Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Tonometry is generally performed upon an anesthetized ocular surface. Anesthesia is generally rendered with a single drop of topical anesthetic, such as proparicaine (Alcaine) or tetracaine (Pontocaine). The tonometer device lightly touches the surface of the eye, ever so slightly indenting the cornea. The resistance to indentation is measured by a precisely calibrated pressure sensing device, the tonometer. Several types of tonometers are available for this test, the most common being the applanation tonometer:
Goldman applanation tonometer: the "gold standard" instrument attached to the slit lamp biomicroscope used in all eye doctors' offices. It requires a cobalt blue light source and a small droplet of fluorescein on the ocular surface. A tiny pressure sensor attached to a spring-loaded arm is gently placed against the tear film, and the doctor or technician reads the pressure through the microscope under the blue light.
Tono-Pen handheld electronic contact tonometer: This widely used, portable, handheld device runs on hearing aid batteries and calibrates digitally with the push of a button. It requires a disposable sterile cover for each patient. The sterile device tip is gently placed against the tear film by the doctor or technician, and the pressure reading appears on the digital readout simultaneous to a faintly audible beep.
pneumotonometer contact device: The device is operated similarly to the handheld tonopen tonometer, but due to its larger size, it's not readily portable. It requires a continuous gas supply and separate gauge container with analog readout attached to a long tube and pressure probe. This is an older technology and has largely been replaced by the handheld tonopen tonometer.
The airpuff noncontact tonometer, which generally requires no anesthetic drop, is widely used in doctor's offices, clinics, and screening facilities. It is very safe due to the "no touch" technology, but
it often produces falsely elevated readings, particularly in patients who squeeze their muscles upon anticipation of the air puff. The patient simply sits then places their chin in a rest while looking straight ahead, while the operator activates the air puff mechanism while aligning each eye individually.
Tactile finger applanation over the closed eyelid by a skilled eye doctor is an age-old traditional method utilized by the experienced
practitioner.
Intraocular sensors for experimental or intraoperative use during surgery are utilized in research and technology development companies. Hopefully, these will become universally available for long-term use and patient self-readout.
Patient self-testing devices are in their infancy. The ProVision device marketed by Bausch & Lomb allows the patient to gently press a calibrated spring-loaded piston against the closed eyelid over the upper, outer quadrant of the eyeball while gazing downward. The true IOP is reached when the pressure applied onto the globe produces faint lights in the eye, or phosphenes, readily perceived by the patient and thereby recorded at home.
After the eye has been numbed by the technician or doctor with anesthetic eye drops, the tonometer's sensor is placed against the surface of the eye. The firmer the tone of the surface of the eye, the higher the pressure reading. The doctor can record the pressure reading, and this can be used to diagnose or monitor the treatment of glaucoma. Also, the pressure reading is lower than otherwise expected if the cornea is thin. Thus, patients with a thin cornea may obtain a falsely low IOP reading when the actual pressure is high. These patients must be watched more closely for glaucoma.
Diabetes mellitus is a chronic condition characterized by high levels of sugar (glucose) in the blood. The two types of diabetes are referred to as type 1 (insulin dependent) and type 2 (non-insulin dependent). Symptoms of diabetes include increased urine output, thirst, hunger, and fatigue. Treatment of diabetes depends on the type.
Glaucoma is a common eye condition in which the fluid pressure inside the eye rises because of slowed fluid drainage from the eye. If untreated, glaucoma may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness.
A cataract is an eye disease that causes the eye's lens to become cloudy and opaque with decreased vision. Causes of cataracts include diabetes, hypothyroidism, certain genetic illnesses, hyperparathyroidism, atopic dermatitis, and certain medications. Symptoms and signs include a decrease in vision and a whitish color to the affected eye. Treatment depends upon the patient's specific visual needs and may involve cataract surgery.
Toxoplasmosis (toxo) is a parasitic infection that causes flulike symptoms, swollen lymph nodes, and muscle aches and pains that may last from a few days to several weeks. Toxoplasmosis can be contracted by touching the hands to the mouth after gardening, cleaning a cat's litter box, or anything that came into contact with cat feces. Toxoplasmosis can also be contracted by eating raw or partly cooked meat, especially pork or lamb, or touching the hands to the mouth after contact with raw or undercooked meat.
Many common eye disorders resolve without treatment and some may be managed with over-the-counter (OTC) products. It's important to visit a physician or ophthalmologist is the problem involves the eyeball itself or the condition hasn't improved after 72 hours of use of an eye-care OTC product.
Uveitis is inflammation of the eye. Symptoms include blurred vision, eye pain, eye redness, and floating spots before the eyes. Treatment may involve prescription eyedrops, antibiotics, and wearing dark glasses.
Herpes of the Eye is developed by the herpes simplex 1 virus that usually lives around the nerve fibers in humans. Symptoms of herpes of the eye include pain in and around only one eye, redness rash or sores on the eyelids, redness of the eye, and swelling and cloudiness of the cornea.
Age-related macular degeneration (AMD) is a disease that gradually destroys the central vision. In people over 60, AMD is a leading cause of vision loss. Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula, leaking blood and fluid and causing rapid vision loss. In dry AMD, light-sensitive cells slowly break down in the macula, resulting in gradual vision loss. Pain is not associated with either form of AMD.
Disease prevention in men includes routine screening tests that are part of basic prevention medicine. Take an active role in your own health care and discuss screening tests with your doctor early in life. Age of screening and timing of screening depends upon the condition being assessed.
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