DRUGS AND THE EYE

According to Health Canada studies, 12.7 per cent of Canadians
consider themselves heavy drinkers, 19 per cent of Canadians over the
age of 15 were current smokers, and 45.1 per cent of Canadians report
using recreational drugs during their life. While these statistics may
make headlines on the front pages of newspaper, why are they listed in
a column on eye health? Recently, during a yearly routine eye
examination a mother asked about the effects of marijuana on the eyes.
Apparently she found out that her son was now part of the 45 per cent
of Canadians who have used recreational drugs and wanted to know if
there visual side effects that she could monitor for or discuss with
the teenager. That question sparked an idea for this article.

A drug can be defined as a chemical substance used in the treatment,
cure, prevention or diagnosis of a disease or used to otherwise
enhance physical or mental well-being. Generally speaking, drugs can
be sub-divided into four categories: over-the-counter, pharmaceutical,
legal non-pharmaceutical and illegal non-pharmaceutical.

The illegal non-pharmaceutical drug category includes cocaine, IV
drugs, marijuana and various other "recreational drugs." Most people
are familiar with the typical side-effects portrayed in the movies,
but few know that these drugs can have an impact on the eyes.

Many drugs that are injected directly into the veins are "cut" with
talc or other agents. These agents may be deposited in the retina and
depending on the location of the deposit can lead to vision loss while
larger particles can block the normal retinal circulation altogether.
The use of recreational IV drugs has the unfortunate possible
side-effect of rapid severe vision loss.

Medically cocaine is used as topical anaesthetic but during
recreational use it is not used on the skin surface. It has been
reported that cocaine can lead to corneal ulcers which can lead to
corneal scarring and depending on the location may lead to permanent
blindness.

The use of marijuana by patients suffering from glaucoma has been a
recent topic of interest in the media. Marijuana does have a pressure
lowering effect but to maintain this effect, it would have to be taken
every two to four hours. However, current glaucoma medications can
achieve the same effect, if not better, in a single dose. Recreational
marijuana use does have visible side effects; eye redness and dilated
pupils. Visually the side-effects are mild but the possible lung
disease associated with marijuana can be very severe.

The legal non-pharmaceutical drug category includes alcohol and
tobacco. Despite the numerous medical complications of chronic alcohol
abuse, the eyes are relatively spared from complications. Short term
use can lead to temporary blurred vision, pupillary dilation, double
vision, or difficulty focusing. Chronic use can lead to nutritional
degeneration of the optic nerve. This could result in permanently
reduced vision, enlarged blind spots and reduced colour vision.

While tobacco is not a drug, the nicotine found in tobacco is
addictive. Nicotine is not proven to cause ocular damage, the myriad
of other chemicals have been shown to lead to ocular side-effects.
Studies have shown that smoking tobacco increases the risk of cataract
formation, increases the risk seven-fold for developing rapid
irreversible vision loss due to macular degeneration, and can lead to
vascular eye disease including ocular strokes.

Some pharmaceutical drugs can have visual side-effects. A short list
of these medications includes accutane, amiodarone, chloroquine,
cimetidine, digitalis, ephedrine, nasal steroids, oral contraceptives,
plaquenil, tamoxifen, and Viagra. Ask your pharmacist for information
before starting any new medication. If you notice any visual changes,
consult your family physician for a referral to your optometrist for
evaluation.

Most "drugs" do not have obvious effects beyond pupil dilation and
general complaints of blurred vision. Neither of these symptoms can
determine what type of drug was used nor rule-out other more serious
conditions. If you are concerned about your vision or the vision of
your child, see your optometrist regularly. Children under 20 years
old are covered yearly for an eye examination by OHIP. Seeing your
optometrist regularly for an eye examination is the best way to limit
visual problems from occurring.