By Teresa Garden, DVM
Cataracts are the leading cause of vision loss in dogs. Visual impairment may be difficult for owners to assess. Dogs are able to compensate for vision loss from slowly progressive cataracts. They certainly compensate well with unilateral cataracts. The three most common types of cataracts we see in the dog are genetic, those secondary to diabetes, and those secondary to Progressive Retinal Atrophy (PRA).
Genetic cataracts are due to a mutation in genes responsible for maintaining normal lens transparency and metabolism. DNA testing, once better developed, will help breeders take affected dogs and carriers out of the breeding pool.
Breeds afflicted with genetic cataracts include Staffordshire Bull Terriers, Boston Terriers, French Bulldogs, and Australian Shepherds. Diabetic cataracts are caused by a change in carbohydrate metabolism of the lens. Sorbitol builds up in the lens due to excessive glucose. This results in lens opacity, lens fiber cell rupture, and other biochemical changes that lead to vision loss. About 70 -75% of dogs with diabetes will develop cataracts within one year of diagnosis. Therefore, therapy for cataracts should be implemented as soon as diabetes is diagnosed. Progressive Retinal Atrophy causes production of toxins that diffuse through the vitreous to cause lens damage. These dogs, just like diabetics, should have treatment instituted early to limit lens damage.
Early cataracts cause inflammation (lens-induced uveitis) and oxidative stress which cause the cataract to progress further. Naturally occurring antioxidants in the lens are depleted due to and during cataractogenesis. A variety of antioxidants with anti-inflammatory properties and free radical scavenging effects may have potential to slow early cataracts. Small non-vision impairing cataracts can stop progressing and tiny pinpoint cataracts have disappeared in some patients.
Many antioxidants are beneficial to all types of cataracts. These include grapeseed extract, lutein, omega-3 fatty acids, green tea extract, alpha lipoic acid, tumeric, and beta-glucans. The combination of grapeseed extract and zinc has been shown to delay progression of diabetic cataracts and decrease blood glucose. Studies suggest increased consumption of foods rich in antioxidants such as selective carotenoids, Vitamin C, and Vitamin E protect human and nonhuman primate lenses against UV radiation induced oxidative stress. This is likely true in other animal species such as our dogs. Vitamin C is protective against cataract formation. It works best when combined with other antioxidants and minerals and taken orally. Vitamin E is inversely correlated with cataract incidence in people. Supplementation may reduce the incidence and progression of cataracts. Current research is focused on possible roles of lutein and zeaxanthin in ocular health. Increased plasma and /or dietary levels of these carotenoids are associated with a significantly decreased risk of developing age-related cataracts.
Omega-3 fatty acids are found in fish oils, flaxseeds, pumpkin seeds, and green leafy vegetables. They have beneficial properties for overall wellness and good health. They are shown to be beneficial for the prevention of cataracts in people. Omega-3 fatty acids suppress ocular inflammation by inhibiting the production of inflammatory mediators.
Green tea extract inhibits diabetic cataracts by lowering glucose and it may increase insulin activity. Alpha lipoic acid is an excellent free radical scavenger that regenerates Vitamin C and Vitamin E. It has anti-inflammatory effects and it increases levels of the potent antioxidant glutathione in the lens. Alpha lipoic acid protects the lens from oxidative stress. It can benefit diabetic dogs since it promotes normal insulin sensitivity and glucose metabolism. Beta glucans are natural plant-derived nutraceuticals with potent immunomodulatory functions. They can boost the immune system and aid in glucose metabolism which can benefit diabetic dogs.
Once visually impairing cataracts are present, surgical removal of the lens via phacoemulsification with intraocular lens implantation can be considered to restore sight. Certain parameters must be met for the dog to be a good candidate for surgery. The dog must be in good health with diabetes and hyperlipidemia under control. There can be no evidence of glaucoma or retinal degeneration and uveitis must be under control. The short-term success rate for this surgery is about 95%. Success rates diminish over time from opacification of the remaining lens capsule, detachment of the retina, and delayed onset of glaucoma.
Antioxidant blends can be employed to help slow progression of all types of cataracts. They will assist traditional western medications to control damage to the lens due to inflammation and oxidative stress. Cataract surgery patients receiving antioxidants seem to recover and do better long term than those patients not receiving antioxidants. Products that may help slow the progression of cataracts in your dog include Ocu-GLO by Animal Neccessity and Eye Support by Dr. Mercola.
Dr. Teresa Garden is chief veterinarian /owner of Animal Health & Healing, a full-service holistic and conventional veterinary practice in the Maplewood /Richmond Heights area. 314-781-1738.
www.AnimalHealthandHealing.com.