Advanced Imaging

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Advanced Imaging Magazine

Updated: January 12th, 2011 10:01 AM CDT

Zapping Retinopathy

FPGA hardware and software make standard treatment safer, more effective
Diabetic retinopathy example
© National Instruments
Diabetic retinopathy is a form of damage to the retina and is the leading cause of visual loss among American adults aged 20 to 74. Often symptoms like blurring or patchy loss of vision appear only after significant damage has been done.
PASCAL user interface
© National Instruments
For the PASCAL user interface, an LCD touch screen display is used to select from predetermined pattern types and administer up to 25 spots at a time.
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By P.J. Tanzillo, National Instruments

According to the World Health Organization (WHO), 171 million people worldwide are afflicted with diabetes, which is about 2.8 percent of the world's population. The situation appears to be worsening, with the American Diabetes Association predicting that one in three Americans born after 2000 will develop diabetes in their lifetime.

Diabetic retinopathy is a form of damage to the retina that is a manifestation of systemic disease. This affects nearly 80 percent of all patients who have had diabetes for 10 years or more. Diabetes is the leading cause of new blindness among U.S. adults aged 20 to 74. Despite these statistics, research indicates that at least 90 percent of new cases could be managed with proper and vigilant treatment.

Since the 1970s, ophthalmologists have used a standard treatment called laser photocoagulation to treat diabetic retinopathy, and the method has changed little since its inception. Laser photocoagulation involves the controlled destruction of the peripheral retina using targeted laser pulses. While this type of treatment has proven effective at reducing the chances of vision loss by as much as 50 percent, ophthalmologists can deliver only one burn at a time, and treatment can require as many as 2,000 burns. A full course of treatment typically requires two to four sessions, each lasting 12 to 15 minutes. The procedure is so painful that some patients do not return for follow-up visits, even though they are fully aware that the untreated condition can eventually lead to blindness.

OptiMedica Corp., (Santa Clara, Calif.) decided to help ophthalmologists treat retinal disease with their PASCAL Photocoagulator. Based on their experience in the ophthalmic laser industry at a major laser systems supplier, OptiMedica founders recognized the need for improved safety, precision, comfort, and speed of photocoagulation procedures. The PASCAL method of photocoagulation was initially developed at Stanford University, and it uses an integrated semi-automatic pattern scan laser to treat the condition using a single shot or predetermined pattern array.

For pattern arrays, a control system applies an electrical current proportional to the desired location of a beam to a galvanometer, which is an analog electromechanical transducer that produces a rotary deflection in response to electric current. The galvanometer can be used as a high-speed, ultra-sensitive, limited rotation motor. When attached to a small mirror, it can be used to precisely control the position of a laser. The control system produces a current, and when the current is changed, the scanner quickly steers the laser beam to the desired location. Closed-loop control circuits ensure that the desired position is precisely reached.

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