Accurate measurements of the keratometry are very important in the management of keratoconus.
13,14 Primary ectasia detection requires TCT measurement as one of the main variables.
15 Accurate ACD is required while planning toric implantable collamer lenses in the management of stable keratoconus and for accurate biometry using modern intraocular lens power calculation formulas.
4,16,17 Though the three machines are based on the same principle, we wanted to ascertain whether they could give repeatable measurements. The Sw that were obtained for Km, TCT, ACD, and pKm in this study with Pentacam HR were higher than seen in earlier studies. McAlinden et al.
18 used the Pentacam HR for normal corneas and found Sw of 0.12 diopters (D), 3.25 μm, 0.01 mm, and 0.03 D for Km, TCT, ACD, and pKm, respectively. Szalai et al.
19 in their study on 84 keratoconic corneas found Sw and TRT for TCT of 4.70 μm and 13.02 μm, respectively, which were higher as compared to our results for the Pentacam HR; the ACD had comparable Sw and TRT (0.04 and 0.128). A recent study by Sideroudi et al.
20 found reproducible measurements for the posterior curvature in keratoconic eyes. Galilei has been reported to have good repeatability in measuring the corneal curvature in healthy corneas.
21 Other studies have found pachymetry measurements from Galilei to be highly repeatable in both normal and postrefractive corneas.
6 Savini et al.
7 in their study on normal and postrefractive corneas reported a TRT of 0.34 D for Km, 4.78 μm for TCT, 0.06 mm for ACD, and 0.09 D for pKm. The Sw and TRT for these parameters have not been measured previously in keratoconus patients, but on comparing with the results obtained with healthy and postrefractive corneas, we had higher Sw and TRT values for Galilei. Sirius performed better than Galilei in all measurements in terms of Sw and TRT, but the results were inferior to those obtained from Pentacam for Km and pKm. On comparing TRT reported by Savini et al.
22 in keratoconus patients, our results were better only for pKm measurements.