Tunnel vision
Tunnel vision: Excerpt from Signs & Symptoms: A 2-in-1 Reference for Nurses
Resulting from severe constriction of the visual field that leaves only a small central area of sight, tunnel vision (also known as gun barrel vision or tubular vision) is typically described as the sensation of looking through a tunnel or gun barrel. It may be unilateral or bilateral and usually develops gradually. (See Comparing tunnel vision with normal vision, page 662.) This abnormality results from chronic open-angle glaucoma and advanced retinal degeneration. Tunnel vision also can result from laser photocoagulation therapy, which aims to correct retinal detachment. Also a common complaint of malingerers, tunnel vision can be verified or discounted by visual field examination performed by an ophthalmologist.
History
Ask the patient when he first noticed a loss of peripheral vision, and have him describe the progression of vision loss. Ask him to describe in detail exactly what and how far he can see peripherally. Explore the patient’s personal and family history for ocular problems, especially progressive blindness that began at an early age.
Physical assessment
To rule out malingering, observe the patient as he walks. A patient with severely limited peripheral vision typically bumps into objects (and may even have bruises), whereas the malingerer manages to avoid them.
If your assessment findings suggest tunnel vision, refer the patient to an ophthalmologist for further evaluation.
Medical causes
Chronic open-angle glaucoma
With chronic open-angle glaucoma, bilateral tunnel vision occurs late and slowly progresses to complete blindness. Other late findings include mild eye pain, halo vision, and reduced visual acuity (especially at night) that isn’t correctable with glasses.
Retinal pigmentary degeneration
This group of hereditary disorders, such as retinitis pigmentosa, produces an annular scotoma that progresses concentrically, causing tunnel vision and eventually resulting in complete blindness, usually by age 50. Impaired night vision, the earliest symptom, typically appears during the first or second decade of life. An ophthalmoscopic examination may reveal narrowed retinal blood vessels and a pale optic disk.
Special considerations
To protect the patient from injury, be sure to remove all potentially dangerous objects and orient him to his surroundings. Because visual impairment is frightening, reassure the patient and clearly explain diagnostic procedures, such as tonometry, perimeter examination, and visual field testing.
Pediatric pointers
In children with retinitis pigmentosa, night blindness foreshadows tunnel vision, which usually doesn’t develop until later in the disease process.
Patient counseling
If tunnel vision is permanent, teach the patient to move his eyes from side to side when he walks to avoid bumping into objects.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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