ODM (Ophthalmodynamometry) gives an approximate measurement of blood pressures in the central retinal arteries of the eye. As pressure is applied to the surface of the eye with a plunger-like device, an ophthalmologist uses a hand-held magnifying instrument (ophthalmoscope) to observe blood flow through the retinal arteries.
ODM is used as an indirect means to assess blood pressure in the carotid arteries in the neck, which supply the eyes and the brain. Reduced retinal artery pressure indicates carotid artery narrowing (a risk factor for stroke).
Purpose of the ODM
- To aid in the evaluation of patients with suspected carotid artery narrowing or blockage due to the buildup of plaques (atherosclerosis)
- To measure the blood pressure in the vessels of the eye’s retina
Who Performs It
- An ophthalmologist
- This test is not appropriate for people who have recently had eye surgery.
Before the ODM
- If you wear contact lenses, remove them before the test.
- The doctor will administer topical anesthetic eye drops 5 to 10 minutes prior to the procedure. Your eyes may burn slightly after the drops are instilled.
What You Experience
- A plunger-like device is used to apply gradual pressure to the surface of one eye, while the doctor observes pulsations in the central retinal artery through an ophthalmoscope.
- The retinal artery pressures are recorded.
- This procedure is repeated in the other eye.
- The test takes 5 to 15 seconds for each eye.
Risks and Complications
- This test may result in corneal discomfort or abrasion and slight bleeding under the conjunctiva (the mucous membrane lining the front of the eye and eyelid).
After the ODM
- Do not rub your eyes for at least 30 minutes (until the anesthesia wears off) to avoid injuring the cornea.
- If you wear contact lenses, do not reinsert them for at least 2 hours after the test.
- An ophthalmologist reviews the test data. Retinal artery pressures are compared to systemic blood pressure, and pressures are also compared between eyes. A difference of more than 20 percent in retinal artery pressures between the two eyes indicates impaired blood flow in the carotid artery on the side with the lower reading.
- If no carotid blockage is indicated, no further testing is needed.
- If a carotid blockage is suspected, additional tests, such as carotid Doppler ultrasound or arteriography, will be needed to establish the location and extent of any plaques.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media