Electroretinogram (ERG)
The electroretinogram (ERG) is an eye test that evaluates the function of the retina, the film that lines the inside of the eye. The ERG test helps diagnose diseases of the retina.
During the ERG test, the cells of the retina (rods and cones) release tiny amounts of electricity in response to flashes of light. If we know exactly how much light enters the eye and how much electricity comes out, we can figure out how the rods and cones are working. To pick up the electricity from the retina, a special contact lens is placed on the surface of the eye.
To prepare for the ERG test, drops are placed in the child's eyes to dilate the pupils. These drops are the same drops that eye doctors routinely use for eye examinations. The child then sits in a dark room (with the parent) for 30 minutes to allow the pupils to dilate. Since the retina becomes more sensitive to light with increasing time in the dark, the retina will give its strongest response following this period of dark adaptation.
After dark adaptation, anesthetic drops are given and a contact lens is placed on the child's eye. (Often, both eyes are tested at the same time.) Once the contact lens is in place, responses are recorded to a series of blue and red lights. This part of the test may take 30 to 45 minutes. The total time for the ERG test (including the period of dilation and dark adaptation) is approximately 1.5 hours.
The electroretinogram (ERG) is an eye test that evaluates the function of the retina, the film that lines the inside of the eye. The ERG test helps diagnose diseases of the retina.
During the ERG test, the cells of the retina (rods and cones) release tiny amounts of electricity in response to flashes of light. If we know exactly how much light enters the eye and how much electricity comes out, we can figure out how the rods and cones are working. To pick up the electricity from the retina, a special contact lens is placed on the surface of the eye.
To prepare for the ERG test, drops are placed in the child's eyes to dilate the pupils. These drops are the same drops that eye doctors routinely use for eye examinations. The child then sits in a dark room (with the parent) for 30 minutes to allow the pupils to dilate. Since the retina becomes more sensitive to light with increasing time in the dark, the retina will give its strongest response following this period of dark adaptation.
After dark adaptation, anesthetic drops are given and a contact lens is placed on the child's eye. (Often, both eyes are tested at the same time.) Once the contact lens is in place, responses are recorded to a series of blue and red lights. This part of the test may take 30 to 45 minutes. The total time for the ERG test (including the period of dilation and dark adaptation) is approximately 1.5 hours.
The Burian-Allen corneal contact lens used during testing.
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The Espion color dome
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The RETeval - a Handheld ERG Device
The RETeval is a handheld device that is used to record signals from the retina. It is clinically used and is approved by the FDA.
For ERG testing using the RETeval, we will test one eye. The ERG test will be performed in darkness, and the subject will wait in the dark for 30 minutes prior to testing to allow the retina to adapt to the dark. When we are ready to begin testing, we will ask the subject to sit on a chair facing forward. We will then patch the eye that we are not testing.
We will record the responses with skin electrodes that are embedded in an adhesive pad. We will wipe the skin below the eye with an alcohol swab and then place the electrode pad on the skin. The electrode pad will connect to the handheld RETeval device. The RETeval has a small dome that will be placed over the eye. During the test, the subject will watch a series of flashes of light presented in the dome. Most flashes are very brief; they vary in brightness and in color (blue, red, white). It takes approximately 10 minutes for a full set of responses to be obtained. Upon completion of the series, the electrodes will be carefully removed from the skin of the subject.
For more information, see the product website: http://www.lkc.com/products/RETeval/index-us.html
For ERG testing using the RETeval, we will test one eye. The ERG test will be performed in darkness, and the subject will wait in the dark for 30 minutes prior to testing to allow the retina to adapt to the dark. When we are ready to begin testing, we will ask the subject to sit on a chair facing forward. We will then patch the eye that we are not testing.
We will record the responses with skin electrodes that are embedded in an adhesive pad. We will wipe the skin below the eye with an alcohol swab and then place the electrode pad on the skin. The electrode pad will connect to the handheld RETeval device. The RETeval has a small dome that will be placed over the eye. During the test, the subject will watch a series of flashes of light presented in the dome. Most flashes are very brief; they vary in brightness and in color (blue, red, white). It takes approximately 10 minutes for a full set of responses to be obtained. Upon completion of the series, the electrodes will be carefully removed from the skin of the subject.
For more information, see the product website: http://www.lkc.com/products/RETeval/index-us.html
Left: The handheld RETeval device. Right: The RETeval in use - no dilation is needed or use of a corneal contact lens electrode.
Image source: http://www.dvmmedical.com.au/products/category/XTKJGAEV-ophthalmoscopes/WA-RETeval-001