What to Expect During Your Visit
New patients visiting the Ophthalmic Genetics Clinic undergo a series of tests, which can include some or all of the following:
- Genetic Counselor
- Visual Field Testing/Microperimetry
- Genetic Testing
- Adaptive Optics
Please note that individuals undergoing specialized testing, ophthalmic exam, and consultation should prepare for a long appointment. Initial testing may need to be split over multiple days. Please ask our administrative assistant to estimate your appointment length for you.
Most of the patients seen in our clinic have an inherited eye disease. In order to help determine the likelihood that an individual's disease is inherited, and in what manner, all patients seen at the Oregon Retinal Degeneration Center meet with a Genetic Counselor. The Genetic Counselor will ask specific questions pertaining to the vision and overall health of family members. If you do not know much about your family history, but have a close relative (like a mother or sibling) who can attend the appointment with you, they may be able to provide valuable information.
At the conclusion of the family history, the Genetic Counselor will consult with the physician. Together, they will try to determine whether or not your condition is genetic. If it is, they will help you to understand the likely inheritance pattern and discuss possible molecular tests to confirm the diagnosis and inheritance.
All patients undergo a comprehensive dilated eye exam. The ophthalmic technician begins the evaluation with measurements for near and distance visual acuity, manifest refraction (which determines the need for glasses), color vision, and ocular pressure. The physician then performs an examination of the entire eye, with particular focus on the retina and macula.
Many individuals with a retinal dystrophy or degeneration will experience loss of their peripheral (or side) vision. Individuals with macular dystrophy may have blind spots in their central vision. In clinic, we measure this loss with a test of the visual field.
Many ophthalmologists and some optometrists use visual field testing machine, usually the Humphrey visual field analyzer. Humphrey visual fields are very good for screening patients to determine whether a given individual has peripheral vision loss or blindspots. In our clinic, we test the visual field much more extensively, using an Octopus visual field analyzer. which can measure all areas of the visual field in one test. The Octopus visual field test takes approximately an hour and a half to complete.
Individuals with a known or suspected retinal disease will probably be scheduled for an electroretinogram (ERG). The electroretinogram measures the electrical impulses of the retina in response to light. Because the ERG measures the actual cells of the retina, it provides an extremely valuable objective measure of the disease state.
There are two major types of ERG; the full-field ERG, and the multifocal ERG. The full-field ERG measures the responses of the rods and cones as an average across the entire retina. The multifocal ERG measure local responses across the central 24 degrees. Prior to your appointment, the coordinator will determine whether you need a full-field ERG, multifocal ERG, or both.
The full-field ERG takes nearly 2 hours to perform, including 45 minutes of dark adaptation, where the patient sits (or sleeps!) in a dark room. The multifocal ERG is done in a light environment, and takes just 45 minutes.
Some patients with symptoms of a macular dystrophy will be scheduled for a similar test called an electro-oculogram (EOG). The EOG takes 1 hour.
Genetic testing is becoming increasingly vital to the diagnosis and management of retinal dystrophies. Patients who are interested in genetic testing to confirm their diagnosis can have their blood drawn on site by a trained phlebotomist. Children undergoing sedated exams or tests can have blood drawn by the anesthesiologist or anesthesia nurse while under sedation. Individuals choosing to participate in one of our genetic research studies can also have their blood drawn by one of our phlebotomists at the conclusion of the appointment. Some genetic tests can be done using a saliva kit.
Participation in genetic research studies is always voluntary.
Many patients will have photographs taken of their dilated eyes. With specialized cameras, our photographers can accurately document the appearance of individualized structures of the eye, including the retina, macula, and optic nerve. The photographs serve as a baseline for comparison in the future, and can effectively allow the physician to later determine whether or not the disease has progressed.
Color Vision Testing
Our visual function service provides detailed color vision testing, used for the diagnosis of certain inherited disorders of color vision. The time required for these tests varies, but can be estimated by the administrative assistant making the appointment.