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Case Study 2:
Detecting Diseases of the Eye Using Multi-Spectral Imaging

Multi-Spectral Imaging Digital Ophthalmoscope from the Annidis Corporation Captures Data through the Retinal and Subretinal Layers

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When presented with a design task, optical engineers start with the system requirements, perform initial calculations, and then design an optical set-up to meet the project’s goals. One step is often left out: evaluating the possibility of using stock optics prior to creating custom designs. That’s a mistake. Designers who use stock optics where possible are often able to reduce risk, decrease costs, and improve the time to market for their products.

Many times, product engineers are able to leverage stock optics for their proof-of-concept and prototype systems to rapidly verify the capabilities of their optical instruments. But designers need not limit the use of stock optics to those preliminary design set-ups. Off-the-shelf or stock optical components can be incorporated at the volume production stage as well. Systems built with stock optics can have powerful custom capabilities. An example is the Retinal Health Assessment (RHA™) Instrument from Annidis Corporation, built using stock optics wherever possible.

Non-invasive Choroidal Imaging with Multi-Spectral Imaging at 940nm. Deep retinal imaging is made possible by the use of longer wavelengths which penetrate deeper into the structures of the eye. Photo courtesy of Annidis Corp.
Figure 1: Non-invasive Choroidal Imaging with Multi-Spectral Imaging at 940nm. Deep retinal imaging is made possible by the use of longer wavelengths which penetrate deeper into the structures of the eye. Photo courtesy of Annidis Corp.

Translating Research to the Clinic

Researchers at the University of Ottawa Eye Institute, the Ottawa Health Research Institute, and the University of Montreal, School of Optometry had performed some intriguing research with significant clinical implications. They found that various diseases and conditions of the human eye showed specific signatures at given spectral bands. That is, although traditional retinal imaging methods may not indicate problems in the eye, images taken in particular narrow wavelength regions can reveal signs of disease or degeneration. But the one-of-a-kind type of apparatus, which is acceptable in a research setting, would not work in the medical clinic. The Annidis Corporation (Ottawa, Ontario, Canada) took on the task of converting that research into a viable clinical tool.

The retina is a complex multi-layer structure at the back of the human eye that contains photoreceptor cells that detect light and send electrical signals to the brain. In addition, the retina rests on the choroid, a thin, highly vascularized membrane; and the choroid in turn is built on the sclera, the tissue that surrounds the eyeball.

Ophthalmologists commonly use an instrument called a fundus camera to examine the eye for signs of disease or degeneration. The fundus camera takes images of the back of the eye, but there can be some limitations requiring additional screening tests. If you think of the layers of the eye as something like a plastic wrap covering a few sheets of construction paper on top of a sheet of aluminum foil, then the fundus camera would take a picture of the plastic wrap and maybe a bit of the first layer of construction paper. If there’s a wrinkle in the aluminum foil, it will be invisible to the camera until the wrinkle becomes so large it affects the top layer. In the eye, that means problems beginning in the deeper layers can be more difficult to detect.

Multi-spectral imaging (MSI) of the human eye isolates each of those layers. If there’s a “wrinkle” in the bottom layer, MSI can see it far before the effects reach the top layer. The Annidis instrument is a turnkey device designed to capture images in up to twelve different wavelength ranges, capturing anatomical features through the retina and choroid. The RHA illuminates the eye with light emitting diode (LED) sources from 520 to 940nm. Spatial and spectral filters further condition the beam to highlight the anatomical features of interest.  

The Path to a Clinical Instrument

Annidis was founded in 2007 with the mission to “improve healthcare through eye-centric products and services that help eye care professionals screen, detect, diagnose, treat and manage ocular diseases.” They faced the typical questions for medical device startup companies:

  • Can research results be translated into clinically useful measurements?
  • Can complicated, unique lab instrumentation be converted into a physically and operationally robust instrument?
  • Will physicians find clinical utility in the approach?
  • Can the instrument be produced at a price point customers will buy — and have a path to profitability?

Those questions can only be answered by producing a device and getting it in clinical settings. Patients, clinicians, and investors would all like the answer to those questions as soon as possible, which means getting a product on the market as soon as possible. That’s when Annidis came to Edmund Optics (EO).  

Selecting Quality Components

When developing their laboratory prototypes, Annidis took advantage of Edmund Optics’ position as the world’s largest inventory of optical components. They placed multiple orders of imaging lenses and other components as they fine-tuned the design and performance of their instrument – a common practice when creating new or improved optical set-ups. Annidis’ next step was a little out of the ordinary.

Annidis continued to design their production model around stock optics, wherever possible, and use custom designs when stock optics were not available to meet the exact system requirements. This reduced risk, both for Annidis and EO, as any challenges in the fabrication process had been resolved. By utilizing multiple stock components, overall lead time was also reduced. For example, customers often customize a lens by selecting a non-standard glass, which can immediately add 4 to 6 weeks to the lead time. If the customer selects an exotic material, the fabrication time might be longer as well since each material’s unique optical properties may require additional manufacturing steps. The established and highly repeatable processes for stock optics manufacturing also mean reduced component costs. So, by designing with numerous stock optics, Annidis reduced risk, lowered the lead time, and kept costs down. All those steps allowed them to rapidly get their first product to market.  

Description Necessary Manufacturing Steps Cost Lead Time
Material Sourcing Grinding Polishing Edging Coating
Stock Optic           $ Immediate
Modified Stock: Custom Coating           $$  
Modified Stock: Dimension Modification         ( ) $$($)   ( )
Modified Stock: Surface Improvement           $$$$      
Modified Stock: Surface Modification           $$$$$        
Custom Optic           $$$$$$          
Figure 2: Whether selecting optical components for prototypes or volume production, it's important to understand the balance between cost and leat time.
  Lead time
$ Cost
() Additional Lead Time Depending on Modifications

Performance Matters

Lower costs and simplicity in the supply chain don’t mean much if product performance isn’t there. If you’re producing products that are not valuable to the customers, the rate and cost-effectiveness in which it was built does not matter. So how is Annidis’ RHA performing in the clinical setting?

The RHA’s ability to image multiple planes within the retina and choroid has been cited as a valuable tool for ophthalmologists. Published papers have stated, “A direct, noninvasive, unobstructed view of melanin disruption associated with AMD [age-related macular degeneration] can be observed using MSI”[1]; “Multispectral imaging may detect the choroidal lesions of Type 1 neurofibromatosis that are not easily seen with clinical examination or with other imaging modalities”[2]; and “Multispectral imaging can reveal highly defined hyperreflective polyp-like structures – indicating preliminarily the advantages of noninvasiveness, simplicity, and effectiveness of MSI in diagnosing PCV [Polypoidal Choroidal Vasculopathy].”[3]

When stock optics do not meet your needs, designing with semi-custom or custom components are excellent options. In fact, EO is supporting Annidis in their next design iteration, where the next version of the RHA may include custom filters and aspheres to allow the device to be packaged more compactly. By using stock optics, Annidis was able to produce a complex spectral imager that provides unique clinical value in the diagnosis and detection of retinal pathologies. By taking the same path, design engineers may reduce their development risk, decrease their time-to-market, and stay on budget when producing new optical products.  

Figure 3: By employing the Annidis Corp. RHA instrument, users are able to detect early RPE changes and see the choroid like never before. Photo courtesy of Annidis Corp.
Figure 4: Annidis Corp.’s RHA instrument is a multi-spectral imaging digital ophthalmoscope with a patented optical system that captures high-resolution image data from the retinal and subretinal layers. Photo courtesy of Annidis Corp.
Figure 5: Aspheres are an ideal choice when looking to reduce overall system weight or reduce element count in a system.
The Future Depends on Optics

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