Applanation tonometry measurements of intraocular pressure (IOP) pulsation may be useful in diagnosing carotid-cavernous fistula (CCF), according to findings published in BMC Ophthalmology

Since many ocular manifestations of CCF (red eye, diplopia, blurred vision, headache, and murmur) can also indicate a variety of other pathologies and lead to misdiagnosis, investigators sought to establish a link with IOP pulsation. They reported 3 cases related to CCF differential diagnosis based on IOP signs obtained through applanation tonometry. Ultimately, they confirmed a diagnosis of  CCF in 2 of the cases, while the remaining patient was diagnosed with conjunctivitis with corkscrew conjunctival vessels. 

In case 1, a 64-year-old man reported diplopia 1 week prior to examination, but no murmur. His IOPs were 22 mm Hg OD and 11 mm Hg OS. He exhibited significant IOP pulsation in the affected eye, and magnetic resonance angiography revealed an engorged right superior ophthalmic vein and an enhancing right cavernous sinus, leading to a diagnosis of indirect CCF with sixth cranial nerve palsy.


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In case 2, a 77-year-old woman reported asymmetric (right) upper eyelid swelling that started approximately 1 year prior to examination. The patient did not show other typical symptoms of CCF. Her IOPs were 20 mm Hg OD and 15 mm Hg OS, and IOP pulsation was noted in both eyes. Based on radiology findings (bilateral superior ophthalmic vein enlargement), the patient was diagnosed with Barrow type C bilateral CCF. 

In case 3, a 55-year-old man was referred for differential diagnosis of CCF. The patient reported conjunctival redness of his left eye beginning 3 days prior to examination. He had corkscrew conjunctival vessels in both eyes, which had appeared after cardiopulmonary resuscitation 25 years prior. His IOP was not elevated in either eye, and he did not exhibit IOP pulsation. Radiology evaluations revealed no remarkable findings for CCF.

“Arterial blood flow in CCF can cause pulsation of IOP in applanation tonometry,” according to the investigators. “IOP pulsation can provide a diagnostic clue in clinical evaluation of CCF patients by provoking suspicion of the vascular disease.”

Limitations of the study include a very small sample size. 

Reference

Lee H, Yoon S, Baek S. Diagnostic clues of IOP pulsation on applanation tonometry in carotid-cavernous fistula patients. BMC Ophthalmol. 2022;22(1):37. doi:10.1186/s12886-022-02254-9