Evidence Update- Ocu-GLO for Prevention of Cataracts in Diabetic Dogs

About a year ago, I wrote a review of Ocu-GLO, an oral supplement marketed for a variety of purposes:

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.

At the time, I concluded that the theoretical premise behind the product and the specific ingredients included was plausible but supported only by weak evidence, and there was little direct clinical research in humans, and virtually none in dogs, showing actual benefits. Therefore, no firm conclusion about the safety and efficacy of the product was possible.

I also noted that:

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…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.

I was pleased, therefore, to see a clinical trial investigating Ocu-GLO published this month which adds to the evidence regarding this product.

Williams, D. Fitchie, A. Colitz, C. An Oral Antioxidant Formulation Delaying and Potentially Reversing Canine Diabetic Cataract: A Placebo-controlled Double-masked Pilot Study. Int J Diabetes Clin Res 2015, 2:1

This trial targeted a specific disease, cataracts developed by diabetic dogs. The process of cataract formation in diabetics is well understood, and there is reason to expect at least some of the ingredients in Ocu-GLO might influence this process, so again there is a plausible potential mechanism here that is consistent with established science.

The study involved giving either the supplement or a control containing antioxidant vitamins but not several of the other ingredients in Ocu-GLO, to 15 dogs each and monitoring them for changes in their lenses that would indicate cataract formation. It was not considered ethical to allow actual cataract development, so once such signs appeared, the treatment was identified and dogs who had been getting the control vitamins were switched to the supplement.

The results were quite impressive.

Mean time without change in lens opacification at the time of writing was 278±184 days with Ocu-GLO Rx™ and 77 ± 40 days in the placebo group. Median duration without lens change was 261 and 84 days, respectively, this difference being statistically significant at p=0.0003.

Twelve of the 15 dogs (80%) taking the placebo developed significant lens changes while on the study protocol. Five of 15 dogs (33%) taking Ocu-GLO Rx™ developed significant cataract, in three of these animals Ocu-GLO Rx™ was not being given as directed…

These differences between the groups is not only statistically significant but, far more important, they are clinically relevant. While the supplement did not absolutely prevent lens changes in treated dogs, it appeared to dramatically delay these changes. In one subject who was switched from the control supplement to the test product, it appeared that the product even reversed changes that had already begun.

Like all research, there are flaws and limitations to this study which require some skepticism about even such dramatic results. To begin with, several key methodological factors were not mentioned in the published report. This is unfortunately extremely common in veterinary research. However, I contacted Dr. Williams, the lead author, and he was kind enough to answer a few questions and provide at least some of this missing information.

There is no mention in the paper of how the subjects were assigned to the two groups. Random assignment, and a process which prevent anyone from intentionally or unconsciously influencing the selection and assignment of patients, is a critical component to reducing bias and error in clinical trials. According to Dr. Williams, the subjects were individually randomized to the two groups. It is not entirely clear, though, how this process was protected from being unintentionally influenced by study personnel or how the exact balance in number between the groups was achieved.

Blinding of investigators and owners to the treatment assignment is another critical element of an effective clinical trial. It appears that investigators were effectively blinded to the treatment each patient received. This is especially important because the outcome being measured was subjective and not very precisely defined as “significant progression of lens opacity, as documented photographically.” It is not clear if the owners could distinguish the two treatments, but this would be less likely to have a significant impact on the results since owners were not involved in assessing the outcome.

A number of other potential limitations exist in this study, including minimal comparison of the two groups before treatment to ensure there were no relevant differences and a small number of subjects, but in general the design and execution seem quite good.

One of the authors, Dr. Colitz, is affiliated with the company marketing Ocu-GLO. This raises the potential of unconscious or overt bias, but this is likely mitigated by the blinding, randomization, and other typical bias-control aspects of the study. Dr. Williams also indicated that there was no financial support of the study from the manufacturer, reducing the risk of any funding bias.

The issue of adverse effects was not specifically addressed in the published report. The company has previously indicated that some unpublished data exist demonstrating the product is safe, and there is no specific evidence to suggest any risk, though unintended effects with long-term use or in particular patients cannot be completely ruled out. With the limited evidence currently available, there seems to be little risk to the use of this product.

I have previously discussed the Decline Effect, which is a well-recognized phenomenon in which small, early studies of a scientific hypothesis give dramatic results which diminish, and sometimes disappear entirely, in subsequent research with better control for bias, confounding, and other sources of error. So it is important to remember that no single study ever definitively proves or disproves a scientific hypothesis. As the researchers themselves acknowledge, further research is not only desirable but necessary to allow confidence in these findings and this treatment.

Bottom Line

This is a small but well-executed clinical trial with a large, clinically relevant difference in the progression of changes in the lens clarity of dogs with diabetes treated with Ocu-GLO compared with a control supplement. The trial is not perfect, of course, and no single trial should ever be viewed as definitive. And this study applies only to the issue of using this supplement to slow the development of cataracts in diabetic dogs. It does not provide good evidence that the supplement can completely prevent or cure cataracts or that it is effective for other uses.

As always in veterinary medicine, however, we must make decisions on the basis of the imperfect evidence we have, while still pursuing more and better evidence. Though the evidence is still limited at this point, I believe it is good enough to recommend the use of this supplement for cataract prevention in diabetic dogs.





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38 Responses to Evidence Update- Ocu-GLO for Prevention of Cataracts in Diabetic Dogs

  1. Art Malernee Dvm says:

    Art says:
    July 30, 2014 at 4:21 pm
    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.>>>>
    When pigs fly.>>>>>>>>>

    Not only will I need to eat my “when pigs fly” words but since I have a diabetic dog who is not completely blind I may end up using the stuff on my own dog. Having said that study’s show that the first study that shows a positive effect is usually a false positive. Vet medicine has a history of eye medicines such as cyclosporine for dry eye being used years before it was approved for human dry eye use. Let’s hope this will be another example.

  2. Manny Katz says:

    All of these ingredients are used alone or in combination as human supplements. Do you think this can not be used for humans? Could humans even use the dog formula or even the dog product itself? It has been written often that an excess of antioxidants has negative consequences in the body. What about that idea when adding so many antioxidants at one time here?

  3. skeptvet says:

    There is some research concerning the use of some of these ingredients in humans, though I am not sure if there is a combination product similar to this.

    I absolutely would not recommend a supplement not specifically made for humans.

    I agree that antioxidants can have risks as well as benefits. So far, the limited evidence concerning this product has not identified any risks. But it is common for much more extensive research to fail to identify health risks to pharmaceuticals and supplements until after they have been widely used for some time, so we cannot discount the possibility of some unintended harm with long-term use.

  4. Myrna says:

    Hello again. My dog has been on OcuGlo for PRA for 2 years. In a previous post, I mentioned that he had a very slow deterioration rate, which I do not know if it’s related to OcuGlo or coincidental. He does, however, enjoy an entirely home prepared diet which includes broccoli, carrots, blueberries and plenty of fish and organic meats. As he has recently become very opposed to taking pills of any sort (after a course of antibiotics for an infected foot), I am thinking of trying to provide the beneficial eye vitamins through food alone. As you said before, supplemental antioxidants have not proven as beneficial as diet provided antioxidants. Do you think he could achieve optimal antioxidant amounts through diet? Thank you

  5. skeptvet says:

    I think the real question would be “what is an optimal amount of antioxidants?” and perhaps a corollary would be “Does it matter which ones?” I don’t have the answers. There is evidence showing both benefit and risk associated with antioxidant supplements, but OcuGlo has some reasonable evidence to suggest a benefit only for cataract formation in diabetics. Whether or not it affects PRA, and whether foods rather than a supplement would have the same effects, is nothing but guesswork.

    Good luck!

  6. Joan Harkness says:

    My dog, Shemo, was diagnosed with diabetes Jan ’15. He started to get cataracts in June, and I started him on OCU Glow. He has limited vision at night – following a laser light. I did a lot of research and want to ask you if you have heard of Life Extensions? They claim they have a supplement ‘Mitochondrial Optimizer’ which will reverse glycation – it includes Carnosine, Benfotiamine (a form of B1 differs from Ocu Glow) & Beta-alanine. My authorized supplier for Ocu Glow is in Toronto Ontario Canada – he has heard of Life Extensions – but has not heard of the product. Thank you Joan

  7. skeptvet says:

    Not a supplement I am familiar with. I’ll try to take a look at it, time permitting.

  8. Christi Edmondson says:

    Would you put your own dog on it?

  9. skeptvet says:

    If my dog was in the same category as the dogs in this study (e.g. a new diabetic without existing evidence of cataracts), then I would use it based on this level of evidence.

  10. Rosalind Folman says:

    My 14 yr. old schnauzer has cataracts covering about 90% of his right eye & about 75% of his left eye. I would really like to be able to slow down his already advance cataract formation.

    However, he is not diabetic. Since your study is on diabetic dogs, do you know if it will have the same positive effect on a non-diabetic dog. I sure hope so.

    Thanx for your reply.

  11. skeptvet says:

    There is no research on non-diabetic cataracts, so it’s unclear. The specific mechanism by which cataracts form is different in diabetics and in other patients, so it’s not clear that the product will make any difference, though it is also unlikely to be harmful. I would consider consulting a veterinary ophthalmologist.

    Good luck!

  12. Deepika Bangia says:


    I have 6 year old labrador diagnosed with PRA. He has symptoms of reduced vision but he has not completely lost night vision. Cataracts have started to form in both his eyes. The dr says he will lose day vision as well in sometime. The dr did not recommend or disregard the use of Occu Glo.
    Can someone please help. Has anyone used Occu Glo on PRA affected dogs and has it slowed the rate of loss of vision. It is really painful to see my dog like this. Please help.


  13. skeptvet says:

    There is not research evidence on this question. Based on how the product works for cataracts in diabetics, there is not reason to think it would affect PRA directly since they are very different diseases. I would suggest seeing a veterinary ophthalmologist if you haven’t already.

    Good luck!

  14. Sushil Shirke says:

    My dog was losing his vision rapidly when he was around 7-8 years old and we lost time before he was diagnosised with PRA. We were advised to put him on Ocuglo and we have definitely seen the deterioration get arrested or slowed down. He is now 13 and he still has partial vision in both his eyes. I rue the fact that I didn’t get him onto the capsules earlier but definitely happy that we did get him onto them as soon as we were advised. As for other antioxidants and other healthy treats, he began eating broccoli, blueberries and carrots much later. So I wouldn’t attribute the arrest or slowing down of his PRA during the initial years to these veges but they are helping him now for sure. I hope this helps.

  15. Sushil Shirke says:

    Hi Deepika,

    Please see my response. My dog too was diagnosed with PRA around 5 years back. In my opinion and experience, using Ocuglo has definitely helped. I wouldn’t waste time.

    – Sushil

  16. Madeleine Manire says:

    Hello Deepika – My miniature poodle was hit with a double whammy… PRA and diabetes. Our veterinary ophthalmologist put him on OccuGlo within a month of his diabetes diagnosis by his general veterinarian and the v. ophthalmologist diagnosed the PRA. He is now 1.2 years post diagnosis for both conditions and has virtually no cataracts and seems to see as well at night as during the day. I would say this is an excellent recommendation for OccuGlo. I wouldn’t be without it. Good luck with your sweet friend.

  17. Dave says:

    Yes it works!! Get him on it. Eye specialist told me my Blue Healer was going to be 100% blind in a matter of a year and I strongly believe that Ocu Glo helped slow down the blindness. It helped him adapt slowly and helped me adapt( emotionally) while getting prepared for his total blindness. 5 years later… my Blue can still see shapes on a sunny day!! We don’t play frisby anymore but he doesn’t care! He now uses his sniffer and we play ball and it’s great!
    —there is hope!

  18. Pam says:

    My Westie is on it. If I were you, I would get your diabetic dog on it so it would lessen vision loss. My dog’s opthomologist recommended it. It’s got good stuff in it.

  19. Nancy says:

    My 10-year-old schnauzer was diagnosed with progressive retinal atrophy and beginning cataracts nine months ago and we started using Ocu-Glo. I have recently noticed that she seems to be seeing better, and last week it was confirmed by the veterinary ophthalmologist. The vet reported that my dog is responding better to light and that the blood vessels in her eyes are healthier. I could not be more pleased. My only complaint is the size of the capsules. My dog swallowed them in pill pockets just fine for a long time but she suddenly started to balk. Since then I’ve tried a multitude of ways to hide the pills but each method tends to only work for a few days before she gets wise. Because the pills are so large, she needs to chew them, which tips her off to the fact that they’re in her treats. I even tried the technique where you roll it down the dog’s throat. It worked, she swallowed it, but then still somehow managed to get it back out! Hoping I am smart enough to stay one step ahead of her…

  20. Madeleine Manire says:

    I had the the same experience with my mini poodle (20#), so I compared the ingredients and amounts in the small dog OcuGl0 (small capsules) with that in the med – large dog OG (large capsules). Ingredients were exactly the same and the large capsules were exactly twice the amounts as the small caps. Although a bit more expensive, I started ordering the small caps and giving my dog 2 small caps instead of 1 large cap. I also put them in the pill pockets and he takes them just fine. Hope this is helpful.

  21. Malathy C says:

    My 56 lb. labrodoodle was diagnosed with PRA 2 years ago. I have been giving him Ocu-Glo since then and he has retained his day vision. He’s pretty blind in the dark, but manages to mostly not bump into anything. He will turn 12 in December 2019. On our 2nd opthamology check-up last week, the vet found that his cataracts are growing fast. He says cataracts are inevitable with PRA. Looks like Ocu-Glo has not helped my dog with cataracts. Anyone else with this PRA-cataract combo? I am looking into giving him Can-C eye drops and capsules for cataract while continuing him on Ocu-Glo. Worried about the potential side effects of giving him so many different supplements. Any guidance would be appreciated. Thanks.

  22. Dennis T Strubbe, DVM, DACVO says:

    The Ocuglo study referenced above is contaminated by the fact that the authors moved control patients into the treatment group whenever their cataracts progressed, as stated in the materials and methods section of the paper. This not only invalidates their findings, but it also reveals that the researchers were not blinded as to which patients were receiving Ocuglo and which were controls. Furthermore, analysis of cataract progression was extremely subjective, as evidenced by the photographs included in the paper. Images of supposedly progressing cataracts were clearly taken in a lighted room, with ambient light reflecting off periocular hair, while supposedly regressing cataract photos were taken in darkened rooms. Finally, the product contains grape seed extract, and the AVMA currently recommends avoiding grape products in dogs due to the risk of renal toxicity. Given all of this, I cannot in good conscience support this product, which is particularly unfortunate since I have the greatest respect and admiration for Dr. Colitz as a fellow veterinary ophthalmologist.

  23. skeptvet says:

    Fair points, and such methodological limitations are common and significantly reduce the reliability of much of the veterinary literature. On terms of the concern regarding grape seed extract, I will mention that some poison-control sources list grape-seed extract as non-toxic, and there is some limited research evidence to support this. I have no case reports of toxicity associated with the product, so I would have to judge the risk as probably quite low.

    Thanks for the comment.

  24. art malernee says:

    The Ocuglo study referenced above is contaminated by the fact that the authors moved control patients into the treatment group whenever their cataracts progressed, as stated in the materials and methods section of the paper. This not only invalidates their findings, but it also reveals that the researchers were not blinded as to which patients were receiving Ocuglo and which were controls. >>>

    is this information open source only on this website?

  25. Dennis T Strubbe says:

    I have included this information in a recent lecture, along with other unrelated topics regarding new ocular therapies, but I haven’t posted it anywhere else. I posted it here to highlight the problems with the referenced paper, which, unlike most veterinary ophthalmology articles, has several major flaws in methodology. It should be noted that these opinions are mine alone, of course, and they may change as new information comes to light. Hope that answers your question.

  26. Dennis T Strubbe says:

    On a side note, thank you so much for all of your hard work. This website is invaluable to me, and I greatly appreciate everything you do. 🙂

  27. Amy Moore says:

    My dog was diagnosed diabetic in June 2018. I immediately booked an appointment with an ophthalmologist to have his eyes checked. He had small pinpoint cataracts. So we started him on Ocu-Glo and eye drops for dry eye. We go back every three months for eye checks. It has been a year and a half from diagnosis and he has perfect tear production now and his cataracts have not progressed in size. She never definitively states that it is the Ocu-Glo but always says.. whatever you are doing is working… so lets continue. I have a big dog, and the $75 dollar bottle lasts me 1 month. But his eyesight is priceless and its worth it. I don’t know if it truly is helping but its obviously not hurting.

  28. Cissy torrez says:

    My chihuahua hated it, the pills are to big so I got the powder ones thinking that would be easier to hide it in her food wrong she could smell it and wouldn’t taste her food, this week 7/31/2020 I tried it again no way. She throw up had a bad stomach and now won’t eat anything so I had my sister try to feed her since she didnt trust me. My dog also has diabetes and going blind. I wish I hadn’t given her the pills cause now she wont eat

  29. Lisa Shrewsbury says:

    My Chocolate Lab has been on Ocu-Glo for over a year now. For about six months, his night vision has been severely impacted and now, recently, his day vision is getting worse. My vet suggested staying on it as it won’t hurt him. However, at $75 a bottle and him having other health issues, I’m thinking going off would not hurt him either. He is not diabetic. Thoughts?

  30. skeptvet says:

    His night vision is likely declining due to lenticular sclerosis, a normal age-related thickening of the lens that is also the reason most people in their 40s and older need reading glasses or bifocals. Ocu-Glo has not been tested for this condition, and there isn’t any reason to think it would help since the process is entirely different from that which causes diabetic cataracts. It sure sounds like the money could be better spent on other health issues to me.

  31. L says:

    My dog is a senior, s/p cataract removal 2 years ago, the dog has minimal if any vision.
    Now being treated for glaucoma and dry eye, several eye drops per day and routine visits to a board certified ophthalmologist who recommends the Ocu-Glo.
    Like Lisa, I am concerned with the expense too, especially if it isn’t helping. The eye drops alone are $$
    I just bought a new bottle of the stuff 🙁

    PS: Anyone thinking of having their dogs cataracts removed, I wouldn’t do it again, the eye drops are forever and the surgery is much more complicated for dogs than for humans. It doesn’t always go smoothly. Read the fine print.

  32. I just found out my dog has diabetes , I put him on ocu-glo I just hope it works. My dog chases birds and squirrels that’s his life. When the time comes when he is blind I will have to decide what to do. He would not be happy being blind, I just hope the ocu-glo works and he does not go totally blind. I don’t know what else there is I can give him!

  33. Nancy Crichton says:

    Skeptvet: I have a 9 year old, spayed, diabetic Min Pin (Lily); diagnosed 9/2/20 and is on Vetsulin 1U x 2 a day, 12 hrs apart; food is Purina Pro Plan Salmon/Rice for sensitive stomachs which is higher in FAT but she can not tolerate chicken products.

    I am considering using Ocu Glo as it has been recommended to us. Lily has one eye (R) that is showing signs of possible cataract beginning. My vet is not familiar with the product and I question whether or not it will interfere with the efficacy of the insulin??

    Eye drops have been recommended also for keeping the eyes lubricated; is there one that you recommend for canines?

    Thank you, I appreciate your comments very much. Nancy @ muffys2720@me.com

  34. skeptvet says:

    I don’t see any reason it ought to interfere with insulin, so it should be safe to try. Wetting drops aren’t usually needed unless there is a deficiency in tear production, so I’m not sure what this has been suggested. I would check with your vet or consider a consult with a veterinary ophthalmologist.

  35. Nancy Crichton says:

    Thank you very much for your response. I got in a hurry and meant to add one other question about her diabetes.

    I test before meals am/pm; she has been at the vet’s office for one 8 hour curve, but that has been her only curve. She is not cooperative with testing or with insulin shots. She is a very strong dog and we have the arm scars to prove it.

    Her glucose numbers run in the low 100’s to the low 200’s. She is always ready to eat, never throws up food, she drinks water well and asks to go outside to pee about every 1 1/2 to 2 hours.

    She gets 7g or her Purina Salmon for sensitive stomach at 5 am/pm; in between meals she gets a heaping teaspoon of plain Greek yogurt with a cranberry capsule emptied in the yogurt and mixed up; other treats include: plain white turkey breast; cut up celery, fresh green beans, plain canned pumpkin, broccoli. Very rare, but special would be a small piece of a Milkbone mini bone or bit of carrot sliced paper thin. She is very satisfied.

    If her BG numbers continue running pretty evenly between 130-240 with no other issues, I should consider that reasonably stable, generally?

    Thanks again. Nancy

  36. skeptvet says:

    The goal for diabetes management is to control clinical symptoms (drinking and urinating excessively, weight loss) while never having dangerous episodes of low blood sugar. The specific numbers will likely look different for each pet, but generally we like them between 100-200 in dogs. Some dogs will drop below 100 if we try to control them too tightly, so we may let them run higher if necessary to prevent this, especially if they don’t have severe clinical symptoms. Your numbers seem generally within the ballpark, though perhaps a touch high.

    A great new tool for some dogs is the Freestyle Libre, a continuous glucose monitor for humans that we are starting to use to monitor dogs and cats. It is attached to the skin and will check BG continuously for up tp four weeks (though they often only stay on 2-3 weeks), which gives us a better idea of how things are going than other measures (spot Bas, curves in hospital, fructosamine, etc.). You might look into trying this if your dog is tough to test.

    Here are the latest guidelines from the American Animal Hospital Association for treatment.

    Good luck!

  37. L says:

    Luckily I have not opened the last bottle I ordered and received, I am still able to get a refund (over $70)!

    The ophthalmologist is now recommending enucleation, obviously the supplement that the dog was on for almost a year (Ocu-GLO) did nothing to help the dog’s vision. Dog is now totally blind. Dog is also on multiple prescription eye drops.

    Also, I can’t prove it but I believe the Ocu-GLOW was causing GI distress.

    Buyer beware!

  38. Maunette Bacon says:

    I began giving my 14 pound Pomeranian Ocu-Glo about for five months ago, it did improve the cloudiness in her eyes. However yesterday my vet informed me that she’s been diagnosed with pancreatitis, and I’m wondering if this product may have contributed because I noticed there is zinc in Ocu-Glo And zinc is listed as one of the pancreatitis toxins. I cannot think of another reason my dog would come down with pancreatitis, she doesn’t eat fatty food, she’s had no trauma, we don’t even give her table scraps.

    Further I am aware that she did not have pancreatitis a year ago when she had her blood work performed. So it’s a rather new development for us. She’s going to be 12 years old. I wonder if anyone else has made a connection between this product and pancreatitis or if it’s just a coincidence.

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