Inherited Retinal Disease
PracticeUpdate: Inherited retinal diseases are known to cause legal blindness, but are all necessarily associated with grim outcomes?
Dr. Kondapalli: So, inherited retinal diseases just describe any sort of retinal disease with a gene mutation associated with it. They have varying degrees of visual symptoms, including significant vision loss. However, other times people can have visual field defects, other times people can actually not even know they have any sort of inherited retinal disease. There are times where we’ll see patients who come into the office for a routine exam and are found to have abnormal findings in terms of their peripheral retinal exam and then with further investigation are found to be either carriers or partially expressing an inherited retinal disease.
Retinitis pigmentosa is of significant concern
PracticeUpdate: What types of IRDs are associated with unfavorable outcomes, and how are they currently being treated?
Dr. Kondapalli: One of the most worrisome types of inherited retinal diseases is retinitis pigmentosa. It’s one that can ultimately lead to significant vision loss because there is poor peripheral vision as well as diminishing central vision with time. Currently, we do a lot of supportive therapy for these patients; obviously we treat different eye conditions as they come up. It’s somewhat controversial in terms of management with vitamin A or lutein in these patients and with different groups of people providing different opinions in terms of their benefit. Carbonic anhydrase inhibitors, whether topical or systemic, can be used in patients with RP who have macular edema and have been shown to have some success. However, in terms of those patients with RP with significant vision issues, we don’t really have great mechanisms to currently treat them.
Available, affordable genetic testing will open up therapeutic possibilities
PracticeUpdate: Is treatment outcome in IRD dependent on stage at diagnosis or type of IRD? Or both?
Dr. Kondapalli: In terms of treatment that’s at least currently available for inherited retinal diseases, the one that immediately comes to mind is Luxturna. Luxturna is a treatment for those patients who have a Leber’s variant of retinitis pigmentosa. So, they have a very specific mutation that causes their retinitis pigmentosa. The drug is delivered subretinally in the operating room, and, usually, it’s preferred to give it to patients earlier in their disease course because that can allow them to have preservation of their vision long term. With the advent of available and affordable genetic testing that can be done in the office or by the patient at home and then subsequently mailed in, we are given greater options to know what mutations are causing specific inherited retinal diseases and, therefore, allow us to know what therapies we can do and provide them if and when they become available for us.
Optogenetics
PracticeUpdate: Are new treatments in the works for IRDs? If so, can you talk about them briefly?
Dr. Kondapalli: In terms of new therapies that are available, there are none currently. However, there are quite a few that are being studied in both phase II and phase III clinical trials. There are several studies that are looking at X-linked retinitis pigmentosa and gene therapy for them, but also Leber’s hereditary optic neuropathy and Usher syndrome. Optogenetics is another really interesting pathway, which might be beneficial for those patients with inherited retinal diseases, that is very different from a gene therapy pathway. With optogenetics, what they do is essentially try to manipulate the cells that are not photoreceptors in the retina. So, these would be changing neuronal activity so that they make certain retinal cells that are not light-sensitive, light-sensitive, essentially bypassing any dysfunctional photoreceptors. Optogenetics may be a treatment option for those patients that have Stargardt’s disease, and that’s what is currently being investigated now.
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