How to Cure Night Blindness Naturally

How to Cure Night Blindness Naturally

You're driving along a country road at night. There's very little traffic, and nothing breaks the dark monotony except the play of your own car's headlamps and the winking of the cats'-eyes on the road ahead.

Suddenly, from around the next curve speeds another vehicle — the high beams of its headlamps exploding like a piercing slow-motion flash across your field of vision. Instinctively, you begin braking, while squinting off to the left side of the road, away from the glare.

After the other car passes, you breathe a sigh of relief and begin to accelerate again, only to discover that you can barely see. All is darkness. There are no reassuring cats'-eyes, reflective signs or even dimly perceived shoulders. Shaken, you somehow manage to pull over to the side to wait for the internal darkness to subside.

You are the victim of unexpected night blindness.

For years, night blindness or the loss of visual dark adaptation has been recognized as an early and classic sign of vitamin A deficiency. (It is also seen in some people with a malfunctioning thyroid gland). When we go from bright sunlight into the darkened confines of a cinema, for instance, it's natural that for a few moments, at least, we will be able to see next to nothing. But our eyes adapt. The person with impaired dark adaptation, on the other hand, may still be struggling to find an empty seat, and bumping shins and spilling popcorn in the process, many minutes after entering the cinema.

Vitamin A is not enough

Traditionally, victims of such episodes of night blindness have been urged to consume more vitamin A. (Remember all the old jokes about eating a lot of carrots?) And, as we'll see a bit later, adequate levels of vitamin A are absolutely essential for healthy eyes.

However, it now turns out that a person may be getting all the vitamin A that a balanced diet and even supplementation can supply, and still suffer from night blindness. At that point, a small amount of the essential dietary mineral zinc may work more wonders than all the carrots in the world.

As Dr. Stanley Morrison told the 17th annual meeting of the American Society for Clinical Nutrition in Washington, DC, patients suffering from liver disease often have a poor dark adaptation response, but among these people — often alcoholics with liver cirrhosis — extra vitamin A brings very disappointing results.

Dr. Morrison, a gastroenterologist, described a clinical study carried out by him and three co-workers at the Veterans Administration Hospital and University of Maryland School of Medicine in Baltimore. Six people with poor night vision who had been heavy drinkers for at least 15 years were selected for the trial.

Two of the patients were given supplements of 10, 000 IU of vitamin A daily, but after two weeks, dark adaptation was unchanged in one, and improved but still abnormal in the other. (In the tests, subjects were first exposed to a temporarily blinding bright light, then exposed to a series of flashing lights of various intensities until a threshold of discernment was regained). However, when 90 mg of zinc was given to the same two people daily, dark adaptation improved dramatically in the one and returned to normal in the other.

Three other patients were treated right from the start with zinc, and their dark adaptation improved within eight days. The sixth subject was given both zinc and vitamin A from the first day, and night vision was restored to normal within a week. 'Correction of zinc deficiency in some cirrhotics is an effective treatment for night blindness, ' Dr. Morrison concluded.

Why zinc is needed

How was zinc able to succeed where supplementary vitamin A had failed? Dr. Morrison believes that, although many people have all the vitamin A they require stored in their lives, it isn't being mobilized. Zinc, however, apparently steps up the formation of a critical binding protein that latches on to vitamin A in the liver and gets it flowing through the bloodstream to those sites where it's needed. Also, he says, zinc appears to be instrumental in enhancing a vital enzyme's activity in the retina of the eye, necessary for normal visual function.

Dr. Morrison noted that the problem of night blindness related to zinc deficiency has also surfaced in West Germany, where a surprisingly high number of applicants for driver's licenses have failed night-vision tests. German authorities apparently don't relish the prospect of thousands of visually impaired drivers hurtling down dark autobahns behind the wheels of swift Porsches and Mercedes-Benzes. Many of the Germans who failed the screening tests, Dr. Morrison said, had chronic liver disorders.

Similar unsuspected cases of night blindness may be wide-spread in the United States, Dr. Morrison told us. 'Most Americans eat pretty well,' he said, 'so they're getting vitamin A in their diet, but they're getting only marginal amounts of zinc, at best. Then you must superimpose on this the renal clearance problem — the fact that exorbitant amounts of zinc are excreted by the kidneys of people with cirrhosis. '

Just how widespread may the problem be? Leaving out for the moment those sober individuals whose diets may simply be deficient in zinc, Dr. Morrison noted that 'In the US, we're probably talking about 20 or 30 million people who drink heavily. And a substantial number of them probably have marginal zinc reserves. '

Drinking drains your zinc

Actually, the knowledge that alcohol tends to flush vital zinc right out of the body is not new. 'Zinc deficiency has been indicated as a concomitant of both alcoholism and cirrhosis for the last quarter of a century,' Jack Wang and Dr. Richard N Pierson, Jr reported at a meeting of the Federation of American Societies for Experimental Biology.

The pair, associated with St Luke's Hospital Center in New York City, reported that alcoholic rats showed a very sharp drop in liver stores of zinc within two weeks of beginning their alcohol diet. Levels of the mineral in muscle and blood also fell, but more gradually. 'The fact that liver fractions lose zinc rapidly when compared with muscle and [blood] plasma, suggests that the organ most susceptible to alcohol toxicity is the liver,' they said.

However, as we are now finding out, zinc deficiency ultimately shows itself in the eyes also, through its inhibiting effect on vitamin A. To better grasp the link, let's see how our night vision works.

In the light-sensitive layer across the back of the eye — the retina — are hundreds of thousands of tiny nerve endings. Some are cone-shaped and some are cylindrically shaped, like rods. Light energy that strikes and stimulates the cones and rods is transformed into nerve impulses, which register in the brain as vision.

Now it happens that night vision, or 'twilight seeing', depends almost entirely on the rods, which are more sensitive to faint light than the cones. The ability of the eye to adapt to changes in light depends on the presence of light-sensitive pigment in the rods called 'visual purple'. When light hits the retina (those high beams on the car approaching you), visual purple is split into its component parts. Back in the dark again (the other vehicle has passed), normal vision is not regained until adequate levels of visual purple have been regenerated.

Without vitamin A on hand, visual purple can't be formed. And Dr. Morrison's team and other researchers have now shown that without adequate zinc, the vitamin A to build visual purple just won't be available.

So if you have to venture out after the sun's gone down, whether on the road or simply to take out the rubbish, the message seems clear. Get enough vitamin A, but also be sure to get enough zinc. You'll probably never be able to see as well at night as the wise old owl, but hopefully, you'll never wind up lost in the dark, either.