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January 20 2013
Choosing an OCT imaging device is a difficult decision for any practitioner. Optometrist Daniel Hardiman-McCartney discusses his experience
Three-years ago, owning an optical coherence tomography (OCT) imaging device marked an optometrist out as clinically forward-thinking, but now in 2013 they are increasingly becoming a standard instrument in High Street practice. Consequently, the OCT you choose and how you decide to integrate it into your clinical practice has never been more important.
When I was choosing an OCT device two years ago, I gave considerable thought as to which instrument would offer the most unique features and benefits and how I would integrate its use into our patient pathways. I wanted an instrument which I could use for specialist shared care schemes as well as routinely when clinically indicated within the eye examination. I wanted to see beyond the capacity of a Volk lens; improve my ability to detect and monitor pathology and increase the quality of our practice referrals.
I chose the Heidelberg Spectralis because of its enormous range of functionality and the exceptional quality of its images. While there were many easier to use ‘point and shoot’ OCTs on the market, I was confident that the flexibility of the Spectralis offered the greatest clinical benefit to our patients and I have not been disappointed.
Image quality and adjustability
The Spectralis instrument has the ability to take images at a remarkably high resolution. This enables the practitioner not only to examine known pathology in great detail, but also to see beyond what is visible with indirect ophthalmoscopy. I have had a number of patients with a small, unexplained reduction in VA whose OCT examination showed a small amount of vitreoretinal traction, along with a posterior vitreous detachment (PVD) . Although no treatment is required, knowledge of the cause empowers the patient and reduces undue worry.
The high-resolution images are achieved by combining a confocal scanning laser ophthalmoscope with an OCT. This allows a single scan to be repeated between nine and 100 times at exactly the same position, producing a composite image through a process called Automatic Real Time Averaging (ART), which gives an extremely clear and reliable result. This process is surprisingly fast; a single line scan repeated 100 times takes around eight seconds. The combination of confocal scanning laser ophthalmoscope and OCT also enables active eye tracking, which locks the OCT to the fundus. This means that whatever quality you select, the patient can move their eye, blink or move their head and the instrument will not suffer motion artefact.
Rather than a handful of pre-set options, the Spectralis gives the practitioner complete control over a number of parameters: quality (ART), location, orientation, area and size. This enables users to tailor scans to clinical need and is particularly useful for assessing pathology outside the central 30° field, such as diabetic retinopathy.
While the quality and adaptability of the scans is fantastic, it does mean that the Spectralis is not an easy-to-use machine. The large number of options can be overwhelming and it takes time to learn your way around; it is not designed with ease of use by unqualified staff in mind. As a result you need to allow more time than you would for other OCTs on the market to either train staff in its use or for you as the practitioner to incorporate the process into your examination. However, ours is confidently used by all our optometrists and dispensing opticians.
Two years from purchase, I find one of the most useful features of the Spectralis is the auto-rescan, which allows the instrument to automatically carry out repeat scans, ensuring exact alignment and with the same parameters at follow-up appointments. This is completed by automated alignment of the blood vessels from a historic OCT image, so the exact location and orientation is repeated, and like-for-like scans can be compared. This is especially useful in cases where the patient is at risk of developing glaucoma, enabling comparison of precisely the same area of retinal nerve fibre, in order to detect an early notch or avoid the unnecessary referral which may result if a repeat OCT were misaligned. The ability to detect small changes over time is a clear benefit of this particular instrument, which is readily perceived by patients and encourages them to return to our practice for follow-up examination.
Like many other OCTs, the Spectralis is available with a range of optional modules. These include anterior segment imaging and MultiColor Scanning Laser Imaging for high-resolution fundus images. I chose to add the BluePeak Fundus Autofluorescence (FAF) module, which maps metabolic activity within the retina. This has proven exceptionally useful for our patients with dry AMD, as it enables us to distinguish high-risk groups, such as those with reticular drusen, from low-risk groups.
The Spectralis platform is network-ready and designed for integration into a multi-consulting room environment. I have ours in a separate diagnostic area, which allows our dispensing optician to run an OCT clinic at the same time as the optometrists are conducting eye examinations. Images and analysis are easily accessible across the network. I had to ensure our network was good enough to handle the large image sizes in order to use it in this way. The exceptional image quality also means that the files produced per patient are large and this has implications for data storage and backup.
When I purchased the Heidelberg Spectralis two years ago I hoped it would enable us to detect pathology at an earlier stage and give us more confidence with regards to macular disease. While it has exceeded our expectations in both respects, it has also provided the additional benefit of decreasing unnecessary referrals. I have found that the use of OCT, considered alongside other examination findings, has given me the confidence to refer less, particularly in the case of macular degeneration. The value of robust differential diagnosis of wet versus dry macular degeneration cannot be understated; it reduces unnecessary anxiety for patients, avoids the time and cost of unnecessary hospital visits and alleviates pressure on busy ophthalmology clinics. I could not now imagine our clinical practice without an OCT – it is an important part of our clinical proposal and an integrated part of our patients’ eye care.
About the Author
Daniel Hardiman-McCartney is an optometrist in an independent practice in evidence based clinical decision-making. Daniel is also a visiting clinician at Anglia Ruskin University and the Eastern region Council member for the College of Optometrists.
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