- Eye Health
|Welcome to the sixth issue of IMAGE – the first in a two-part series on glaucoma.|
Currently it is estimated that approximately 300,000 Australians have glaucoma, with only half being diagnosed. With an ageing population and the likelihood of developing glaucoma increasing with age, a growing proportion of Australians are at risk of developing this disease.
|Once detected though, the progression of the disease can be altered. This means that early detection is crucial and the services offered through CFEH critical in combating glaucoma.|
Importantly, to comply with the new Guidelines for use of scheduled medicines (Optometry Board of Australia, 2010) to provide care for glaucoma patients, optometrists must have access to equipment that enables them to measure intraocular pressure and visual fields, allow nerve head and nerve fibre analysis and imaging, measure and analyse anterior chamber angles and measure corneal thickness.
With this in mind, it is encouraging to see that 50% of referrals to the Centre are for glaucoma and optic nerve related tests and assessments. In addition, we are provisionally diagnosing glaucoma in a number of patients referred to CFEH.
With the Centre housing all the necessary equipment and providing its services free of charge, this is another clear way that CFEH can assist optometrists in providing best practice patient management and ensuring unnecessary vision loss does not occur.
Prof. Michael Kalloniatis
Dora is worried that she might have glaucoma
After talking to her neighbour who is being treated for glaucoma, Dora presents to her optometrist worried that she might also have glaucoma.
Dora is a 65 year-old lady who is generally quite happy with her vision. She is currently being treated for depression but otherwise she is enjoying good health.
Her optometrist noted a suspicious optic nerve in her right eye
Figure 1: Suspicious optic disc in Dora’s right eye.
Issues to consider
1. How can the optic nerve be assessed further with scanning laser tomography?
2. What additional information can be provided with this instrument to assist in patient management?
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The optometrist referred Dora to CFEH for glaucoma assessment due to a suspicious optic nerve head appearance in the right eye (Figure 2). Dora does not have a known family history of glaucoma, and best corrected visual acuity was 6/6 in each eye.
Applanation intraocular pressure was 17mmHg in each eye. Central corneal thickness was 523µm in the right eye and 513µm in the left. Anterior chamber angles were open to the ciliary body in all four quadrants in each eye.
The tests performed included GDxPRO, Optical Coherence Tomography (OCT) imaging of the optic disc, visual fields, optic disc photography, and Heidelberg Retina Tomograph (HRT3).
The HRT3 allows quantitative assessment of the optic nerve head and is useful in detecting and following optic nerve head changes in glaucoma. It revealed an average-sized optic disc in Dora’s right eye.
The topography image of the right optic disc from the HRT3 (Figure 3) revealed a relatively large vertical cupping, which is shaded in red. The neuroretinal rim is shaded in blue (sloped area) and green (flat area). A superotemporal notch (white colour) can be seen on the image (Figure 3), which corresponds to the area of marked thinning observed in the superior rim on fundoscopy (Figure 2).
The HRT3 reflection image of the optic disc (Figure 4) is divided into six regional sectors, which are compared to a normative database and classified as ‘within normal limits’ (as indicated by a green check mark), ‘borderline’ (yellow exclamation mark), or ‘outside normal limits’ (red cross).
The superotemporal and inferotemporal sectors of the neuroretinal rim in the reflection image of the right optic disc were classified as outside normal limits, according to the Moorfields Regression Analysis (Figure 4). However, only the superotemporal sector is consistent with the other findings.
The retinal nerve fibre layer (RNFL) profile (Figure 5), which relates to the retinal nerve fibre layer thickness, showed a marked depression superotemporally in the right eye where it dips into the red region (i.e. outside normal limits). This corresponds to the superotemporal notch shown in Figure 3. A p-value less than 0.05 (p<0.05) is considered significantly outside the normal range. Note: superotemporal is referred to as TS in the HRT3 printout, Figure 5.
Visual field testing with FDT Matrix 24-2 Threshold showed an inferior arcuate defect in the right visual field (Figure 6), which correlates with the superior rim thinning detected on HRT3 and fundoscopy. Based on these results, a provisional diagnosis of glaucoma was made. CFEH therefore recommended that the patient be referred to an ophthalmologist to confirm the diagnosis.
Prepared by: Agnes Choi, CFEH Staff Optometrist
Glaucoma is a group of optic nerve diseases that is characterised by progressive damage of the optic nerve as shown by changes in the optic disc, retinal nerve fibre layer, or visual field(1).
The word glaucoma is thought to come from the ancient Greek meaning clouded or blue green hue(2). This is understandable if patients presented in those times with eyes such as shown in Figure 7b.
Figure 7a: Patient’s normal right eye.
Figure 7b: Patient’s left eye. Note the greenish colouration of the iris, the lack of iris detail due to corneal oedema and the vertical oval pupil. The intraocular pressure in this eye with a non-contact tonometer was 93mmHg.
Glaucoma is responsible for a significant part of the health-care costs for eye disease in Australia and brings with it a considerable economic burden. The total cost of vision impairment in 2009 was estimated to be $16.6 billion, with $224m (8%) spent on glaucoma alone(3).
Glaucoma ranks fourth on the list of visual impairment in Australia by cause – behind age-related macular degeneration, cataract and uncorrected refractive error – and is responsible for 16% of blindness in the over 40 age group. This represents over 66,000 Australians(3).
The prevalence of glaucoma in Australians over 50 is thought to be 2.5%(3). Glaucoma Australia estimates that in total approximately 300,000 Australians have the condition, with only half being diagnosed(4).
The likelihood of developing glaucoma increases with age, such that one in ten people over the age of 80 are thought to have this disease(4).
With the ageing of the Australian population, more patients are likely to present to ophthalmic practitioners with glaucoma. Thus, improved diagnosis of glaucoma, and subsequent treatment, would reduce visual impairment and the economic cost of the disease in Australia.
Perhaps even more importantly, visual impairment can have a significant effect on a person’s quality of life, such as increased risk of falls by a factor of two, risk of depression increasing three times and being twice as likely to use health services(3).
In the first instance, identifying individuals at risk of either having or developing glaucoma requires a careful history. The National Health and Medical Research Council in Australia (NHMRC) has recently produced two documents in relation to glaucoma, which are currently available on the internet(5).
In the Literature Review final report, the NHMRC identifies risk factors to help identify patients who may be glaucoma suspects. These include:
In the next edition of IMAGE we will discuss the components of an eye examination that the NHMRC discussion document suggests for examining the suspected glaucoma patient.
CFEH Staff Optometrist
Staff Optometrist Agnes Choi has a special interest in glaucoma, a “silent disease” affecting an estimated 300,000 Australians.
“Since there are usually no symptoms in the early stage of the disease, an individual has likely suffered some irreversible damage by the time they show symptoms. So early detection and treatment are the keys to prevent vision loss,” says Agnes who joined the Centre a year ago.
Agnes loves the diversity and challenges of her role at CFEH:“The Centre has a very supportive professional environment and I’m constantly learning from and being challenged by the experience and different expertise of my colleagues. Many of our patients have complex eye conditions and it’s a privilege to assist them with the testing and diagnostic information our Centre provides.”
Agnes is a graduate of the UNSW School of Optometry and Vision Science. She brings clinical experience from private practice and the Institute for Eye Research (now the Brien Holden Vision Institute).
Frank, a 47 year-old white male presented to his optometrist with problems seeing small print. At the consultation his intraocular pressures were measured and found to be 24mmHg in the right eye and 26mmHg in the left eye. Visual fields were full but unreliable, but the optic discs looked suspicious superiorly in both eyes. He was referred to Centre for Eye Health for further investigation.
What imaging results would help you to better review this patient?
CFEH offers a range of services to assist optometrists in referring to the Centre, which we strongly encourage you to take advantage of.
To ensure CFEH is best able to support optometrists to utilise the services available through the Centre, a Referrer Services Coordinator, Leon Fernandes, has recently been employed.
As part of our continued development and refinement of our services, CFEH welcomes your feedback. Please email email@example.com.
Disclaimer: This newsletter is not intended to provide or substitute advice through the appropriate health service providers. Although every care is taken by CFEH to ensure that this newsletter is free from any error or inaccuracy, CFEH does not make any representation or warranty regarding the currency, accuracy or completeness of this newsletter.
Copyright: © 2010, Centre for Eye Health Limited. All images and content in this letter are the property of Centre for Eye Health Limited and cannot be reproduced without prior written permission of the Director, Centre for Eye Health Limited.