N-Acetylcarnosine Eyedrops for Cataracts in Dogs and Cats (Can-C, Bright Eyes NAC, etc)

A client recently asked for my opinion about the value of some over-the-counter eye drops purported to treat cataracts in dogs and cats. Not having read much about this product, I did a little research.

What Is It?
There are a number of eye drops marketed for prevention or treatment of cataracts in humans and pets. Most commonly, they contain a chemical called n-acetylcarnosine, which is made up of a couple amino acids and an acetyl group. In vitro research suggests this chemical has anti-oxidant effects, so it has been hypothesized to prevent or reduce the gradual opacification of the lens of the eye through this mechansism. As I have pointed out before, the role of oxidative damage in disease, and the value of anti-oxidant therapies, is a developing area of research. Many of the exuberant and enthusiastic hopes in this area have proven false, so while it is an area deserving further investigation, claiming something is an anti-oxidant is not automatic validation of its safety or benefits (e.g. 1, 2, 3).

Does It Work?
There have been a number of studies of n-acetylcarnosine, both in vitro studies and clinical trials in humans. Interestingly, almost all of these appear to have been published by the same researcher and his team, Dr. Mark Babizhayev. A clinical trial was published in 2001 (and it appears the same data was published again in a different journal in 2002, which if true is quite a significant science no-no). The trial was randomized and controlled in a small number of patients, and it appeared to show significant changes in a number of objective measures of cataract severity.

I am not familiar with the specific techniques used to measure the disease or response to treatment, so I will presume they are standard and appropriate measures for this kind of study. One thing that is not clear from the published report is whether the individuals making these measurements were blinded to the treatment status. This obviously has a significant bearing on the reliability of the results, especially when they stem from only one researcher, as such debacles as the Benveniste affair show.

A number of subsequent papers have been published by Dr Babizhayev and his team, mostly in vitro or lab studies investigating properties of n-acetylcarnosine, not clinical trials. Dr. Babizhayev has also become the leader of a commercial firm marketing n-acetylcarnosine for cataract treatment, and many other uses (including skin care, wound care, respiratory disease, and neurologic disease).

This commercial effort, and the spreading of claims for n-acetylcarnosine to a wide range of apparently unrelated applications, does raise some questions about the reliability of Dr. Babizhayev as the sole source of scientific validation for this compound. Overall, the status of the evidence for use of n-acetycarnosine for cataracts in humans is best summarized by the Royal College of Opthalmology:


The evidence for the effectiveness of N-acetyl carnosine eye drops is based on experience on a small number of cases carried out by a Russian researcher team. To date, the research has not been corroborated and the results replicated by others. The long-term effect is unknown.

Unfortunately, the evidence to date does not support the ‘promising potential’ of this drug in cataract reversal. More robust data from well conducted clinical trials on adequate sample sizes will be required to support these claims of efficacy.

Furthermore, we do not feel the evidence base for the safety is in any way sufficient

Unusually, there is actually some clinical trial evidence in veterinary species as well. An uncontrolled, unblended pilot trial has been published on an n-acetylcarnosine product (not the one Dr. Babizhayev sells) in dogs with cataracts.

David L Williams, Patricia Munday. The effect of a topical antioxidant formulation including N-acetyl carnosine on canine cataract: a preliminary study. Vet Ophthalmol. 2006 Sep-Oct;9(5):311-6. The results showed marginal improvement in all groups, though it was only significant in patients with 2 out of 5 types of cataract treated. However, subjectively owners reported improvement in 80% of the subjects.

Dr. Williams  has apparently performed a blinded, placebo-controlled follow-up trial on this product which did not show any benefits (in fact improvements were greater in the placebo group than in the treatment group), showing once again the importance of proper controls for bias, confounding, and other sources of error in clinical trials. Unfortunately, it appears unlikely this trial will be published for reasons which are not completely clear, though one implied issue is that journals are often reluctant to accept papers that show negative results, which are less exciting for readers than positive studies. All of this is, of course, through word-of-mouth among veterinarians, so I cannot confirm it is true.  

Is It Safe?
I have not found any reports of adverse effects from ophthalmic application of N-acetylcarnosine itself, and given its chemical makeup it seems unlikely to be hazardous. As usual, products containing this agent are not regulated as licensed medicines are, and there is no way to ensure label accuracy, proper manufacturing quality standards, or the safety of other ingredients that may be included with the N-acetylcarnosine. 

Bottom Line
The theoretical arguments for why this drug might be useful I the treatment of canine cataracts are plausible but largely unproven. There is limited clinical trial evidence in humans suggesting a benefit, but this has not been replicated and is at high risk of bias. The limited clinical trial evidence available in dogs does not suggest a benefit. There are minimal safety concerns with products containing N-acetylcarnosine.

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172 Responses to N-Acetylcarnosine Eyedrops for Cataracts in Dogs and Cats (Can-C, Bright Eyes NAC, etc)

  1. andrew torok says:

    Dogs or people are pretty close as far as eyes are concerned except that dogs have better vision and are a lot smarter. Have you read about Lanosterol eyedrops for shrinking cataracts in dogs. Remarkable success. They were on the market (still listed on Amazon) but are now completely unavailable. I have no doubt they were too good and have been suppressed by parties marketing eye drops and services for cataracts. Please post if you uncover something.

  2. BB says:

    There is a new product that is going to be approved hopefully this year. The product contains lanosterol, maybe researching that and holding out for it to hit the market will be of benefit to you and the puppy.
    Good luck to you.

  3. Robert A. Brown says:

    BB: Do you have any more information on that product???

  4. andrew torok says:

    I’m surprised more people haven’t shown an interest in Lanosterol. Trials on dogs have been astounding. These trials have been conducted in universities and have been replicated and resulted in commercial production. Personally, I am interested using lanosterol for humans but information on its availability has dried up. Reason?

  5. Breakneckwind says:

    I used it for about two months -no change. I am waiting for Lanosterol to become available. (They replied to my email and told me by the end of this month)

    Note: It is VERY important to keep the Can C refrigerated. Your eyes will know if you didn’t.

  6. michael mifsud says:

    I have had very good results with Can C and Magic Eye Drops and discussed the issue with a few very skeptical vets who simply throw the book at you. I have brought up 25 dogs over the last fifteen years and shared every moment of their lives as I would with children. One totally blind elderly dog started to show improvements within the first month. The problem was the number of times it had to be done per day. Most of the drops simply fell out as he struggled to avoid it. The heavy white coverings dissolved slowly and even if it was pure cosmetics, it gave me hope that he would somehow see something. I noticed he seemed to manage much better, but I cannot say that he actually recovered his eyesight. He died of other problems associated with bad circulation. I am now doing the same for a younger dog who alas, is also a bind to try and aim for the pupil and with dropper in one hand without cap and two hands to hold her head, it is not long before she pulls out and spin dry with her head. I have therefore utilized more than I realized I would ever need. In any case, money, as pet owners who enjoy that special relationship, has little meaning in this context and I will continue, but even now, one eye is clear in so far as the white film is concerned and the other now has one half white and other half clear right across the iris and pupil . I have studied her behaviour patterns which show that she can see or is trying to do so as I stand up and crouch etc. She looks at me straight in the eye when I do, but again, I could not tell you whether she actually sees or has a shadow consciousness. I do not trust objects because she might be smelling them but there is reaction where there was none before. I will struggle until I get them as clear as they were. I am also giving her the tablets with pate which she takes readily. I have to say I often think that perhaps clearing the eyes may need eye memory of some sort after they have perhaps turned their attention to a smell sight which could be using the same brain area in them. Just a thought so no heresy arrows please……(from vets)

    I have utilized many vets and argued myself out of the back door mainly and despite being a professional researcher and writer and fellow of an academic society, I cannot get through to them with respect to anything which an owner may notice but which I regrettably think vets do not even look for. I believe that most of them in the early stages of their careers are pure theorists and lack genuine clinical experience. One even tried to operate without help or full information and practically killed what I called my daughter rushing to her cries on the phone (vet´s) who panicked when she woke up mid uterine operation ! I got there in time to help her revive her (half sown) and without memory of having cleaned her up internally properly. The dog survived a few more years but emotionally, she was gone. I have never recovered from that nightmare as she struggled to regain her body temperature via hot water bottles etc.

    In any case, when it comes to alternatives, it is best to ascertain any possible contras with the vet and then follow genuine critiques to determine whether it is worth a try. The drops are certainly worth it and if cash strung, get help in getting them on the pupil and keeping their eyes closed gently with the palm of the hand – as if simply playing – for at least a minute. Sorry to be so long winded-

  7. skeptvet says:

    The problem, of course, is that personal observations and anecdotes are deeply unreliable. All the significant and unprecedented improvements in human health in the last couple of centuries are due to the substitution of scientific evidence for trial and error and anecdote. So regardless of your professional background or the number of dogs you have owned, your anecdotes are stilljust that, and while they are useful for suggesting possible hypotheses, they can’t be used as proof of anything.

    Why We’re Often Wrong
    Testimonials Lie
    The Role of Anecdotes in Science-Based Medicine
    Why We Need Science: “I saw it with my own eyes” Is Not Enough
    Don’t Believe your Eyes (or Your Brain)

  8. michael mifsud says:

    My comments have not been published despite success on two occasions.[personal abuse deleted]

  9. skeptvet says:

    As you will see if you read comments throughout this blog, I am happy to permit posting of civil, substantive criticism or disagreement. I am under no obligation, however, to allow comments that are personally insulting or abusive. If you say, “You’re wrong and here’s why,” your comments will be posted. If you say “You’re stupid/arrogant/closed-minded/a tool of Big Pharm/etc…” or anything else directed at me personally, the comment will not be posted. And if you persist in doing so, you will be banned from commenting. Pretty simple and fair rules, so the choice is yours.

  10. Ashley says:

    I am in search of cataract drops for my 7 year old lab and was wondering if the Diclofenac sodium ophthalmic solution worked or if you have any other information? Thanks in advance!
    Ashley- concerned doggie lover 🙂

  11. skeptvet says:

    Diclofenac is a non-steroidal anti-inflammatory, sort of like an ibuprofen for the eye. It doesn’t treat cataracts in any way. It is often used to reduce inflammation after cataract surgery, but it has nothing to do with cataract prevention or treatment directly. I would strongly recommend consulting a veterinary ophthalmologist.

  12. Helen says:

    Admittedly I am not a vet. But for the record, although it doesn’t have any effect on the cataracts themselves, diclofenac is also used to reduce inflammation that can occur as a complication of cataracts that have not yet been removed. If Ashley has been reading that dogs with cataracts have been prescribed diclofenac, this would be the reason.

  13. Lawrence Phillips says:

    The last post on this topic is Sept 2014. It’s now two years later. Are there any updates? Our 15-years old cross breed terrier has great vision difficulty due to cataracts. Money is not an issue and too much has been mentioned about the money in previous posts. He can’t have surgery due to neurological risk etc. following a vestibular episode a couple of years back. I just want to make the little fella’s life more pleasant. Is there any update on Can-C safety?

  14. skeptvet says:

    Unfortunately, there does not appear to have been any new research or any confirmation of the initial findings of one researcher since this post was published. At this point, there is no convincing evidence this product is helpful. I would speak with your veterinary ophthalmologist about other options, but I think using this product would be grasping at straws.

    Good luck!

  15. silvia says:

    I think like any other med you take, it can have different effect on people. For example, I have been told by my doctor in France that Singulair is useless for asthma and considered a useless drug, and will be taken out of the market soon. My doctor here in the US told me it does work and that I should take it. Who to believe? try it for yourself and see if it works. Singulair works for me and control my asthma. It might not work on 70% of the general public, but it works for me. The same goes for that product Can-c. Doctors most of the time rely on studies because that’s all they can rely on, they refuse to look and consider different results. Studies are done on a sample population which is not the whole population so they are as accurate as they can be.

  16. skeptvet says:

    Unfortunately, the idea that personal experience is more reliable than population studies is a popular but dangerous misconception. While it is true that population studies can’t perfectly predict outcomes for any single individual, it is also true that trial-and-error has failed spectacularly throughout history at identifying effective treatments. While it is almost impossible to believe, the fact remains that if you do something and then feel better, that is NOT reliable evidence that what you did made you feel better, and the outcomes of population studies on that treatment are actually more reliable. Even in such a seemingly clear case as asthma, people get fooled by placebo effects and feel better when their lung function is completely unchanged by a placebo treatment. (Placebo Treatment for Asthma: Works for the Mind but not the Lungs)

    I would encourage you to look at some of the articles I’ve written on why such experiences can’t be trusted.

  17. Retired MD says:

    Going to try Can C on my 12 year old Brittany. Remember how long it took the medical world to accept the fact that a bacteria causes stomach ulcers. Currently, gluten restriction and low carb diets are only being recommended by a few. Maybe Can C is in the same boat in that more studies are not being done because there is no ECONOMIC reason for anybody else to do one. Almost every drug we ever accept is studied by it’s first inventors. If you don’t have a dog , there may be something wrong with your life!

  18. skeptvet says:

    And almost every drug that is promising in theory and pre-clinical studies fails to make it to clinical use because of inadequate safety and efficacy. Over 90% of new therapies don’t work despite early promise, so trying just because some theories and treatments have turned out to work is ignoring the odds.

    As for economic motives, they favor selling things without evidence of safety or efficacy because you can make money without the expense or effort of first proving your product works. This is not in the best interests of patients, which is why we regulate drugs and require such evidence before a company can profit off them. The fact that we don’t have the same standards for all medical treatments is a failing of our legal and political system, not a reason why we should accept products without good evidence. You are free to roll the dice with your pet’s health, but you should be clear about the risks involved.

  19. Any follow up research on the newer Lanosterol eye drops for cataracts?

  20. skeptvet says:

    The latest study using human cataractous lens nuclei was unable to replicate the earlier study using rabbit lenses, so at this point there is mixed positive and negative in vitro research and no clinical studies I am aware of.

  21. andrew torok says:

    re comment asking about anything new on Lanosterol. Bottom line: I tried it and it worked to some degree. Have eye appointment in February to compare the stats to before use. Company has stopped selling retail and claims to have resumed wholesale to Amazon and such. however, amazon has no mention of it.

  22. karen says:

    What does skeptvet think about eye bright and lutein for cataracts in animals ?

  23. skeptvet says:

    Haven’t looked into either, so no firm opinion. One relatively neutral source on eyebright suggests insufficient evidence and some possible risks. And here is some information about research into lutein, which also sounds pretty limited.

  24. Janet says:

    vitamin e does work. it is not useless. I was in my 40s an got what they call a trigger thumb, I used vit e for a while an it went away. Then when I was inmy 70s I got it again. My doctor said if my thumb was bent down an I could not get it up I would need surgery. I started with vit e again an it went away. If u say its useless how can I believe what u say about other things.an zinc works to on boils etc: Lyzine works to for animals an us. so does slippery elm. I know because itall an more has worked for my family.

  25. Pingback: cataracts - Pirate4x4.Com : 4x4 and Off-Road Forum

  26. Terrel says:

    Walmart tried to charge me over $60 per small bottle. Shopko’s price under $12. Be sure to get price quotes. We think our dog’s eyes are some what better after using the drip for 2 months.

  27. skeptvet says:

    Not lying, mistaken.

  28. skeptvet says:

    Not lying, just mistaken.

  29. Maria Kagelind says:

    I started giving my 17 year old cat Can-C the 13 of april2017. I give him one drop 2 times a day. His eyes where very red and his eyesigth is very bad. After 3 days the inflamation is almost gone. His eyesigth seems to become worse after these 3 days, he is confused and have difficult decide where to go. He have got instabel in his backlegs. I am very confused about what to do. I continue some more days and see what is taking place. I come back with information. My cat have Hyperthyroidproblems on special Medicatinfood Hill’s yd wet and dryfood.
    Maria Stockholm Sweden

  30. Priya Bansal says:

    There is nothing that indicates these drops are harmful (except for some reports that say the drops cause redness which goes away once usage is discontinued). There are multiple testimonials which indicate that the drops work as promised. Therefore, if you want to be skeptical about the drops’ effectiveness, you should be even more skeptical that the drops could cause harm.

    Either way there’s a risk. Cataract surgery for dogs is only 90% effective, and if the surgery doesn’t work, not even Can-C would be able to bring the eyesight back (since Can-C clears away cloudiness in the lens and surgery removes the lens — the reason it is only 90% effective is that it sometimes leads to scarring, which again results in blindness). The reported success rate for Can-C is much higher than 90%. But then there is the slight risk that if you wait too long for surgery, surgery might not be possible.

    It doesn’t make any sense to jump to any “it will definitely work” or “it definitely won’t work” conclusion. Like with most other things, you have to make a judgment call. I believe the risk of surgery is greater than the risk of waiting for surgery. It sucks that I have to make this kind of choice, but no matter what choice I made I would be elated if I was right and hate myself if I was wrong.

  31. Priya Bansal says:

    So… there’s this research study out there that you can’t prove exists yet you want us to believe that you’re not lying but the hundreds of people who say this product works are…

  32. skeptvet says:

    I agree that neither “it works” nor “it doesn’t work” can be substantiated based on the existing evidence. However, testimonials and anecdotes are effectively useless, and yet we tend to rely on them much more than scientific evidence. And I would also emphasize that the lack of good evidence not only means we don’t know for certain whether or not it is effective, it also means we don’t know for certain if it is safe. People always assume the lack of anecdotes indicating harm means something is probably safe, but that has been proven untrue repeatedly.

    The best we can say about this product is that there is insufficient evidence to be certain about its safety or effectiveness, that the positive claims made for it by the company ar unjustified, the anecdotes are unreliable, and using it is a gamble. Cataract surgery is certainly a surer bet, even though it is imperfect snd not always an option.

    Why Anecdotes Can’t Be Trusted

  33. skeptvet says:

    I never said anyone ways lying, so you are attacking a straw man of your own creation. I have said anecdotes are unreliable, and that is clearly true. And it really doesn’t matter if the unpublished study exists. If it does, then of course it is evidence against the effectiveness of the product, as well as the deceptive practices of the company. But even if it doesn’t, the fact remains that there is no good-quality or convincing evidence the product is safe and effective, only low-quality research funded and conducted by a biased party (the company selling the product) and anecdote. As I’ve said over and over, this doesn’t means the product doesn’t work, only that we don’t know if it works and is safe, so we’re rolling the dice if we use it.

  34. Priya Bansal says:

    Wanted to reply to Skeptvet’s replies to posts I made, but I can’t seem to find them.

    Saying personal statements are “effectively useless” is absurd. If something isn’t as good as something else, doesn’t make it useless. If personal statements were useless, witness accounts wouldn’t be a thing. And many court cases which lack reliable proof that a crime was or wasn’t committed rely on witness accounts. People spend their entire lives in jail because of witness accounts. So if this way of thinking is good enough for the justice system, why do you insist that it shouldn’t be good enough for us?

    You also replied to one of my comments with “I never said anyone ways [sic] lying.” By saying that personal accounts of this product’s effectiveness are unreliable, you are saying that the people making those accounts could be lying. Like another commenter said, cataracts do not just heal on their own. If a human who’s used it said that his cataracts healed after using it and he never underwent surgery, the only way his comment would be unreliable is if he were lying.

  35. Priya Bansal says:

    It’s funny how you go around saying stuff like “the fact remains that there is no good-quality or convincing evidence the product is safe and effective, only low-quality research funded and conducted by a biased party (the company selling the product) and anecdote[sic] . . . this doesn’t means the product doesn’t work” and then turn around and say “tje[sic] clinical trials show it doesn’t work.”

  36. G says:


    I applaud you for the time and energy to expend to bring forth the facts, or lack of facts, to some of these topics.

    Your tireless energy and effort it appreciated by those searching for the truth.

  37. skeptvet says:

    then turn around and say “tje[sic] clinical trials show it doesn’t work.”

    You appear to be quoting me, but I don’t see where I said this, in the article of the comments. Where is this quite from?

  38. skeptvet says:

    Nope, wrong on both counts.

    “Effectively useless” means that anecdotes cannot be used to reliably demonstrate whether or not a medical treatment is safe or effective. This has nothing to do with eyewitness testimony in court, which is a matter of law, not medical science. Such testimony is often in error as well, and this creates a huge problem, but in any case science and law are entirely different fields.

    And if you cant understand the distinction between being mistaken and lying, I’m not sure how I can make it clear to you. If you use a treatment and your condition gets better, that doesn’t mean the treatment is responsible. If you say that you used the treatment and got better, you may be mistaken, but you aren’t lying.

  39. Priya Bansal says:

    Still don’t know where my previous comments and their replies are, but here’s another quote:

    “If you use a treatment and your condition gets better, that doesn’t mean the treatment is responsible.”

    That implies that the only way the Can-C anecdotes could be unreliable (if the individual is not lying) is if the cataracts healed on their own, correct?

  40. skeptvet says:

    No it implies that there are many reasons why diseases improve or appear to improve, and the primary factor is not always the one thing we happen to remember doing or have decided must be the reason for the change. The concept of “I did X and got better so X made me better” is so consistently wrong, it even has it’s own name among the most common logical fallacies, the post hoc ergo propter hoc fallacy.

    Here is a detailed listing of possible reasons why the apparent cause of improvement in a disease may not be the real cause:

    Why We Are Often Wrong

  41. Charlotte says:

    Hello, I can’t afford the surgery, we have ordered the eye drops for my little baby, I will video document the whole process. I will keep you updated.


  42. juvy says:

    hi guys after reading all youre conversations I think I will take a risk to use CAN C eye drops for my dog ,he suddenly have cataract on his both eyes now ,I will pray that this medicine can help him to restore his vision…

  43. Jody Beskini says:

    Dear Sceptvet,
    I was looking at L-Carnosine by NOW Brands, seeing as the good reviews were rated A as valid reviews via fakespot. It appears ingestion of this might be okay for cats, but I am going to order some for myself, then ask my vet if she thinks it will be okay for my cat who has been recently diagnosed with glaucoma in one eye. I also wish there was a veterinary CBD for the eye pressure as the Dorzolamide HCL 2% – Timolol Maleate 0.5% that is prescribed might be harsh on this elderly cat whose kidneys are okay now, but I am concerned because this prescription can have some effect on feline’s kidneys?. Any feedback is welcome and thanks for your awesome articles!

  44. skeptvet says:

    I would discourage any use of cannabis-derived products for two reasons. First, the latest review of the evidence suggests they probably don’t work for glaucoma in humans. Second, cats are much more sensitive to side effects from medicines than humans and dogs, and we have no evidence for the safety of using cannabis medically in this species.

    Good luck!

  45. kay says:

    I’m buying can c for my dog Ronnie cataracts in both eyes I will let u know

  46. L says:

    My 9 year old little poodle mix was bit in the face by my terrier (food aggressive). To make a long story short one eye is a mess, totally shattered, eye has to come out, surgery tomorrow morning.
    Now, her other eye has a cataract 70%, the eye responds to light and there is one more test to do but I am leaning toward cataract surgery to improve the quality of her life.
    I know it is my decision and the ophthalmologist recommends it, I can’t afford another opinion. The surgery is not cheap. I am doing it on borrowed money.
    Any thoughts?

  47. L says:

    Oh, and regarding the terrier (Cairn) I am told he should be tested for ocular melanosis once a year. He is 5 years old. Am I looking for trouble? He goes to the regular vet for exams…..
    Just looking for opinions.

  48. L says:

    Okay, poodle mix (age 9) went in for a follow-up s/p right eye removal due to a traumatic injury.
    She is doing well, getting around the house and yard okay, with a little help.
    Here is my dilemma, the remaining eye is 70% cataract, she is blind.
    The ophthalmologist says if we opt for the cataract surgery, this, that and the other thing can happen including glaucoma. Also, if we don’t do the surgery, this, that and the other thing can happen including glaucoma.
    Then ophthalmologist says there is a 80 to 90 % success rate.
    Does the surgery usually work out well? Any vets out there? What would you do?
    I am leaning toward having the surgery done but I am worried…….

  49. L says:

    See, here in lies the problem. Trying to get quality care, for big bucks. Most of the time the vet techs over rule the dr (specialist). It’s really ridiculous. One says one thing, the other one says something different, all kinds of judgmental crap.

    Just wish I was wealthy so I could go to another place that I have had better results with to get another opinion.

    No one wants to tell you flat out what the real deal is.


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