Personalized medicine, the new form of medical treatment that uses a person’s genetic profile to come up with tailored treatment options, has made waves in the scientific community for the way it has changed treatments for cancer, cystic fibrosis, and other chronic diseases.
Ophthalmology was one of the first fields to adopt the use of these personalized, precision treatments for patients suffering from a variety of diseases affecting the eye, specifically the retina.
Genetic testing has allowed researchers to better understand eye diseases, particularly inherited and therefore genetic, eye diseases. By dissecting the molecular components of these diseases and examining the genetic profile of patients, researchers have been able to break up diseases that were once considered (and treated) as the same condition into smaller, more specific subtypes. This is known as the stratification of diseases.
Genetic profiling has also allowed the individualization of eye diseases: a personalized treatment approach based on a patient’s genome. Individualization is at the heart of personalized medicine, and recent studies have shown that it can have an enormous impact on how retina therapies should be applied to individual treatment plans.
In 2015, a major study into the impact of individualization on retina therapies focused on nutritional supplements to help prevent age-related macular degeneration was released. Researchers analyzed the genetic information of participants who were given various combinations of zinc and antioxidants to see if there was a link between the effectiveness of the supplements and the genetic profiles of the test subjects.
They found that whether patients benefitted from supplements depended on the alleles (alternative forms of the same gene) present in their genome. Patients with one set of alleles experienced a great benefit from taking zinc, but the same zinc supplements caused the vision of patients with a different set of alleles to degenerate further. The researchers concluded that, though the study had its limitations, it set an important precedent for understanding the link between patients’ genetic profiles and the best treatment options to offer them.
Even earlier than the AMD study, in 2014 researchers examined the impact of personalized stem cell treatments on retina therapies with great success.
They found that a form of retinitis pigmentosa, a condition in which the back wall of the eye is damaged, was caused when mutations at the genetic level interrupted the protein structure that gave the retina its fixed shape. By using genetic stem cell technology to transform patients’ skin cells into new retinal cells, researchers were able to reverse this disruption.
More than 60 different genetic mutations have been linked to retinitis pigmentosa, leading to a huge variation in how the diseases progresses in different patients. This has typically made it difficult to treat with traditional medicine — a problem common to inherited and degenerative eye diseases.
Personalized medicine offers a new approach, one that takes these genetic components into account through stratification and identifies a treatment that can be tailored to work with an individual’s genetic needs.
When it comes to retina therapies for children, one of the biggest concerns is retinoblastoma, a cancer of the retina that can develop before birth and affects approximately one in every 15,000 children born. As with most cancers, doctors have a better chance of eradicating tumors on the retina if they are identified early. With children, this can be difficult to do, leading to later diagnosis and worse outcomes.
In 2014, however, researchers at the Children’s Hospital Los Angeles identified a new genetic test for mutations linked to retinoblastoma. The test determines not only whether children are at risk but also how their tumors are likely to develop.
Traditionally, doctors treating retinoblastoma had to assume that both eyes would be affected and treat with higher levels of systemic chemotherapy than they would for tumors in a single eye. This type of chemotherapy came with a high risk of morbidity in young children and infants. With the new test, however, researchers were able to identify the gene that showed whether children would develop tumors in one or both eyes. As a result, doctors were able to tailor their treatments, creating better outcomes with lower levels of risk.
These type of personalized genetic tests and treatments don’t just improve outcomes for a single child. Researchers were also able to determine whether the child’s siblings — or even their own eventual children — were likely to be at risk for developing these tumors. This improves the chances for exponentially more children to survive childhood cancer.
September 07, 2016
Christopher Nystuen, MD, MBA