We obtained excellent intraexaminer reliability scores (>0.9) for Goldmann-correlated IOP and CRF
(Table 1)and found clinically useful reliability estimates (>0.7)
33 in the IOP-ORAc and CH. These values are similar to those for other tonometers and are considered by previous authors as clinically adequate.
33 The ICCs for rebound tonometry
34 were 0.82, 0.73, and 0.87, respectively, for the first, second, and third examiners, and the ICCs for the GT and tonometer (Tono-Pen; Reichert) were 0.97 and 0.95, respectively.
35 Although no significant difference was found, ORA corneal biomechanical metrics showed a trend toward slightly better than ORA IOP readings, perhaps because corneal tissue biomechanical properties are fairly constant, whereas the IOP changes with the cardiac cycle, and NCT measures the IOP within 1 to 3 ms, making the ocular pulse a crucial source of variability.
36 Kotecha et al.
22 found that the coefficient of variation of ORA IOP measurements was four to five times greater than that of GT IOP measurements. However, they calculated coefficients of variation for CH and CRF nearly twice as high as those for IOP-ORAc. Differences between the studies might have occurred because our ORA was a commercially available unit, whereas theirs was a prototype,
22 and because we averaged three repeated ORA readings and they did not, with averaging favoring more corneal biomechanical metrics than ORA IOP readings. The ability to yield reliable corneal biomechanical metrics is an outstanding feature of the ORA when determining candidates for keratorefractive surgery or for retreatments.
13 14 15 16 Given the growing concern about iatrogenic keratectasia,
12 13 14 15 ORA biomechanical parameters may contribute significantly to preoperative screening of patients who are not candidates for keratorefractive surgery or who seek surgical alternatives because of a biomechanically compromised cornea.
12 16