I don’t know about you, but by 2021 I always hoped that the scientific community could have made some seriously cool progress with gene therapy … you know, really unlock the gene pool sci-fi style. I’m talking about the ability to shoot laser beams from my eyes, or change my appearance like a chameleon, or even disappear entirely. Needless to say, we haven’t quite reached the lofty ambitions of my childhood dreams.
But just because the very laws of nature and physics are not being violated to adhere to a young child’s fantasy doesn’t mean that gene therapy isn’t cool. In fact, this science is behind some absolutely fantastic developments in many aspects of medicine. Human gene therapy is being used to treat a wide range of diseases including cystic fibrosis, adenosine deaminase deficiency, familial hypercholesterolemia, cancer and more. More specifically, gene therapy is beginning to be applied in ophthalmology too, for conditions ranging from age-related macular degeneration to Leber’s congenital amaurosis.
You Could Have a Gene that Causes Blindness
For all the uses of gene therapy, the most interesting generally — and for optometry specifically — is in its potential for treating inherited retinal diseases (IRDs). Also known as monogenic retinal diseases, IRDs are a major cause of blindness in the pediatric and working-age population in many countries, and pathogenic variants in more than 250 genes can cause various forms of IRDs. For most of these diseases, no medical or surgical treatments currently exist, but this may change as a number of therapeutic trials are underway.1
There are many different IRDs that clinicians should be aware of, however, a specific few are encountered more commonly. These include retinitis pigmentosa (a group of related eye disorders caused by variations in 60 different genes); choroideremia (which causes progressive vision loss and is usually associated with night blindness); and Stargardt macular dystrophy, (which causes damage to the macula). These and the other IRDs may be relatively rare, but they significantly impact a patient’s quality of life and usually cause a gradual loss of vision or even total blindness.
Gene therapy may seem like the cutting-edge of science fiction to some, but the technology is actually relatively simple when broken down into its key components. The technique usually involves one of two related concepts: Firstly, a faulty or inactive gene that can cause diseases is replaced before it can cause the patient harm. Secondly, an entirely new gene can be introduced to the patient. Regardless if it’s a replacement or entirely new, any gene that is entered into a patient’s body is delivered by a vector, usually a modified and harmless virus, which itself is delivered by either an injection or an intravenous drip.2
Now you may be saying to yourself that this is all very interesting, and certainly, injecting a gene via a specially modified virus is pretty cool — but what does this have to do with optometry? Even if gene therapy can be used to treat IRDs and other eye diseases, surely this has more to do with ophthalmology? Well, hold on to your outrage tweets as there is a growing body of research that points to the important role optometry could play in this field.
Should Optometrists Start Taking Blood Samples?
If optometrists could expand their patient offerings to include genetic testing, for example, by collecting blood or saliva samples from their clients, they would be well placed to act on the front line of screening for IRDs. Working on creating a system like this is already underway “Down Under,” and research has emerged highlighting the role optometrists can play. An Optometrist’s Guide to the Top Candidate Inherited Retinal Diseases for Gene Therapy is one such study, which examines a number of gene therapy trials and their applicability to IRDs.
The study points out that “optometrists are well placed to help establish a clinical profile, determine the level of visual function, monitor disease progression, and work as part of a multidisciplinary team in establishing a genetic diagnosis.” Pointing out that if suspected in younger, working-age adults with visual field loss and abnormal photoreceptor function, the study highlights how optometrists can act as the first line of defense in IRD treatment. This is by quickly identifying these young patients who might not be aware of their risky genetic profile. The study recommends that visual acuity be closely monitored: In potential IRD patients, it can range from 6/5 to no light perception, with approximately 10% of individuals with an IRD having visual acuity less than 6/60.3
It might be difficult for some optometrist to persuade their clients that adding saliva and/or blood testing to their usual check-up is a good idea, but the patients (especially younger ones) really stand to benefit. It will be for clinicians to persuade their charges, as well as to set up the infrastructure required for facilitating this change. However, they should do this as genetic testing, leading to timely gene therapy, could certainly save the sight of many.
References
- Pontikos N, Arno G, Jurkute N, et al. Genetic Basis of Inherited Retinal Disease in a Molecularly Characterized Cohort of More Than 3000 Families from the United Kingdom. Ophthalmology. 2020;127(10):1384-1394.
- Gene Therapy. The Cleveland Clinic. Available at https://my.clevelandclinic.org/health/treatments/17984-gene-therapy. Accessed on Monday, July 12, 2021.
- O’Hare F, Edwards TL, Hu ML, et al. An Optometrist’s Guide to the Top Candidate Inherited Retinal Diseases for Gene Therapy. Clin Exp Optom. 2021;104(4):431-443.
