What tests or exams led to a diagnosis of glaucoma?
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How is glaucoma diagnosed?
An eye doctor (ophthalmologist) can usually detect those individuals who are at risk for glaucoma (because of, for example, a narrow drainage angle or increased
intraocular pressure) before nerve damage occurs. The doctor also can diagnose patients who already have glaucoma by observing their nerve damage or visual field
loss. The following tests, all of which are painless, may be part of this evaluation.
Tonometry determines the pressure in the eye by measuring
the tone or firmness of its surface. Several types of tonometers are available for this test, the most common being the applanation tonometer. After the eye has
been numbed with anesthetic eyedrops, the tonometer's sensor is placed against the front surface of the eye. The firmer the tone of the surface of the eye, the
higher the pressure reading.
Pachymetry measures the thickness of the cornea. After the eye has been numbed with anesthetic eyedrops, the
pachymeter tip is touched lightly to the front surface of the eye (cornea). Studies have shown that corneal thickness can affect the measurement of intraocular
pressure. Thicker corneas may give falsely high eye pressure readings and thinner corneas may give falsely low pressure readings. Furthermore, thin corneas may be
an additional risk factor for glaucoma. Once a doctor knows the thickness of a patient's cornea, he or she can more accurately interpret the patient's tonometry.
Gonioscopy is done by
numbing the eye with anesthetic drops and placing a special type of contact lens with mirrors onto the surface of the eye. The mirrors enable the doctor to view the
interior of the eye from different directions. The purpose of this test is to examine the drainage angle and drainage area of the eye. In this procedure, the doctor
can determine whether the angle is open or narrow and find any other abnormalities, such as increased pigment in the angle or long-standing damage to the angle from
prior inflammation or injury. As indicated earlier, individuals with narrow angles have an increased risk for a sudden closure of the angle, which can cause an
acute angle-closure glaucomatous attack. Gonioscopy can also determine whether the eye is subject to chronic angle closure, whether blood vessels are abnormal, or
whether hidden tumors might be blocking the drainage of the aqueous fluid out of the eye.
Ophthalmoscopy is an examination in which the doctor uses a handheld device, a head-mounted device or a special lens and the slit lamp to look
directly through the pupil (the opening in the colored iris) into the eye. This procedure is done to examine the optic nerve (seen as the optic disc) at the back of
the eye. Damage to the optic nerve, called cupping of the disc, can be detected in this way. Cupping, which is an indentation of the optic disc, can be caused by
increased intraocular pressure. Asymmetry in the degree of optic nerve cupping between the two eyes can be a sign of glaucoma, as can increase in optic nerve
cupping over a period of time. Additionally, a pale color of the nerve can suggest damage to the nerve from poor blood flow or increased intraocular pressure.
Special cameras can be used to take photographs of the optic nerve to compare changes over time.
Visual field testing actually maps the visual fields to detect any early (or late) signs of glaucomatous damage to the optic nerve. In order to find
and follow glaucoma, visual fields are measured by a computer one eye at a time. One eye is covered and the patient places his or her chin in a type of bowl. Lights
of various intensity and size are randomly projected around inside of the bowl. When the patient sees a light, he or she pushes a button. This process produces a
computerized map of the visual field, outlining the areas where each eye can or cannot see. In glaucoma, there are characteristic changes in the visual field
Confocal Laser Scanning systems and Optical Coherence Tomography are non-invasive imaging systems that create a three-dimensional image of the optic
nerve and retina to evaluate the degree of cupping and the thicknesses of the retinal nerve fiber layer and ganglion cell layers to better evaluate and quantify the
presence of ocular damage from all types of glaucoma.