Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely (i.e. abruptly) or chronically (i.e. over a long period of time). The effects of visual loss can, before the acquisition of alternative adaptations and skills, be devastating; especially when a person's vision disappears over a short period of time.
Ranges of vision loss
Various scales have been developed to describe the extent of vision and vision loss based on
visual acuity.International Council of Ophthalmology. [http://www.icoph.org/pdf/visualstandardsreport.pdf "International Standards: Visual Standards — Aspects and Ranges of Vision Loss with Emphasis on Popular Surveys."] April 2002.] Early editions of the World Health Organization's ICDdescribed a simple distinction between "legally sighted" and "legally blind". The ICD-9 released in 1979 introduced the smallest continuous scale which consisted of three tiers: normal vision, low vision, and blindness. [World Health Organization. "International Classification of Diseases, 9th Revision (ICD-9)", World Health Organization, Geneva, 1977.]
Acute visual loss
"Acute visual loss" may be dramatic in presentation, and is almost always alarming to the person experiencing the loss.It may be caused by media opacities,
retinal disease, optic nervedisease, visual pathway disorders, or functional disorders, or it may be in fact an acute discovery of chronic visual loss.
Opacities of the clear refractive media of the
eyesuch as the cornea, anterior chamber, lens, and vitreous humormay cause acute visual loss as manifested by blurry vision or reduced visual acuity.While pupillary reflexes may be affected, these conditions generally do not cause a relative afferent pupillary defect.
Causes of media opacity include
corneal edema, hyphema, cataractand vitreous hemorrhage.
Retinal diseases may cause sudden visual loss.Because the retina is being affected, there is usually a concomitant relative afferent pupillary defect.Conditions that affect or destroy the retina include
retinal detachment; macular disease ("e.g.", macular degeneration); and retinal vascular occlusions, the most important of which is central retinal artery occlusion.
Optic nerve disease
Diseases which affect the optic nerve may cause acute visual loss.
Signs include an abnormal pupillary reflex, with an afferent pupillary defect when the optic nerve disease is unilateral. can ao be caused by
optic nervecan be affected by many diseases including optic neuritis, retrobulbar neuritis, papillitis, papilledema, glaucoma, ischemic optic neuropathy, and giant cell arteritis.
The eye is very sensitive to restriction of its supply of oxygen. A dimming of vision (a brownout or greyout) accompanied by loss of peripheral perception may result from low blood pressure, shock,
g-LOC(an aviation related problem) or simply standing up suddenly, especially if sick or otherwise infirm. Vision usually returns readily once the conditions restricting blood flow are lifted.
Visual pathway disorder
Visual pathway disorders are any problems that may impede the
visual pathway.Rarely, acute visual loss is caused by homonymous hemianopiaand, more rarely, cortical blindness.
The term functional disorder is now used where
hystericaland malingeringwere historically used.This shift recognizes the inherent inability of the physician to identify the subjective experience of a patient (and thus whether that patient can truly see or not).
* [http://www.afb.org/seniorsite AFB Senior Site] Expanding possibilities for people with vision loss
* [http://www.cdc.gov/ncbddd/autism/actearly/vision_loss.html CDC's "Learn the Signs. Act Early." campaign] - Information for parents on early childhood development and developmental disabilities such as vision loss
* [http://www.afb.org/visionloss.asp Living with Vision Loss - American Foundation for the Blind]
* [http://www.visionaware.org VisionAWARE - Self Help for Vision Loss] Independence for adults with low vision
* [http://www.icoph.org/standards/visionres.html International Standards: "Visual Standards - Aspects and Ranges of Vision Loss" - International Council of Ophthalmology]
* [http://www.accdv.org/en/ Catalan Association for the Blind and Visually Impaired]
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