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Nickolaos Savidis, Gholam A. Peyman, Nasser Peyghambarian, Jim Schwiegerling; An Adaptive Binocular Phoropter Developed using Fluid Lenses and Shack-Hartmann Sensors. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4068.
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© ARVO (1962-2015); The Authors (2016-present)
Develop an adaptive binocular see-through phoropter that automatically measures spherical and cylindrical error and nulls this error with a compound sphero-cylindrical fluidic lens. The designed system corrects for astigmatism and spherical refractive error.
Previously, a monocular automated phoropter had been designed and fabricated. The system is comprised of three modules: a fluidic lens, a relay telescope and a Shack-Hartmann sensor. The fluidic lens is a stack of three adjustable lenses composed of a spherical lens and two astigmatic lenses oriented 45 degrees to one another. Any sphere, cylinder and axis combination can be achieved by adjusting the fluid volume within the fluidic lenses. Following the fluidic lenses, are a relay telescope and a beamsplitter. The beamsplitter directs infrared light towards the Shack-Hartmann wavefront sensor, while passing visible light, allowing for the subject to view external targets. The system works as follows. (1) Infrared light is shone into the eye and scatters from the retina. (2) The scattered light exits the eye as an emerging wavefront that is relayed through the fluidic lens to the Shack-Hartmann sensor. The sensor reconstructs the wavefront and extracts the sphero-cylindrical refractive error. This prescription is then applied to adjust the volume of the fluidic lenses to null out the refractive error. Feedback of the wavefront from the eye/fluidic lens combination is then used to monitor the fluid volume and minimize the net refractive error. The first binocular prototype adjusts for the patient’s interocular separation while concurrently measuring refractive error for both eyes and fits in approximately a 1 ft by 1 ft area.
Our first prototype shows the capability of measuring refractive error from -10 to 10 D. The Shack Hartmann sensor is capable of measuring spherical refractive error from -25 D to 40 D. Even in cases of extreme myopia or hyperopia, a limited number of spots are needed to drive the fluidic lens power, forcing the Shack-Hartmann pattern into a more usable range. The range of the prototype may be increased beyond the Shack-Hartmann sensor limits through fluid control experimentation.
Fluidic lenses coupled with a Shack-Hartmann sensor applied in an eye examination have the potential of creating an automated means of measuring and nulling refractive error. The goal is to produce a reliable binocular device that allows for quick and inexpensive objective measurement of a subject’s refractive error.
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