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HP Apple, EE Hartmann; Measurement of Ocular Vergence and Accommodation for Vision Screening: A New Wavefront Technology . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1495.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The purpose is to demonstrate the feasibility of a new combined wavefront sensing and eye-tracking technology (OVAS) capable of dynamically and unobtrusively measuring binocular line of sight and refraction. The long-term goal is to develop improved means for vision screening of preschool children. Methods: As a first step, a mathematical simulation has been written for the new wavefront sensor, which uses shadow patterns. Inputs are sphere, cylinder, and axis in diopters and degrees. The shadow pattern is simulated and is then inverse solved for sphere, cylinder, and axis without knowledge of the inputs. As a second step, a working prototype of the OVAS technology has been tested with engineering model eyes for eye-tracking, refraction, field of view, and depth of field. Results: The mathematical simulation has been validated by comparing the simulated patterns with patterns generated from the model eyes in the working prototype. These comparisons yielded excellent agreement. An error analysis of the simulation shows a maximum error of 0.05 D and 0.5º between the inputs and outputs of the simulation over a wide range of input values (+/- 15 D and 0-360º.) In the engineering tests, the accuracy of refraction was better than +/- 0.25 D in sphere and cylinder with a range of +/- 3 D. Accuracy of eye-tracking was better than +/- 0.1º. Field of view and depth of field were both +/- 5 mm. Preliminary pilot work with children has shown this to be sufficient. Conclusion: We have demonstrated the technical feasibility of the OVAS for vision screening. Future work on adults and young children is warranted.
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