Logistic Regression Model Using Scheimpflug-Placido Cornea Topographer Parameters to Diagnose Keratoconus

Table 1

The mean values of summary indices, keratoconus indices, specially calculated indices, keratometry readings, and keratoconus indices in keratoconus and normal groups.

Parameter	Keratoconus mean ± SD (range)	Normal mean ± SD (range)	value
Summary indices
TCT (μm)	445.08 ± 49.19 (212, 542)	540.28 ± 33.12 (465, 607)	0.01>
TCT r (mm)	0.76 ± 0.44 (0.20, 3)	0.63 ± 0.24 (0.13, 2)	0.012
CCT (μm)	459.5 ± 49.95 (243, 557)	543.59 ± 31.98 (471, 611)	0.01>
Kmax (D)	54.12 ± 5.71 (44.50, 68.41)	45.70 ± 2.33 (41.98, 57.07)	0.01>
Apex r (mm)	1.31 ± 0.79 (0.20, 3.40)	1.67 ± 0.97 (0.20, 3.40)	0.01>
CV (mm^3)	54.03 ± 3.05 (45.6, 62.4)	58.03 ± 3.22 (49.4, 66.3)	0.01>
AD (mm)	3.3 ± 0.32 (2.57, 4.24)	3.13 ± 0.34 (2.4, 3.95)	0.01>
Specially calculated indices
Kmax/TCT (D/μm)	0.26 ± 1.60 (0.08, 18.1)	0.08 ± 0.007 (0.07, 0.12)	0.01>
Kmax^2/TCT (D^2/μm)	0.049 ± 0.54 (0.0001, 6.09)	0.0001 ± 0.00002 (0.0001, 0.0002)	0.01>
Keratometry readings
Sim-K1 (D)	45.01 ± 3.14 (40.11, 57.77)	42.61 ± 1.36 (39.45, 46.28)	0.01>
Sim-K2 (D)	48.19 ± 4.02 (40.92, 62.46)	43.94 ± 1.53 (41.15, 49.46)	0.01>
Anterior Ø = 3 mm K1 (D)	45.46 ± 5.27 (41.01, 67.90)	42.56 ± 1.35 (39.65, 46.33)	0.01>
Anterior Ø = 3 mm K2 (D)	49.72 ± 3.43 (40.82, 60.03)	44.06 ± 1.57 (41, 49.99)	0.01>
Anterior Ø = 5 mm K1 (D)	45.29 ± 4.5 (31.61, 73.12)	42.56 ± 1.33 (39.55, 46.3)	0.01>
Anterior Ø = 5 mm K2 (D)	49.06 ± 5.96 (40.96, 86.01)	43.95 ± 1.54 (41.06, 49.58)	0.01>
Posterior Ø = 3 mm K1 (D)	−6.37 ± 1.5 (−9.89, −0.26)	−5.88 ± 0.36 (−6.36, −2.57)	0.01>
Posterior Ø = 3 mm K2 (D)	−7.96 ± 1.69 (−15.4, −1.02)	−6.37 ± 0.39 (−9.87, −5.82)	0.01>
Posterior Ø = 5 mm K1 (D)	−6.26 ± 1.25 (−8.91, −0.44)	−5.9 ± 0.31 (−6.36, −3.36)	0.01>
Posterior Ø = 5 mm K2 (D)	−7.38 ± 1.48 (−15.88, 1.97)	−6.35 ± 0.27 (−8.06, −5.82)	0.01>
Keratoconus indices
SIf (D)	4.96 ± 3.68 (−7.36, 14.82)	−0.08 ± 0.56 (−1.43, 2.35)	0.01>
KVf (μm)	28.07 ± 17.91 (4, 102)	4.58 ± 3.65 (2, 37)	0.01>
BVCf (D)	2.74 ± 1.95 (0, 11.81)	0.13 ± 0.19 (0, 1.01)	0.01>
SIb (D)	1.29 ± 0.93 (−1.77, 4.46)	0.09 ± 1.37 (−0.77, 15)	0.01>
KVb (μm)	65.10 ± 40.18 (9, 264)	13.35 ± 9.88 (0, 111)	0.01>
BCVb (D)	2.74 ± 1.90 (0, 9.83)	0.08 ± 0.15 (0, 0.80)	0.01>

Mann–Whitney U test. SD = standard deviation; TCT = minimum corneal thickness; TCT r = distance of the thinnest point to the center of the cornea; CCT = central corneal thickness; K_max = keratometry of the steepest point recorded from anterior tangential map; Apex r = distance of K_max to the center of the cornea; CV = corneal volume in 10 mm central corneal zone; AD = distance from the corneal endothelium to the anterior surface of the lens; Sim-K1 = simulated flat keratometry; Sim-K2 = simulated steep keratometry; K1 = flat keratometry; K2 = steep keratometry; Ø = central corneal zone; SI_f = symmetry index front; KV_f = keratoconus vertex front index; BCV_f = Baiocchi Calossi Versaci front index; SI_b = symmetry index back; KV_b = keratoconus vertex back index; BCV_b = Baiocchi Calossi Versaci back index.