Fluidic lens sees clearly

05 Mar 2009

Eye examinations could become faster and much less intrusive thanks to the first fluidic lenses that correct vision.

Seeing clearly with a liquid lens

Opticians could one day use fluidic lenses to determine ophthalmic prescriptions simply and quickly say researchers in the US. A team from the University of Arizona has developed the first fully adjustable fluidic lenses that can correct for near- or far-sightedness as well as astigmatisms (Optics Letters 34 515).

"An instrument based on fluidic lenses could be made much smaller than the conventional tool used by opticians today and would be less intrusive to the patient," David Mathine, a researcher at the University of Arizona's College of Optical Sciences, told optics.org. "In addition, examination time could be reduced since the focus of the fluidic lens could be controlled by computer."

Routine eye examinations usually involve the use of a bulky spectacle frame into which different lens combinations are mechanically switched until the patient can see a standard eye chart clearly. By changing to fluidic lenses, an optician could continuously vary the wavefront of light entering the patient's eye without having to manually change the lenses.

The lenses developed by the Arizona group are composed of an elastic membrane filled with fluid. By altering the volume of the fluid in the lens using a syringe attached to the fluidic chamber, the membrane can be stretched in either a concave or a convex manner.

"The concept is simple, the lens is filled with a fluid, which causes an elastic membrane to change shape, very similar to filling a water balloon," explained Mathine. "The curved surface of the elastic membrane then works as a lens to change the wavefront of the light (i.e. focus the light)."

Mathine and colleagues have developed two lenses to tackle near- or far-sightedness and astigmatism respectively. The first lens uses a circular restraint of the membrane to provide changes in the spherical power of the lens in the range of ± 20D. The second lens uses a rectangular restraint to provide a varying amount of cylindrical power, which corrects for astigmatism.

While the Arizona team has currently focused on applications during the eye examination itself, it believes that there should be other functions associated with vision enhancement.

"Wearing fluidic lenses as spectacles or contact lenses is a definite possibility, we just need to overcome some practical issues," concluded Mathine. "Currently, we are working on a more thorough optical characterization of the lenses and refining the construction process to improve optical quality."