Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus

Table 1

The mean, SD, and 95% confidence interval (CI) of all tested KC detecting parameters. Radii of curvature are in mm, elevations in μm, pachymetry in μm, and decentration in mm.

Indices	Normal			Keratoconus stages 1 to 4
	Mean	SD	95% CI	Mean	SD	95% CI
Curvature indices
Central 3 mm
Mean radius of curvature of anterior 3 mm corneal surface	7.725	0.2305	7.323–8.149	6.954	0.6640	5.296–8.124
Mean radius of curvature of posterior 3 mm corneal surface	6.425	0.256	6.040–6.809	5.624	0.685	4.145–6.777
Mean eccentricity of the anterior corneal surface	0.519	0.132	0.210–0.730	0.799	0.3312	−0.034–1.310
Determinants of BFS
Radius of curvature of the 8 mm anterior BFS	7.786	0.2252	7.413–8.200	7.350	0.445	6.191–8.230
Radius of curvature of the 9 mm anterior BFS	7.833	0.2225	7.462–8.269	7.488	0.398	6.535–8.284
Radius of curvature of the 7 mm posterior BFS	6.390	0.2147	5.991–6.758	5.935	0.4148	5.109–6.700
Radius of curvature of the 8 mm posterior BFS	6.464	0.3544	6.031–6.790	6.125	0.3842	5.465–7.022
Radius of curvature of the 9 mm posterior BFS	6.548	0.3426	6.101–6.899	6.280	0.3041	5.765–6.981
Determinants of BFTE
Flattest radius of curvature of the 7 mm posterior BFTE	6.644	0.2495	6.143–7.152	5.972	0.7057	4.312–6.947
Steepest radius of curvature of the 7 mm posterior BFTE	6.175	0.2317	5.741–6.609	5.273	0.6972	3.971–6.630
Eccentricity of the 7 mm posterior BFTE	0.181	0.3173	−0.441–0.765	0.618	0.5282	−0.447–1.350
Flattest radius of curvature of the 8 mm posterior BFTE	6.655	0.2507	6.143–7.169	5.972	0.7057	4.312–6.947
Steepest radius of curvature of the 8 mm posterior BFTE	6.175	0.2317	5.741–6.609	5.278	0.6936	3.971–6.630
Eccentricity of the 8 mm posterior BFTE	0.181	0.3173	−0.441–0.765	0.618	0.5282	−0.447–1.350
Flattest radius of curvature of the 9 mm posterior BFTE	6.658	0.2665	6.143–7.169	5.972	0.7057	4.312–6.947
Steepest radius of curvature of the 9 mm posterior BFTE	6.175	0.2317	5.741–6.609	5.287	0.7092	3.971–6.630
Eccentricity of the 9 mm posterior BFTE	0.181	0.3173	−0.441–0.765	0.618	0.5282	−0.447–1.350
Elevation indices
Using BFS
Elevation of the thinnest point from the 7 mm posterior BFS	1.5	3.13	−4.0–9.9	46.2	32.7	2.3–115.4
Maximum elevation from the 7 mm posterior BFS	32.8	15.12	17.1–72.6	79.9	34.3	27.7–153.7
Minimum elevation from the 7 mm posterior BFS	−34.4	15.4	−75.0–−14.1	−76.5	33.5	−160.9–−29.3
Maximum minus minimum elevation from the 7 mm posterior BFS	67.2	29.2	34.0–142.8	156.48	64.2	60.6–296.0
Elevation of the thinnest point from the 8 mm anterior BFS	2.6	1.5	0.0–6.0	26.7	17.7	2.0–68.7
Elevation of the thinnest point from the 8 mm posterior BFS	4.1	4.7	−2.0–17.8	58.4	39.0	6.3–143.4
Elevation of the thinnest point from the 8 mm posterior BFS minus that of anterior BFS	1.5	4.5	−5.0–14.0	31.8	22.5	1.0–77.0
Maximum elevation from the 8 mm posterior BFS	51.4	23.3	21.0–107.9	89.6	33.3	35.0–159.4
Minimum elevation from the 8 mm posterior BFS	−43.0	18.3	−93.9–−22.1	−90.9	41.1	−198.9–−32.0
Maximum minus minimum elevation from the 8 mm posterior BFS	94.5	37.9	49.2–188.6	180.5	71.4	67.6–351.8
Elevation of the thinnest point from the 9 mm anterior BFS	4.5	2.0	1.0–9.0	34.0	21.5	6.0–90.7
Elevation of the thinnest point from the 9 mm posterior BFS	9.9	6.8	2.0–31.9	72.7	43.9	11.0–171.8
Elevation of the thinnest point from the 9 mm posterior BFS minus that of anterior BFS	5.3	6.2	−2.0–24.9	38.7	24.0	2.3–89.0
Maximum elevation from the 9 mm posterior BFS	76.5	28.16	43.1–145.9	112.836	41.9722	48.7–212.7
Minimum elevation from the 9 mm posterior BFS	−57.2	21.2	−124.0–−33.2	−104.8	61.0	−248.4–−40.3
Maximum minus minimum elevation from the 9 mm posterior BFS	133.7	45.7	77.6–284.5	217.6	89.23	87.3–428.0
Using BFTE
Elevation of the thinnest point from the 7 mm posterior BFTE	3.5	2.8	−1.0–10.0	37.6	24.9	0.0–97.01
Maximum elevation from the 7 mm posterior BFTE	18.0	10.7	6.1–40.0	71.3	54.8	17.7–225.6
Minimum elevation from the 7 mm posterior BFTE	−25.8	8.6	−47.8–−12.1	−72.8	39.6	−187.4–−18.3
Maximum minus minimum elevation from the 7 mm posterior BFTE	43.8	16.3	23.0–80.3	144.1	88.3	39.3–393.1
Elevation of the thinnest point from the 8 mm posterior BFTE	4.3	3.9	−2.0–13.0	39.5	26.45	−3.0–104.0
Maximum elevation from the 8 mm posterior BFTE	43.9	22.2	11.1–114.8	103.1	84.1	23.0–360.0
Minimum elevation from the 8 mm posterior BFTE	−33.4	11.7	−62.9–−16.1	−89.9	40.9	−185.1–−29.0
Maximum minus minimum elevation from the 8 mm posterior BFTE	77.3	28.2	32.1–141.7	192.9	114.2	68.0–557.4
Elevation of the thinnest point from the 9 mm posterior BFTE	3.6	5.6	−5.0–16.9	38.7	30.8	−18.34–111.8
Maximum elevation from the 9 mm posterior BFTE	89.9	39.5	35.2–174.6	170.8	152.9	39.6–665.5
Minimum elevation from the 9 mm posterior BFTE	−42.1	15.5	−88.3–−21.1	−114.5	50.2	−217.5–−32.7
Maximum minus minimum elevation from the 9 mm posterior BFTE	132.0	43.3	65.2–231.4	285.2	177.1	107.3–859.2
Pachymetry indices
Apex thickness	545.3	35.4	471.7–624.3	482.5	39.4	384.3–573.4
Central corneal thickness	545. 5	35.5	471.7–623.4	491.4	35.3	408.9–573.4
Thinnest point thickness	543.5	35.7	471.7–622.3	465.1	68.1	361.8–566.7
PPI-Min	0.543	0.1512	0.300–0.800	1.504	0.8265	0.500–3.570
PPI-Avg	0.826	0.1365	0.600–1.100	2.104	1.0454	0.900–4.967
PPI-Max	1.077	0.1716	0.800–1.400	2.800	1.3960	1.232–6.705
PPI-Max minus PPI-Min	0.534	0.189	0.300–0.992	1.296	0.763	0.400–3.835
ART-Min	1109.9	430.9	613.0–2044.2	423.3	272.5	94.0–1045.4
ART-Avg	677.6	131.4	395.7–975.2	276.6	138.2	75.7–616.9
ART-Max	517.8	90.6	326.6–697.0	207.1	100.6	54.6–427.5
Horizontal decentration of the thinnest point from the apex	0.026	0.569	−0.948–1.019	−0.087	0.574	−0.940–0.827
Vertical decentration of the thinnest point from the apex	−0.273	0.208	−0.639–0.214	−0.519	0.347	−1.394–0.110
Diagonal decentration of the thinnest point from the apex	0.618	0.240	0.202–1.088	0.799	0.288	0.366–1.525

SD: standard deviation, 95% CI: 95% confidence interval, BFS: best-fit sphere, BFTE: best-fit toric ellipsoid, PPI-Min: Pachymetry Progression Index-Minimum, PPI-Avg: Pachymetry Progression Index-Average, PPI-Max: Pachymetry Progression Index-Maximum, ART-Min: Ambrósio’s Relational Thickness-Minimum, ART-Avg: Ambrósio’s Relational Thickness-Average, and ART-Max: Ambrósio’s Relational Thickness-Maximum.