page_title: Tunnel vision
section_title: Mask, goggle, and helmet users
hierarchical_section_title: Tunnel vision / Mask, goggle, and helmet users
caption_attribution_description: English: Fort A.P. Hill, Va. (July 27, 2005) - Electrician's Mate 2nd Class Shane Portton emerges out of the Navy Diver/Explosive Ordnance Disposal (EOD) dive tank exhibit at the 2005 National Scout Jamboree held at Fort A.P. Hill, Va. Sailors assigned to Explosive Ordnance Disposal Mobile Unit Two (EODMU-2), stationed at Naval Amphibious Base Little Creek, Va., provided a MK-21 diving helmet intercom demonstration, a diving tank with a Navy diver and various exhibits pertaining to Navy Diving and EOD. Held every four years, thousands of Boy Scouts assemble from across the United States and the World for nine days to take part in the National Scout Jamboree to camp, earn merit badges and provide an educational program to build character, train for responsibilities and promote physical fitness. This year's jamboree is held from July 25, 2005 to Aug. 3, 2005. U.S. Navy photo by Photographer's Mate 2nd Class Daniel J. McLain (RELEASED)
context_page_description: Tunnel vision is the loss of peripheral vision with retention of central vision, resulting in a constricted circular tunnel-like field of vision.
context_section_description: Activities which require a protective mask, safety goggles, or fully enclosing protective helmet can also result in an experience approximating tunnel vision. Underwater diving masks using a single flat transparent lens usually have the lens surface several centimeters from the eyes. The lens is typically enclosed with an opaque black rubber sealing shell to keep out water. For this type of mask the peripheral field of the diver is extremely limited. Generally, the peripheral field of a diving mask is improved if the lenses are as close to the eye as possible, or if the lenses are large, multi-window, or is a curved wrap-around design.
  Protective helmets such as a welding helmet restrict vision to an extremely small slot or hole, with no peripheral perception at all. This is done out of necessity so that ultraviolet radiation emitted from the welding arc does not damage the welder's eyes due to reflections off shiny objects in the peripheral field.
caption: Wide-field, wrap-around diving mask
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