[Design of a quantitative keratoscope used for ocular microsurgery]

A new quantitative keratoscope used specially for ocular microsurgery to measure corneal astigmatism is reported. A combined cylinder-lens, which power can be changed by rotating lens in anti-direction equally, was designed according to the principal of the crossing cylinder lens. The axis direction is fixed when the lens is rotated. The corneal astigmatism can be measured by changing the power of the combined lens to adjust the corneal ring images. The keratoscope could be used to measure the corneal astigmatism quantitatively specially for ocular microsurgery. At the work-distance of 0.025 m, the maximum power of measured astigmatism was up to 8.50 D. The error of the measurement was less than 0.20 D. The keratoscope is a portable lens to be used easily during the ocular microsurgery. The reporting keratoscope is a simple combined cylinder-lens that can be used to measure corneal astigmatism, including the power and the axis of astigmatism, easily during ocular microsurgery.