“The eye is such a beautiful and marvelously small organ, a highly specialized instrument with which we can perceive our environment in all its beauty and complexity.”

Unfortunately, a lot can also go wrong with the eye. As an ophthalmologist, Prof. Dr. Camiel Boon focuses primarily on diseases of the retina, hereditary eye diseases, and microsurgical retinal operations. Camiel Boon is an ophthalmologist and professor of Ophthalmology at Amsterdam UMC and LUMC.

His strong motivation for conducting innovative scientific research stems from daily interactions with patients confronted with serious eye diseases. Prof. Boon says, “There are still too many eye diseases that we cannot treat effectively. That’s what my team and I are striving to change!”

Many patients diagnosed with Usher syndrome in the western part of our country visit ophthalmologist Camiel Boon and his team for biennial check-ups or treatment for eye problems. A treatment to halt the progression of vision loss in Usher syndrome is not yet available. But there are hopeful developments!
It’s time to ask Prof. Boon about his work, his scientific research, and the future innovative treatments for Usher syndrome.

Ophthalmologist Prof. Camiel Boon and Prof. Dr. Arthur Bergen in the laboratory of AmsterdamUMC ©Mark Horn

Hope for the future: pioneering in gene therapy
Prof. Camiel Boon trained as an ophthalmologist and earned his Ph.D. (cum laude, on a dissertation about hereditary retinal disorders, 2009) at Radboudumc in Nijmegen. As an ophthalmologist and now a professor, he conducts research on genetic retinal diseases, such as retinitis pigmentosa (RP), also in the context of Usher syndrome, at Amsterdam University Medical Centers (and part-time at Leiden University Medical Center). He sees patients at Amsterdam UMC, which has been designated as an expert center by the Dutch Federation of Universities and the European Network for Rare Eye Diseases. The gene therapy that Camiel is working on with the laboratory of Prof. Dr. Arthur Bergen (also at Amsterdam UMC) and Dr. Jan Wijnholds (LUMC) could potentially help prevent blindness in the future.

Viral envelopes or non-viral ‘nanoparticles’
Boon states, “At Amsterdam UMC, we are now treating people with a specific type of retinitis pigmentosa (RP) for the first time, which is X-linked and inherited due to a mutation in the RPGR gene. Together with Radboudumc, we are truly pioneering in this area.” Camiel Boon is the lead researcher of this study and the one performing these microsurgical interventions in Amsterdam. “It is a privilege to finally be able to offer potential treatment to the first patients and to carry out these procedures myself. But it is still truly a pioneering time, and we still need to thoroughly investigate whether these techniques are truly effective and safe.”

Gene therapy for hereditary retinal degeneration due to the RPE65 gene is already available and is reimbursed by insurers for some patients with this gene who qualify. Camiel Boon explains, “However, over the past 2 years, it has been found that a significant percentage of patients experience a very unpleasant and concerning complication, namely accelerated thinning of the retina. That is exactly what you don’t want.” Dr. Boon suggests that this may be because the gene therapy causes the newly administered gene to ‘overexpress,’ which is too much for the retina. But it could also be that the viral envelopes used to inject the gene under the retina cause inflammation and damage.

Boon says, “This indicates that much research still needs to be done on the safety and effectiveness of these brand-new techniques. It may be better not to use viral envelopes for this gene therapy. At Amsterdam UMC, we are researching the use of non-viral ‘nanoparticles,’ a type of lipid vesicles as carriers to deliver the genetic treatment to the retina.”

Initiating Sirius for RNA therapy
As the lead researcher at Amsterdam UMC, ophthalmologist Boon was closely involved in initiating the Sirius study for RNA therapy for Usher syndrome type 2A with exon 13 mutations, by the company ProQR. However, it ended in disappointment. Boon says, “I was truly shocked that this company abruptly pulled the plug on this research due to financial setbacks, before the first patients could be treated. We had informed and selected many patients to participate. It was a bitter experience that companies can do this so arbitrarily, and the study seemed to depend on the company’s stock value. This has made me even more critical of the agreements and logistics of such studies and companies, and I hope that colleagues internationally will also do the same. Of course, I hope that the study, now that RNA therapy has been taken over by a new company, will still start. In that case, we will undoubtedly participate again in Amsterdam UMC, under the right conditions and in close collaboration with Radboudumc. We strive to collaborate as much as possible with Amsterdam UMC and Radboudumc on such innovative and challenging studies.”

Retrospective study on Usher syndrome type 2c due to an abnormal ADGRV1 gene
Recently, we issued a call to participate in the retrospective study for people with Usher syndrome type 2c.
Boon says, “With this study, we aim to map out as large a group of patients with RP in the context of Usher syndrome type 2c due to the ADGRV1 gene mutation from Amsterdam UMC as possible. This is essential to provide a good assessment of the clinical picture, the course, and the prognosis. Additionally, it is important to understand the picture well to select the right candidates for treatment in case of any future treatments. Because you don’t want to take risks if, for example, it’s no longer beneficial because the RP has already progressed too far. We are working to conduct this research with all expertise centers for hereditary retinal diseases from the Dutch RD5000 network. But we also include data from patients from Belgium, Italy, Portugal, and even Australia.
I strongly believe in good collaboration with as many research groups as possible. Within such a network, studies and their impact can be greatly expanded, and thus the results are much more relevant for clinical practice. Therefore, we often collaborate within national and international networks from Amsterdam UMC. For treatment research, we also work closely with Radboudumc. Our lines of research complement each other well. While Radboudumc conducts a lot of research on, for example, RNA therapy, we conduct research on other techniques such as the ‘genetic scissors’ CRISPR/Cas and other new techniques.”

Read here: The very first ADGRV1-zebrafish model has been presented

Confusing Usher syndrome with another syndrome
Usher syndrome is the most common form of deafblindness. Therefore, a DNA diagnosis is crucial because there are other syndromes where hearing and vision are affected. We recently published a study on the PHARC syndrome. Boon says, “In practice, sometimes patients are diagnosed with Usher syndrome when they actually have the PHARC syndrome. We have published an article describing how this distinction from Usher syndrome can best be made. And this is important because it not only affects possible other physical symptoms and their management but also the prognosis and hopefully future treatments.”

Read here the publication.

Cataract surgeries in people with Retinitis Pigmentosa and Usher syndrome
Cataracts at a younger age are common in RP, also in the context of Usher syndrome. Until recently, it was not well known whether this is effective in RP and whether there might be increased risks in the case of cataract surgery in this group. Camiel Boon has wanted to investigate this in a good scientific study for years and recently published a large international study, coordinated from Amsterdam UMC, on the outcomes and risks of cataract surgery in people with RP. Based on the results in 226 patients (295 operated eyes), he found that the procedure often leads to a significant improvement in vision but that the risk of complications is also somewhat higher. Prof. Boon says, “The chances and risks should therefore be clearly discussed in advance with potential candidates for cataract surgery in combination with RP.”

Read here the referentie

Know what you measure: the REPEAT study
A unique study that Prof. Boon proudly talks about is the REPEAT study. Boon says, “It is remarkable that gene therapy is already being tested in people with RP, while we actually still do not know sufficiently how to reliably measure the effect of the treatment. We don’t even know the variation of the same measurement at different times in RP. That is a significant problem because if you don’t know how reliable your measurement is, the interpretation of it is questionable. And then gene therapy studies may fail based on that alone. We have taken a unique initiative: the REPEAT study. PhD candidate Jessica Karuntu is testing how variable and reliable the important measurements for RP are in no less than 50 RP patients (some with Usher syndrome), in various stages of the disease. Think of visual field tests, measurement of visual acuity, but also questionnaires about quality of life. This has never been done before, and the impact of this for research into RP and its treatment (and measurement) is going to be enormous. The pharmaceutical industry has been moderately interested in conducting and supporting this research so far. While the importance of this for their gene therapy studies is significant. I am quite proud that we are achieving this independently of those companies because this has not been done anywhere in the world so far.”

The big picture
Finally, Camiel Boon points out another huge task that he and his group have been working on recently. “We are writing a very large article about all syndromes that can present with RP. A large part of this article is about Usher syndrome. This article is so important because it will help doctors and researchers recognize and distinguish between the different conditions more quickly. And therefore, hopefully start treatment more quickly if available. It will be an article of about 150 pages, more like a book…!”

Exploring new paths with patients
Prof. Boon says, “It is truly a privilege to work as an ophthalmologist in this pioneering time, where we can finally test the first treatments in the laboratory and now even in clinical practice. It is extra motivating to explore these new paths together with patients and patient organizations and to join forces to make as much research as possible into these rare and serious diseases possible.”

During our conversation with Prof. Camiel Boon, Camiel also had a question for us. How can we improve care for patients with Usher syndrome? In Nijmegen, multidisciplinary teams are already working where ophthalmologists and ENT specialists collaborate in the care for people with Usher syndrome. Boon is working to establish this collaboration in Amsterdam UMC together with the ENT department there.

Webinar: Hereditary eye diseases
On April 15, 2024, a free webinar for knowledge sharing was organized by Prof. Camiel Boon (professor of Ophthalmology at Amsterdam UMC), Prof. Dr. Arthur Bergen (professor of Human Genetics of Eye Diseases at Amsterdam UMC), and Dr. Jessica Karuntu (researcher at LUMC). This webinar was organized by the Eye Research Society with the aim of sharing knowledge about hereditary eye diseases such as Retinitis Pigmentosa (RP) and Macular Degeneration and the development of new treatments.

The webinar was conducted in English and was subtitled. You can watch the recording of the webinar here: