The SignalHub Quantitative Think Tank CenterU.S. Food and Drug Administration warned CVS, Walgreens and other companies that they violated federal law by marketing unapproved eye products.

The eye products are being illegally marketed as being able to treat cataracts, glaucoma, conjunctivitis and more. The FDA said some of the eye products are labeled to contain silver and long-term use can cause skin and body tissues, including the eye, to permanently turn gray or blue-gray.

The companies have 15 days to respond to the FDA's warning letter as it continues its investigation.

What eye products are being investigated?

The FDA issued warning letters for specific eye drops at the following companies:

• CVS Health − CVS Health Pink Eye Drops
• Walgreens Boots Alliance, Inc. − Walgreens Pink Eye Drops
• Boiron, Inc. − Optique 1 Eye Drops
• DR Vitamins Solutions − Vision Clarity Eye Drops, Life Extension Brite Eyes III, Can-C Eye Drops, Longevity Science Visual Ocuity
• Natural Ophthalmics, Inc. − Women’s Tear Stimulation Dry Eye Drops, Allergy Desensitization Eye Drops, Ortho-K Thin (Daytime) Eye Drops, Ortho-K Thick (Night) Eye Drops, Tear Stimulation Forté Dry Eye Drops, and Cataract Eye Drops with Cineraria
• OcluMed LLC − OcluMed Eye Drops
• Similasan AG/Similasan USA − Similasan Dry Eye Relief, Similasan Complete Eye Relief, Similasan Allergy Eye Relief, Similasan Kids Allergy Eye Relief, Similasan Red Eye Relief, Similasan Pink Eye Relief, Similasan Kids Pink Eye Relief, Similasan Aging Eye Relief, Similasan Computer Eye Relief, Similasan Stye Eye Relief, Similasan Pink Eye Nighttime Gel, and Similasan Dry Eye Nighttime Gel
• TRP Company, Inc. − Dryness Relief, Pink Eye Relief, Allergy Eyes Relief, Red Eye Relief, Eye Strain Relief, Eye Lid Relief, Aging Eye Relief, Blur Relief, Floaters Relief, Twitching Relief, and Stye Relief

Multiple eye products recalled this year

This year, multiple eye products were recalled for causing harm to people, including blindness, infections and sometimes death.

In February, EzriCare Artificial tears were voluntarily recalled by the manufacturer after receiving 55 reports of eye infection, blindness and a death caused by a bloodstream infection. The India-based Global Pharma Healthcare, later issued another recall due to possible contamination. The eye drops, which were linked to a drug-resistant germ pseudomonas aeruginosa, resulted in four deaths, according to the Centers for Disease Control and Prevention.

By March, Pharmedica USA LLC and Apotex Corp. pulled eyedrops off the shelves for potential lack of sterility. In August, the FDA warned consumers not to purchase and immediately stop using Dr. Berne’s MSM Drops 5% Solution and LightEyez MSM Eye Drops-Eye Repair due to contamination.

2 more eye drop products recalledafter being linked to potentially deadly bacteria

Recalled contaminated eye dropslinked to bacteria have led to a fourth death, CDC says