The latest incarnation of the Retina Scan (RS) OCT from Nidek (distributed in the UK by Birmingham Optical) is likely to turn a few heads at the forthcoming Optrafair event in April. I was fortunate enough to have a brief look at a prototype instrument at last year’s SCLOSS conference (Optician 30.01.15) and liked what I saw. When I heard an old colleague of mine had just had delivery of the full version, I invited myself to Dr Sandip Doshi’s practice to try out the machine (Figure 1).
The Duo boasts a number of new features, most prominently as suggested by the name, a near seamless combination of fundus camera (full colour for the first time, and also with autofluorescence capability) and spectral domain OCT. Immediately, you are struck by its compact design and integrated touch screen control pad which, even hooked up to the adjacent computer, offers a reasonable footprint for most busy practice spaces.
Clinical advantage
I am sure most readers are familiar by now with the benefits of having an OCT in primary care practice. It allows accurate assessment of retinal structure, along with options for anterior anatomy assessment, and so helps in the detection and monitoring of a broad range of eye diseases. High resolution scanning allows detailed measurement of retinal layer thickness, visualisation and analysis of individual lesions or anatomical variations, and important functions such as disc assessment, retinal nerve fibre and ganglion cell layer assessment, measurement of anterior chamber angle, corneal pachymetry mapping to name but a few. The accuracy of the instruments means that intra-machine repeatability is very high and serial scans are very sensitive to changes in structure that may signify the very earliest signs of diseases such as glaucoma. I have, for example, using OCT, found a number of suspect (and subsequently confirmed) glaucoma patients who had no detectable field defects even on full threshold assessment. Asymmetry of tissues and changes over time raised enough doubt to trigger a report to secondary care and intervention at an earlier stage of the disease helped limit the damage of glaucoma.
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The RS Duo takes all of these functions in its stride (see later article for a gallery selected from our session). The RS Duo also incorporates a 12-megapixel 45-degree non-mydriatic camera capable of excellent quality images of the retina (Figure 2) or, indeed anterior eye if appropriately set. I also like the inclusion of autofluorescence. As a weakly pigmented Celt now hitting a half century and with a history of some exposure to tobacco products, I am interested in the early detection of any evidence of maculopathy. Autofluorescence imaging shows any atrophic or damaged tissues as black against the normal grey coloured retina. However, lipofuscin, as might build up in early maculopathy, often is seen concentrated around areas of atrophy as brightly shining areas. The technique offers a useful clue as to who might benefit by discussion of risk factor avoidance and further, fine-tuned, monitoring (Figure 3).
Ease of use
The RS Duo really shows itself as a major new player, however, when you come to use it. Once programmed to undertake any specific sequence of OCT data capture or imaging, the machine is, in essence, a one-touch operation system. It incorporates an auto setting (which can, obviously, be over-ridden when the view is difficult, such as with pupils of 2mm or with a less than stable patient) which, once aligned even approximately, positions and focuses to provide the optimal capture. When OCT data is taken, a fairly typical colour scale signals a scale from 1 (in red representing poor detail) through to 10 (green, optimal capture). During my brief clinic session, I did not once manage a scoring of less than 7, even when not really trying!
The essence of the one-touch approach is that capture can be delegated to any trained member of staff in a busy clinic, perhaps in pre-screening, and thus free up more time to analyse the data and explain findings to a patient within the consulting room. Data transfer is simple with this system, either through hardware means of memory transfer or via Wi-Fi linkage (exploiting the Navis-Ex software on the adjoined network linked computer).
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Setting a combo
Dr Doshi had already pre-configured his machine to run through a pre-set sequence of capture that best suits his clinic. The ‘combo’ setting enables you to select whichever OCT scans you wish, applicable perhaps for macular disease or glaucoma, along with a fundus image (Figure 4). You are still able to individually set up for each patient from the list of scans and imaging options (colour or autofluorescence or anterior, for example), but the combo setting might be best if delegating screening. OCT options are various, such as the high resolution single line scan (Figure 5), a macular cross (Figure 6), a macular map, which would allow a volume scan of the central retina and enable a 3D visualisation, always guaranteed to wow the patient (Figure 7), and so on.
Our combo undertook four tasks; single line, macular cross, macular map and disc scan. Even with fundus image added, the process per eye is a minute or so at most. After each capture you save or repeat on the touch screen to ensure the end result is up to requirements for any one patient. Once saved at the end, analysis of the data can begin. This includes the usual disc analysis, represented as a two-peak retinal nerve fibre layer map, or segmented disc arrangements, along with thickness maps that can all be layered to individual segments (such as ganglion cell layer) and coded to reveal comparison with a normative database. Deviation maps show change from the norm and may also be used for serial monitoring. A follow-up article showing some of these analyses from our session will appear in Optician in the next few weeks.
Anterior options
As somebody with a very low van Herick grading yet a perfectly patent angle when viewed with OCT, I have always been impressed with anterior OCT functions. The Duo has an anterior adaptor lens and head rest allowing excellent quality pachymetry (Figure 8) and angle assessment (Figure 9).
All in all, I would suggest the RS Duo is an excellent new addition to the OCT market and one which anybody should be able to use to great effect with the minimum of technical ability. Of course what you do with this high quality data is down to your professional abilities.
Further details from www.birminghamoptical.co.uk
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