Comparison of Keratometry Measurements With Scheimpflug, Placido Disc, and Manual Keratometry in Patients With Normal and Suspicious Topography
Narrative Responses:
Purpose
To compare keratometry measurements obtained with Scheimpflug, Placido Disc, and Manual Keratometry in patients with normal and suspicious topographies in order to determine if technologies are equally efficacious in these groups.
Methods
keratometry measurements were obtained with Scheimpflug (Pentacam), Placido Disc (Orbscan II) and Manual Keratometry in patients with normal topographies (Normals), and with topographies suspicious for ectatic disease (Suspects). Results were compared in both groups in order to determine relative efficacy for the various keratometry measurements, both for magnitude of steep and flat K and axis of astigmatism.
Results
There were 75 eyes from 75 patients in both groups. For Normals, Steepest and Flattest measurements were not significantly different between methods (p > 0.05). For Suspects, Scheimpflug yielded flatter flat-K values than Placido (average 43 vs 44, p < 0.05), and Manual (average 43 vs 44, p = 0.07). There was good agreement for both groups between Manual and Placido steep axis (≤ 10° in 67% Normals and 63% Suspects) and poor agreement between Scheimpflug and other measures (≤ 10° from Manual in 11% Normals and 4% Suspects, and ≤ 10° from Placido in 15% Normals and 5% Suspects).
Conclusion
Agreement was good between Manual K and Placido for all metrics in both groups but poor between Scheimpflug and other techniques. There was no significant difference in outcomes based on normal or suspicious topography.