Comparison of the potential acuity meter and the visometer in cataract patients

To compare the Guyton-Minkowski Potential Acuity Meter (PAM) and the Haag-Streit Lotmar Visometer (Visometer) in their ability to predict postoperative best corrected visual acuity (BCVA) in cataract surgery.

University of British Columbia/Vancouver General Hospital Eye Care Center, Vancouver, British Columbia, Canada.

In total, 292 eyes (223 patients) of subjects with cataracts and no known macular or optic nerve pathology were recruited over 6 months. Preoperative predictions of postoperative BCVA were compared with actual postoperative BCVA. The usefulness of these instruments as a 'diagnostic test' for predicting true surgical success (defined as postoperative BCVA of 20/40 or better) from predicted surgical success (PAM or Visometer predicted acuity 20/40 or better) was analysed.

Neither the PAM nor the Visometer predictions were statistically significant predictors of postoperative BCVA. The sensitivities of PAM and Visometer for predicting surgical success were 84.7% and 96.1%, respectively. The specificity of the PAM and Visometer for predicting surgical success was 27.3% and 9.1%, respectively. Overall, 92.7% of patients had 'successful surgery'. Given a predicted success from the PAM or Visometer the post-test probability of success was 93.5% and 93.1%, respectively. Given a predicted failure from the PAM or Visometer there was a post-test probability of surgical success of 87.5% and 84.6%, respectively.

We found no clinical benefit to support using the PAM or Visometer in the preoperative assessment of cataract patients with no known retinal or optic nerve pathology.