What is DNA health testing?
DNA health testing is the analysis of an individual’s DNA, the set of genetic instructions for their body. It can provide information about a person's genetic makeup and risk for diseases, including eye conditions. This can help eye doctors manage and treat inherited eye conditions.
These tests detect mutations or changes in DNA that may be responsible for vision loss. Lower costs and quicker results have made testing more accessible. This has made it increasingly valuable in diagnosing and understanding inherited eye conditions.
What is DNA?
DNA is short for deoxyribonucleic acid. It is a double-stranded molecule that carries an individual’s genetic information. It’s found in every cell and passes down hereditary traits from one generation to the next. For example, your eye color genetics are passed down from your parents through DNA.
Genes are specific segments of DNA. They serve as the blueprints for making proteins and other molecules essential for proper cell function.
Proteins perform a wide range of tasks. They:
- Provide structure to cells and tissues
- Aid in chemical reactions
- Transport molecules
- Regulate various processes in the body
Proteins are necessary for the body to perform vital functions and maintain overall health and well-being. But a gene mutation can alter the instructions for protein production. This can severely disrupt the cell’s function, resulting in illness.
How does DNA testing work?
Genetic testing examines DNA samples from blood or saliva. Specialized DNA sequencing technology compares a person’s DNA with known genetic patterns to identify mutations.
Genetic diseases result from mutations inherited from parents. Genes are typically found in pairs, with one copy from each parent. Having two copies of each gene provides a backup system and allows for greater genetic variety. It also plays a fundamental role in how traits are passed down through generations.
DNA tests detect various types of genetic alterations:
- Dominant mutations – Result from changes in one copy of a gene
- Recessive mutations – Require changes in both copies of a gene
- X-linked recessive mutations – Found on the X-chromosome. This primarily affects males due to their single X-chromosome. (Females usually have a second healthy X-chromosome.)
What does DNA testing detect?
Most genetic tests screen hundreds of genes associated with a particular condition. DNA testing can:
- Indicate if you carry a gene for a disease (even if you don't have it)
- Identify a disease you already have (even if you don’t show symptoms)
- Detect gene mutations that alter the structure and function of the eye
Keep in mind that genetic testing isn't always conclusive. A genetic alteration may be detected, but its link to a specific illness may be unknown.
DNA testing for eye diseases
Because many eye diseases are inherited, genetic testing is particularly valuable in eye care. Doctors can enhance disease management and provide personalized treatments through genetic testing.
Benefits of genetic testing for eye diseases
Early diagnosis is crucial for the successful management of numerous eye conditions. For example, some disorders lead to progressive vision loss over time. Early intervention can often slow down these diseases, helping to maintain an individual’s vision.
Genetic testing can help doctors:
- Confirm and clarify diagnoses earlier than with traditional testing alone
- Prevent delays in diagnosis, particularly with rare diseases
- Understand how a disease will likely progress
- Select which therapies are most likely to be effective
- Identify clinical trials for which a patient may be eligible
- Determine inheritance patterns to predict whether a condition will be passed on
Common eye diseases detected by genetic testing
Doctors can screen for over 300 genes linked to eye diseases. Some genetic eye diseases that can be screened by DNA testing include:
Inherited retinal disorders
The retina is the light-sensitive tissue located at the back of the eye. It converts light into signals that the brain can interpret as visual images. Retinal dystrophies are a group of eye diseases that damage the retina's cells, causing vision impairment.
Inherited retinal disorders are caused by mutations that impair the retina. Many inherited retinal diseases share similar symptoms. Genetic testing in addition to clinical findings can be crucial for accurate diagnosis.
Examples of inherited retinal disorders include:
- Retinitis pigmentosa – A group of genetic disorders that cause progressive degeneration of the retina’s cells that sense light, leading to vision loss. Symptoms can begin in childhood and include difficulty seeing in low light and progressive loss of peripheral vision.
- Stargardt disease – An inherited form of macular degeneration. It causes impairment in central vision and typically appears during childhood or adolescence.
- Leber congenital amaurosis – A group of inherited retinal diseases. They cause severe vision loss from birth, including being crossed-eyed and having a high level of farsightedness.
Corneal dystrophies
The cornea is the transparent outer layer of the eye that focuses light. Corneal dystrophies typically affect both eyes. They are a group of eye diseases in which abnormal deposits accumulate in the cornea, impairing vision.
Keratoconus
Keratoconus is a condition in which the collagen structure of the cornea is affected. This causes it to thin and bulge, leading to blurry vision. It’s likely that it is the result of both genetics and environmental factors.
Glaucoma and cataracts
Several factors are usually involved in the development of both glaucoma and cataracts. Genetic testing can be a valuable tool in understanding the development of these conditions. It is particularly valuable when they occur at a young age or are part of a syndrome.
The role of gene therapy in managing eye diseases
Gene therapy is a procedure that treats diseases by modifying a person's genes. This can involve:
- Replacing a non-functional gene with a healthy one
- Fixing a faulty gene
- Regulating the activity of a malfunctioning gene
There are several ongoing clinical trials for gene therapy. DNA testing can help determine eligibility.
Luxturna
Luxturna is a drug used in gene therapy to treat RPE65-related retinal dystrophy. The procedure is performed in an operating room while the patient is under anesthesia.
During the procedure, the vitreous (a clear gel-like fluid inside the eye) is removed. Then the drug Luxturna — which includes a healthy version of the RPE65 gene — is injected beneath the retina. A single injection can help restore the retina's light sensitivity. Improvements are generally seen within a month.
The second eye is treated six days after the first injection. A patch will be placed over the eye for 24 to 48 hours post-procedure. Because eye gene therapy is done on an outpatient basis, the patient can go home the same day as the procedure.
Implications for family health
Genetic testing can be valuable for assessing the risk of inherited eye disease in family members. This information is especially valuable for autosomal and X-linked recessive inheritance patterns. This is when carriers of a gene mutation show no symptoms yet can pass the condition to their offspring. Family planning and reproductive decisions can be guided by this type of testing.
Counselors can interpret test results to help families understand genetic testing results. They explain the hereditary risks for the patient and their family. They can also provide guidance and support on the emotional and ethical issues that arise from genetic testing.
How to get tested
It's essential to consult your eye doctor regarding genetic testing so they can guide you through the process. You should also check with your insurance to confirm whether coverage is available for this procedure.
The genetic testing process is usually straightforward and can be performed in many medical centers. Just confirm that your testing is done at a CLIA-approved laboratory.
The following steps are essential:
- Get a thorough eye exam – Your eye doctor will perform a clinical exam and refer you to a genetic counselor.
- Meet with a genetic counselor – A genetic counselor can evaluate your need for genetic testing. They can recommend the appropriate test, and explain the costs and insurance options.
- Provide a DNA sample – A blood or saliva sample will be collected for analysis.
- Receive results – Test results can take several weeks to months.
- Interpret the results with a genetic counselor – The counselor will explain the results and discuss the next steps.
- Discuss the results with your doctor – Your doctor will recommend a management plan for your condition based on the results of the test.
DNA health testing offers patients and their eye doctors valuable insights into the inherited causes of vision impairment. It can also aid in understanding disease inheritance patterns, management plans and treatment options.
Gene therapy, which aims to treat diseases by modifying a person's genes, is an emerging field with many ongoing clinical trials. Information about enrollment can be found on ClinicalTrials.gov.
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