This patient has an unusual eye when you compare it to what you are used to. That’s because the patient here is a canine with white cataracts. Our veterinary ophthalmologist colleagues frequently watch CataractCoach videos because there are so many similarities between canine cataract surgery and human cataract surgery. There are, however, some important differences.
While the average human cataract / crystalline lens has a diameter of about 9mm and a thickness of 4+ mm, the canine cataract is much larger with a diameter of 10-12 mm and a thickness of 7 to 10mm. That is much more cataract lens material to remove, at least double what we are used to in human patients.
Image courtesy of David Ramsey, DVM, DACVO
The canine lens is so much thicker because it has a higher dioptric power, about 40 D, than a human lens which is usually around 20 D. Since most dogs are close to emmetropia, detailed IOL calculations are not typically performed and a 40 D IOL is used for almost all cases. Surprisingly, this is relatively constant among all breeds, from small to large. It should be noted that dogs are nicer than people and they will not complain of 0.5 D of residual astigmatism and 20/25 vision on post-op day 1.
