EYE DISORDERS - Medicine for Mountaineering and Other Wilderness Activities - page 200

Globe rupture is a specific type of globe injury that requires slightly different initial
treatment. As previously mentioned, it can be a complication from a variety of globe injur-
ies,includingforeignbodies,lacerations,andblunttrauma.Becausepressureonaruptured
globe absolutely should be avoided, patching or bandaging is not recommended.
Instead the eye should be protected from pressure with a rigid shield. Many authorities
do not recommend topical antibiotics for fear of introducing high concentrations of anti-
biotics inside the eye. Therefore, the only initial response is to secure a rigid shield over
the eye, making sure it is not applying any pressure on the eye. Evacuation to the nearest
medicalfacilitymustbeimmediate.Ifevacuationrequiresdaysorlonger,abroadspectrum
antibiotic should be administered systemically.
Chemical Injuries and Burns
Chemicalinjuriesandburnsareextremelyserioustraumasthatoftenresultinpermanent
loss of vision. Treatment can help salvage vision but often must be carried out quickly.
Among chemical injuries, alkali burns tend to be more serious than acid burns because an
elevated pHcauses disruption ofcell membranes, resulting incell death. Thealkali usually
penetrates the cornea; on the other hand, acids tend to cause proteins in the corneal epithe-
lium and stroma to coagulate, limiting ocular penetration.
The most important concept to remember about chemical burns is that immediate and
abundant irrigation of the eye could save the person's vision. The longer a chemical is in
contact with the eye, the more damage is done. Irrigation can help to quickly remove any
chemical from the eye, neutralize the pH, and prevent irreversible damage. Ideally, the eye
shouldbeirrigatedforatleasttenminutes.Suchburnsaretrueocularemergencies,andthe
person should be evacuated to the nearest medical facility as quickly as possible.
RETINA AND OPTIC NERVE DISORDERS
The retina is the photosensitive layer that lines the back of the eye. It contains a meshwork
of photoreceptor nerve cells that absorb light and transform it into an electrical signal that
is sent to the brain through the optic nerve. The macula is an area of dense photorecept-
or cells near the center of the retina that is responsible for central vision, which permits
a person to read, drive, and perform other activities that require sharp, straight-ahead vis-
ion. Peripheral vision is the ability to see objects and movement outside the direct line of
vision—“out of the corner of the eye.” Damage to the retina that causes loss of peripheral
vision may go unnoticed for some time, but damage to the macula usually results in imme-
diately noticeable loss of central vision.
The delicate nerve cells in the retina connect directly with nerve cells in the brain and
shareasimilarphysiology.Bothrequirealargeandsteadysupplyofoxygen.Aspecialized
network of blood vessels supplies the retinal cells. To allow clear focusing of light, a barri-