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Our Diagnosis: Bilateral Transient Visual Loss due to transient hypotension causing acute reduction in blood flow to central retinal artery in both the right and left eyes.
This patient has a heart dysrhythmia causing transient episodes of low blood pressure. The important part of the history is that they can occur while he is sitting at rest, which points towards an intermittent heart rhythm disturbance. Other causes from overtreatment of blood pressure usually become symptomatic when changing posture which causes a sudden drop in blood pressure. In this patient example, one would refer for evaluation of a heart dysrhythmia and usually a 24-hour heart monitor would be ordered or an event heart monitor that the patient activates during an episode. If the episodes only occurred with postural changes, then the blood pressure treatment is most likely too aggressive, and the patient may need 24-hour ambulatory blood pressure monitoring to determine how much the blood pressure fluctuates and if his blood pressure medication needs adjustment.
The darkening of the peripheral vision first is a sign that there is decrease in perfusion pressure and blood flow to the central retinal artery. This is because the perfusion pressure is highest in the branches of the central retinal artery supplying the macula and lowest in the peripheral retinal branches of the central retinal artery. So, when the blood pressure drops, the peripheral retina is the first area that is affected, followed by the central retina, if the blood pressure drops low enough.
If the darkening of vision in both eyes occurs simultaneously in the center of vision and not in the periphery, then one should consider that the decrease in blood flow is affecting the occipital pole in primary visual cortex. Although the blood supply to the occipital cortex pole (topographically mapping to the central visual field) may vary, developmentally from one person to the next, most people have a dual blood supply to the occipital pole from both the distal branches of the posterior cerebral arteries and the middle cerebral arteries, forming a “watershed zone” at the occipital pole. Watershed zones of the circulation are where two blood supplies feed an area of the brain and the intersection of the two blood supplies have the lowest perfusion pressure, making it susceptible to drops in blood pressure.
Emboli are usually unilateral and not simultaneous and would not affect the peripheral retinal first, followed by the central retina. If emboli are coming from the carotid artery on one side then, the episodes usually would occur only in the eye on the ipsilateral side. If there are multiple episodes, some in the right eye and some in the left eye, then an embolic source would be looked for in the aorta or from the heart.
Your Differential:
Preparation Planning : Case Review #31921375
Malmö, Sweden
September 2021
Assignment Instructions
Purpose
The purpose of this assignment is to work through one case at a time of a patient presenting with Transient Visual Loss. The order in which you request information, and your text responses will be and provided to the instructor. The goal of this exercise is to enhance classroom discussion and your answers may be presented in the class as talking points.
How to Complete the Assignment
The assignment requires you to investigate the patient history and additional patient results to determine a differential diagnosis. The elements of the history can be requested in any order you think is appropriate. You will be required to select each element of the history you think is most relevant to the patient’s chief complaint in a step-by-step manner, then you will be given the patient history for your inquiry, and then you will enter a free text response to indicate if the information was helpful in determining your diagnosis, and then you should enter you current differential diagnosis in order of most likely and what causes can be eliminated from your differential at that point in the process. You will then repeat the process to determine other parts of the history that you think are the most relevant, until you are ready to submit your refined differential diagnosis of probable entities, ranked in order of their likelihood. You may enter your differential diagnosis at any time by clicking the "Differential Diagnosis" button. Once the diagnosis is submitted the assignment is complete and no further action is required until attending the lecture, where each case will be discussed as a group interaction.
Materials
You are provided a suggested outline for taking a history from a patient presenting with the symptom of Transient Visual Loss.
After the Lecture
You will be provided with a link to review the suggested way to work through the case along with keys points for evaluating each piece of the information from the patient history.
Patient Presentation
Bilateral Transient Visual Loss
What would you like to know?
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Exam Results
Ophthalmologic exam was completely normal, in terms of pupil exam, ocular motility, visual field testing and fundus appearance. Intraocular pressures were 20 mmHg OD and 21 mmHg OS.
