OPG (oculoplethysmography) is a procedure that gives an estimation of blood pressure in the ophthalmic arteries of the eye. This information is used as an indirect means to assess blood flow in the carotid arteries in the neck, which supply the eyes and brain. The detection of impaired blood flow in the ophthalmic arteries indicates carotid artery narrowing, which is a major risk factor for stroke.
Purpose of the OPG
- To aid in the evaluation of patients with suspected carotid artery narrowing or blockage due to the buildup of plaques (atherosclerosis)
- To monitor the effectiveness of carotid endarterectomy, a surgical procedure to remove plaques from carotid artery walls
Who Performs OPG
- A doctor, a nurse, or a trained technician
Special Concerns about OPG
- OPG is not appropriate for people who had eye surgery within the last two to six months, nor those who have cataracts, unmanaged glaucoma, conjunctivitis (pinkeye), artificial lens implantation or a history of ; retinal detachment. Those with diabetes mellitus or who take anticoagulant medications such as warfarin (Coumadin, Panwarfin) are also not advised to get this test.
- OPG is usually not performed on people who are allergic to local anesthetics.
Before the OPG
- Inform your doctor of all medications and supplements that you are taking.
- Inform your doctor if you have a history of bleeding disorders or if you are taking medications that affect clotting, such as blood thinners or aspirin.
- Arrange for someone to drive you home after the test.
- If you wear contact lenses, remove them before the test.
- If you have glaucoma, continue to take your usual eye drops or oral medications before the test.
- The doctor will administer topical anesthetic eye drops to the eyes 5 to 10 minutes prior to the procedure. Your eyes may burn slightly after the drops are instilled.
What You Experience
- You will lie on your back on a bed or table.
- You will be asked to be mindful not to blink or look around too much; results can be skewed if you do.
- Eye cups resembling contact lenses are placed directly on the surface of each eye. These sensors detect and record pulsatile changes in the pressures of the eyes. (This information is translated into a graphic recording for later review.)
- Next, vacuum suction is applied to the eye cups, and gradually increased until the pressure in the eye (intraocular pressure) is higher than the arterial pressure, causing pulsation to stop in the arteries. (This may cause a pulling sensation and brief loss of vision.)
- The suction is then released, and the time needed for the arterial pulsation to reappear is recorded.
- The procedure generally takes about 20 to 30 minutes.
Risks and Complications of OPG
- Possible rare complications of this test include bleeding from the conjunctiva (the mucous membrane that lines the eye surface), corneal abrasion, and temporary sensitivity to light.
After the OPG
- You may experience temporary blurred vision or mild burning in the eyes as the anesthetic drops wear off, and your eyes may be bloodshot for several hours. Artificial tears may be instilled to soothe any irritation.
- You are free to leave the testing facility. Arrange for someone to drive you.
- Do not rub your eyes for at least 2 hours after the test.
- If you use contact lenses, do not reinsert them for at least 2 hours after the test.
- If your eyes feel sensitive to light, wear sunglasses.
- Report any severe burning, pain, or prolonged sensitivity to light to your doctor.
- The OPG test data are reviewed by a physician. If the arterial pulse pressures in the eye are reduced or there is a delay in pulsation, a carotid artery may be blocked or narrowed.
- If a carotid blockage is suspected based on the results of OPG, additional tests—such as carotid Doppler ultrasound or arteriography—will be necessary to establish the location and degree of any plaques.
- If no carotid blockage is indicated, no further testing is needed.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media