Case Report: Recurrent Transient Monocular Vision Loss Secondary to Protein C Deficiency

Protein C deficiency is a thrombophilic condition that increases the risk of venous and arterial thrombi, the latter of which can cause transient monocular vision loss. In cases of recurrent transient monocular vision loss, in which the typical stroke workup has been unrevealing, investigation for hypercoagulable states is warranted.

This study reports a case of transient monocular vision loss secondary to protein C deficiency in a patient with no known personal or family history of venous thromboembolism and highlights the eye care provider's role in helping with diagnosis of this condition.

A 59-year-old woman presented with recurrent transient monocular vision loss of the right eye. Her history was remarkable for suffering an ischemic stroke with hemorrhagic conversion shortly after experiencing episodes of transient monocular vision loss. These episodes initially waned but recurred 3 months later. Extensive workup at the time of recurrence of her visual symptoms was unrevealing. Given the timing of her visual symptoms and history of stroke, her presentation was suggestive of transient ischemic attacks. Her previous extensive workup and chronicity of symptoms did not necessitate emergent evaluation. However, additional workup for hypercoagulable conditions was initiated. The testing revealed protein C deficiency, which prompted initiation of oral anticoagulants for stroke prophylaxis.

Transient monocular vision loss is a symptom commonly encountered by eye care providers, which necessitates emergent evaluation to reduce stroke risk if the symptom appears vascular in origin. Testing for hypercoagulable conditions is indicated in patients demonstrating recurrent transient monocular vision loss, even if there is no known personal or family history of venous thromboembolism. Eye care providers need to be aware of this association between hypercoagulable conditions and transient vision loss to aid in prompt diagnosis and treatment with the goal of preventing stroke and permanent vision loss.