Vitamin C and Cataracts
We've talked a number of times before about how the press frequently gets stories about health and nutrition wrong. Often it's because they literally copy summaries of recently published studies that were sent to them by the big news agencies such as Reuters, AP, and UPI. Never bothering to even glance at the original studies, the press takes what the news agencies supply them as gospel and republish those stories making some minor changes in wording to make it look like an original story. Unfortunately, the news agencies frequently get the story wrong when writing up their summaries--or more accurately, leave out key parts to "simplify" the story for their clients in the press--so that misleading information is often published by hundreds of media outlets throughout the world…and assumed to be gospel by the public. After all, if everyone is saying the same thing, it must be true.
In other cases, universities or technical journals blast out a press release to the world's media--with much the same result. And that's what happened last month when the American Academy of Ophthalmology sent out a press release on a study from their latest issue of their journal, Ophthalmology, concerning vitamin C and cataracts.
However, before we get to that study and the key information that got left out of the press release, let's take a brief look at cataracts--what they are and how you get them.
Cataracts affect about 24 million people in the US and are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.1 Worldwide, cataracts are the leading cause of blindness,2 accounting for about 48% of all cases--with about 18 million people blind in both eyes as a result.3
Essentially, there are:
- Multiple triggers for cataracts
- Two primary pathways
- But when all is said and done, only one cause.
Cataracts occur when there is a buildup of protein in the lens that makes it cloudy. The lens itself is primarily made up of water and proteins. The proteins in the lens are arranged in a perfect physiochemical balance, ensuring that the lens is perfectly transparent. Once a cataract starts, however, it progresses as new lens cells form on the outside of the lens, compacting all the older cells into the center of the lens resulting in the cataract getting progressively denser and more opaque. These are known as nuclear cataracts. (Two variations are cortical cataracts, which are wedge-shaped and form around the edges of the nucleus, and posterior capsular cataracts, which form faster than the other two types and affect the back of the lens.) In any case, that's the sole cause of all cataracts: damage to the proteins in the cells of the lens. But as I mentioned earlier, there are multiple triggers that can spark the initial seed, without which there is no cataract to progress. These triggers include:
- Age-related cataracts. These are the most common type of cataract and develop as a result of aging, as the name suggests--or perhaps more accurately, as a result of a continual assault on the cells of the eyes until the cumulative damage over the years ultimately triggers the seed of a cataract to form.
- Genetic factors may play a role in age-related cataracts as cataracts tend to run in families.4
- Congenital cataracts in which babies are sometimes born with cataracts as a result of an infection, injury, or poor development before they were born. Or they may develop during childhood.
- Secondary cataracts. These develop as a result of other medical conditions, like diabetes or glaucoma or exposure to toxic substances or certain drugs (such as corticosteroids and diuretics). Other factors that can increase a person's risk of developing cataracts include:
- Cigarette smoke.
- Air pollution.
- Heavy alcohol consumption.
- Exposure to radiation when a person undergoes radiation treatment for cancer has been shown to trigger cataracts.
- Ultraviolet radiation from excessive exposure to unfiltered sunlight.
- Traumatic cataracts develop after an injury to the eye, but it can take several years for this to happen.
But that leaves a gap in our understanding of cataracts. We have identified the actual cause of cataracts (damage to protein) and have listed a number of triggers, but what we haven't done is actually connect the dots and explain the pathways that the triggers use to damage protein and thus form the seed of a cataract. Or to put it another way, what do aging, trauma, diabetes, and drinking alcohol share in common that can ultimately lead to cataracts. And the answer is that they all head down one of two pathways: free radical damage and/or glycation.
Free Radical Damage
We've certainly covered this topic in detail many times in the past. Nevertheless, let's do a quick review.
A free radical is an especially reactive atom or group of atoms that has one or more unpaired electrons. If you remember your high school chemistry, you will remember that electrons come in pairs. When one electron is lost from that pair, it makes the atom "highly reactive" as it looks to replace that lost electron anywhere it can. In your body, those replacement electrons come from cells in your body--destroying those cells in the process. Free radicals put your body in a state of oxidative stress in which your body is no longer able to maintain a balance between the appearance of reactive oxygen species and its ability to detoxify those free radicals or to repair the resulting damage. A single free radical can destroy an enzyme, a protein molecule, a strand of DNA, or an entire cell. Even worse, that one free radical can unleash, in a fraction of a second, a torrential chain reaction that produces a million or more additional killer free radicals--each out hunting for living cells to destroy like a herd of sharks in a mindless feeding frenzy. The proteins in the lens of the eye are especially vulnerable, which is why a number of antioxidants are concentrated in the eye to protect it from free radical damage. Free radical damage can be halted by anti- oxidants, but as we age, our bodies produce more harmful free radicals and less natural antioxidants. The net result is that damage from free radicals gradually begins to accumulate. Such free radical damage can happen in the cells of the eye, which, coupled with the damage caused by glycation, worsens the situation with regard to cataracts.
Antioxidants, quite simply, are compounds that render free radicals harmless and stop the chain reaction formation of new free radicals. Antioxidants and vitamin/antioxidants that are found in a healthy eye include:
- Vitamin E
- Beta carotene
- Vitamin C
Protein Glycation and Advanced Glycosylation End-products
As with free radicals, we've also covered this topic previously in great detail. To summarize from those reports:
Glycation is the uncontrolled reaction of sugars with proteins. It's kind of like what happens to sugars when you heat them and they caramelize. In effect, glycation is what happens when excess sugars and alcohols caramelize the proteins in your body. It's a major factor in the aging process -- and it's particularly devastating to diabetics since they tend to have higher circulating levels of sugar--the fuel that drives glycation. These oxidized sugars are also called Advanced Glycosylation End-products or AGEs for short. That's really the caramelization thing that I just mentioned. Thanks largely to the destructive effect of sugar and aldehydes (compounds formed by the oxidation of alcohol), the protein in the lens of your eye tends to undergo destructive changes as we age. This destruction, as we've already discussed, is the primary factor in both the onset and growth of cataracts.
Glycation Specific to the Eye
A 2003 study published in the Journal of Cataract & Refractive Surgery found that "Advanced glycation end products (AGEs) formed oxidatively and nonoxidatively occurred to a higher degree in cataractous lenses than in noncataractous lenses." Or to put it another way, "The strong relationship between the lenses' AGE content, color/opacity, and the state of the cataract may indicate that advanced glycation plays a pivotal role in cataract formation."5
One of the primary reasons that the lens of the eye so readily develops cataracts, as revealed in a 2009 study published in Biomedical Research, is that "Since the lens proteins are long-lived, they are highly susceptible to post-translational modification such as glycation."6 In other words, the longer a cell lives, the more exposure to free radicals and glycation it faces. And as already mentioned, the process is much more "vigorous" in diabetics because the higher levels of sugar and aldehydes in the blood are like throwing gasoline on a fire.7
So, now that we have some background on cataracts, let's take a look at the vitamin C study and see where the headlines once again got things wrong.
The Cataracts and Vitamin C Study
As we mentioned earlier, the media took their lead from a press release sent out by American Academy of Ophthalmology.8 So let's take a look at that release, starting with the headline that blasted across the computer screens of all the world's media outlets.
Eating Foods High in Vitamin C Cuts Risk of Cataract Progression by a Third
Research on UK twins is first to show that diet, lifestyle may outweigh genetics
when it comes to common eye condition9
Researchers at King's College London looked at whether certain nutrients from food or supplements could help prevent cataract progression. They also tried to find out how much environmental factors such as diet mattered versus genetics. According to the release, the study found that vitamin C had a protective effect against cataracts getting worse during a long-term study of twins--with people who had a higher dietary intake of vitamin C seeing cataract progression decrease by one-third over the course of a decade. The research is also the first to show that diet and lifestyle may play a greater role than genetics in cataract development and severity.
The twist in the study that most of the press latched onto from the press release was that this benefit was only experienced by participants who consumed more vitamin C as part of their diet; no such luck for those who took vitamin C supplements.
For the study, researchers examined data from more than 1,000 pairs of female twins from the United Kingdom. Participants answered a food questionnaire to track the intake of vitamin C and other nutrients, including vitamins A, B, D, E, copper, manganese and zinc. To measure the progression of cataracts, digital imaging was used to check the opacity of their lenses at around age 60. They performed a follow-up measurement on 324 pairs of the twins about 10 years later. During the baseline measurement, diets rich in vitamin C were associated with a 20 percent risk reduction for cataract. After 10 years, researchers found that women who reported consuming more vitamin C-rich foods had a 33 percent risk reduction of cataract progression. How vitamin C inhibits cataract progression may have to do with its strength as an antioxidant. The fluid inside the eye is normally high in vitamin C, which helps prevent oxidation that clouds the lens. More vitamin C may increase the amount present in the fluid around the lens, providing extra protection. Researchers noted, however, that the findings only pertain to consuming the nutrient through food and not vitamin supplements.
In the end, genetic factors accounted for 35 percent of the difference in cataract progression. Environmental factors, such as diet, accounted for 65 percent. These results make the study the first to suggest that genetic factors may be less important in progression of cataract than previously thought.
While the researchers note conclusions based on the study should be limited because participants were a limited group--predominantly British women between the ages of 60 and 70--and other parts of their diets may also have an effect on how their cataracts progress. Regardless, the researchers said the study suggests a possible benefit from more dietary vitamin C, which the body needs anyway. "The most important finding was that vitamin C intake from food seemed to protect against cataract progression," said study author Christopher Hammond, M.D., FRCOphth, professor of ophthalmology at King's College London. "While we cannot totally avoid developing cataracts, we may be able to delay their onset and keep them from worsening significantly by eating a diet rich in vitamin C."
What the Headlines Missed
Based on the reports, you would think that vitamin C supplements had no impact on cataracts and that it was only the vitamin C in food that helped. In fact, neither conclusion is true as stated.
To quote from the study:
"Our results are similar to those of the Carotenoids in Age-Related Eye Disease Study that showed vitamin C intake, assessed with an FFQ 10 years before cataract assessment, to be protective of nuclear cataract prevalence.10 The Blue Mountains Eye Study also found that vitamin C intake, through both diet and supplements together, resulted in a lower nuclear cataract incidence over 10 years.11 This study is the first, to our knowledge, to show that dietary vitamin C intake protects against progression of nuclear lens opacity."
In other words, saying that supplemental vitamin C provides no benefit in terms of cataracts is both highly inaccurate and highly misrepresentative of the study's actual conclusions. According to the current study, as well as several previous studies, Vitamin C supplements are effective at reducing the incidence of cataracts; they just don't work in terms of slowing the progression of cataracts once you get them. And this makes sense because, as we've already stated, the fluid inside the eye is normally high in vitamin C, which helps prevent oxidation that clouds the lens. As the study pointed out, in order to slow the progression of a cataract you actually have to eat foods that contain vitamin C. Which brings us to the second major point from the study that never made into the news stories--and could possibly explain why supplements don't slow progression.
As stated in the study's conclusion, "As in any observational study, ours is potentially susceptible to residual confounding, missing data, or misspecification of variables."
So what got missed?
As I have mentioned on numerous occasions, nutrients exist in complexes, not in isolation. Nature never packs nutrients as isolates. When you find vitamin C in foods, it always comes packaged with bioflavonoids and/or phenols. Beta carotene always comes packaged with a host of other carotenoids. Vitamin B1 always comes packaged with a number of the other B vitamins. It's the main reason I always try to use nutrient complexes in my formulas. As a case in point, in my ultimate antioxidant formula, certain nutrients that list separately on the label are actually part of complexes. For example:
- The beta carotene and alpha carotene list as separate ingredients on the label, but they are actually both part of the same natural carotenoid complex ingredient (as well as a number of other carotenoids that come with the complex are not even listed on the label).
- Likewise, lutein and zeaxanthin are listed separately on the label, but they are both part of the same complex extracted from flower petals.
Which brings us to vitamin C and why dietary vitamin C and most vitamin C supplements do not behave identically in the human body. And the reason, if you've been following along, is that most supplemental vitamin C is pure ascorbic acid whereas dietary vitamin C does not exist in isolation, but exists as part of a rich bioflavonoid nutritional complex that includes:
- Rutin. A 2013 study published in Graefe's Archive for Clinical and Experimental Ophthalmology found that rutin can ameliorate the progression of free radical induced cataracts.12 This pairs up nicely with a 2012 British Journal of Nutrition study that demonstrated the potential of rutin to both prevent and inhibit protein glycation and the prospects for controlling AGE-mediated diabetic pathological conditions in vivo--specifically demonstrating its beneficial effect on eye lens proteins.13
- Naringin. Although tested primarily for its anticancer benefit, there is evidence that it can prevent cataract formation by functioning as an aldose reductase inhibitor (ARI).14 The role of ARI's in the prevention of diabetic
cataract in animals is now well established.15, 16
- Hesperidin. In a study of 40 flavone derivatives, hesperidin was found to be a potent ARI like naringin.17
- Quercetin and its close cousins, the bioflavonoids quercitrin (found in buckwheat), and myricitrin (found in bayberry root bark), are all potent aldose reductase inhibitors18 and, thus, highly effective in preventing the formation of diabetic cataracts. A study published earlier this year in Experimental Eye Research found that a blueberry leafextract (which contained both quercetin and rutin, along with several polyphenols) effectively prevented the formation of cataracts both in vitro and in vivo. The study specifically showed that quercetin slowed down the hardening of the eye lens, and that rutin helped moderate the breakdown of lens proteins.19
- Nobiletin is one of the most abundant polymethoxyflavones. (Polymethoxyflavones (PMFs) and hydroxylated polymethoxyflavones exist exclusively in citrus genus, especially in the citrus peels which have been used as herbal medicine for several diseases for thousands of years.) It appears to play a major role in preventing the formation of cataracts.20
The bottom line is that although vitamin C itself may be instrumental in stopping the onset of cataracts, it's not unlikely that the ability of vitamin C rich foods to stop the progression of cataracts actually comes from some of the associated bioflavonoids and polyphenols which are present in vitamin C foods, but not specifically tracked by the researchers--in other words, the missing data to which they referred.
Surgery is the only "medically approved" way to remove cataracts and restore your vision. Cataract surgery is one of the most commonly performed surgical procedures in the U.S. It is also one of the most successful. Over 95 percent of cataract surgeries result in improved vision.21 However, like any surgery, there can be complications that can be severe or even sight threatening. (Note: your chance of developing complications is greater if you have another eye disease or serious medical condition.) In any case, these complications can usually be successfully treated, which means that, ultimately, cataract surgery is one of the safest and most successful forms of surgery in the world today. If you opt for surgery, there are several progressive options with associated progressive costs.
- Basic. The surgeon will make a small incision in the cornea with a scalpel. A small probe breaks up and removes the cataract; a new lens is inserted. In most cases, the incision is so small that stitches are not required. Once the cataract surgery is completed, the surgeon covers the eye with a bandage or shield. In many cases, the bandage may be removed within a few hours. After a short recovery period, you can have someone drive you home. Basic surgery is usually covered by Medicare and private insurance.
- Laser. Essentially the same as basic surgery, but instead of a handheld scalpel, the incision is made using a precision guided laser. This is more expensive since the laser equipment itself is quite expensive, but allows for much more accurate surgery and a smaller incision. Usually, no bandage is needed after surgery, and the recovery time is much faster. In most cases, the added expense for laser surgery is not covered by Medicare or private insurance--in which case you will have to make up the difference.
And then there are the lenses used to replace the cataract damaged lens in your eye. As with the surgery, there are choices when it comes to intraocular lenses (IOLs).
Monofocal lenses are the cheapest option. Once made of glass, these lenses are usually made of a foldable plastic nowadays that allows for a much smaller incision for inserting. Medicare and private insurance typically cover monofocal lens. The downside is that they will only focus at one distance (usually far rather than near) so you will need to wear glasses or contacts for everyday activities--usually for reading and close up work. But even within the world of monofocal lenses, there is a range of choices.
- Traditional intraocular lenses have a spherical optical design, meaning the front surface is uniformly curved from the center of the lens to its periphery. Though a spherical IOL is relatively easy to manufacture--one size fits all, for the most part--this design does not mimic the shape of the natural lens inside the eye, which varies in curvature from center to periphery. In other words, the eye's natural lens is aspheric ("not spherical"). Why is this important? A spherical intraocular lens can induce minor optical imperfections called higher-order aberrations, which can affect quality of vision, particularly in low-light conditions such as driving at night.
- Premium aspheric IOLs, on the other hand, match more closely the shape and optical quality of the eye's natural lens, and thereby can provide sharper vision--especially in low light conditions and for people with large pupils. As the word "premium" implies, they are more expensive than spherical lenses.
- Toric IOLs are premium intraocular lenses that correct astigmatism as well as nearsightedness or farsightedness. They get their name from their shape, which is torus-like; a torus is donut shaped. Again, they are more expensive than basic spherical lenses.
Accommodating lenses are premium IOLs with small hinges built-in that allow for a degree of flexibility in the lens, which gives them "some" ability to focus. The hinges allow the accommodating IOL to move forward slightly when you look at near objects, which increases the focusing power of the eye enough to provide better near vision than a conventional monofocal lens but not as good as a multifocal lens. They are not an option if you also need vision correction--especially for astigmatism.
Multifocal lenses afford you the opportunity to be free of glasses for activities and at all distances -- near, far, and everything in between. And if you're willing to stretch even further financially, multifocal lenses can also be made so as to correct vision problems such as near- and far-sightedness as well as moderate astigmatism. As with laser surgery, the added cost of multifocal lenses is not usually covered by Medicare and private insurance--in which case you will have to make up the difference out of pocket. Note: one downside to multifocal lenses is that they can tend to produce a halo effect around bright lights. However, over time, as the brain adapts, the problem tends to diminish if not necessarily completely disappear. It's a tradeoff that you have to evaluate: is the risk of halos worth the advantage of not having to wear glasses?
Monovision is another option. It doesn't refer to a type of lens but to the technique of using lenses (multifocal and toric) that intentionally make one eye better at focusing close up and the other eye better at distance focusing--so that between them your vision is optimized across the full spectrum of distance.
Bionic lenses are the future--and not necessarily that far off in the future. Bionic lenses are IOLs that promise not just to restore your sight, but claim to be able to boost it to three times better than 20/20. The first of such lenses has already been developed by a company called Ocumetics22 and is undergoing testing. Approval is anticipated at two years for Canada and Europe and four to seven years in the US.23
Is There an Alternative to Surgery?
Well, as we've seen--and scientific research confirms it--you can certainly make dietary and supplement choices that can dramatically decrease your odds of ever getting a cataract or slowing its progression if you ever do get one. This includes:
- Vitamin C rich foods
- Vitamin C supplements (naturally sourced whole complexes being a better option than pure ascorbic acid)
- Potassium and magnesium
- L-carnosine based formulas
Other than Surgery
Slowing down and preventing cataracts is one thing, but can you actually get rid of a cataract using diet and supplements? And here the answer gets a little cloudier. I've seen two things work for some people, but not everyone.
- Carnosine eye drops. There are no blood vessels that actually feed the lens of the eye so getting dietary sources of carnosine into the lens is problematic. But there is an option. N-acetylcarnosine (not to be confused with N-acetyl-cysteine) is a stable form of carnosine that can be used in eye drops and actually reach the lens of the eye. It's early stages in the research, but there are at least some studies that indicate that it may actually reverse cataracts.24, 25 My personal experience working with N-acetylcarnosine eye drops is inconsistent. They definitely work for some people--but not everyone.
- Dr. John Christopher recommended an eyewash consisting of bayberry bark, eyebright herb, golden seal root, red raspberry leaves, and cayenne. To use the extract he recommended that you:
- Boil distilled water and then fill a glass eye cup with the hot boiled distilled water. Start by adding one drop of eyebright formula to each cup and work up to between three to five drops of extract per cup. Let cool. There will be a burning sensation when using the eyewash at first. This is due to the stimulating effect of the cayenne pepper and will do nothing but good to the eyes. Tip your head back and apply the eye cup to your eye. Exercise your eye while doing this--moving it left, right, up, down, and in circles--as though you were swimming under water. Do this three to six times a day and take two capsules or a cup of the tea, morning and evening.
- This treatment has been around for decades and many people swear by it. But many people have also found that their cataracts remained unchanged. I played with the formula myself just to see what it felt like with the cayenne in it. At first, it really did sting, and my eyes turned bright red for about 15 minutes. But the more I did it (and the more drops of extract I used), the more used to it I became. After a couple of weeks, it was actually extremely refreshing to the eyes. And about 10 minutes after doing the wash, the whites of the eyes were brilliantly clear. No red whatsoever. Again, as with the carnosine eye drops, you have nothing to lose by giving it a try.
These options are certainly worth giving a shot before you opt for surgery. If they work for you, you get to keep your own lens. If not, you still have the surgical option.
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- 2. "Global Data on Visual Impairments." WHO /NMH/PBD/1201, 2010. http://www.who.int/blindness/GLOBALDATAFINALforweb.pdf
- 3. "Cataract." International Agency for the Prevention of Blindness. (Accessed 2 Apr 2016.) http://www.iapb.org/vision-2020/what-is-avoidable-blindness/cataract
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- 5. Sybille Franke, Jens Dawczynski, Jürgen Strobel, et al. "Increased levels of advanced glycation end products in human cataractous lenses?" Journal of Cataract & Refractive Surgery , Volume 29 , Issue 5 , 998 - 1004. http://www.jcrsjournal.org/article/S0886-3350(02)01841-2/abstract
- 6. Ashok V. Katta, A.N. Suryakar, R.V. Katkam, et al. "Glycation of lens crystalline protein in the pathogenesis of various forms of cataract." Biomedical Research. Vol. 20, No. 2 (2009-05 - 2009-08). http://www.indmedica.com/journals.php?journalid=12&issueid=136&articleid=1795&action=article
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- 9. Yonova-Doing, Ekaterina, Forkin, Zoe A., Hammond, Christopher J., et al. "Genetic and Dietary Factors Influencing the Progression of Nuclear Cataract." Ophthalmology. Manuscript no. 2015-1709. 23 Mar 2016. http://www.aaojournal.org/article/S0161-6420(16)00114-7/pdf
- 10. Mares JA, Voland R, Adler R, et al. "Healthy diets and the subsequent prevalence of nuclear cataract in women." Arch Ophthalmol 2010;128:738--49. http://archopht.jamanetwork.com/article.aspx?articleid=425821
- 11. Tan AG, Mitchell P, Flood VM, et al. "Antioxidant nutrient intake and the long-term incidence of age-related cataract: the Blue Mountains Eye Study." Am J Clin Nutr 2008;87:1899--905. http://www.scopus.com/record/display.uri?eid=2-s2.0-45749086416&origin=inward&txGid=0
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- 13. Muthenna P, Akileshwari C, Saraswat M, Bhanuprakash Reddy G. "Inhibition of advanced glycation end-product formation on eye lens protein by rutin." Br J Nutr. 2012 Apr;107(7):941-9. https://www.ncbi.nlm.nih.gov/pubmed/21864418
- 14. S K Gupta, V Kalai Selvan, S S Agrawal, and Rohit Saxena1. "Advances in pharmacological strategies for the prevention of cataract development." Indian J Ophthalmol. 2009 May-Jun; 57(3): 175--183. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683438/
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- 17. Varma SD, Kinoshita JH. "Inhibition of lens aldose reductase by flavonoids - their possible role in the prevention of diabetic cataracts." Biochem Pharm 1976;25:2505-2513. http://www.sciencedirect.com/science/article/pii/0006295276904573
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- 19. Ferlemi AV, Makri OE, Mermigki PG, et al. "Quercetin glycosides and chlorogenic acid in highbush blueberry leaf decoction prevent cataractogenesis in vivo and in vitro: Investigation of the effect on calpains, antioxidant and metal chelating properties." Exp Eye Res. 2016 Jan 22;145:258-268. https://www.ncbi.nlm.nih.gov/pubmed/26808488
- 20. Miyata Y, Oshitari T, Okuyama Y, Shimada A, et al. "Polymethoxyflavones as agents that prevent formation of cataract: nobiletin congeners show potent growth inhibitory effects in human lens epithelial cells." Bioorg Med Chem Lett. 2013 Jan 1;23(1):183-7. http://www.ncbi.nlm.nih.gov/pubmed/23199882
- 21. "Cataract Procedure." myeyes.com. (Accessed 2 Apr 2016.) http://www.myeyes.com/cataracts/laser-cataract-surgery-procedure.shtml
- 22. http://ocumetics.com/
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- 24. Babizhayev MA, Micans P, Guiotto A, Kasus-Jacobi A. "N-acetylcarnosine lubricant eyedrops possess all-in-one universal antioxidant protective effects of L-carnosine in aqueous and lipid membrane environments, aldehyde scavenging, and transglycation activities inherent to cataracts: a clinical study of the new vision-saving drug N-acetylcarnosine eyedrop therapy in a database population of over 50,500 patients." Am J Ther. 2009 Nov-Dec;16(6):517-33. http://www.ncbi.nlm.nih.gov/pubmed/19487926
- 25. Babizhayev MA, Yegorov YE. "Biomarkers of oxidative stress and cataract. Novel drug delivery therapeutic strategies targeting telomere reduction and the expression of telomerase activity in the lens epithelial cells with N-acetylcarnosine lubricant eye drops: anti-cataract which helps to prevent and treat cataracts in the eyes of dogs and other animals." Curr Drug Deliv. 2014;11(1):24-61. http://www.ncbi.nlm.nih.gov/pubmed/24783234