Figure 17-10.  Signs and symptoms of altitude decompression sickness.  evolved gas can occur during exposure to low altitude and  create a serious inflight emergency.  The eye functions much like a camera. Its structure includes  an aperture, a lens, a mechanism for focusing, and a surface  for registering images. Light enters through the cornea at the  front of the eyeball, travels through the lens, and falls on the  retina. The retina contains light sensitive cells that convert  The recommended waiting time before going to flight  altitudes of up to 8,000 feet is at least 12 hours after diving  that does not require controlled ascent (nondecompression  stop diving), and at least 24 hours after diving that does  require controlled ascent (decompression stop diving). The  waiting time before going to flight altitudes above 8,000  feet should be at least 24 hours after any scuba dive. These  recommended altitudes are actual flight altitudes above  mean sea level (MSL) and not pressurized cabin altitudes.  This takes into consideration the risk of decompression of  the aircraft during flight.  Of all the senses, vision is the most important for safe flight.  Most of the things perceived while flying are visual or heavily  supplemented by vision. As remarkable and vital as it is,  vision is subject to limitations, such as illusions and blind  spots. The more a pilot understands about the eyes and how  they function, the easier it is to use vision effectively and  compensate for potential problems.  Figure 17-11.  To avoid the bends, scuba divers must not fly for  specific time periods following dives.  17-19  DCS Type  Bubble Location  Signs and Symptoms (Clinical Manifestations)  BENDS NEUROLOGIC Manifestations CHOKES  SKIN BENDS  Mostly large joints  of the body (elbows,  shoulders, hip, wrists,  knees, ankles)  Brain  Spinal cord  Peripheral nerves  Lungs  Skin  • Localized deep pain, ranging from mild (a “niggle”) to excruciating–sometimes a dull  ache, but rarely a sharp pain  • Active and passive motion of the joint aggravating the pain  • Pain occurring at altitude, during the descent, or many hours later  • Confusion or memory loss  • Headache  • Spots in visual field (scotoma), tunnel vision, double vision (diplopia), or blurry vision  • Unexplained extreme fatigue or behavior changes  • Seizures, dizziness, vertigo, nausea, vomiting, and unconsciousness  • Abnormal sensations, such as burning, stinging, and tingling, around the lower chest  and back  • Symptoms spreading from the feet up and possibly accompanied by ascending  weakness or paralysis  • Girdling abdominal or chest pain  • Urinary and rectal incontinence  • Abnormal sensations, such as numbness, burning, stinging and tingling (paresthesia)  • Muscle weakness or twitching  • Burning deep chest pain (under the sternum)  • Pain aggravated by breathing  • Shortness of breath (dyspnea)  • Dry constant cough  • Itching usually around the ears, face, neck, arms, and upper torso  • Sensation of tiny insects crawling over the skin  • Mottled or marbled skin usually around the shoulders, upper chest, and abdomen  accompanied by itching  • Swelling of the skin, accompanied by tiny scar-like skin depressions (pitting edema)  Vision in Flight 