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Chapter 38 — 5
The hearing function test (
pure tone audiogram
) measuring hearing up to 8000 Hz is
performed. Any significant hearing loss is regarded seriously since there is a risk of further
hearing loss if
barotrauma
to the ears occurs during the diver's exposures.
Damage to the hearing organ may also be associated with disturbance of the balance organ. A
special type of balance test is used to detect this, called the Sharpened Romberg, and further
investigation is by an electronic measurement (electronystagmogram) if necessary. It is
important to detect any balance organ dysfunction since it can lead to
vertigo
and
vomiting
underwater.
EYES
Good
vision
is essential for the diver to see his boat or buddy, if he surfaces some distance
away. A diver who has impaired vision can have
corrective lenses
included into his face mask,
but should always dive with a visually fit buddy in case the mask is lost or broken during the
dive. See Chapter 5.
Contact lenses
can pose problems and advice is needed about these. Hard lenses can trap
bubbles between them and the cornea, causing pressure damage. Soft lenses are susceptible to
loss – especially during mask removal. These divers are advised to keep the eyes closed when
removing the mask, either underwater or on the surface. See Chapter 32.
The operation of
radial keratotomy
, used to surgically correct short sightedness, can cause
problems. With this procedure, the cornea is cut radially in a sunburst pattern to change the
curvature of the cornea. These cuts weaken the cornea which is prone to burst if the eye is
bumped or subjected to external pressure reduction. If such a diver develops face mask squeeze
(see Chapter 12), the eyeballs may actually rupture. Anyone who has undergone this operation
should not dive. Most modern techniques, such as Laser resections for myopia, involve only
minimal damage to the cornea, and are not a problem.
Colour vision
is of lesser importance, apart from a few professional diving situations involving
colour coded cylinders or wires (involving explosives).
BRAIN
Any disorder of the nervous system will complicate and confuse diagnosis and treatment of
diving illnesses such as cerebral air embolism and decompression sickness.
Epileptics
, even if controlled by drugs, should not dive as an epileptic fit underwater could
prove fatal. The higher partial pressures of oxygen encountered during a scuba dive may render
these persons more vulnerable to such attacks. Hypoxia, hyperventilation and sensory
deprivation can aggravate fits. Many divers have had their first fit underwater.
Migraine
is often made worse by diving (see Chapter 32). Severe migraine attacks leading to
incapacity have occurred during dives in previously mild sufferers. It may also complicate
recompression treatments. If certain precautions are observed some migraine sufferers can