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CSO 22.3 Hara

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									CE Credit Article

Clinical & Refractive Optometry is pleased to present this continuing education (CE)
article by Dr. Timothy B. White and Dr. Nathan A. Whitaker entitled Ocular and
Systemic Manifestations of Decompression Illness: A Case Report and Review.
In order to obtain 1-hour of COPE-approved CE credit, please refer to page 110 for
complete instructions.



Ocular and Systemic Manifestations of                                          His best corrected visual acuity measured 5/500
Decompression Illness: A Case Report and Review                           (20/2000) in each eye with normal pupil and muscle
Timothy B. White, OD; Nathan A. Whitaker, OD, FAAO                        functions OU. Because of the profound vision loss, he
                                                                          was unable to perform visual fields or any other form of
                                                                          subjective testing. Anterior segment findings were
ABSTRACT
                                                                          unremarkable OU and intraocular pressure measured
Pressure changes affect compressible structures
                                                                          20 mmHg OU. Dilated fundus examination revealed
within the body. The gases of hollow spaces and
                                                                          clear media OU, healthy optic nerves, maculae and
organs, as well as gases dissolved in the blood, are all
                                                                          peripheral retinae.
subject to variations in pressure. As an individual
                                                                               Review of our patient’s medical records revealed that
descends, the total pressure of the air he/she breathes
                                                                          imaging had been performed and magnetic resonance
increases and in turn, the partial pressures of the
                                                                          imaging (MRI) demonstrated bilateral occipital lobe
individual components of air increase proportionally.
                                                                          infarction secondary to occlusion of the basilar artery
A reduction in pressure, such as occurs while
                                                                          (Figs. 1, 2). He was treated with hyperbaric therapy soon
ascending from a dive, releases dissolved gases
                                                                          after the episode, but experienced no visual recovery.
(primarily nitrogen) from solution in the tissues
                                                                          Subsequent to our examination, we referred him to a
and blood, into various sites throughout the body.
                                                                          regional blind rehabilitation center.
These bubble formations present the potential for
complications that range from mild joint pain to
unconsciousness or death.                                                 DISCUSSION
     Herein, we report the case of a 41-year-old male                     The air we breathe is primarily composed of nitrogen
who went scuba diving while on vacation. He failed to                     (78%) and oxygen (21%). Since nitrogen is not
observe proper decompression procedures and a gas                         metabolized by the body, most of what we breathe in is
embolus occluded his basilar artery resulting in                          expelled when we exhale. At sea level only small amounts
infarction of each occipital lobe and profound vision                     of nitrogen dissolve into the blood and tissues.
loss in each eye.                                                              During a dive the pressure of compressed air
                                                                          increases in proportion to the surrounding water pressure.
                                                                          Since the body continuously uses oxygen, excess oxygen
CASE REPORT                                                               molecules that accumulate under higher pressure are of no
A 41-year-old white male presented for his initial
                                                                          consequence. However, when nitrogen in compressed air
examination indicating that two months prior he had been                  is inhaled at a higher pressure it dissolves into the tissues
scuba diving and after ascending too quickly, experienced                 and stays there until the diver begins to surface. The
bilateral vision loss. There were no other associated                     amount of excess nitrogen entering the tissues during a
neurological symptoms. He had no history of ocular                        dive is variable and depends on the depth and duration of
surgery or trauma and reported no family history of                       the dive. Tables are readily available that specify how long
ocular disease.                                                           divers can remain at certain depths, and when these limits
                                                                          are exceeded, the diver must pause at specified intervals
                                                                          during their ascent (known as decompression stops) to
                                                                          allow for diffusion of nitrogen out of the tissue into the
T.B. White, N.A. Whitaker — Tuscaloosa Veterans Affairs Medical Center,
                                                                          bloodstream so that it can be safely expelled through the
Tuscaloosa, AL                                                            pulmonary capillary bed.1 If a diver surfaces too quickly
Correspondence to: Dr. Nathan A. Whitaker, 3701 Loop Road, Tuscaloosa     and the rate of ascent exceeds that at which nitrogen can
Veterans Affairs Medical Center, Tuscaloosa, Alabama 35404;               safely be cleared, potentially dangerous nitrogen bubbles
E-mail: Nathan.Whitaker@med.va.gov                                        form in the tissues and bloodstream (in a manner similar



104    Clinical & Refractive Optometry 17:3, 2006
Fig. 1 Major arterial supply to the brain. The internal carotid artery divides
into the anterior cerebral artery (ACA) and middle cerebral artery (MCA),
with the ACA responsible for perfusion of the medial aspect of the
cerebral hemisphere and the MCA supplying the lateral aspect. The
posterior circulation, or the vertebrobasilar system, supplies blood to the
brainstem, cerebellum, and occipital lobes via paired vertebral arteries.
The vertebral arteries converge at the base of the pons to form the              Fig. 2 Anatomy: circle of Willis. (1) posterior cerebral artery, (2) superior
basilar artery. Cerebellar and pontiene arteries branch from the basilar         cerebellar artery, (3) basilar artery, (4) anterior inferior cerebellar artery,
artery before it bifurcates to form the paired posterior cerebral arteries.      (5) vertebral artery, (6) posterior inferior cerebellar artery. The site of
The posterior cerebral artery (PCA) perfuses areas of the cortex below the       occlusion in our patient occurred at the junction of the basilar artery
bold black line including the visual cortex.                                     (3) and posterior cerebral arteries (1).




to opening a bottle of soda too quickly) resulting in the                        occurs when nitrogen is unable to be exhaled efficiently
complications associated with decompression illness                              during ascent and bubbles form in the blood and tissue.
(DCI). Approximately 50% of cases of DCI will occur                              With inadequate decompression, the bubbles increase in
despite claims of compliance with these ascension                                size as the diver surfaces and injures tissues through
intervals.2 Other factors that increase a diver’s risk for                       compressive mechanisms, ischemia, or by the initiation of
developing DCI are included in Table I.                                          a local inflammatory response that produces swelling in
     An estimated 9 million dives occur in the United                            the muscles, joints, or tendons. Pain is the most common
States annually.3 According to the Divers Alert Network                          symptom among divers that experience type 1 DCS and
(DAN), a non-profit medical and research group                                   occurs in 70% to 85% of affected patients.7 The pain is
dedicated to the safety of divers, less than 1% of divers                        typically described as deep, dull, or throbbing and is
will experience DCI. Seventy-two percent of those who                            usually located in the vicinity of a joint or tendon. The
experience DCI are males, most of whom are between the                           most commonly affected sites include the shoulder,
ages of 30 and 59.4                                                              elbow, hip, and knee joints.8-10 Divers with cutaneous
                                                                                 involvement, also know as “skin bends”, frequently
Decompression Sickness (DCS)                                                     manifest symptoms that include pruritis and a burning
Decompression illness (DCI) is a term that encompasses                           sensation in their skin. A mottled, papular, plaque-like,
two conditions which includes decompression sickness                             violaceous rash, known as “cutis marmorata”, is also
(DCS) and arterial gas embolization (AGE).5                                      characteristic of type 1 DCS. Lymphedema and pain in
Decompression sickness, often referred to as “the bends”                         the regional lymph nodes is known to occur if nitrogen
or “caissons disease”, is categorized as either type 1 or                        bubbles affect the lymphatic system.6
type 2 sickness. Type 1 DCS represents the mildest form                               Patients who experience type 2 DCS will often
of disease and exists when i) the illness is limited to the                      manifest components of type 1 sickness in addition to
musculoskeletal, cutaneous, and/or lymphatic tissues, ii)                        complications that arise secondary to the effects of
there is a normal neurological examination before the                            nitrogen bubbles on the spinal cord, heart, and lungs.11
initiation of treatment, and iii) symptom resolution occurs                      Neurological deficits of type 2 sickness are varied, but
within 10 minutes of the initiation of oxygen at 2.8 ATA                         often include sensory deficits, hemiplegia, paraplegia,
(atmosphere of absolute pressure).6 Type 1 sickness                              paresthesia, dizziness, and neuropathies.12 Hypovolemic



                                                       Ocular and Systemic Manifestations of Decompression Illness — White, Whitaker                     105
Table I Factors that increase the risk of decompression illness6,26-30
Cold water dive              Gases dissolve better in cool liquids than warm. If a diver is cold, nitrogen uptake into tissues is greater.
A working dive               Working dives require greater physical exertion and greater intake of air. Increased levels of oxygen and nitrogen
                             are inhaled under these circumstances.
Obesity                      Nitrogen dissolves 5 times better in fat than in water.
Skip breathing               Skip breathing (holding your breath for short periods of time) is a technique employed by some divers to make air
                             last longer while submerged. This results in an accumulation of CO2 which, in turn, causes vasodilation and
                             increased nitrogen uptake.
Multi-day diving             If making multiple dives during a week, it is recommended that divers take a day off in the middle
and diving to the            of the week to allow all tissues to return to normal atmospheric pressure.
limit of dive tables
Older age                    It is estimated that 60-year-old divers have 30% more “silent” bubbles than divers half their age. Silent bubbles
                             are nitrogen bubbles that form after a “safe” dive, and generally cause no obvious symptoms.
Smoking                      Heavy smokers who develop DCI are at approximately twice the risk of experiencing severe symptoms as non-smokers.
Patent Foramen               Thirty percent of adults have a patent foramen ovale. This congenital opening in the heart generally closes at birth.
Ovale                        When it fails to close, there is a direct route for gas emboli to enter the circulatory system and bypass the normal
                             filtering that occurs in the capillary bed of the lungs.
Pregnancy                    Diving is not recommended for those who are pregnant as the fetus absorbs nitrogen from the mother through
                             the umbilical cord. A fetus doesn’t clear nitrogen as quickly as the mother and if nitrogen bubbles form,
                             the bubbles may bypass the lungs through the foramen ovale and an embolus travel directly to the brain.
                             Fetal blindness has been reported as a consequence of hyperbaric therapy for pregnant divers who developed DCI.
Flying after a dive          In an attempt to save fuel costs, commercial airlines set cabin pressure much lower than the pressure at sea level.
                             This means that for those who have just completed a dive, further decompression continues as the plane ascends
                             to cruising altitudes. Recommendations are to wait 12 hours before flying after a no-decompression dive, at least
                             24 hours after a decompression dive and 72 hours after hyperbaric therapy.
Dehydration                  In a review of patients requiring hyperbaric therapy, 90% were dehydrated. Pushing fluids during diving
                             periods is essential.
Alcohol consumption          Impairs judgment and can predispose to dehydration, vasodilation, and heat loss.
Physical injury              Scarring and alterations in local tissue may increase a divers risk.


shock, pulmonary emboli and myocardial infarction                                from a dive.13 Presentations may include unconsciousness,
represent potentially fatal cardiopulmonary complications.                       hemispheric deficits (motor and/or sensory), convulsions,
Pain is reported in only about 30% of cases of type 2                            and confusion.14 Peripheral neuropathy and pain, which
DCS, and occurs most often in the abdominal and thoracic                         are commonly encountered in DCS, are not typically
regions.7                                                                        experienced by patients suffering from AGE. Common
                                                                                 signs and symptoms of DCS and AGE are included
Arterial Gas Embolization                                                        in Table II.
The most severe form of decompression illness, known as
arterial gas embolization (AGE), results from pulmonary                          Temporal Profile of Decompression Illness
barotrauma. If a diver surfaces too quickly and/or fails to                      The temporal profile, in relation to the most recent dive,
exhale appropriately, air trapped in the lungs expands                           is imperative as most clinicians define DCS as the
during ascent and ruptures the alveoli introducing gas                           emergence of signs and symptoms 10 minutes after a
emboli directly into the pulmonary venous system where                           diver has surfaced. Symptoms of DCS develop more
they are carried to the heart and then into the systemic                         slowly than those associated with AGE. Approximately
circulation. Emboli can travel throughout the body and                           50% of individuals diagnosed with DCS will develop
occlude vessels, inducing damage through ischemic                                symptoms within 1 hour after surfacing and 90% of
mechanisms and infarction.6                                                      patients will have symptoms within 6 hours of surfacing.6
     Complications from AGE are generally localized                              In less than 2% of cases will problems develop beyond
to the cerebral circulation but, on occasion, cardiac                            the 24-hour, post-dive interval and it is extremely rare
involvement may occur if emboli occlude coronary                                 for symptoms of DCS to develop 48 hours after the
vessels. Classically, symptoms of AGE are sudden in                              completion of a dive.15 Symptoms of AGE typically
onset, occurring within seconds to minutes after surfacing                       manifest suddenly and within minutes after surfacing.



106    Clinical & Refractive Optometry 17:3, 2006
Table II Common signs and symptoms of decompression illness31
Decompression Sickness (DCS)                                              Arterial Gas Embolization (AGE)
Symptoms                                                                  Symptoms
           Fatigue                                                                     Dizziness
           Pruritis (skin itching)                                                     Blurred vision, loss of vision
           Pain in joints (shoulders, elbows, hips and knees)                          Sensory deficits
           Dizziness, vertigo, tinnitus                                                Chest pain
           Numbness, paresthesias                                                      Disorientaion
           Shortness of breath                                            Signs
Signs                                                                                  Bloody froth from mouth or nose
           Skin rash                                                                   Paralysis, weakness
           Paralysis, weakness                                                         Seizures
           Difficulty with urination                                                   Unconsciousness
           Personality changes, confusion                                              Shortness of breath
           Amnesia                                                                     Death
           Tremor
           Staggering
           Cough with bloody, frothy sputum
           Collapse or unconsciousnes

Table III Ophthalmic manifestations of decompression illness27            Table IV Crucial elements of a dive history in cases of suspect DCI31
Diplopia                                                                  1.      What is the dive history for the previous 48 hours? Describe
Nystagmus                                                                         dive times, depths, intervals between dives, symptoms before
Visual field deficits                                                             or after the dive, and breathing gases.
Orbicularis pain                                                          2.      Determine symptoms onset and progression after the diver
Cortical blindness                                                                surfaced.
Central retinal artery occlusion
Optic neuropathy                                                          3.      Describe any previous medical interventions, such as oxygen
Convergence Insufficiency                                                         delivery since the dive.
                                                                          4.      Determine extent of neurological involvement if possible.

Currently, AGE is responsible for approximately 10% of                    5.      Describe location of all pain.
cases of DCI annually. Various dive series suggest that                   6.      Describe and record distribution of skin rashes.
recreational divers are more likely to experience more                    7.      Describe any traumatic injuries suffered before, during
severe forms of DCI, specifically type 2 DCS and AGE,                             or after the dive.
while the majority of DCI among professional divers
tends to be type 1 DCS.16                                                epithelial abnormalities indistinguishable from those
                                                                         seen in eyes with choroidal ischemia, with these changes
Ophthalmic Manifestations                                                being attributed to decompression-induced intravascular
Eye care providers rarely encounter decompression                        gaseous micro-emboli.21 In general, estimates of the
illness in an acute setting as divers are generally well-                incidence of ocular findings associated with DCS ranges
educated about the signs and symptoms that warrant their                 from 7% to 12%.22, 23
seeking recompression therapy. However, we may see
residual ocular sequelae, such as field loss or cortical                 Management
blindness, in those cases where therapy is unsuccessful.                 Common sense and careful observation of dive tables are
In one series, visual disturbances were identified 30% of                critical in creating a safe diving environment and reducing
the time in patients who developed type 2 DCS.17 The                     the risk of DCI. If symptoms occur within 24 hours of
etiology of visual disturbances while diving are varied,                 surfacing, DCI should be suspected and an accurate
and frequently include ultraviolet keratopathy, corneal                  diving history (Table IV) and a neurological assessment
edema secondary to bubbles being trapped under a rigid                   should be obtained. Table V summarizes U.S. Naval
lens, and other contact-lens related issues such as lens                 recommendations for determining the order and urgency of
displacement and lens adherence syndrome.18-20 Other                     actions that need to be taken for divers experiencing DCI.
ocular complications, directly associated with                                 In cases of DCS, the initial treatment should include
decompression sickness, and specifically arterial gas                    the administration of 100% pure oxygen. This will cause
embolization, are included in Table III. Angiography                     oxygen levels in the body to increase significantly and in
studies of divers have also documented retinal pigment                   those areas where nitrogen bubbles impede blood flow,



                                                  Ocular and Systemic Manifestations of Decompression Illness — White, Whitaker               107
Table V Recommended protocols of care for those suspected of DCI31
Category A – Emergency Cases

Symptoms:       Onset typically sudden and progressively worsening. Generally occurs within an hour of surfacing from dive.

Intervention:   If unconscious, begin CPR and arrange for immediate evacuation. If available and the patient regains consciousness, 100% oxygen
                should be administered and continued until arriving at medical facility. If trained medical personnel are available intravenous fluids
                should be pushed. Contact DAN for advice about nearest hyperbaric chamber location.

Category B – Urgent Cases

Symptoms:       Primary symptom is pain that is either unchanged or has only slowly progressed over several hours.

Intervention:   Immediately place injured diver on 100% oxygen and arrange medical transport. Continue oxygen until arriving at medical center.
                Push fluids by mouth. Do not administer analgesics for pain. Get detailed history and attempt to determine extent of neurological
                involvement. Contact DAN for advice about nearest hyperbaric chamber location.

Category C – Timely Cases

Symptoms:       Symptoms are not obvious or have progressed slowly over a period of days. Signs and symptoms are generally mild, vague and are
                usually associated with complaints of pain or decreased sensation.

Intervention:   Obtain diving history, perform neurological evaluation and transport diver to the nearest medical facility.


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108    Clinical & Refractive Optometry 17:3, 2006
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                                          Ocular and Systemic Manifestations of Decompression Illness — White, Whitaker   109

								
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