| 摘要 |
18 A method for performing intrastromal photorefractive keratectomy in the cornea of an eye, using a pulsed laser beam, includes the initial step of focusing the beam to a spot size at a start point in the stroma. The start point is located in the stroma and at a predetermined distance behind the epithelium of the cornea. Beginning with the start point, a volume of stromal tissue which is substantially equal to the volume of the spot size is disrupted by the laser beam. Importantly, the photodisruption is accomplished using an irradiance for the beam which is less than ten times greater the threshold for optical breakdown of the stromal tissue. Subsequently, the beam is focused in a patterned sequence to spot sizes at other discrete points in the stroma. At each point the stromal tissue is photodisrupted. With this progressive pattern of photodisruption, each spot is placed substantially adjacent a volume of previously disrupted tissue. The resultant photodisrupted tissue creates a layer which is substantially centro-symmetrical around the optical axis and in which all points in the layer are substantially equidistant from the epithelium. A plurality of layers can be created.
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