Eye Genetics FAQs
Why should I have genetic testing?
Genetic testing can be an important tool in diagnosing and managing retinal diseases. Unlike traditional diagnoses, these tests can screen for several diseases at once, and can show if you have a disease before you have symptoms. What should I expect during my first visit? New patients visiting the genetics clinic undergo a series of tests. This can include some or all of the following:
- Eye exam and imaging tests
- Visual field testing
- Family history and DNA testing
- Additional testing
How long will my appointment be?
A full appointment might take several hours to complete, or may require several days of visits. Patients who require specialized testing, ophthalmic examination, and clinical consultation might need longer appointments. Clinic staff might be able to tell you before the appointment how long you can expect your visit to take.
What genes does the test screen for?
There are over 200 genes that can cause retinal disease, but your exam and family history might be able to narrow down the conditions you should be screened for. Depending on the conditions you might have, your physician might order testing for any of the following genes:
- Achromatopsia - CNGA3, CNGB3
- Albinism – Recessive: TYR, OCA2, TYRP1, SLC45A1; X-linked: GPR143 (OA1)
- Best disease - BEST1
- Choroideremia - CHM
- Cone rod dystrophy - ABCA4, RPGR, CRX, GUCY2D (codon R838)
- Congenital stationary night blindness - GPR179, RHO, NYX, TRPM1
- Corneal dystrophy - TGFBI, KRT3, KRT12
- Doyne honeycomb dystrophy - EFEMP1
- Familial exudative vitreal retinopathy - FZD4, LRP5, NDP, TSPAN12
- Glaucoma (juvenile open-angle and congenital types only) - CYP1B1, OPTN, MYOC
- Juvenile X-linked retinoschisis - RS1
- Leber hereditary optic neuropathy (LHON) - LHON panel (MT-ND4, MT-ND1, MT-ND6/mutations 11778G>A, 3460G>A, 14484T>C, and 14459G>A)
- Microphthalmia and Anophthalmia - RAX, SOX2, OTX2, VSX2, STRA6 and SIX6del/dup analysis
- Neurodegeneration with brain iron accumulation (NBIA) - FA2H, MMIN, PANK2, PLA2G6
- Occult macular dystrophy - RP1L1 (R45W)
- Optic atrophy, dominant - OPA1, OPA3
- Pattern dystrophy - PRPH2
- Retinitis pigmentosa (RP) and retinal degenerations – Dominant: panel** (includes RHO, PRPH2, RP1, IMPDH1, PRPF8, NR2E3, PRPF3, TOPORS, PRPF31, RP1, KLHL7, SNRPN200), CA4, CRB1, CTRP5, X-linked RPGR, RP2; Recessive: single genes available on as needed basis.
- Retinoblastoma - RB1
- Early onset macular degeneration - ABCA4, ELOVL4, RDS
- Usher syndrome - Usher panel** (CDH23, CLRN1, DFNB31 (WHRN), GPR98, MYO7A, PCDH15, USH1C, USH1G, USH2A)
You can find more about the genetics of eye diseases at the national eyeGENE website.
Why might I have electrophysiology?
Testing with electrophysiology can narrow down the number of possible genes to screen, and give your eye doctor information about the overall quality of your vision. Many patients will have a kind of electrophysiology test called an electroretinogram (ERG). There are two types of ERG: full field and multifocal.
What is the difference between full field and multifocal ERG?
A full field ERG shows the average rod and cone responses across the entire retina, while a multifocal ERG measures responses in a small area in the center of the retina. A full field ERG takes about 2 hours to perform. For this test, you will first sit or lie in the dark for roughly 45 minutes to allow your eyes to adjust to darkness. Once you have finished this part, you will move to a lighted room. The doctor will then perform the ERG test. The multifocal ERG only takes 45 minutes, and the entire test takes place in a lighted room
How does the visual field test work?
The visual field test allows the eye doctor to see whether a person has any areas of vision loss. Many ophthalmology clinics perform this test with a tool called a Humphrey visual field analyzer. While this tool works very well, in our clinic, we perform a more comprehensive test that uses an Octopus visual field analyzer. This tool allows our physicians to check every area of the visual field for changes. The visual field test takes about 1.5 hours.
How does the family history exam work?
For the family history part of your exam, a genetic counselor will ask questions to determine whether you have an inherited eye disease, and how it might have been inherited. Once you have given your family history, your eye doctor and genetic counselor will discuss your information. If your condition is inherited, your doctor and genetic counselor can tell you:
- Your family’s inheritance patterns for the condition, and possible effects on family members
- Genetic screening and testing options available to you, including prenatal screening, clinical genetic tests, and research tests.
- Opportunities you might have for involvement in research studies or clinical treatment trials (such as gene therapy)
- Educational and support resources that can help you cope with a genetic diagnosis
What if I don’t know my family history?
Because the genetic counselor will need specific information about the vision and overall health of family members, it is important to be familiar with your family medical history. If you do not know your family history, you should try to bring a close relative (such as your mother or sibling) to this appointment.
How long is the color vision test?
The duration of this test can vary from person to person. If you need to schedule an appointment for color vision testing, ask a member of our staff to give you an estimate of how long yours will take.
How does the photography test work?
For this test, your eye doctor will use imaging equipment to photograph the inside of your eye. If you have this test, you will have your pupils dilated first. Your eye doctor will use these photographs during your later visits to help determine whether any of the structures of your eye have changed.
Why might I have a blood test?
Blood tests can confirm your diagnosis. If you are interested in doing this, you can have blood drawn in the clinic by a trained phlebotomist. Children who are sedated for their tests can have their blood drawn while under sedation.
If you choose to participate in a genetic research study at Columbia, you can have your blood drawn by a phlebotomist at the end of your appointment. You do not have to participate in genetic research and your decision has no impact on your care.
Will my insurance cover genetic testing?
Some private insurance companies cover genetic testing, but others do not. For patients without insurance, the National Institute of Health offers cost-free genetic testing through Columbia. Results from these tests can take time, often years.
Are there any new treatments for genetic diseases on the horizon?
One possible treatment is gene therapy, which involves correcting or modifying the genome through injections. The recent successes of this approach might soon pave the way to human treatments. In 2012, Eye Institute physician Stephen Tsang, MD, PhD provided evidence that a mouse model of retinitis pigmentosa can be treated with AAV gene therapy. After their mutant PDE6 genes were corrected, a significant portion of mice showed vision improvement. Additional information about this approach can be found at the following link: http://www.ncbi.nlm.nih.gov/pubmed/23108158