Monocular Painless Vision Loss

Eye complaints, particularly vision complaints, can seem daunting to a provider in an urgent care or emergency department setting. The eye is a complex structure. The anatomy and the neurology behind vision is intricate. Often, you may be practicing in an environment without the ability to consult an ophthalmologist. An understanding of urgent and emergent eye and visual problems is crucial. This post will deal with painless vision loss.

A good pathway to deal with eye/vision problems is to try to determine if there are issues of trauma, exposure, or infection involved. Painless vision loss rarely involves these elements. Next, is the vision loss partial, full, blurry, monocular, or binocular. Binocular vision loss is usually cerebral, thus a neurologic, rather than an ophthalmic pathology. Was it sudden, or gradual, constant or intermittent? Is the eye red, or normal appearing? Below is a schematic that can be helpful in evaluating vision loss:

vision loss workup graph

Think of vision as a process “from front to back”. Light reaches the eye. The surface is covered with corneal epithelium. Light passes through the cornea, the anterior chamber, to the pupil, through the vitreous humor (the jelly like substance inside the globe), to the retina (the layer of cells on the posterior aspect of the eye that contains the photoreceptor cells). Signals are then passed through the 1st cranial nerve (the optic nerve) to the visual cortex of the brain.

So, the main causes of monocular painless vision loss include retinal vein occlusion (central or branch), retinal artery occlusion (central or branch), retinal detachment, optic neuritis, optic nerve ischemia, and possibly temporal arteritis.

In retinal vein occlusion, patients will present with full monocular vision loss in central vein occlusion, partial in branch vein occlusion. The cause of this disease is uncertain, however, the retinal artery and vein share a common sheath and pass through a small canal in the skull. The tight anatomy of the space is thought to play a role. Risk factors are similar to coronary artery disease, but also includes dysrhythmia’s, vasculitis, and auto immune disease. Classic fundoscopic findings are “blood and thunder” due to multiple retinal hemorrhages and “cotton wool spots” (these phrases sometimes appear on exams). There is no immediate treatment other than aspirin, but the patient is at risk for other thromboembolic events, therefore admission is recommended.

Retinal artery occlusion presents similarly, and is complete versus partial based on central versus branch artery. Blood flow is blocked to the retina, and the light detecting cells die. Risk factors are similar to retinal vein occlusion. The fundoscopic buzz phrase is a “cherry red spot” on the macula. There is a potential treatment by an ophthalmologist within 90 minutes of onset (aqueous fluid extraction), however, by the time most patients seek treatment, the window has expired. Direct massage of the globe may disrupt the clot and is recommended. Transient artery occlusion is possible, and this is termed amaurosis fugax. Admission is recommended to evaluate the patients stroke risk.

Retinal detachment is sometimes preceded with “flashers and floaters”. Classically patients will describe vision loss in a “window shade” pattern, ie., a veil of darkness spreading downward. Diabetes and previous cataract surgery are significant risk factors. Ultrasound can be very helpful in this diagnosis, and can be performed easily and quickly at the bedside. Treatment within 24 hours has a slightly higher success rate, however, prognosis is mixed. Consultation with an ophthalmologist is mandated, however, admission is not needed in most confirmed cases.

Optic neuritis is most often associated with multiple sclerosis and patients will describe pain with eye movement. Treatment is similar to MS exacerbation and the use of high dose IV steroids is common. 

Optic nerve ischemia occurs when blood flow is stopped to a portion of the optic nerve, most commonly near the globe. This is essentially an ischemic stroke of the optic nerve, no specific treatment exists. Causes include temporal arteritis, and thromboembolic events. Temporal arteritis is an inflammatory disorder of the temporal artery. This is usually associated with advanced age, pain over the temple with palpation, and an elevated sedimentation rate—but not always! All of these conditions mandate admission with neurology and ophthalmology consults. 

In summation, monocular painless vision loss can be caused by many different processes. It is unlikely, and not expected, that you as a primary care, acute care, urgent care or emergency medicine provider will be able to make the final diagnosis. Onset is crucial since there are potential treatment options at 90 minutes and 24 hours, depending on the cause. Unless directed to discharge the patient by an ophthalmologist, admission (or transfer to a facility with neurology and ophthalmology) is strongly recommended. Vision is not only complex, but loss of vision can have devastating effects on livelihood, lifestyle, and quality of life. And often, vision loss is a marker for other serious conditions.

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