Contact lens measures drug concentration in the anterior eye

Dec. 1, 2005
Although the idea had been proposed by previous researchers, scientists at the University of Strathclyde and Glasgow University (both in Glasgow, Scotland) are the first to actually fabricate and test a fiberoptic-coupled corneal contact lens that provides direct, minimally invasive, real-time measurements of drug concentration in the anterior portion of a human eye.

Although the idea had been proposed by previous researchers, scientists at the University of Strathclyde and Glasgow University (both in Glasgow, Scotland) are the first to actually fabricate and test a fiberoptic-coupled corneal contact lens that provides direct, minimally invasive, real-time measurements of drug concentration in the anterior portion of a human eye.1

To develop any ophthalmic medication, it is necessary to measure the ocular concentration of the drug within the eye. Previously, the only working method was to use animal eyes at various time intervals after the topical application of the drug-a wasteful, laborious, and inaccurate process.

The goal of the scientists is to turn the anterior chamber of the eye into a spectrophotometer cuvette. A specially designed contact lens is attached to optical fibers that guide light from a laser or a xenon arc lamp into the eye of the human test subject and carries it back to a spectrograph for analysis (see figure, top). The contact lens, measuring 25 × 8 × 6 mm and machined from fused silica, is mirrored on two opposite faces to send the beam through a thin tear layer, through the cornea, and across the anterior chamber of the eye, following a path approximately 8.6 mm in length for the human subjects tested.

Because the eye transmits light between 300 and 1400 nm, and because many pharmaceutical drugs of interest for the eye have broad, easily resolvable peaks in the UV and visible (VIS) regions, the UV/VIS spectral region was chosen for analysis. The xenon arc lamp was used for absorption spectroscopy, while an argon-ion laser at 488 nm was used for fluorescence measurements. For all measurements, a reference spectral scan was obtained by filling the concave lens surface of an upturned sensor head with deionized and distilled water. This reference scan was then subtracted from signal scans taken in recorded intervals after application of fluorescein or brimonidine, two ocular solutions used in the experiment.

“The real-time measurement capability is able to easily detect the presence and monitor the time course of a topically applied drug, such as brimonidine, in the human eye,” explains Joe Miller, now at the Lions Eye Institute in Western Australia. The scientists also observed that the human-eye uptake of topical fluorescein was poor as confirmed by previous research.

“Our work is yet another example of the rapid strides being made in the field of biomedical photonics, and its application in drug discovery,” adds Deepak Uttamchandani, a professor at the University of Strathclyde.

REFERENCE

1. J. Miller et al., British J. Ophthalmology 89,1147 (September 2005).

About the Author

Gail Overton | Senior Editor (2004-2020)

Gail has more than 30 years of engineering, marketing, product management, and editorial experience in the photonics and optical communications industry. Before joining the staff at Laser Focus World in 2004, she held many product management and product marketing roles in the fiber-optics industry, most notably at Hughes (El Segundo, CA), GTE Labs (Waltham, MA), Corning (Corning, NY), Photon Kinetics (Beaverton, OR), and Newport Corporation (Irvine, CA). During her marketing career, Gail published articles in WDM Solutions and Sensors magazine and traveled internationally to conduct product and sales training. Gail received her BS degree in physics, with an emphasis in optics, from San Diego State University in San Diego, CA in May 1986.

Sponsored Recommendations

Request a quote: Micro 3D Printed Part or microArch micro-precision 3D printers

April 11, 2024
See the results for yourself! We'll print a benchmark part so that you can assess our quality. Just send us your file and we'll get to work.

Request a Micro 3D Printed Benchmark Part: Send us your file.

April 11, 2024
See the results for yourself! We'll print a benchmark part so that you can assess our quality. Just send us your file and we'll get to work.

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!