== Voor een Nederlandse beschrijving van sommige gepubliceerde studies, zie onderaan ==

EGRET+ fellows have published the results of their research in high-ranked scientific journals. Below you can find an overview their published work.

For an overview of all our work (published and as preprint), see also our project page on ResearchGate


Konstantinos Pappelis (1) (UMCG):

‘OCT-angiography (OCT-A) is one of the most promising recent additions to the evaluation of glaucoma and other ocular pathologies. However, there currently exists little consensus towards an objective and reliable quantification algorithm for this diagnostic technique. This makes it unsuitable – or to the very least problematic – for use in the routine individualized clinical care. With this publication we propose an analysis method that could allow for harmonization between different OCT-A brands. At the same time, we are the first to provide objective feedback on the semi-commercial OCT-A device produced by Canon. Our hope is to improve the decisions made on the clinical setting.’

This work is published in Translational Vision Science & Technology in January 2019. The paper, entitled “Quantification and Repeatability of Vessel Density and Flux as Assessed by Optical Coherence Tomography Angiography”, can be accessed here.

Nederlandse vertaling:

‘OCT-angiografie (OCT-A) is een van de meest veelbelovende recente toevoegingen in de beoordeling van glaucoom en andere oogaandoeningen. Er is op dit moment geen objectieve en betrouwbare toepassing voor deze diagnose techniek. Dit maakt OCT-A ongeschikt voor het gebruik in de klinische zorg. Wij introduceren een methode die ervoor kan zorgen dat verschillende OCT-A metingen gedaan op apparaten van verschillende merken goed met elkaar vergeleken kunnen worden. Ook zijn we de eersten die objectieve feedback bieden voor het OCT-A apparaat van Canon dat op dit moment semi-commercieel verkrijgbaar is. Hiermee hopen wij dat artsen in de kliniek makkelijker betere en meer objectieve beslissingen kunnen maken.’

Dit werk is gepubliceerd in Translational Vision Science & Technology in Januari 2019. Het geschrift, met de titel “Quantification and Repeatability of Vessel Density and Flux as Assessed by Optical Coherence Tomography Angiography”, kan hier worden gevonden.

Konstantinos Pappelis (2) (UMCG), in collaboration with Allison Loiselle (EGRET-cofund):

This study looks into how systemic treatment of seemingly unrelated pathologies pertains to the progression of glaucoma, as well as to the probability of glaucoma suspects fully converting to the disease. This is important, as it is currently not being taken into account in clinical decisions, when managing glaucoma. The population we used comes from the extensive Groningen Longitudinal Glaucoma Study and consists of subjects followed in the clinic for more than 15 years. We found that certain medication used for the treatment of blood pressure (Angiotensin II receptor blockers and ACE inhibitors) were associated with more favorable glaucoma outcomes. It is possible that these medications exhibit a neuroprotective effect, perhaps mediated through improved blood supply to the retina and the optic nerve. We hope that more extensive studies will help further elucidate this interesting observation, in order to better understand the mechanisms of the disease, but also to improve treatment protocols.

This work is published in Investigative Ophthalmology & Visual Science in November 2019. The paper, entitled “Association of Systemic Medication Exposure With Glaucoma Progression and Glaucoma Suspect Conversion in the Groningen Longitudinal Glaucoma Study.”, can be accessed here.


Stephen Kelly (1) (CITY):

Standard automated perimetry is the usual way that people are tested and monitored for visual field defects, which can occur as a result of certain eye diseases such as glaucoma. The examination itself can be tiring and there has been previous work showing that long test times can produce artificially lower scores. Much of this work was done over 15 years ago when the testing machines were older and used older (slower) software, but little had been done to check if this effect still happened with modern testing. The aim of this research was to see if there was a measurable difference in the scores between the first eye tested and the second eye tested.

To do this, we looked at the exam results of thousands of patients who had sit several of these standard automated perimetry exams over the course of 10 years in England. We then only considered people who had always been tested in the same order (right eye first and then the left eye second). We checked how much more variable (or less reliable) the left eye was compared to the right eye.

The main result of the study was that there was indeed, on average, a small increase in the left eye’s variability, about 3%, relative to the right eye. While this result is measurable it is quite small and unlikely to impact the exam results in a meaningful way. We do recommend however that as these examinations can already be quite variable, that the testing order is kept constant (always the same eye first) as to not introduce even more variability. 

This work is published in Acta Ophthalmologica in February 2019. The paper, entitled “Does eye examination order for standard automated perimetry matter?”, can be accessed here.

Stephen Kelly (2) (CITY):

The eye is a complicated organ and it is susceptible to a variety of diseases. Sometimes an eye can have more than one of these diseases together, which can make it more difficult to manage than managing them individually. Some ophthalmologists (eye-doctors) noticed in their clinics that people who had a combination of two diseases, uveitis and glaucoma, tended to have worse outcomes than people that only had one or the other. Not much research had been done on the topic and the goal of our work was to see if this was the case.

To answer this question, we looked at the hospital records of people in England who had been diagnosed with some form of uveitis and glaucoma together and compared them to people who just had glaucoma on its own. We looked at how the visual fields in each group changed over time and if one group changed more quickly than the other.

We found that people with the combination of uveitis and glaucoma had visual fields that were changing (getting worse) more quickly than those with only glaucoma. In fact, the combination group were almost twice as likely to have what is considered “rapid” changes. As a result, we recommend that ophthalmologists make sure they take extra care when dealing with these patients. This can be quite difficult to manage however, as some of the medications used to treat uveitis (corticosteroids) can increase the pressure in the eye, while medications used to treat glaucoma want to keep this pressure low.

This work is published in American Journal of Ophthalmology in July 2019. The paper, entitled “Evaluating the Impact of Uveitis on Visual Field Progression Using Large Scale Real-World Data”, can be accessed here.

Stephen Kelly (3) (CITY):

For over 20 years, hospitals and eye clinics in the UK have been slowly introducing electronic medical record systems to replace paper records. As well as making it easier to find and manage patient’s records (such as lab results, scans or medications), these data can also be used for audit. With paper records, it can be very difficult to get a “big-picture” look at what is happening within a clinic. This work shows one way that electronic records from eye clinics can be used to audit aspects of health service delivery.

We looked at records from over 70,000 patients from five different glaucoma clinics in England. For each clinic we investigated several different data points about the glaucoma patients, including their age, the severity of their glaucoma and how frequently they were being seen. There were some differences between how well the clinics were managing their patients but much of this could be related to differing demographics. The key takeaway message is that it was relatively easy to analyse these electronic records to get an idea of clinic performance. In the future, this could potentially lead to better targeting of patients in the clinics who are at a higher risk of vision loss and consequently preventing blindness.

This work is published in British Medical Journal of Open Ophthalmology in July 2019. The paper, entitled “Auditing service delivery in glaucoma clinics using visual field records: a feasibility study”, can be accessed here.

Stephen Kelly (4) (CITY):

We examined the conversion rates of elevated eyepressure to primary open-angle glaucoma (POAG) in England and assessed factors associated with risk of conversion. We found that less than one-fifth of glaucoma patients with elevated eye-pressure managed in glaucoma clinics in the UK converted to POAG over a 5-year period, suggesting many patients may require less intensive follow-up. Our study provides real-world evidence for the efficacy of current management (including pressure-lowering treatment) at reducing risk of conversion.

This work is published in British Medical Journal of Open Ophthalmology in March 2020. The paper, entitled “Progression from ocular hypertension to visual field loss in the English hospital eye service”, can be accessed here.


Shereif Haykal (UMCG):

The presence of brain degeneration in glaucoma patients has been originally described over a decade ago, but the source and nature of this degeneration has yet to be fully understood. Most of the evidence points towards this brain degeneration being secondary to the changes occurring at the level of the eye due to glaucoma. However, some studies have found evidence suggesting that the eye changes found in glaucoma are in fact secondary to brain degeneration, and not the other way around. This hypothesis challenges our view of glaucoma as simply a disease of the eyes. 

In this study, we used a novel MRI analysis technique known as “fixel-based analysis” to better understand the changes occurring in the brain visual pathways in glaucoma. By using this new technique, we have found evidence that the pathways closer to the eyes show signs of more advanced degeneration compared to the pathways farther away from the eyes. Based on this finding, we concluded that visual pathway degeneration occurring in the brain of glaucoma patients most likely starts at the eyes first and then spreads to the brain.

This work is published in Investigative Ophthalmology & Visual Science in September 2019. The paper, entitled “Fixel-Based Analysis of Visual Pathway White Matter in Primary Open-Angle Glaucoma”, can be accessed here.


Daniel Asfaw (1) (CITY)

This paper explains the eye movement dataset of 46 glaucomatous patients and 32 age-similar healthy controls (all anonymised). Eye movements were recorded at 1000Hz while participants watch three separate clips binocularly. Demographics and visual field data of the patients are also published. The data is published for ‘open research’ to encourage researchers to investigate and share their insights on the data.

This work is published in Data in Brief in May 2018. The paper, entitled “Does glaucoma alter eye movements when viewing images of natural scenes? A between-eye study”, can be accessed here.

Daniel Asfaw (2) (CITY)

The study assessed eye movements of glaucoma patients with asymmetric vision field loss (one eye more afflicted than the other eye).  The patients watched a series of pictures on a computer. Results show that eye movements can be used to easily separate the worse eye of a patient from their better eye. This preliminary finding indicates that eye movements recorded while patients watching videos and pictures can potentially be used to detected age-related visual field loss due to glaucoma.

This work is published in Investigative Ophthalmology & Visual Science in July 2018. The paper, entitled “Does glaucoma alter eye movements when viewing images of natural scenes? A between-eye study”, can be accessed here.


Iris Tigchelaar (OCU) and Georgia Demaria (UMCG):

In this study, we describe, refine, evaluate, and provide normative control data for two freely available tablet‐based tests of real‐world visual function. The tests measure visual search and face discrimination. This preliminary assessment indicated that both tablet‐based tests are able to provide simple, quick, and easy‐to‐administer measures of real‐world visual function in normally‐sighted young adults. Further work is required to assess their accuracy and utility in older people and individuals with visual impairment. Potential applications are discussed, including their use in clinic waiting rooms, and as an objective complement to Patient Reported Outcome Measures (PROMs).

This work is published in Investigative Ophthalmic & Physiological Optics in December 2019. The paper, entitled “Refinement and preliminary evaluation of two tablet‐based tests of real‐world visual function, can be accessed here.