Purpose

The ERG is an objective test that measures the electrical response evoked from the entire retina following brief flashes of light. The test provides an overall functional assessment of the retinal cells (rods, cones, Muller, bipolar, ganglion and other cells) that compose the retina. Diagnoses for which this test is commonly ordered include:

• Retinitis pigmentosa
• Stargardt disease
• Macular dystrophy
• Rod-cone dystrophy
• Leber congenital amaurosis
• Color vision loss
• Night blindness

Duration

Approximately 1 hour. Please allow an additional 30 minutes for the test if your eyes have not been previously dilated for an earlier test.

Procedure

Dilation is required for this test! After dilating your eyes, the technician will clean the skin on your forehead and earlobes with an exfoliant cream. A clean, dry surface is needed to ensure a strong signal from the skin electrodes. After numbing your eyes with a drop of topical anesthetic, a thin silver wire electrode will be placed across the eye just above the lower eyelid. For small children and sensitive individuals, a skin sticker electrode will be placed on the lower eyelid.

• You will still be able to blink and move your eyes normally with the electrode in place.
• When the technician has prepared for the test, you will be seated comfortably in front of the ERG machine. The machine will present a series of flashing lights as it measures the retinal response via the electrodes. The test is performed in two parts: one part is performed in standard lit room and theother part is performed following a 20 minute period of dark adaptation. This is not a painful or difficult test, but you will be asked to remain relatively still for a period that could be as long as 45 minutes.

Restrictions

• Avoid wearing makeup and facial lotion on the day of your appointment.
• It is generally recommended that you do not drive until the effects of pupil dilation have subsided. These effects include blurry vision, increased glare, increased light sensitivity and difficulty reading within arm’s length. You should be okay to return to an indoor job, unless close-up visual tasks are a critical part of your work.
• Swimming is discouraged for the remainder of the day.
• Contact lens wearers should wear glasses for the remainder of the day.

Purpose

The mfERG is an objective test used to quantify the central cone photoreceptor function of the retina. Retinal regions affected by eye disease may show responses with reduced amplitude and/or delayed timing. Diagnoses for which this test is commonly ordered include:

• Macular dystrophy
• Plaquenil (hydroxychloroquine) maculopathy
• Unexplained vision loss

Duration

Approximately 1 hour. Please allow an additional 30 minutes for the test if your eyes have not been previously dilated for an earlier test.

Producedure

Dilation is required for this test. After dilating your eyes, the technician will clean the skin on your forehead and earlobes with an exfoliant cream. A clean, dry surface is needed to ensure a strong signal from the skin electrodes. After numbing your eyes with a drop of topical anesthetic, a thin electrode will be placed across the eye just above the lower eyelid. For small children and sensitive individuals, a skin sticker electrode will be placed on the lower eyelid. You will still be able to blink and move your eyes normally with the electrode placed. Once the technician has prepared for the test, you will be seated comfortably in front of a large computer monitor. You will be asked to watch the monitor and focus on the center of the monitor in 30 second intervals as black and white shapes are presented. The electrodes measure the macular response. This is not a painful or difficult test, but you will be asked to remain very still for a period lasting as long as 30 minutes.

Restrictions

• Avoid wearing makeup and facial lotion on the day of your appointment.
• It is generally recommended that you do not drive until the effects of dilation have subsided. These effects include blurry vision, increased glare, increased light sensitivity and difficulty reading within arm’s length.
• You should be okay to return to an indoor job, unless close-up visual tasks are a critical part of your work.
• Contact lens wearers should wear glasses for the remainder of the day.

Purpose

The VEP measures the functional integrity of the entire visual pathway from the retina and optic nerve to the occipital cortex. The test measures the electrical responses that reach the brain after each eye is exposed to certain stimuli. The time for the signals to reach the brain and the strength of the responses are measured. This test is useful for patients with communication difficulties and optic nerve disorders including optic neuritis and ocular albinism.

Duration

Approximately 1 hour

Procedure

Dilation may not always be required when performing a VEP test. The technician will first take several measurements around the skull, marking certain landmarks with a washable marker. Once the landmarks are established, the technician will clean the areas with an exfoliant in order to prepare the surface for the electrodes. We typically clean a small area on the forehead, an earlobe, and 1 or 3 small areas on the back of the head. It is not necessary to shave your head or cut your hair to place the electrodes. The electrodes on the back of the head are held in place using a thick gel. What you see during the test will depend on the type of VEP you are undergoing − pattern reversal VEP or flash VEP. For the pattern reversal VEP, you will be asked to focus on a computer monitor with a shifting checkerboard pattern in the background. For the flash VEP, you will look into a small dome that produces flashes of light every 1-2 seconds. This is not a painful or difficult test, but you will be asked to remain very still for a period that could last as long as 30 minutes.

Restrictions

• Avoid wearing makeup and facial lotion on the day of your appointment.
• If your eyes were dilated for this test: It is generally recommended that you do not drive until the effects of dilation have subsided. These effects include blurry vision, increased glare, increased light sensitivity and difficulty reading within arm’s length.
• You should be okay to return to an indoor job, unless close-up visual tasks are a critical part of your work.
• Contact lens wearers should wear glasses for the remainder of the day.

Purpose

Electro-oculography measures the standing electrical potential over the eye, which is generated by the supportive cells of the retina (called the retinal pigment epithelium). The test is useful in the diagnosis of retinal dystrophies that involve the retinal pigment epithelium, including Best disease.

Duration

Approximately 1 hour. Please allow an additional 30 minutes for the test if your eyes have not been previously dilated for an earlier test.

Procedure

Dilation is required for this test! After dilating your eyes, the technician will clean the skin around your eyes with an exfoliant cream. Adhesive skin electrodes will be placed on the inside and outside corners of your eyes. A dome fixture will be lowered over your face. Inside the dome, there is a single red light that shifts back and forth at regular intervals. You are to track the light with your eyes as it moves left and right. This exercise is carried out in both dark and light background conditions. This is not a painful or difficult test, but you will have to follow the light in intervals over a period of almost 30 minutes, which can be quite monotonous.

Restrictions

• Avoid wearing makeup and facial lotion on the day of your appointment.
• It is generally recommended that you do not drive until the effects of dilation have subsided. These effects include blurry vision, increased glare, increased light sensitivity and difficulty reading within arm’s length.
• You should be okay to return to an indoor job, unless close-up visual tasks are a critical part of your work.
• Contact lens wearers should wear glasses for the remainder of the day.

Dark Adaptometry (or, scotopic sensitivty) Testing

The dark adaptation test measures the change in retinal sensitivity that occurs during adjustment to darkness following exposure to a bright light. This test can be useful in evaluating conditions with decreased night vision including:

• Congenital Stationary night blindness (nyctalopia)
• Vitamin A deficiency

Duration

Approximately 30 minutes. Please allow an additional 30 minutes for the test if your eyes have not been previously dilated for an earlier test.

Procedure

Dilation is required for this test! After dilating your eyes, you will be exposed to a bright “bleaching” light for 2 minutes. Following the 2 minute adaptation period, the light will turn off and the machine will generate periodic flashes of light. The intensity of the flash will be gradually increased until you signal (with a buzzer) that you are able to see it. After detection of this test light, the intensity will be gradually decreased until it is once again invisible. This cycle is repeated over a period of about 25 minutes.

Restrictions

• It is generally recommended that you do not drive until the effects of dilation have subsided. These effects include blurry vision, increased glare, increased light sensitivity and difficulty reading within arm’s length.
• You should be okay to return to an indoor job, unless close-up visual tasks are a critical part of your work.
• Contact lens wearers should wear glasses for the remainder of the day.

Purpose

Visual field testing is universally regarded as one of the most important visual assessments for many diseases, including inherited retinal degenerations. Visual field testing allows detailed analysis of the complex patterns of progressive visual loss. Depending on the disease, vision loss can develop in a number of ways. Some individuals will experience loss of their peripheral (side) vision. Others may have scotomas (blind spots) in their central vision. With visual field testing, these defects can be identified, mapped and evaluated over time.

Duration

Approximately 30 minutes for a static visual field test. Approximately 1 hour for a Kinetic Visual Field test.

Procedure

This test does not require dilation.

Static Visual Field

This type of visual field test is used to assess the visual field at specific locations. You will sit in front of a large dome-shaped instrument and focus straight ahead. Looking inside the dome, you will be presented with single, non-moving spots of light that appear for only 1-2 seconds at a time. When you notice the lights, you will hit a button to indicate to the test giver that you saw the light. This technique allows us to map what you are able to see above, below and to the side of the center of the vision.

Semi-automated Kinetic Visual Field

This type of visual field test is comprehensive, assessing both central and peripheral vision using a moving target. You will sit in front of a large dome-shaped instrument and focus straight ahead. Looking inside the dome, you will be presented with lights that move in order to map out an area that can be detected. The technician may ask you to press a button as soon as you become aware of a light moving into your vision. This technique allows us to map how much you are able to see above, below and to the side of the center of your vision.

Restrictions

• There are no restrictions following this test.

Color vision tests are used to screen for inherited and acquired color vision defects. The following standard color vision tests are available: Farnsworth D-15, Ishihara and Hardy-Rand-Rittler color plates.

Purpose

Color vision testing is used to differentiate between inherited and acquired color vision defects and to quantify color vision deficiencies. This test is often done in conjunction with other tests in order to provide supplemental information when problems involving the retina and/or optic nerve are suspected.

Duration

The test will be limited to a few minutes per eye. Retesting may be performed if indicated.

Procedure

This test does not require dilation. Color vision can be tested using several different methods. Most likely, you will arrange a series of colored caps or identify numbers on a card. The test will be administered one eye at a time (with the other eye patched).

Restrictions

There are no restrictions following this test.