To mark World Glaucoma Week (6-12 March), world-leading glaucoma expert, Professor Jonathan Crowston, reveals the latest in glaucoma research.
As the leading cause of irreversible blindness world-wide, glaucoma is a serious public health problem.
It’s estimated that around 300,000 Australians have glaucoma. As our population ages, the number of people developing glaucoma will increase, placing a significant burden on health and social systems. Access Economics estimates that the costs associated with glaucoma total almost AUD$2 billion each year. By 2025, this cost is expected to climb to AUD$4.3 billion a year.
The devil is in the Detail
Early glaucoma can be notoriously difficult to diagnose. Research shows that half of all glaucoma patients go undiagnosed, despite 50 per cent of these cases having had an eye test in the past year. Clinical manifest cases are therefore being missed.
Research shows that half of all glaucoma patients go undiagnosed
One reason is that in diagnosing glaucoma, eye care practitioners can place too much emphasis on intraocular pressure (IOP). While IOP is an important tool in glaucoma diagnosis, population studies have shown that a significant proportion of patients do not have elevated IOP. Early diagnosis is best achieved by a detailed assessment of the optic nerve and nerve fibre layer structure and function.
Benchmarking Examination Skills
To help eye care practitioners assess their diagnostic skills in optic nerve examination, researchers at the Centre for Eye Research Australia (CERA) have developed a series of training tools.
One tool is the Glaucomatous Optic Neuropathy Evaluation (GONE) project (www.gone-project.com), an online program which asks participants to grade disc characteristics and score glaucoma likelihood on 42 disc photographs.
At the end of the assessment, the grader can compare their ratings with those of an international panel of glaucoma subspecialists.
GONE aims to highlight common problems in glaucoma diagnosis and inform the development of a customised training program in optic disc examination.
Data derived from this study shows that eye care practitioners tend to underestimate glaucoma likelihood in around 20 per cent of cases.
Researchers hope the GONE project will provide a useful tool for practitioners to hone their skills in optic nerve evaluation.
The test is available to all eye care practitioners. Australian optometrists who complete the program will benefit from two Continued Professional Development (CPD) points on completion of the assessment. The anonymous assessment takes only 45 minutes and is available to all eye care practitioners. Best of all it’s free and gives participants instant feedback.
To date more than 1,500 eye care professionals have registered to participate in the study.
All in the Gaze
In another CERA study Research Fellow, Dr. Evelyn O’Neill, has been tracking the eye movements of glaucoma subspecialists and trainees as they assess optic disc photographs for the changes of glaucoma.
The exercise seeks to discover whether there are any specific gaze patterns that specialists adopt when assessing optic nerves. To conduct the study, eye care practitioners of varying expertise and experience examined photographs of the optic disc displayed on a machine used to monitor and assess eye movement, known as an eye tracker machine.
It’s hoped the research will inform the teaching of optic disc assessment and allow comparison with less experienced viewers to discover more about how certain disc characteristics may be misinterpreted or missed.
Results so far have shown that glaucoma specialists demonstrate a very systematic viewing pattern with more time spent assessing the areas of the disc and nerve fiber layer that are more likely to display signs of damage. On the other hand, trainees typically displayed a more random pattern of viewing.
It was also found that clinicians who correctly diagnosed a particular optic nerve disc were more likely to use systematic gaze behaviour compared to those who misdiagnosed the same optic disc. These results indicate that there is a need for increased training in disc examination.
The Ageing Optic Nerve
CERA researchers are conducting glaucoma research at the cellular and molecular level to better understand how aging contributes to glaucoma pathophysiology.
It is well known that as we age, the functioning of our mitochondria, the part of the cells responsible for energy production, begins to decline resulting in reduced energy supply and increased oxidative stress. Research by CERA in collaboration with Professor Algis Vingrys and Dr. Bang Bui from the Department of Optometry at the University of Melbourne has shown that optic nerves in mice are less able to withstand the effects of short term IOP elevation compared to younger animals.
Interestingly, diet restriction, which is known to prolong life and reduce the risk of age-related diseases such as cancer and diabetes, dramatically improved the ability of old mice to handle the IOP challenge, such that old diet restricted animals behaved much more like healthy young mice. This protection was strongly associated with improved mitochondrial function in the retina.
While the findings provide important insights implicating mitochondrial decline in glaucoma development, dietary restriction as a therapy has obvious limitations and isn’t feasible in a clinical setting. The challenge for scientists then, is to find a way to replicate the protective effects of dietary restriction in a more practical way.
Linking the Senses
Anecdotal evidence suggests that patients with glaucoma can suffer hearing loss, yet researchers are yet to reach a consensus on the issue.
To find a definitive answer, CERA in conjunction with the Department of Otolaryngology at Melbourne University and the Royal Victorian Eye and Ear Hospital are investigating specific aspects of auditory function in glaucoma patients.
The research will focus on the temporal processing abilities of glaucoma patients. Temporal processing, or the time-related aspects of sound processing, is often described as the foundation of the hearing process.
If patients can detect changes in pitch and timing, they’re more likely to perceive changes in articulation, vowels and speech sounds, which is important for speech recognition and communication in general.
Preliminary results from the study suggest that sub-groups of glaucoma patients can have impairment in temporal auditory processing which can particularly manifest itself in difficulty in hearing speech in the presence if background noise.
Discovering the impact of glaucoma on the other senses may help us to better understand the impact on a patient’s quality of life.
Professor Jonathan Crowston is a clinician-scientist who specialises in glaucoma and is the Managing Director of the Centre for Eye Research. He completed his ophthalmology training at Moorfields Eye Hospital, London and subsequent Fellowships at Westmead Hospital, Sydney and the Hamilton Glaucoma Centre, University of California, San Diego. His research is focused on age-related neurodegeneration and neuroprotection of the optic nerve.