York County Medicine Fall 2020 - 19

Eyes Can Be Damaged
By A Variety Of Light Sources
By: Catherine Bene, MD, Ophthalmologist
ermanent loss of vision by looking directly into the sun was
recorded by Galileo in the 1600s. Our eyes are designed
to concentrate and focus light onto our retina. Brighter,
especially the short wave length light sources, can be toxic to our
Light enters the eye, is absorbed by rod and cone pigments in
the retina. The light is processed and travels to the brain by the
optic nerve. Our brain turns these signals into visual perceptions
and helps in regulating the circadian rhythms. Our retinas are
particularly sensitive to ultraviolet (UV) light. This high energy
non-visible light is known to produce direct cellular damage. Our
retinas are highly sensitive and easily damaged by photo-chemical
and photo-thermal reactions occurring in the retinal tissues
It is widely recognized that prolonged exposure to sunlight
can damage skin. These same rays of direct sunlight can have
equally toxic effects on our susceptible ocular structures.
The Ozone Layer surrounding our earth provides an
important layer of protection for our eyes but it is far from
sufficient to allow direct viewing of our sun. Eyebrows and
eyelids provide some shade for our eyes. The tear film, cornea
and aqueous humor absorb some of the ultraviolet rays. Our
pupils constrict and narrow the beam of light directly entering
out eye. Our eye lenses, particularly the yellowed/clouded lenses
(cataracts) of older adults, shield and reduce the penetration of
the harmful UV rays. Protective macular pigments provide some
help by absorbing these short wavelengths of blue light as well.
Those with Dry Eyes produce fewer anti-oxidant enzymes in the
tear film; impairing the ocular surface and making it less resistant
to UV penetration.
One would think most people understand the dangers
inherent with sun gazing or prolonged exposure to artificial
light. Sun glasses and eyewear lenses that automatically shade
in bright light are good things. Yet, most do not realize we face
a cumulative impact from the effects of UV light on our eyes.
Worse, most parents probably don't realize that children (under
the age of 18) are especially vulnerable to ultraviolet irradiation
(because of their larger pupils and more transparent ocular
media). It is a FACT that as much as 80% of a person's lifetime
exposure to UV radiation occurs before the age of 18.
Chronic low dose exposure to UV light may lead to
cataract, pterygium, scleral plaque and squamous cell CA of
the conjunctiva and cornea as well as macular degeneration.
Acute high dose exposure to UV light occurs in sports with
high sunlight reflection: at the beach, while skiing or mountain
climbing, and welding. Such exposure may produce painful
photokeratitis and photo conjunctivitis, blurred vision,
chromotopsia, metamorphopsia, central or paracentral scotomas.
Our military personnel stationed in countries such as Afghanistan
are exposed to intense sunlight and may also risk damaging
exposure from high power military lasers. Even a simple laser
pointer commonly used in lectures can produce retinal damage if
viewed directly.
Poor choices such as solar gazing during an eclipse or
staring at the sun while on illegal drugs are both well described
as " burning a hole in your macula. " Still, however, people
need to understand that the toxic effects of UV light can be
intensified by certain prescribed medications (such as antibiotics,
antidepressants and topically applied anti-inflammatories).
The use of good protective eyewear (sunglasses) is important
for everyone and starting at a very young age. The best are those
tinted to block or filter near UV, UVA and UVB light. Tinted
spectacles and contact lenses offer an extra barrier as do hats with
wide brims. Even more protection can be had from tints for auto,
home and office glass.
So, remember, the effects of the sun are more than skin deep.
Take care of your eyes - you only get one pair.
SUMMER 2021 | York County Medicine 19

York County Medicine Fall 2020

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