Potential Acuity Meter versus Scanning Laser Ophthalmoscope to predict visual acuity in cataract patients

Purpose: To compare the relative abilities of the Potential Acuity Meter (PAM) and the Scanning Laser Ophthalmoscope (SLO) to predict the, postoperative: visual acuity in patients with mild to dense cataract. Setting: Gimbel Eye Centre, Calgary, Alberta, Canada. Methods: in this single-masked prospective study of 31 consecutive eyes,with mild to dense cataract and a best corrected visual acuity (BCVA) of 20/40 or less, patients had predictive visual acuity (PVA) testing using the PAM and SLO. Preoperative and postoperative BCVA was recorded using Snellen charts, Differences between PVA and postoperative BCVA results were assessed by a two-tailed t-test and correlation analysis. Results: The SLO was correct within two lines of outcome in 30 of 31 eyes and, the PAM, in 19 of 31 eyes. A two-tailed dependent t-test showed a significant difference between predicted and final visual acuity for the PAM (P = .0001) and a nonsignificant difference for the predicted and final visual acuity for the SLO. A correlation analysis showed a mild correlation for the PAM (r = .49) and a good correlation for the SLO (r =.81). For a prediction of better or worse than 20/40, the SLO showed a sensitivity of 0.964 and specificity of 1.0 and the PAM of 0.67 and 1.0, respectively. Conclusion: The SLO was more accurate than the PAM in predicting visual acuity after cataract surgery. The relative cost of the SLO is potentially restrictive to its widespread clinical application. However, the cost/benefit in terms of patient satisfaction with predictable surgical results should be considered.