It is much more effective when applied topically rather than orally, as it is true with a lot of other compounds. From our own experience, we couldn't tell much difference in the optical state from oral l-carnosine supplementation, as in comparison to dramatic (and also instant) effects experienced from an eye drop form.
The NAC molecular structure is identical to carnosine with the exception that it carries an additional acetyl group. It is only n-acetyl-carnosine that has been clinically proven as suitable for eye use. When applied as eye drops l-carnosine cannot penetrate the eye.
Antioxidants decrease dry eye symptoms and although the factors that lead to DED are often complex you can expect improvements by addressing free radical damage, as that is most certainly one of those factors.
Your eyes will benefit from the drops especially when in a severely antioxidant deficient state, including situations when there is a lower expression of antioxidant enzymes, like in the eyes with Sjogren's syndrome.
N-acetyl-carnosine first became popular for its use in eye drops as a cataract remedy, we do not however promote our product as such. The drops are meant to help positively affect eye health and can be used to universally benefit any ocular condition, including this of cataracts. Nevertheless we don't recommended our drops as an alternative to medical treatment of cataracts.
According to a board-certified veterinary ophthalmologist, almost all over-the-counter ocular lubricants are safe for pets. The only ones you need to avoid are redness reliever eye drops. Our drops don't contain any artificial vasoconstrictors, only an antioxidant that helps reduce inflammation naturally.