Off-the-shelf hardware and software helps keep eye on the prize

Over the years, as we built a company and developed a unique medical device, the use of off-the-shelf hardware and software allowed us to concentrate on innovation and reduce both business and technical risks.

Sep 1st, 2007
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Mike Wiltberger

Over the years, as we built a company and developed a unique medical device, the use of off-the-shelf hardware and software allowed us to concentrate on innovation and reduce both business and technical risks. We relied on National Instruments’ expertise, product volume, and economy of scale to give us higher quality and greater system reliability than a less cost-effective custom solution could have achieved in our relatively small market. This strategy allowed us to spend our time and energy (and venture capital) identifying and addressing clinical needs in ophthalmology.

Our challenge was to create a novel device in a market in which methods of retinal laser photocoagulation had changed little in 35 years. Laser photocoagulation involves the controlled destruction of the retina using targeted laser pulses, denaturing a portion of the unhealthy tissue so that the remainder can live. With traditional systems, ophthalmologists can deliver only a single laser pulse at a time. While this type of treatment is extremely effective at reducing the chances of vision loss by as much as 50%, it can be very tedious for both the patient and the physician. A full course of treatment typically requires two to four sessions, each lasting 12 to 15 minutes, requiring a total of approximately 2000 laser pulses.

To answer the challenge, OptiMedica created the Pascal photocoagulator, an integrated pattern-scanning laser system designed to treat retinal diseases using a single spot or a predetermined pattern array of up to 56 spots (see figure).


The Pascal photocoagulator is a pattern-scanning laser system designed to treat retinal diseases using short 532 nm laser pulses in a single spot or a predetermined pattern array of up to 56 spots. The laser system leaves an array pattern on the retina after pan-retinal photocoagulation treatment (inset). (Photo of Pascal system courtesy of OptiMedica; photo of retinal image courtesy of Steven Schwartz, University of California, Los Angeles.)
Click here to enlarge image

The Pascal technology platform is based upon the use of a proprietary, semiautomated, pattern-generation method that uses short 532 nm laser pulses. These laser pulses are delivered in a rapid predetermined sequence, resulting in improved precision, safety, patient comfort, and a significant reduction in treatment time compared to single-spot photocoagulation. Pre-clinical animal studies, as well as initial pilot studies in humans, indicate that in addition to reducing treatment duration for typical patients with proliferative diabetic retinopathy, the number of individual treatment sessions can also be reduced. These are tangible benefits.

FPGA hardware

From breadboard to production, the Pascal design project used National Instrument’s field-programmable-gate-array (FPGA) hardware developed within its LabVIEW programming environment as its main controller. We chose the National Instruments PCI 7833R FPGA, a reconfigurable input/output (I/O) device that has 96 digital lines, eight dedicated analog-to-digital converters, and eight dedicated digital-to-analog converters, making it possible to sample all channels simultaneously.

For those not familiar with FPGAs, imagine a large circuit board filled with parts, like clocks, counters, logical and mathematical functions, and digital I/O. Shrink that board down to the size of a postage stamp, and add digital-to-analog and analog-to-digital conversions to it. The result is a control and data-acquisition system that can be reprogrammed as needed, as we required in the Pascal system. The parts are effectively wired together using software.

To program the FPGA, use of low-level hardware-description languages such as VHDL or Verilog is not necessary. The LabVIEW FPGA module allows the designer to directly synthesize code from LabVIEW to the FPGA hardware, all from within its graphic-based programming environment. This integrated approach provides fast, robust, deterministic, and easily reconfigurable control architecture. A few of the advantages to this approach include a shorter time to market, the ability to upgrade features in the field, and lower nonrecurring engineering costs-all critical elements for an early-stage company.

The programmed FPGA comprises independent circuitry that allows for simultaneous measurement and control of all aspects of the Pascal system. Unlike embedded controllers that use procedural imperative programming, the inherent parallelism of the FPGA and its ability to adjust numeric precision and range allows for overall enhanced computational efficiency.

Similarly, designers can use LabVIEW to produce elegant and dynamic graphical user interfaces (GUIs). The stock LabVIEW controls can be completely customized to yield a professional-looking user interface. The Pascal system uses a liquid-crystal touch-screen display that allows the user to select treatment parameters from a single panel. The GUI is operated on a standard Windows-based computer, and communicates to the FPGA though the peripheral-component-interconnect (PCI) bus. Because safety is a primary concern, Pascal does not rely on Windows for any time-critical functions. Instead, the personal computer is only used as a human and network interface.

The inherent speed and flexibility of this approach has allowed OptiMedica to concentrate on providing innovative and adaptable solutions for clinical needs while minimizing our dependence upon traditional R&D roles and structures, as well as improving our time to market. Furthermore, this control scheme can be leveraged to form the basis of future applications and products.

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MIKE WILTBERGER is cofounder and principal engineer at OptiMedica, 3130 Coronado Dr., Santa Clara, CA 95054; e-mail: michael@optimedica.com; www.optimedica.com.

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