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Prevention is the best way to treat off-axis ablations, with a scheduled timeout at a specific point in the procedure being one of the surest methods of ensuring that the axis has been entered correctly, according to Robert K. Maloney, MD, director of the Maloney Vision Institute, Los Angeles.
During his procedures, Dr. Maloney insists on a timeout before the laser treatment to confirm the laser settings orally with the technician. There should be confirmation that the refractive axis is the same as the axis on the surgical plan, and confirmation that the axis on the surgical plan is the same as that entered into the laser.
Dr. Maloney described a case in which a 23-year-old male was scheduled to undergo conventional LASIK for simple myopic astigmatism. During his surgery, the laser was programmed at axis 88 instead of 08 for treatment of the right eye. Two weeks postoperatively, the patient's astigmatism had doubled, from 4.6 to 9.5 D, although his best-corrected visual acuity was 20/20. The patient underwent a conventional enhancement and subsequent wavefront analysis and treatment because of continuing dissatisfaction with the vision in his right eye.
"Remarkably, 3 months later the patient thought his right eye was better than his left eye," Dr. Maloney said. BCVA in the right eye was 20/15, better than in the contralateral eye, and RMS error was 0.66, compared with 0.74 in the left eye.
Several lessons can be learned from this case report.
"The first is that the initial cylinder increase does partly regress, so it's worth waiting for re-treatment," Dr. Maloney said. Some regression of the cylinder typically occurs between 2 weeks and 3 months postoperatively.
Also, re-treatment of off-axis ablations should be a two-stage process.
"After the erroneous ablation, use conventional treatment to reduce the astigmatism to a manageable level, then use the wavefront treatment to eliminate the aberrations and residual refractive error," Dr. Maloney said.