Myopia can be hereditary, but reading in low light conditions or glaring sunlight may also affect how the eyes perform later in life. Until it is known whether vision problems are strictly hereditary or how great a role the environment plays, it is best to care for the eyes by using good reading lamps for close work.
Nature vs. Nurture
Vision naturally changes with age. The eyes require more light and corrective lenses to deal with the changes. A person aged 60 requires twice the light intensity as a 20-year-old performing the same task. Light coming into the eye from an unwanted direction causes headache, obscured vision and fatigue. This glare, whether direct or indirect, should be minimised to minimise eyestrain. A correctly positioned reading lamp with adequate illumination is key.
The light source for an individual sitting at a desk should be placed slightly above and behind the head. This will allow light to shine over the left shoulder for the right-handed reader and over the right shoulder for left-handed individuals. The room should also have a second light source to reduce unwanted contrast and shadows. Bedtime lamps should be bright enough to read by but not bright enough to create shadows or glare.
Lighting for computer work should not produce a glare on the screen or originate from a window behind the screen. Regular breaks away from the screen will reduce the incidence of tired or burning eyes and eyestrain headaches. Posture is also important. Poor posture can affect blood circulation in the spine and head and produce shallow breathing that can affect vision effectiveness.
Correct light intensity makes print appear darker against a white page. Natural light coming in a window gives off 100 to 500 foot candles of light while a 60W bulb offers only 80. (One foot candle is the amount of light produced by one candle placed one foot away from a page of print.) Natural light is preferable to any artificial source of illumination.
At night, when natural light is not an option, a tall table lamp with a 150W bulb is the next best thing. The lamp should be placed on the table to the left of your chair. If glare from the lamp is detected on the page of the book or on the computer screen, the position of the light on the table should be adjusted until the glare is gone.
It is important to take regular breaks or make it a habit to look away from the television, book or computer screen to give the eyes a rest. Overuse of any part of the body can cause injury. The eyes are no exception.