(Neuro) Optometry in Focus: Strokes

So, as I discussed in my Introduction: Hannah Vollmer, OD post, one of my greatest optometric passions is neuro-optometric rehabilitation, which is the field that I completed a year long residency in.  During my residency, I had the opportunity to work in an in-patient rehabilitation hospital, which was one of the most rewarding experiences in my career to date.

As a neuro-optometry resident, I worked with a significant number of people who were in the process of recovering from strokes. Prior to residency, I honestly had little understanding of the effects of strokes or the potential treatment strategies to be implemented in stroke survivors, despite having four years of graduate level, medically based education and a positive family history for the condition.

Maybe I lived under a rock, but I’m guessing I’m not alone.

Over the past year, I have learned a lot about working with stroke survivors, but I’m still nowhere near an expert.  Nevertheless, in today’s post, I’ll try to share a few things that I’ve learned over the past year, especially regarding how strokes impact visually related tasks.

Enjoy!

Strokes: In Focus

What is a Stroke?

I suppose talking about what a stroke is would be a good first step…

Medically, strokes are called cerebrovascular accidents, or CVAs.  This term does a good job at explaining what a stroke is: a condition in the brain (cerebro) that occurs as a result of problems with blood flow (vascular).

Strokes can be either ischemic or hemorrhagic.

Ischemic strokes occur secondary to a blockage that prevents blood from entering an area of the brain.  This is the most common type of stroke, accounting for nearly 90% of all strokes.

Hemorrhagic strokes, on the other hand, occur when a blood vessel breaks or leaks within the brain.  These are relatively rare, and are most often associated with aneurysms (essentially an outpocketing of the blood vessel) or very high blood pressure.

Who Gets Strokes?

According to the CDC, approximately 795,000 people in the US alone have a stroke each year.  This equates to one person every about 40 seconds.

Out of these, approximately 140,000 people die (1 every 4 minutes).

Around 610,000 are first time strokes.  The other 185,000 are a recurrence.

Crazy, right?

Strokes are more common in patients with vascular problems, such as high blood pressure, high cholesterol, and diabetes.  Higher risk is also associated with smoking and obesity.

While strokes are often associated with older age, over 1/3 of the people who are hospitalized with strokes are under the age of 65.

Takeaway: Anyone can have a stroke at any time.  However, certain conditions or behaviors significantly increase the risk of having a stroke!

Symptoms of a Stroke

Considering how little information I hear about strokes on a regular basis, I feel like this is one aspect that the public health community has made huge strides in – knowing the symptoms of strokes.

Remember the acronym? FAST?

For a review, it stands for:

  • Facial droop
  • Arm weakness
  • Slurred speech
  • Time to act

These are some of the most common symptoms associated with a stroke.  However, it’s important to know that these can also occur as part of what’s called a transient ischemic attack, or TIA.  In these cases, as the name implies, the symptoms are transient, or short lived.  Just because the symptoms are not permanent, though, does not negate the seriousness of the presentation.  TIAs are considered a medical emergency, as they often precede a full-scale stroke.

Despite the widespread knowledge of the FAST acronym, these symptoms fail to include any visual symptoms that may precede or accompany a stroke.  I guess that’s where I come in…

Visual Symptoms of a Stroke

First things first: strokes may often be preceded by visual TIAs.

These visual phenomena can be described in a number of different ways, such as:

  • Vision loss (typically in one eye)
  • Double vision
  • Dizziness/sensation of world moving
  • Loss of part of the visual field

As with all TIAs, these symptoms are relatively short lived, normally lasting under an hour, but are still suggestive of an impending full-scale stroke, with the greatest risk being in the first 24 hours after the event.

While these three symptoms may precede a stroke as visual TIAs, they may also present consistently, either before or with a stroke.
For instance, sudden vision loss in one eye may be a result of occlusion (blockage) of the central retinal artery, or a branch of the central retinal artery (CRAO or BRAO).  These conditions are both considered a stroke of the eye and require immediate medical attention due to the strong association between these conditions and risk of large-scale stroke.
New onset, persistent double vision, from my experience, is more likely to occur in conjunction with the full ischemic or hemorrhagic event.  This annoying symptom presents secondary to damage to the neural pathways responsible for controlling the four cranial nerves that innervate the six extraocular muscles.  With improper innervation, the musculature becomes imbalanced, changing the natural position of gaze for one eye, creating the symptom of double vision.  This eye turn may or may not be easily observable, depending on the direction and degree of turn.

Dizziness, or a sensation of the world shaking or moving (oscillopsia), again may present as a symptom of the stroke itself.  Oscillopsia occurs as a result of damage to a part of the brain that normally inhibits movement of the eyes (if you inhibit an inhibitor, you get movement).  Visually, this presents as nystagmus, or a shaking of the eyes.  The direction that the eyes move is directly determined by the location of the stroke itself.  This is one of the most frustrating visual symptoms for patients who have had strokes, as it not only reduces vision (because the eyes never sit still long enough to fully focus on an object), but also causes dizziness (frequently with nausea and vomiting) and disorientation.

Loss of part of the visual field is another significant visual sign associated with strokes.  This symptom may occur secondary to damage to a number of areas in the visual pathway – whether it be in a lobe of the brain that the nerve fibers traveling from the eye to the visual cortex pass through, or in the visual cortex itself – with symptoms varying by the specific location affected.  Interestingly, due to the crossing of nerve fibers from each eye relatively early in the ocular pathway, visual field deficits generally present as loss on the right or left halves of both eyes.  This is referred to as a homonymous hemianopsia – homonymous meaning same, hemianopsia meaning half of the visual field.  Due to the oddly reversed nature of physical placement of retinal nerve fibers and the corresponding visual field, a stroke on the left side of the brain will be associated with right sided visual loss, and vice versa.

What to Do?

If you, or someone you know, experiences any of these symptoms, immediate action is imperative!  When you’re working with brain tissue, time is money.  Or, in this case, life.  The sooner an impending, or even large-scale stroke is caught, the better the outcome.  If caught soon enough (under 5 hours from onset), a medication may be administered to get rid of the blockage, potentially reducing or completely reversing the effects of the stroke.

However, unfortunately, simply going to the hospital isn’t always enough, as not all stroke centers are created equal (though, if you only have the option of hospital or no hospital – get to the hospital).  Optimal treatment would be at a comprehensive stroke center, which is required to have:

  • The ability to treat ALL types of strokes
  • 24/7 access to minimally invasive procedures to treat stroke
  • Neuroscience ICU
  • Neurosurgery

Treatment after a stroke varies widely by symptoms and their severity.  For the sake of time, though, I’ll discuss stroke rehabilitation (specifically the role of optometrists in stroke rehab) in a later post.  Stay tuned!

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