Commonly Performed Diagnostic Testing

After a visit with our doctors, certain diagnostic tests may be recommended. Some commonly performed in-office procedures are described in detail below.

Visual Fields

The eye's visual field is the entire area that can be seen while looking at a specific point, from the center to the far periphery in all directions. Certain diseases- particularly glaucoma, retinal disease, and neurologic disorders- can cause loss of certain parts of the visual field, typically in patterns fairly specific to the type of disease. Testing the eyes' visual fields can therefore provide very useful information towards diagnosing or monitoring treatment of numerous conditions.

Visual field testing is conducted in the office using the Humphrey Visual Field Analyzer, a computerized device capable of performing accurate, relatively quick exams. The testing procedure is as follows:

  • Dilation is usually NOT required for this test.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • Each eye is tested individually. The eye not being tested is covered with a patch.
  • Sit at the device with your forehead and chin comfortably positioned against rests.
  • The technician performing the test will give you instructions, and will ask you to look directly ahead at a fixation target throughout the entire procedure.
  • The device will begin to present a pattern of flashing lights. When you see a light you will press the button on the controller in your hand. Press the button only when you truly see the light- do not pay attention to sounds made by the computer.
  • Most test programs will adjust the pace to your personal response speed- do not feel rushed. If you begin to feel tired or are uncomfortable, the test can be paused at any point. Simply ask the technician for a break.
  • When the test is complete you are free to go. Results will be mailed to you after your doctor has reviewed them, and will be discussed at your next visit.
  • This test typically takes about 20 to 30 minutes to complete.

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Heidelberg Retinal Tomography (HRT)

This test is performed primarily to help diagnose and monitor glaucoma. It uses a laser to scan the back of the eye, providing a very detailed, three-dimensional image of the optic nerve as it enters the eye. A computer then analyzes the data, comparing numerous measurements to a database of normal and abnormal optic nerves in order to help diagnose glaucoma or other abnormalities. Measurements can also be compared to previsouly performed scans, looking for changes in the shape of the optic nerve which might indicate progression or worsening of disease. The testing procedure is very simple, as follows:

  • Dilation is usually NOT required for this test.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • Sit at the device with your forehead and chin comfortably positioned against rests.
  • The technician performing the test will give you instructions, and will ask you to look into the device at a blinking fixation target.
  • You will be asked not to blink for appoximately three seconds as each eye is scanned. You may notice some dim blinking light from within the device.
  • When the test is complete you are free to go. Results will be mailed to you after your doctor has reviewed them, and will be discussed at your next visit.
  • This test typically takes about 15 to 20 minutes to complete.

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Optic Nerve Photographs

The optic nerve can appear abnormal in a number of disorders, most commonly glaucoma. A change in the appearance of the nerve over time can indicate progression or worsening of disease. In our practice we use a state-of-the-art stereoscopic fundus camera, the Nidek 3Dx, to take accurate, repeatable, stereo-paired photographs of the optic nerve and retina. Stereo pairs allow for three-dimensional viewing, providing more detail than a standard, single-image photograph. The procedure is performed as follows:

  • Dilation IS REQUIRED for this test. If you do not like to drive with your eyes dilated, you may want to arrange for someone to drive you to the office.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • The eye not being tested may be covered with a patch.
  • Sit at the device with your forehead and chin comfortably positioned against rests.
  • The technician performing the test will give you instructions, and will ask you to look into the device at a blinking fixation target.
  • The camera will be focused and you will be asked to hold very still and to not blink for a few seconds as the photo is taken. The flash may seem very bright, but is not harmful.
  • When the test is complete you are free to go. Disposable sunshades will be provided, if necessary. Results will be mailed to you after your doctor has reviewed them, and will be discussed at your next visit.
  • This test usually takes about 30 to 50 minutes to complete, depending upon how quickly your eyes dilate.

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Orbscan/Corneal Topography

The cornea is the clear 'window' at the very front of the eyeball. If you've ever poked yourself in the eye, chances are you've touched your cornea. While the eye does have an internal lens, approximately two thirds of the eye's focusing power is actually performed by the cornea. The shape and smoothness of the cornea is therefore extremely important, and any disease or disorder that alters that shape can cause significant visual problems. The exact three-dimensional shape and curvature of the cornea can be "mapped" using the Bausch and Lomb Orbscan automated topographer, a device which scans the cornea with a beam of light. The scan is analyzed by a computer and the information is presented in both numerical and graphical formats, assisting with the diagnosis of numerous corneal irregularities. The procedure is performed as follows:

  • Dilation is NOT required for this test.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • Sit at the device with your forehead and chin comfortably positioned against rests.
  • The technician performing the test will give you instructions, and will ask you to look into the device at a fixation target.
  • You will be asked to hold very still and not to blink for a few seconds as a beam of light moves back and forth across your eye.
  • When the test is complete you may be free to go or may return to the examination room to see your doctor. If the test is being performed to evaluate a disease, results will be discussed with you. If it is being performed as part of an evaluation for cataract or refractive surgery, results may not be specifically discussed.
  • This test usually takes about 10 to 15 minutes to complete.

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Biometry/IOL Measurements

As discussed in the library articles regarding cataract surgery and intraocular lens (IOL) implants, the eye must be precisely measured in order to properly calculate the power of the IOL to be implanted during surgery. There are two methods used to perform these measurements in our practice- the Zeiss IOL Master® and the Accutome® A-scan.

The Zeiss IOL Master uses a laser light to perform a number of measurements of the eye, including its overall length (axial length), corneal curvature (keratometry), corneal width ("white-to-white"), and distance from the cornea to the lens (anterior chamber depth). A computer then processes these measurements using complex formulas to determine the specific IOL necessary to provide the clearest vision at the desired distance. The IOL Master is the most advanced technology for this purpose, and represents the state-of-the-art in IOL calculations for cataract or lensectomy surgery.

The Accutome A-scan uses ultrasound to measure the length of the eye (axial length). Ultrasonic measurements may be performed if a cataract is too dense to obtain accurate measurements with the Zeiss IOL Master, or if certain other ocular disorders exist. Modern ultrasonic biometry is very accurate, on par with laser-based devices like the IOL Master.

The IOL Master procedure is performed as follows:

  • Dilation is NOT required for this test.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • Sit at the device with your forehead and chin comfortably positioned against rests.
  • The technician performing the test will give you instructions, and will ask you to look into the device at a pattern of blinking lights.
  • You may be asked to blink occasionally as the series of measurements are taken.
  • This test takes from 3 to 10 minutes per eye to perform.

If ultrasound A-scan biometry is performed, the following will occur:

  • Dilation is NOT required for this test.
  • Information, such as your name, age, and certain ocular measurements, is entered into the computer.
  • You will be seated in an examination chair which will then be reclined.
  • The technician performing the test will give you instructions, and will anesthetize your eye with an eyedrop.
  • You will be asked to look up and down as a small, plastic cup is placed on your eye. Most patients feel only a slight pressure sensation against their eyelids as this is done.
  • The cup will be filled with a watery solution and your vision will become blurry. There will be no discomfort.
  • A red light will be seen and some beeping noises heard as measurements are taken. You may be asked to look at a fixation target with your other eye in order to properly align the measurements.
  • When finished, you will be asked to tilt your head to the side to drain the fluid from the cup, and the cup will be removed.
  • The procedure typically takes about 5 to 10 minutes per eye to perform.

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