Cataracts in Dogs with Diabetes

KEY POINTS

• Diabetic dogs can live healthy and fulfilling lives, once they have been stabilised, however there is a common complication of diabetes in dogs – cataracts
• Statistically 70% of patients succumb to cataracts within 12 months of the diabetic diagnosis (Beam, Correa, Davidson 1999)
• Cataract is defined as opacity associated with the lens fibres or the lens capsule
• Sequel to diabetic cataract formation include: –
  • Visual impairment with a very high chance of progression to blindness
  • Intra-ocular inflammation, known as lens-induced uveitis (LIU) and, in the worse-case scenario, the LIU can develop into secondary glaucoma necessitating eye removal
• The treatment for LIU is topical PREDNEFRIN FORTE (prednisolone acetate 10mg/ml, phenylephrine 1.2mg/ml) applied to both eyes q 12h can reduce the impact of LIU, however at times the dosing frequency may need to be increased
• Treating LIU has been advocated in all cases of cataract (Lim, Bakker, Waldner, Sandmeyer, Grahn, 2011) regardless of whether surgical intervention is an option
• The use of a commercially available cocktail of anti-oxidants and enzyme inhibitors (OCU-GLO www.ocuglo.com) was shown to significantly reduce the onset of cataract formation in dogs with diabetes mellitus (Williams, 2015) and therefore starting patients at the start of diabetic diagnosis has been advocated.
• Success rates for cataract surgery in dogs are lower than those encountered in humans: 89% of dogs were visual 2.3 years post-surgery (Lim, Bakker, Waldner, Sandmeyer, Grahn, 2011). With time, this % further decreases
• The canine lens is 2x the size compared to the human lens and the cataracts tend to be far harder, requiring more ultrasound energy for removal, when compared to human cataract surgery
• Cataract extraction in canine patients with immature cataract was shown to have greater success rates compared to blind dogs with mature or hyper-mature cataracts (Lim, Bakker, Waldner, Sandmeyer, Grahn, 2011). Early referral was advocated.

CASE STUDY

Cataract surgery in a diabetic Rottweiler

Ranger, a 6 year-old Rottweiler presented for evaluation and treatment of bilateral cataracts secondary to diabetes mellitus. Ranger had demonstrated visual disturbance to his owner.

OPHTHALMIC EXAM

On ophthalmic exam both of Ranger’s eyes were similar. Ranger was menace positive with no signs of pain. There was no abnormal discharge. Neurophthalmology showed normal direct and consensual PLR. Dazzle and Corneal Reflex were also normal. The internal eye showed immature cataracts. I was unable to visualise the fundus. The external eye and adnexa were unremarkable.

ADDITIONAL TESTS

1. Schirmer tear test: 24mm for the R and 25mm for the L
2. Intra-ocular pressure (IOP -Tonopen): 13mmHg for the R and 9mmHg for the L

Following this ophthalmic examination it was determined that Ranger would be a good candidate for cataract surgery, and PREDNEFRIN FORTE (prednisolone acetate 10mg/ml, phenylephrine 1.5mg/ml) was dispensed immediately (1 drop into both eyes q12h) and an appointment made for surgery 1 week later. 3 days prior to surgery the PREDNEFRIN FORTE was increased to q 6h. Additionally CHLORSIG (chloramphenicol 0.5%) (1 drop into both eyes q 6h) and MYDRIACYL tropicamide 1% (1 drop onto both q 6h) was also started.

SURGERY

On the day of admission Ranger was fasted and half the normal dose of insulin was administered.  Pre-anaesthetic bloods were performed, and were found to be essentially unremarkable.  Both eyes were dilated with atropine prior to surgery.

After the induction of anaesthesia the following procedures were performed without complication at the R eye: –

1. Cataract removal by phacoemulsification
2. Insertion of a 13mm 60V Acri-Vet intra-ocular lens (IOL) into the lens capsular bag
3. Closure of the corneal wounds with 9/0 PGA
4. Injection of 0.05mls Depo Medrol into the dorsal sub-conjunctival space

Ranger’s right cataract was removed in a smooth operation and he was discharged later the same day.  Following surgery the pre-op routine was continued, except the MYDRIACYL was stopped.  Oral enrofloxacin and meloxicam were dispensed, to be started 24h post surgery as SQ injections had been given that day.

7 DAY POST OP EXAM

Ranger was responding visually, there was little sign of discomfort and no abnormal discharge. Neurophthalmology was unremarkable. The internal eye showed a well centred IOL and a clearing visual axis.

14 DAY POST OP EXAM

Ranger was visual, with no signs of discomfort and no abnormal discharge. Neurophthalmology was unremarkable. The internal eye showed a well centred IOL and a clear visual axis. The fundus was unremarkable.

CONCLUSION

Ranger’s cataract surgery was successful and remains so (telephone follow-up). Ranger has had a corresponding increase in quality of life with the return of his vision.