I am generally a bit hesitant to recommend most nutritional supplements. I feel more comfortable recommending super foods (ghee, honey, garlic, chlorophyll, aloe vera juice, kale, etc.) and herbs. However, sometimes vitamins and minerals can be helpful when used correctly. I think Vitamin C is one nutrient that deserves special attention by anyone with vision problems.
My advice to anyone with vision problems (or other health problems) is to find the least expensive pure ascorbic acid you can find and take a lot of it (after you educate yourself and possibly check with a doctor who understands Vitamin C). I think of my Vitamin C supplement as simply a source of ascorbic acid. I try to get my bioflavonoids from foods and herbs.
I have not found the "Vitamin C complex" products (those with flavanones, hesperidin, rutin, quercetin, etc.) to be very satisfactory, and most experts seem to echo this opinion. It's not that those other factors are unimportant. Not at all. It's just that those bioflavonoids and such are nutrients we can probably obtain in sufficient quantities from foods or herbs. And I don't think the supplements can provide the full spectrum of "Vitamin C complex" nutrients that foods or herbs such as Amla provide. I look for pure ascorbic acid when I look for a Vitamin C supplement. (For anyone who is curious, I also take Amla in the bulk organic powder form found here - I don't hold much hope of finding a Vitamin C product that could match my Ayurvedic herbs in terms of the "complex" factors.)
Most experts advise using pure ascorbic acid powder. You can find it on the Internet with a search like this. NOW makes a Vitamin C product that I here good things about. I've used many of the NOW products with good results in the past.
However, even though most "serious" Vitamin C consumers use powder, I go with tablets. Ascorbic acid powder can damage your tooth enamel if you don't rinse your mouth after drinking it. (Of course lemon juice can do the same thing, but that's another story.) Anyway, I prefer the simplicity of Vitamin C tablets.
Currently I purchase my Vitamin C at Costco here in the USA. Here is the link: http://www.costco.com/Browse/Product.aspx?Prodid=10015954&whse=BC&topnav=&browse=&s=1
As you can see, the tablets have binders and fillers that the pure powder does not have. One day I may go back to the pure powder if I know I can discipline myself to rinse my mouth every single time I drink it.
Most of the time the tablets cost a bit more. However, Costco currently sells a bottle of 500 one gram tablets for $US 9.99. That's cheaper than the pure powder in many cases.
I have two widely different criteria I apply to nutritional supplements. I apply one criteria to Vitamin C and another completely different criteria to everything else.
Vitamin C is the only supplement I take where I consider price an important factor. I usually look for quality first. Most of my supplements are Ayurvedic herbs, and there is no such thing as a commodity herb in my opinion. However, most Vitamin C experts consider ascorbic acid to be a commodity product. It is fairly easy to find pure ascorbic acid and then make a selection based on price. I look for the United States Pharmacopeia (USP) seal of purity (link: http://www.usp.org/aboutUSP/). It also pays to look at the other ingredients in the product if you choose to use tablets.
I recently spoke with Dr. Robert Cathcart III on the telephone. He is one of the world's top authorities on Vitamin C. I believe he is in agreement with the info above on Vitamin C. Furthermore, he does not recommend any of the mineral ascorbates orally. He has had the best clinical results with plain ascorbic acid. And like all the other real Vitamin C experts I know, he is against Ester-C.
<rant> Find a pure ascorbic acid tablet or powder from a company you trust to sell pure nutritional products. Take a lot of it. Don't take Ester-C. Don't take fancy mineral ascorbates. Don't take AscorbAde or Lypo-Spheric Vitamin C. Don't take expensive Vitamin C products with a bunch of extra ingredients. Do eat the best diet you can and try to get as many of your nutrients as possible from plant sources (foods and herbs & spices). </rant> 
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