Vitamin supplements have no benefit https://www.ncbi.nlm.nih.gov/books/NBK390313/ The results of the studies clearly show that vitamin supplements are not effective against cataracts. People who had taken these products – in some cases for many years – developed cataracts just as often as people who had been taking a placebo. The supplements also didn't slow down the progression of the cataracts, and they didn't have any effect on eyesight. But some products had side effects: Depending on the study, between 7 and 16 out of 100 people who took beta-carotene had their skin turn yellowish-orange. This is a sign that they had taken too much beta-carotene.
Although vitamins are important for the body, a normal, balanced diet usually provides enough vitamins. So there's no reason to take dietary supplements to try to prevent or slow down cataracts. The Cochrane researchers considered the results to be so clear that they see no need for further research in this area.
Nutritional Strategies to Prevent Lens Cataract: Current Status and Future Strategies https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6566364/ Dietary (Table 1) or low dose supplemental (Table 2) Vitamin C reduces the incidence and progression of disease, demonstrated in the majority of the 9 studies. However, a study comparing Vitamin C as part of a multivitamin-mineral (60 mg/day) versus a Vitamin C supplement (1000 mg/day) showed the high dose, single nutrient actually increased the risk of cataracts, while there was no change in the multivitamin-mineral group [15]. Also, Zheng-Selin (2013) [83] reported that a high dose of Vitamin C increased the risk of cataract disease by 21% and Vitamin E increased the risk by 57%. Studies investigating the plasma concentrations of ascorbic acid support findings from the dietary supplement studies that reported higher ascorbic acid concentrations were associated with a lower incidence of cataracts. A small-to-moderate dose of Vitamin C (less than 100 mg/day) appears optimal, while we caution the recommendation of high dose supplemental Vitamin C, deemed to be equal or greater than 500 mg/day, particularly when taken chronically. Intakes of 250 mg/day of Vitamin C did reduce the signs and symptoms of cataracts in a three-month intervention trial [84], suggesting a short-term dose of Vitamin C may benefit those already diagnosed. The value long-term is still in question.