How To Keep Your Eyes Healthy The most important tool you have to see the universe is not your telescope, but rather your eyes. It is critical that you maintain eye health if you enjoy gazing at the night sky. There are certain "tricks" such as averted gaze that can be used to see more, and there are certain vitamin supplements, such as Lutein and trace minerals, that can help keep your eyes healthy. By understanding your eye, and protecting your vision with vitamin supplements such as B complex, Lutein and antioxidants and trace minerals, your observations may actually improve! ALWAYS wear sunglasses outside during the day! Light enters the eye through the cornea, passes across the aqueous humor (the liquid behind the cornea), and passes through the pupil and through the lens. The cornea stops high ultraviolet light. The lens stops violet and blue light, especially as we get older, and is damaged by UV light. The human lens grows continuously with age, with new cells added on the outside of the lens, resulting in an onion-like layering of cells with age. The older, central dead cells degenerate and "yellow" the lens with age. Eventually, cataracts (crystallization) of the inner lens may occur, blocking vision. Cataracts are also promoted by exposure to radiation. After passing the lens, the light then crosses the "vitreous humor" a jelly-like substance that fills the inner eye, and reaches the retina, the light sensitive tissue at the back of the eye. Sometimes clumps of cells detach from the retina and migrate into the vitreous, creating "floaters" when they are in the line of sight, and this gradually progresses with age. Aging is not kind to astronomers. That is where vitamin supplements come in.   Taking certain vitamin and mineral supplements can help our eyes stay healthy for a longer period of time. Vitamin supplements for the eyes can also help prevent many diseases. Although we can theoretically obtain all the vitamins and minerals we need by eating a perfect diet, it is nearly impossible in these fast food dominated times to get a healthy meal with all the vitamins and minerals we need to stay healthy.   Vitamins made for the eye should contain vitamin A, vitamin C, vitamin E, riboflavin and trace minerals, especially Zinc and Selenium. Of course eye vitamins now may contain the popular new Lutein. Lutein is an antioxidant whose true value is still being studied but is already gaining much attention. Lutein is concentrated mostly in the retina, lens and macula and thus it is assumed that having an efficient amount of Lutein will keep the eyes healthy.   Why ‘Averted Vision’ and ‘Flickering’ Can Help You See More: The retina is actually an outgrowth of the brain and processes some of the information it receives before passing the signal over the optic nerve to the visual center of the brain (occipital cortex in the back of the head). The actual receptors are the rods and cones of the retina. There are three types of cones (red, yellow-green, and blue), and they work best in bright light. The cones are also used for acuity (resolution). They unfortunately fail us in dim light situations (this is why night vision is black and white). Cones are concentrated in the fovea, the center point of your vision when you stare at an object. As you increase light intensity, a threshold is reached where color vision recurs (as in using a larger telescope to see color in M42). Night vision is dominated by rods (Black and white vision); but there are no rods in the fovea, increasing rapidly in density in the retina away from the center of vision to peak in an ellipse about 15-20 Degrees out from the fovea. That is why staring 15 degrees away from a dim galaxy improves your view of it. There are about 120 million rods in the human eye (good pixel density). They are identical, but their connections vary significantly. Some are used for normal viewing, but some are only activated by motion. Some are specialized to vertical or horizontal motion; others see only lines for edge sharpening, etc. This is why "flickering" your eye slightly also allows you to see more; you are recruiting more of your rods! Don’t Smoke! Smokers suffer from poor night vision due to a poisoning of their bloodstream with carbon monoxide. For every pack per day you smoke, your blood is 10% diminished in oxygen carrying ability due to the carbon monoxide, and your eye also suffers to this degree as the retina extracts nearly all the oxygen it is presented. High altitudes decrease oxygen pressure, and vision therefore suffers compared to sea level. Vision decreases if blood sugar levels are low. This is why an occasional snack while observing at night can help. Alcohol diminishes both light sensitivity as well as brain function. Do not drink and observe! Treat Your Eyes With Care: Your eyes are remarkably efficient, able to produce a signal with only one photon, though the brain routinely suppresses single photons as noise, and generally you need 2-3 photons over a small area in a short time span to produce a signal (pixel) to the brain. Your eye utilizes nearly all of the oxygen that reaches it, and is also dependent on glucose (sugar). If you protect your eyes from the damaging rays of the sun, and take your daily vitamins, minerals & antioxidants, you can help your eyes stay healthy and continue enjoying the beauty of the night sky long into old age.