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I. W. Porter, E. A. Colby, K. L. Cohen; Preoperative Keratometry and Postoperative Vertical Coma Associated With Pseudophakic Pseudoaccommodation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5736.
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To determine if preoperative or postoperative characteristics are predictive of pseudoaccommodation.
44 subjects over age 60 with cataracts and best corrected distance visual acuity (BCDVA) better than 20/80 were enrolled prior to bimanual microincision phacoemulsification with monofocal pcIOL placement. Preoperative BCDVA, distance corrected near visual acuity, and video keratoscopy including simulated keratometry and vertical coma were recorded. All patients underwent uncomplicated cataract surgery. One month postoperatively, uncorrected distance and near visual acuity (UCDVA, UCNVA) were recorded and all preoperative measurements were repeated. Patients with UCDVA 20/40 or better and UCNVA 20/40 or better were classified as having pseudophakic pseudoaccommodation (PP). Six outcome measures were assessed: cylinder, orientation of astigmatism, spherical equivalent, the difference between steep and flat meridians by simK (simK difference), orientation of steep meridian by simK, and vertical coma. Kruskal-Wallis tests were performed comparing the outcome measures between patients with and without PP. Hypothesized values for each of the outcome measures that would be beneficial for PP were proposed and Fisher’s exact tests were performed.
Pseudophakic pseudoaccommodation was present in 10 patients. The preoperative simK difference was significantly lower in the PP group (p=0.01). Other measures demonstrated no significant difference on Kruskal-Wallis tests. Patients with PP were hypothesized to have more negative vertical coma (<=-0.20 microns) than patients without PP. Fisher’s exact test confirmed this association (p=0.043). No other hypotheses were statistically significant by Fisher’s exact tests.
23% of patients demonstrated pseudophakic pseudoaccommodation, a greater percentage than has been reported in previous studies. Preoperatively, the patients with PP had less difference between the two simK powers (0.51 vs. 0.93 diopters), indicating that greater corneal astigmatism may be detrimental to PP. It is known that astigmatism increases depth of focus, but larger amounts may degrade the quality of vision excessively. Our results support previous studies linking PP with more negative vertical coma. This may provide some degree of corneal multifocality, increasing depth of focus.
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