Identifying and managing disease often requires the delicate and skillful use of temperamental emergency department machinery. The ability to apply these may appropriately help determine a difficult diagnosis.
Glaucoma, we all know, can cause blindness, and acute narrow angle glaucoma refers to the angles within the eye that are not as wide and open as normal. People with acute angle glaucoma have abnormal anatomy within the eye where the angle changes as the eye is dilated. This can cause blockages of fluid drainage from the anterior to posterior changes resulting in increased intraocular pressure. It ca lead to acute angle closure or crisis if the drainage canals become blocked in an eye with narrow angles. A sudden and rapid increase in the intraocular pressure can lead to a variety of symptoms and cause damage. Damage to the optic nerve can occur and cause permanent blindness if the pressure is high enough.
Patients presenting with potential acute angle closure or crisis should be treated without hesitation. Some patients may know their diagnosis, but many may not be aware of the risk. The proper use of the tonopen to measure ocular pressure is crucial to making this diagnosis. Providers must first recognize the classic signs and symptoms of angle closure. Patients often complain of a headache, unilateral eye pain, halos, painful vision, loss of vision, or nausea or vomiting. Patients may have decreased visual acuity or inability to read, an angry red eye, a dilated pupil, or a hazy cornea. Symptoms may mimic a migraine headache, but the astute provider will notice that the ocular symptoms are much more pronounced in angle closure. This is when the tonopen is put to use.
Most tonometry machines come with a user manual and an instructional video that are well worth the time to read and watch. Several types of tonopens are available: Some need to be calibrated, and some are ready to use. Use whichever is easiest for you to master.
The tonopen is delicate and must be handled with care. It should be stored in a hard box with padding. Store it with a cover on the tip to protect it. Use a condom cover cardboard wrapping to cover the transducer while it is in the box. Be sure to use the right tip cover for your tonopen to ensure accurate readings. Photos by Martha Roberts.
- Have the patient sit comfortably in a chair or on a stretcher. You can take a pressure with him lying flat, but it won't be accurate and is more difficult.
- Consider managing the patient's pain first and adding an anxiolytic, such as morphine or valium, especially if the patient is very anxious or uncomfortable. This is painful.
- Anesthetize the eye prior to taking the pressure. Use two to four drops of proparacaine hydrochloride ophthalmic solution 0.5%; that should be enough to anesthetize the eye surface for about five minutes, depending on how much your patient is crying. Have the patient hold a tissue against his cheek while you drop in the medication.
- Tell the patient he will initially feel a burning sensation, then relief, and then more burning.
- Always put the condom cover on the tonopen before using it.
- Calibrate the pen if required after applying the condom cover.
- Wait about 60-90 seconds before taking a pressure. If you wait for more than five minutes, the numbing agent will start to wear off.
- Tap the transducer on the anesthetized cornea. The tonopen tip should be perpendicular to the cornea.
- Use light, quick touches. You will hear the tonopen make a clicking sound to ensure it is reading the taps as it calculates the pressure.
- Keep the transducer head as flat and direct on the cornea as possible. Do not press into the eye.
- Do not hold the patient's eye in any way. You may rest your hand on his forehead or nasal bridge, but holding the eye will give you a false high reading. Don't pull down the lower lid or pull up on the upper lid if at all possible.
- If you have to assist a patient with keeping his eye open, hold onto his eyelashes instead of the lids themselves.
- You will have to touch the cornea 10 times. The machine takes an average of these 10 taps and displays the pressure as a single reading on the window.
- The statistical calculator indicator is the small number (usually) on the window. It is usually in the 90 percent range on readings done correctly. If it is lower than that, consider rechecking the pressures.
- It is suggested you check the pressure in both eyes and compare the values.
- Some tonopens show the message "Or Err," and you should consider this a true concerning pressure that is very high. If you are using the pen correctly and receive this message, it is not because the pen is broken. It is more likely the patient has a severely high pressure and it cannot be measured.
Treatment While Awaiting Consult
Clinicians should provide immediate treatment to reduce intraocular pressure if an ophthalmologist is not available within an hour to confirm the diagnosis and the patient has a significant decline in vision (cannot read text or count fingers). Try to decrease the pressure by instilling cholinergic drops. This results in miosis.
Give one drop of timolol 0.5% to the affected eye, wait one minute, and then give one drop of apraclonidine 1% to the affected eye. Wait another minute, and then give one drop of pilocarpine 2% to the affected eye. Wait one more minute, and then give 500 mg IV acetazolamide (give by mouth if IV is unavailable). (UpToDate. 2018.)
- Recheck the pressures every 30 minutes.
- Systemic medications other than acetazolamide (such as IV mannitol) should be administered under the guidance of an ophthalmologist because angle closure should be confirmed before they are given.
- Ophthalmologists will consider additional treatments like iridotomy to open the angles if pressures are higher than 40 mm Hg. This is a laser procedure and the preferred method of treatment. It can also be used as a preventive treatment for patients at high risk or with borderline pressures.
"Or Err" means the pressure is extremely high. Don't be fooled by this reading. Photo by Martha Roberts.
Several medications can increase intraocular pressure by narrowing the angle. Medications that block acetylcholine may increase the risk for narrow angle closure.
Medical Concern Medications that May
or Diagnosis Increase Intraocular Pressure*
Anxiety, depression SSRIs such as Prozac and Paxil; Vistaril
Nausea and vomiting Phenergan
Muscle spasms Norflex, Artane, Cyclobenzaprine
Asthma, COPD Any steroid (prednisone, Decadron), Atrovent,
GERD H2 blockers, Tagamet, Zantac, Detrol
Incontinence Detrol, Ditropan
Other OTC decongestants, ephedrine, Benadryl,
sulfa-based drugs (Bactrim, Topamax),
- Advanced age, female gender, hyperopia (farsightedness), and family history of angle closure and narrow angle glaucoma may increase the risk for closure.
- Ocular and systemic steroids can increase intraocular pressure. Eye pressure should be checked in patients on long-term steroids and those who need steroids for more than 10 days.
- Other reasons to check the intraocular pressure include trauma from blunt force or significant corneal abrasions.
- Consider possible contraindications to medications for treating increased intraocular pressure (i.e., beta blocker contraindicated with severe bronchospasm, second- or third-degree atrioventricular block, uncompensated heart failure).
- Consider higher doses of Zofran for nausea such as 8 mg. (UpToDate. 2018.) Do not give Phenergan if at all possible.
Watch a video of Dr. Denis Dollard demonstrating how to use a tonopen.
Jim Weighs In
- You should be checking pressures in any painful, angry red eye.
- Put your tonopen back in the same spot every time.
- Consult ophthalmology immediately if a patient has an elevated pressure. Very high ocular pressures are generally between 40 to 70 mm Hg (normal is approximately 8 to 21 mm Hg).
Martha Weighs In
- Does your patient have a corneal abrasion? Give him one 5 mg tablet of PO diazepam to go. Let him get a restful night's sleep so the eye has adequate time to heal.
- Never use the same condom twice and change it between eyes.
- Never check someone's eyes without wearing gloves. You can transfer nasty germs into the eyes even after handwashing, so glove up.
- The American Academy of Ophthalmology has some absolutely awesome information: https://www.aao.org.
Disclaimer: No financial compensation or other compensation was provided by Reichert in the making and publication of this blog.