation and successful bilateral phacofragmentation in a 5-yr-old, 30-kg, male New Zealand fur seal (Arctocephalus forsteri).
The seal was observed by keepers to be exhibiting significantly reduced visual capacity. An ophthalmic examination was conducted under anaesthesia. Topical tropicamide 1% drops (Mydriacyl eye drops 10 mg/ml, Alcon Laboratories, Frenchs Forest, NSW, Australia) and episcleral atropine sulphate (Atropine forte 16 mg/ml injection, Parnell Laboratories, Alexandria, NSW, Australia) resulted in poor pupillary dilation. Topical adrenaline (Adrenaline injection BP 1 in 1,000, Astra Pharmaceuticals, North Ryde, NSW, Australia) 1:10,000 was also not effective. Bilateral cataracts were evident through poorly dilated triangular pupils, the right being more mature than the left. Electroretinography, which is not calibrated for the seal eye, was performed and indicated a strong positive waveform in response to a blue light flash in each eye.
Anaesthetic induction for each procedure, including ophthalmic examinations consisted of medetomidine (Zalopine 10 mg/ml injection, Orion Corporation, Espoo, Finland) 50–70 μg/kg IM plus ketamine (Ketamine 100 mg/ml injection, Parnell Laboratories, Alexandria, NSW, Australia) 2–3 mg/kg IM. The animal was then intubated and maintained on isoflurane in oxygen. Anaesthesia was reversed using atipamezole (Antisedan 5 mg/ml injection, Novartis Animal Health Australasia, Pendle Hill, NSW, Australia) IM at five times the medetomidine dose.
Surgical removal of the lens was attempted in the left eye initially. Mydriasis was attempted with topical atropine ointment (Atropine eye ointment 10 mg/g, Jurox, Rutherford, N.S.W., Australia) BID starting 2 days prior to surgery. This had no mydriatic effect. Prednisolone (Macrolone tablets 20 mg, Mavlab, Slacks Creek, QLD, Australia) 2.0 mg/kg SID, PO was also commenced 2 days preoperatively. The seal was anaesthetized and placed in dorsal recumbency with the neck ventro-flexed so that the eyes presented on a horizontal plane. Pancuronium (Pavulon 2 mg/ml, Organon Teknika, Baulkham Hills, NSW, Australia) 0.3 mg IV resulted in good positioning of the eyeball and had no effects on respiration. Intracameral adrenaline, 1 ml of 1:10,000, resulted in minimal pupillary dilation. The entire lens was very hard and most of the cortex was removed by phacofragmentation. The nucleus, which was too hard to break up, was removed in toto through a widened corneal incision. Dexamethasone phosphate (Dexason 2 mg/ml injection, Troy Laboratories, Smithfield, NSW, Australia) and atropine sulphate were injected episclerally after the procedure and the seal was maintained on prednisolone 2.0 mg/kg SID, PO for 7 days then reduced to 1 m/kg SID, PO, to minimize the risk of lens-induced and iatrogenic uveitis. The seal recovered well with the left eye open the following day. The seal was confined to a darkened, dry pen for 7 days after the surgery and was treated with cloxacillin eye ointment (Orbenin eye ointment, Pfizer Animal Health, West Ryde, NSW, Australia) SID for 5 days and clavulanic acid/amoxycillin (Clavulox tablets 500 mg, Pfizer Animal Health, West Ryde, NSW, Australia) 500 mg BID, PO for 7 days. An improvement in vision was noticed 4 days postsurgery. Severe blepharospasm developed 17 days postsurgery and an examination under anaesthesia revealed an ulcer secondary to the lateral canthotomy suture rubbing on the cornea. The cornea healed quickly after the suture was removed.
The procedure was repeated on the right eye 3 mo later. The seal had been maintained on prednisolone 1 mg/kg SID, PO during the entire 3-mo pre-surgical period. Topical atropine ointment BID was administered 3 days prior to surgery, again having no mydriatic effect. The seal was anaesthetized and pancuronium 0.3 mg IV was administered. A supplemental dose of pancuronium at 0.1 mg IV was given and caused irregular, shallow respiration for approximately 20 min. Intracameral adrenaline, 1 ml of 1:10,000, had almost no effect on the pupil this time, so the injection was repeated with 1 ml of 1:1,000 intracamerally which produced excellent pupillary dilation within 20 secs. Atropine sulphate was then injected episclerally to maintain pupillary dilation. The entire lens of the right eye, which was also very hard, was removed by phacofragmentation. Once again, the seal recovered well and the right eye was open the next day. The same postoperative medication and care was repeated as for the previous surgery. An improvement in vision was noticed 10 days postsurgery when the corneal oedema cleared. The seal was maintained on prednisolone 1 mg/kg SID, PO for an additional 3 mo to reduce the risk of uveitis before gradually withdrawing the medication. Severe blepharospasm developed 23 days postsurgery. A further examination under anaesthesia revealed that there was an ulcer on the lateral cornea, again caused by rubbing of a lateral canthotomy suture. The ulcer resolved quickly after the suture was removed.
Artificial dilation of the pupil with commonly used mydriatics is usually unsuccessful in seals;1,4 however, an intraoperative, intracameral injection of adrenaline 1:1,000 proved effective in dilating the pupil in this case. Histologic examination of the eye of a New Zealand fur seal indicates that the iris and ciliary body contain extensive bands of smooth muscle, but there is no evidence of striated muscle. Due to the hardness of the lenses, prolonged phacofragmentation was required. The pupils remained partially dilated for approximately 7 days after each procedure.
The seal now has vision in both eyes, with the left eye appearing to have better vision than the right as the seal favours the left side. Overall, vision under water and short distance aerial vision show the most improvement. Recovery from surgery was uneventful, other than corneal ulceration caused by the lateral canthotomy sutures. Six months postoperatively, there have been no ophthalmic complications and the seal is doing well. The cause of the cataracts was undetermined.
Literature Cited
1. Dutton, A.G. 1991. Cataract extraction in a fur seal. JAVMA. 198(2):309–311.
2. Greenwood, A.G. 1985. Prevalence of ocular anterior segment disease in captive pinnipeds. Aquatic Mammals. 1:13–15.
3. Hirst, L.W., M.K. Stoskopf, D. Graham, W.R. Green and J.B. Dickson. 1983. Pathological findings in the anterior segment of the pinniped eye. JAVMA. 183(11):1226–1231.
4. Stoskopf, M.K., L.W. Hirst and D. Graham. 1983. Ocular anterior segment disease in captive pinnipeds. Aquatic Mammals. 10(2):34–44.