| 摘要 |
An ultrasonic eye dimension measuring device (B) used preparatory to cataract surgery is fitted with pinhole optics (20, 24) and a fixation target (30). The patient has the cornea anesthetized, and is thereafter told to fixate on the spot of light leaking from the pinhole optics (20, 24) as the examiner brings the instrument interrogating surface (16) into contact with the cornea. As the source approaches, it increases in size, and the fixation target becomes visible. Upon touching of the instrument to the eye, ultrasound measurement of the eye dimension by transducer (T) occurs. By aligning the interrogating ultrasound axis (I) to the line of sight of the fixation target, measuremnt of the visual axis length occurs, minimizing off-axis measurement. In a preferred embodiment, the conjugate image of a pinhole light source is relayed by optics through the lens of the eye. Consequently, the fixation target is not diffraction limited. |
