Vision loss

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Overview
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.

Characterization of vision loss

 * Vision Loss may be:
 * unilateral
 * bilateral
 * transient
 * persistant
 * sudden
 * gradual
 * painless
 * painful

Loss of vision in one eye can quickly lead to loss in the other eye, thus rendering the patient blind. Vision loss can be reversed, however it must be treated promptly. It can be an indication of a more serious underlying condition.

Ranges of vision loss
Various scales have been developed to describe the extent of vision and vision loss based on visual acuity. Early editions of the World Health Organization's ICD described 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.

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 nerve disease, visual pathway disorders, or functional disorders, or it may be in fact an acute discovery of chronic visual loss.

Differential Diagnosis of Vision Loss
 Transient vision loss (<24 hours) 
 * Amaurosis fugax
 * Vision loss is unilateral and lasts only minutes


 * Migrane
 * Vision loss lasts 10-60 minutes


 * Ocular ischemic syndrome (Cartoid Occlusive Disease)
 * Papilledema
 * raised intracranial pressure
 * malignant hypertension


 * Retinal detachment
 * Sudden change in blood pressure
 * orthostatic hypotension


 * Transient acute increase in thraocular pressure
 * Acute Angle Closure Glaucoma
 * retro-or peribulbar hemorrhage


 * Vertebrobasilar artery insufficiency
 * Vision loss is bilateral and lasts minutes

 Vision loss > 24 hours:sudden, painless 
 * Vitreous hemorrhage
 * Vitreous detachment
 * Exposure(Welder's flash)
 * prolonged exposure to intense light/sunlight


 * Ischemic optic neuropathy
 * To prevent permanent loss, rule out giant cell/temporal arteritis


 * Other retinal or central nervous system disease
 * occipital lobe CVA causing cortical blindness

 Vision loss >24 hours:gradual, painless 
 * Optic Neuritis
 * Retinal artery/vein occlusion
 * Retinal detachment
 * Vitreous or aqueous hemmorrhage (hyphema)
 * Cataracts
 * Cerebral Neoplasm
 * Chronic retinopathy
 * age related macular degeneration
 * Diabetic Retinopathy


 * Chronic corneal disease
 * corneal dystrophy


 * Corneal Ulcer
 * Open angle Glaucoma
 * Optic neuropathy/atrophy
 * compressive lesion
 * toxic-metabolic cause
 * radiation

 Vision loss >24 hours:Painful 
 * Pseudotumor cerebri
 * Refractive error
 * Retitnitis pigmentosa
 * Acute Angle Closure Glaucoma
 * Corneal hydrops
 * keratoconus


 * Corneal abrasion/ulcer
 * Herepes simplex/zoster
 * Ocular onchocerciasis
 * "river blindness"
 * Onchocera volvulus worm


 * Optic neuritis
 * Orbital apex/superior orbital fissure/cavernous sinus syndrome
 * Uveitis

Media opacity
Opacities of the clear refractive media of the eye such as the cornea, anterior chamber, lens, and vitreous humor may 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, cataract and vitreous hemorrhage.

Retinal disease
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.

The optic nerve can be affected by many diseases including optic neuritis, retrobulbar neuritis, papillitis, papilledema, glaucoma, ischemic optic neuropathy, and giant cell arteritis.

Hypoxia
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 hemianopia and, more rarely, cortical blindness.

Functional disorder
The term functional disorder is now used where hysterical and malingering were 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).

History and Symptoms
History include:
 * age
 * onset
 * rate of loss
 * any specific trauma
 * headaches
 * medication
 * specific medical history
 * alcohol, drug and/or tabacco use

Eyes
The examination should focus on:
 * acuity
 * blood pressure
 * color vision
 * cranial exam
 * cranial nerve innervation
 * fundus
 * intraocular pressure
 * ocular media opacity
 * optic disc exam

Laboratory Findings

 * ESR
 * fasting blood glucose
 * HgBa1c
 * PPD
 * RPR
 * FTR-ABS
 * ACE level
 * vitamin B12
 * folate

MRI and CT

 * CT/MRI of head and chest

Acute Pharmacotherapies

 * Systemic Steroids can be prescribed for the following:
 * Temporal arteritis
 * Optic neuritis
 * Pituitary apoplexy
 * Herpes zoster


 * Nonarteritic ischemic optic neuropathy patients
 * Asprin


 * Cavernous sinus thrombosis
 * antibiotics
 * anticoagulation


 * Corneal hydrops
 * cycloplegic,hypertonic NaCl ointment

Corneal Hydrops
Corneal transplant

Retinal detachment
Surgical repair

Cataracts
Surgical removal

Temporal arteritis
Temporal biopsy

Acknowledgements
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