The annual Glaucoma Symposium organised by Haag-Streit UK has become an established event on the optometry education calendar. This year the event was held at Stanstead and the audience of mainly optometrists were treated to a range of lectures and workshops delivered by an impressive array of experienced experts in the field.
Epidemiology
Professor Rupert Bourne may be a familiar name as he has had strong connections with the optometry department at Anglia Ruskin University and was also instrumental in the seminal papers detailing the various causes of global blindness. Using his experience as a consultant ophthalmologist based both in the UK and the US, he began with a look at the epidemiology of glaucoma.
As the disease is well known to have an insidious onset, estimating the prevalence is similar to estimating the size of an iceberg with the tip of the iceberg representing the glaucoma known from studies and in clinic and that below the water surface the estimated disease yet to be identified.
Two papers were cited that reflect the problems of such estimation, with the first1 from the US suggesting known glaucoma to be 12% and unknown to be 78% while a second paper2 from Greece had the known to unknown ratio to be 53% to 57%. Citing his work with the Vision Loss Expert Group, Bourne suggested delegates visit the Vision Atlas to be found at atlas.iapb.org, a website that offers up to date eye disease prevalence data for any selected part of the atlas.
Bourne suggested this was more reliable than using published journal data which very quickly is out of date. A paper by Quigley’s team3 has suggested glaucoma prevalence globally will be 65 million people by 2020, so ‘a massive problem.’ As the disease is linked to age, the likelihood is a great increase in prevalence in the future.
Reviews of referral refinement schemes were next discussed, ‘and many good ones have been introduced in the UK’. There is a problem in the UK in that ‘we simply do not understand the burden of glaucoma in our population’. Bourne suggested that most authorities, such as the RNIB, still refer to data collected in the 1990s. Clues as to the burden are offered by those taking part in studies.
Many such studies show that patients entering studies are already at an established stage of the disease. This underlies what many authorities fear about glaucoma, in that there is a later presentation and hence the risk of subsequent vision deprivation is high. The UK currently has no nationwide population-based data on the prevalence and causes of sight loss and the utilisation of services.
To address this, the UK National Eye Health Survey is being set up which will monitor 25,000 adults aged 50 years and over. ‘I hope you will all be touched by this study,’ Bourne said.
Diagnostics and monitoring
Bourne began his review of clinical techniques with a recommendation for all interested in developing their clinical skills to visit the website www.gonioscopy.net which has some excellent material to help in the use of the gonio lens. He insists on the use of a magnifying gonio lens in his clinics (such as the Volk Magna View) which has completely transformed the usefulness of gonioscopy. He also recommended the online GONE tool from Australia which offers some great tips in assessing the disc (www.gone-project.com/gone-intro1.htm). He also presented some recent images helping to visualise the angle as it recedes (figure 1).
With regard to advances in imaging technology, studies have implied that it is not sensible to rely upon one technology alone. Alongside modern OCT techniques, there is still a role for disc photography, including stereoimaging (figure 2). He illustrated this with an example of an image that showed a disc haemorrhage which would not have been identified with OCT assessment alone.
Figure 2: There is still an important role for disc photography in glaucoma assessment
For monitoring glaucoma, there has been an upsurge in the use of imaging as opposed to a downturn in the use of visual fields in monitoring according to studies from the US.4 Bourne felt this was a cause for real concern that may also apply to the UK. ‘You do need both functional and structural tests and their combination allows you greater sensitivity.’
Many centres now use a Medisoft output for monitoring glaucoma (figure 3) and these show data from all measurements in one place over periods of time. These electronic displays ‘are absolutely critical’ in seeing what is happening over time.
It is important to establish progression over the first two years by more regular monitoring, and visual field data over this period is very important.5
Regarding follow up and risk, around 15% end up with severe sight impairment. Bourne followed up this stark figure with a summary of studies looking at the effectiveness of hospital care. ‘There is a lot of concern about the quality of our patients’ care,’ Bourne claimed.
There is often a deterioration despite apparent IOP control, along with iatrogenic deterioration and problems resulting from a lack of risk stratification and inappropriate allocation of resources. ‘Better risk stratification is needed’ to identify those patients likely to progress more vigorously to sight loss and there should not be a single strategy approach to all patients. Early monitoring and prioritising those presenting late in the disease process is important.
Treatment
‘There are lots of exciting things going on in the treatment of angle-closure glaucoma,’ Bourne said. The Eagle study has highlighted the benefit of those at risk of early cataract extraction.
The use of SLT (selective laser trabeculoplasty) has been impressive, the ongoing TAGS study is finding the effectiveness of trabeculectomy in long term disease management and there is some excitement about the use of RhoKinase inhibitors in reducing IOP too. Rehabilitation is also important and understanding how people live with glaucoma, for example mobility issues, are important. ‘This will help us look after our patients.’
A fascinating illustration of effective use of remaining visual field is provided by the Duke of Urbino. Bourne showed a painting of the Duke that is hung in Florence. He is always shown in profile from the right side as he lost his left eye in a jousting accident. Worried about assassination, he had the bridge of his nose removed so he might better see any possible assailant on his blind eye side.
This should remind us of the value of the wider field. Many patients with significant field loss may still have useful mobility because of residual wide field that might not always be monitored in clinic. The key is to ‘organise your clinic holistically.’
Shared care and social help need to be incorporated into management plans – its not just IOP management. One study has looked at doctor activity in glaucoma clinics. Doctors spend about 40% of their time talking. In virtual clinics, this reduces to just 10%. Perhaps ‘we need to make things more efficiently’.
Ultrasound biomicroscopy
Dr Rizwana Siddiqi offered an overview of the technique of using ultrasound in assessing the anterior chamber in primary angle closure glaucoma. This system has four components:
- A pulser
- A transducer
- A receiver
- A display
Alternating current is applied to a piezoelectric crystal and this produces a high frequency vibration that produces a compression wave that then bounces back off objects and this can be converted into an electrical energy response. An A-scan uses a unidirectional beam while a B-scan uses a two-dimensional beam.
The former is an amplitude scan, the latter a brightness scan. Lower frequencies (10 MHz) are able to image deeper structures such as the orbit, while higher frequencies (40 MHz) offer anterior segment detail. Ultrasound biomicroscopy (UBM) is undertaken on the supine patient under local anaesthetic with the lids held back via coupling medium. Obstruction of the trabecular meshwork occurs through a number of mechanisms:
- Iris or pupillary block
- Ciliary body influence (plateau iris)
- Lens influence (phacomorphic)
- Forces posterior to the lens
Identification of the underlying mechanism is important for successful management and UBM significantly improves this process. Siddiqi then showed many images to underline this point – a technique we should all be aware of.
References
1 Shaikh, Coleman. Burden of undetected and untreated glaucoma in the United States. American Journal of Ophthalmology, 2014, 158;1121-1129.
2 Topuzis et al. Factors associated with undiagnosed open-angle glaucoma: the Thessaloniki Eye Study. American Journal of Ophthalmology, 2008, 145;327-335.
3 Tham et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040. Ophthalmology. 2014 Nov;121(11):2081-90
4 Stein JD et al. Trends in Utilization of Ancillary Glaucoma Tests for Patients with Open-Angle Glaucoma from 2001 to 2009. Ophthalmology. 2012 Apr; 119(4): 748–758.
5 Chauhan BC et al. Practical recommendations for measuring rates of visual field change in glaucoma. Br J Ophthalmol. 2008 Apr;92(4):569-73