Halo vision
Halo vision refers to seeing rainbowlike, colored rings around lights or bright objects. This effect can be explained by the physical principle that as light passes through water (in the eye, through tears or the cells of various anteretinal media), it breaks up into spectral colors.
Halo vision usually develops suddenly; its duration depends on the causative disorder. It may occur with disorders associated with excessive tearing and corneal epithelial edema. Among these causes, the most common and significant is acute angle-closure glaucoma, which can lead to blindness. With this disorder, increased intraocular pressure (IOP) forces fluid into corneal tissues anterior to Bowman's membrane, causing edema. Halo vision is also an early symptom of cataracts, resulting from dispersion of light by abnormal opacities on the lens.
Nonpathologic causes of excessive tearing associated with halo vision include poorly fitted or overworn contact lenses, emotional extremes, and exposure to intense light such as in snow blindness.
History and physical examination
First, ask the patient how long he has been seeing halos around lights and when he usually sees them. The patient with glaucoma usually sees halos in the morning, when IOP is most elevated. Ask the patient if light bothers his eyes. Does he have eye pain? If so, have him describe it. Remember that halos associated with excruciating eye pain or a severe headache may point to acute angle-closure glaucoma, an ocular emergency. Note a history of glaucoma or cataracts.
Next, examine the patient's eyes, noting conjunctival injection, excessive tearing, and lens changes. Examine pupil size, shape, and response to light. Then test visual acuity by performing an ophthalmoscopic examination.
Medical causes
Cataract.Halo vision may be an early symptom of painless, progressive cataract formation. The glare of headlights may blind the patient, making nighttime driving impossible. Other features include blurred vision, impaired visual acuity, and lens opacity, all of which develop gradually.
Corneal endothelial dystrophy.Typically, halo vision is a late symptom of corneal endothelial dystrophy. Impaired visual acuity may also occur.
Glaucoma.Halo vision characterizes all types of glaucoma. Acute angle-closure glaucoma—an ophthalmic emergency—also causes blurred vision, followed by a severe headache or excruciating pain in and around the affected eye. Examination reveals a moderately dilated fixed pupil that doesn't respond to light, conjunctival injection, a cloudy cornea, impaired visual acuity and, possibly, nausea and vomiting.
Chronic angle-closure glaucoma usually produces no symptoms until pain and blindness occur in advanced disease. Sometimes, halos and blurred vision develop slowly.
With chronic open-angle glaucoma, halo vision is a late symptom that's accompanied by a mild eye ache, peripheral vision loss, and impaired visual acuity.
Nursing considerations
▪ To help minimize halo vision, remind the patient not to look directly at bright lights.
Patient teaching
▪ Teach the patient how to instill eyedrops if prescribed.
▪ Discuss the importance of reporting eye discharge, eye watering, blurred or cloudy vision, halos, floaters, flashes of light, or eye pain.
Book Source Details
- Book Title: Nursing: Interpreting Signs and Symptoms
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Hallucinations
Read excerpts from these other book chapters related to Hallucinations:
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- DELIRIUM
- "Algorithmic Diagnosis of Symptoms and Signs" (2003)
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- "Differential Diagnosis in Primary Care" (2007)
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- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
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- Delirium
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
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- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
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- DELIRIUM
- "Differential Diagnosis in Primary Care" (2007)
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Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2008 Williams & Wilkins.
More About Causes of Hallucinations
» Next page: Psychotic behavior (Nursing: Interpreting Signs and Symptoms)
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