A reader recently asked me to comment on a dietary supplement marketed for dogs and cats, Ocu-Glo Rx. While this product shares the problem of many such supplements, a shaky theoretical rationale and limited relevant research evidence to support its use, I was pleasantly surprised to find that at least the claims made by the company are fairly circumspect and reasonable compared to many similar products. The founders of the company are board-certified veterinary ophthalmologists with legitimate and relevant training and research experience, and they seem to have approached the design and marketing of this product a bit more scientifically than is commonly the case.
What is It?
The company that makes this supplement is pretty clear and specific about the ingredients, which is unusual compared to many veterinary supplements.
Epigallocatechin Gallate (Green Tea Extract)
Alpha Lipoic Acid
Vitamin B Blend
The site even lists the specific amount of each ingredient in the two sizes of capsule.
The claims made for the product are also refreshingly reasonable compared to many such nutraceuticals. In keeping with the requirements of the minimal regulations governing dietary supplements, the product is marketed as “supporting” the normal function and health of the eye: “These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” Claims for preventing or curing disease would be inappropriate and illegal. Though some of the testimonials and marketing seem to imply more than a purely supportive nutritional role for the product, the web site is pretty good about sticking to allowable claims.
Ocu-GLO Rx™ is needed when your dog is showing any of the following signs:
- Diminished vision at night or in dim conditions – Diminished vision at all times – Cloudy appearance to eyes – Pupils that do not constrict – Obvious cataracts Or… -Your dog is generally healthy, but you want him or her to be placed on an excellent lifetime antioxidant supplement to help support and enhance ocular health and also general health.
We (Drs. Carmen Colitz and Terri McCalla) are also dispensing Ocu-GLO Rx™ for patients predisposed to primary glaucoma (having lost their first eye to glaucoma) and that already have glaucoma; for Golden Retrievers with pigmentary uveitis (also called “Golden Retriever Uveitis” or GRU); for diabetic dogs in which cataracts are immature or have not yet formed; for dogs with senile retinal degeneration; for dogs post-cataract surgery to help reduce the incidence of PCO and ACO (Posterior Capsular Opacity and Anterior Capsular Opacity) and for any dogs for which owners want to provide the best nutritional support for their pet’s eyes.
Please keep in mind, however, that the goal of giving Ocu-GLO Rx™ to your dog is not to cure anything—it is to help lessen ocular damage caused by disease and hopefully “buy some time” in which your dog still has functional vision.
It is very important to understand that for many canine eye diseases, medication and/or surgery might be needed in addition to giving your dog Ocu-GLO Rx™.
Please also know that for dogs that are already completely blind from any of these ocular diseases (especially PRA, SARDs, cataracts, GRU, or glaucoma), it is very unlikely that Ocu-GLO Rx™ will be of significant benefit. As a general rule, Ocu-GLO Rx™ can help to prevent or slow down progression of some ocular diseases but cannot reverse ocular damage that has already occurred. For example– Ocu-GLO Rx™ cannot reverse cataracts.
Does It Work?
The theory behind the product is predominantly a version of the antioxidant hypothesis, the claim that chronic diseases can be partially attributed to free radical damage to tissues or DNA and that these diseases can be prevented or ameliorated by nutritional supplementation with anti-oxidants. This was once a wildly popular idea, but in the last ten years it has taken quite a beating, and generally antioxidant supplements have failed to fulfill their promise in the prevention of most disease for which it was hoped they would be useful. While epidemiologic evidence supports a diet rich in foods containing antioxidants, the use of dietary supplements does not seem nearly as beneficial in most cases.
With specific regard to diseases of the eye, the evidence for benefits from antioxidant supplements in humans is mixed. Systematic reviews do not seem to show a benefit in terms of preventing cataracts (1) or macular degeneration (2, 3, though some positive trials do exists and others are in progress), and the evidence is not strong for other eye diseases. Of course, “Do antioxidants prevent eye disease?” is another of those unanswerably vague questions. The more useful questions would focus on specific compounds for specific diseases in particular populations. Many more specific studies on such focused questions could reasonably be conducted, and it is certainly not unreasonable to hope that some would show beneficial effects.
As usual, there is virtually no relevant clinical research in dogs or cats, so even the inconsistent and preliminary evidence for such products in humans is not available to us for our pets and patients. The company web site does cite a number of scientific studies to support the inclusion of each ingredient in the product, however, these are generally lab animal studies or human studies, not clinical trials investigating the preventative effects of the product or the ingredients for specific diseases, so extrapolation to clinical use in dogs and cats should be tentative at best.
Is It Safe?
For a long time, one pillar of the antioxidant hypothesis seemed to be that antioxidants were necessarily safe since they occur in foods. That has since been clearly shown to be untrue, and there is ample evidence that supplementation can have risks as well as benefits. The benefits of any compound that affects physiology are going to have parallel risks, and the importance of good scientific studies lies largely in helping us to understand these risks and benefits so we can make decisions about the balance between them in specific situations.
While reasonable amounts of nutrients commonly found in foods are unlikely to have dramatic risks, the true safety of these kinds of supplements cannot be known without appropriate research. The product web site indicates that some sort of safety study has been conducted, but I have not been able to find any indication that it has been published, so it isn’t possible to evaluate the reliability of that evidence.
The theoretical rationale behind the selection of ingredients in this product is certainly plausible, and there is some evidence in humans and lab animals to suggest some of them might have beneficial properties. However, the theory of oxidative damage has mostly failed to bear real-world fruit in terms of supplements validated as effective in clinical trials. The human clinical trial evidence for the ingredients in this product varies from weakly positive to mostly negative to insufficient to draw conclusions. There is no published clinical trial evidence in dogs and cats to support the safety or efficacy of this product for preventing or treating any eye disease.
It is unlikely that there are significant risks to using this product, though studies in humans have found dangers to antioxidant supplementation when enough people were studied for long enough, so it is not possible to confidently claim there are no meaningful risks.
Unlike the marketing for many supplements pitched to pet owners, the claims made by this company are pretty measured and reasonable in light of the limited available evidence (though the company has unfortunately been unable to avoid the allure of the meaningless feel-good term “natural” in its marketing). It is debatable whether the evidence is sufficient to justify marketing a product like this at all, but at least the manufacturer is avoiding wild and exaggerated claims. Hopefully, the ophthalmologists behind the product will pursue appropriate research efforts to determine if, in fact, the product has the benefits they suspect and what, if any, risks are associated with its use.