N-acetylcarnosine (NAC) drops for age-related cataract

Full citation: Dubois VDJP, Bastawrous A. N-acetylcarnosine (NAC) drops for age-related cataract. Cochrane Database of Systematic Reviews 2017, Issue 2. Art. No.: CD009493. DOI: 10.1002/14651858.CD009493.pub2.

What is the aim of this review?
The aim of this Cochrane Review was to find out if NAC eye drops can prevent or reverse the progression of cataracts (cloudy lens in the eye).

Key messages
It is uncertain whether NAC eye drops prevent, or reverse, the progression of cataracts.

What was studied in the review? 
The eye has a clear lens that focuses the light on the back of the eye. As people get older this lens can become cloudy, leading to vision problems. A cloudy lens is known as a cataract. Doctors can remove the cataract and replace it with an artificial lens. This is usually a very successful operation. But any operation has risks and can be an unpleasant experience. Cataracts are common in older populations and cataract surgery is expensive for health care systems. This is why there is interest in preventing, or treating cataract, so that surgery can be avoided.

As part of normal metabolism, our bodies produce chemicals that contain oxygen and are reactive ("reactive oxygen species"). One theory of ageing is that these chemicals may be harmful and might lead to age-related changes in our body, such as cataract. This is known as oxidative stress. N-acetylcarnosine (NAC) is thought to be able to combat some of the effects of oxidative stress as it has anti-oxidant properties. If NAC can stop the lens from becoming cloudy, or reduce the cloudiness, this might improve people's vision and quality of life.

What are the main results of the review?
The Cochrane researchers found two potentially relevant studies. The studies compared NAC eye drops with placebo or no treatment. These studies were from Russia and the United States and were conducted by the same research group.The Cochrane researchers were unable to find out enough information about these studies to include in the review. These studies are assigned as ‘awaiting classification’ in the review until sufficient information can be obtained from the authors.

How up-to-date is this review?
The Cochrane researchers searched for studies that had been published up to 28 June 2016.