| 摘要 |
Optical power of a living subject's eye is measured and compared with a calibration value that corresponds to a reference blood-glucose level. The reference level is determined conventionally, as by blood analysis. Optical power of the eye increases with blood-glucose level. The comparison can include interpolation or extrapolation from two or more calibration points. Optical power is measured by projecting an image through an external optical system and through the cornea and lens of the subject's eye onto the subject's retina-while monitoring sharpness of focus at the retina, and systematically modifying the conditions of projection of the image. The relation between sharpness and projection conditions provides the measure of glucose concentration. For example, for presbyopic subjects, (1) the optical power of the external system may be varied, and the value of power that produces sharpest retinal focus may be used as the measure, or (2) the power may be held constant while the object distance is varied, and the distance that yields sharpest focus may be the measure. As another example, in nonpresbyopes the shortest or longest distance at which a subject can sharply focus may serve as the measure; this may be found by fixing the optical power of the external system and varying the object distance.
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