In The Journal Of
Cataract & Refractive Surgery February 2010
Custom selection of aspheric intraocular lenses after wavefront-guided myopic photorefractive keratectomy
Li Wang, M.D., Ph.D., John D. Pitcher, M.D., Mitchell P. Weikert, M.D., Douglas D. Koch, M.D.
Looking to maximize optimize optical quality with an IOL after previous wavefront-guided myopic PRK, investigators here wanted to find the optimal amount of spherical aberration in the lens.In this study of 102 eyes, they simulated aspheric IOL implantation varying the amount of residual ocular spherical aberration from -.5 to +.5 microns.They then looked to determine the amount of spherical aberration which produced the highest image quality.With a six-millimeter pupil and 0 D of defocus, the mean optimal IOL spherical aberration ranged from -.49 to -.42 microns, with -.5 D of defocus this ranged from -.22 to -.18 microns, and with +.5 D defocus ranged from -.75 to -.64 microns.With a 4-mm pupil and 0 D of defocus, the mean optical spherical aberration was from -.34 to -.2 microns, with -.5 D of defocus this optimum spherical aberration levels were between + .08 and .55 microns, and for +.5 D these were between -1.12 to -.83 microns.Investigators here also determined that 4th-order spherical aberration followed by 6th-order were most predictive of optimal IOL spherical aberration.
Anterior capsulotomy with a pulsed electron avalanche knife
Daniel Palanker, Ph.D., Hiroyuki Nomoto, M.D., Ph.D., Philip Huie, M.A, Alexander Vankov, Ph.D., David F. Chang, M.D.
In this study, investigators set out to see whether it was advantageous to create a continuous curvilinear capsulotomy using a pulsed-electron avalanche knife instead of with a mechanical approach.Using 50 bovine and 10 rabbit eyes they determined that optimum voltage level was 410 volts with a burst duration of 20 µS (microseconds).Cutting velocity varied up to 2 mm per second using a burst repetition rate from 20 to 200 Hz.When investigators examined the tissue they found that there were no radial nicks or tears with the pulsed electron avalanche knife.They concluded that, particularly for cases involving factors such as weak zonules or poor visibility, it could be advantageous to use a pulsed-electron avalanche knife which may improve sizing and centration, as well as precision and reproducibility of a continuous curvilinear capsulotomy.
Refractive surgical practices in persons with human immunodeficiency virus positivity or acquired immune deficiency syndrome
Ahmad A. Aref, M.D., Ingrid U. Scott, M.D. MPH, Erica L. Zerfoss, Allen R. Kunselman, MA
Investigators here wanted to feel out what refractive practices were currently doing with regard to performing elective surgery on those who had either tested positive for HIV or, who had Acquired Immune Deficiency Syndrome (AIDS).Of the 285 practitioners who responded to an anonymous, web-based survey emailed to members of the International Society of Refractive Surgery, 50.2% said that they were willing to consider those with HIV positive status as candidates, while just 35% said that they would consider performing elective surgery on those with AIDS.Of those who would perform the surgery, 72.7% claimed that they take extra precautions in such cases, such as wearing double layers of gloves, and evacuating the laser plume immediately after surgery.They also said that they would limit any procedures to one eye and would make sure that the surgery was the last on the schedule for the day in such patients.