New corneal assessment index from the relational thickness and other OCULUS values (CAIRO Index)

Figures & data

Figure 1 Getting the elevation of the thinnest point on mouse click at this exact point.

Abbreviation: BFS, best-fit sphere.

Table 1 The indices with highest AUROC

Indices	AUROC	95% CI	Criterion	Sensitivity	Specificity	AUROC compared with that of CAIRO 9 (P)	AUROC compared with that of CAIRO 8 (P)
CAIRO using 9 mm BFS	0.997	0.973–1.0	≥0.5	95.89	97.09		0.268
CAIRO using 8 mm BFS	0.995	0.970–1.0	≥0.5	93.15	98.06	0.268
ART-Max	0.987	0.957–0.998	≤412	97.26	93.2	0.046	0.087
PPI-Max	0.987	0.958–0.998	>1.4	91.78	98.06	0.033	0.074
Elevation of the thinnest point from the 9 mm anterior BFS	0.979	0.945–0.995	>7	95.89	92.23	0.108	0.138
Elevation of the thinnest point from the 8 mm posterior BFS	0.979	0.945–0.995	>20	86.3	100	0.017	0.024
PPI-Avg	0.978	0.944–0.994	>1.1	87.67	98.06	0.038	0.049
Elevation of the thinnest point from the 9 mm posterior BFS	0.977	0.942–0.994	>22	89.04	96.12	0.027	0.04
ART-Avg	0.976	0.942–0.993	≤496	94.52	94.17	0.028	0.035
Elevation of the thinnest point from the 7 mm posterior BFS	0.971	0.934–0.990	>10	87.67	100	0.049	0.061
Elevation of the thinnest point from the 8 mm anterior BFS	0.968	0.930–0.989	>5	91.78	96.12	0.096	0.099
Elevation of the thinnest point from the 7 mm posterior BFTE	0.953	0.910–0.979	>10	87.67	99.03	<0.001	<0.001

Abbreviations: 95% CI, 95% confidence interval of the AUROC; ART-Avg, Ambrosio’s relational thickness average; ART-Max, Ambrosio’s relational thickness maximum; AUROC, area under the receiver operating characteristic curve; BFS, best-fit sphere; BFTE, best-fit toric ellipsoid; CAIRO, Corneal Assessment Index from the Relational thickness and other Oculus values using 9 mm BFS (CAIRO 9) and 8 mm BFS (CAIRO 8); P from CAIRO indices, probability of chance that the AUROC of the index is less than that of CAIRO 9 or CAIRO 8 indices; PPI-Avg, pachymetric progression index average; PPI-Max, pachymetric progression index maximum.

Table 2 Fallacies of each index included in the CAIRO indices

	PPI-Max	ART-Max	Elevation of the thinnest point from the 8 mm anterior BFS	Elevation of the thinnest point from the 9 mm anterior BFS	CAIRO 8	CAIRO 9
False diagnosis rate	4.55%	5.11%	6.25%	6.82%	3.98%	3.41%

Abbreviations: ART-Max, Ambrosio relational thickness in maximum meridian; BFS, best-fit sphere; CAIRO, Corneal Assessment Index from Relational thickness and other OCULUS values using 8 mm BFS (CAIRO 8) and 9 mm BFS (CAIRO 9).

Figure 2 AUROC of CAIRO indices compared with the 4 indices of highest AUROC throughout all cases.

Abbreviations: ART-Max, Ambrosio’s relational thickness maximum; CAIRO, Corneal Assessment Index from the Relational thickness and other Oculus values using 9 mm BFS (CAIRO 9) and 8 mm BFS (CAIRO 8); PPI-max, pachymetric progression index maximum; AE, anterior elevation from 9 mm BFS (AE 9) 8 mm BFS (AE 8).

Table 3 AUROC of CAIRO indices and some of the conventional indices in both normal and each subdivision of KC groups

Indices	TKC <2 (n= 23) vs normal (n=103)			TKC 2–4 (n= 50) vs normal (n=103)
	AUROC	P-value when compared with CAIRO 8	P-value when compared with CAIRO 9	AUROC	P-value when compared with CAIRO 8	P-value when compared with CAIRO 9
CAIRO 8	0.989		0.533	0.997		0.341
CAIRO 9	0.992	0.533	–	0.999	0.341
ART-Avg	0.934	0.028	0.033	0.996	0.651	0.135
ART-Max	0.968	0.072	0.083	0.996	0.609	0.127
Elevation of the thinnest point from the 8 mm anterior BFS	0.937	0.191	0.182	0.982	0.318	0.318
Elevation of the thinnest point from the 8 mm posterior BFS	0.938	0.011	0.012	0.998	0.612	0.359

Abbreviations: ART-Avg, Ambrosio relational thickness average; ART-Max, Ambrosio relational thickness maximum; AUROC, area under the receiver operating characteristic curve; CAIRO, Corneal Assessment Index from the Relational thickness and other Oculus values; TKC, Topographic Keratoconus Classification.

Figure 3 AUROC of CAIRO indices compared with the 4 indices of highest AUROC in differentiating early KC from normal corneas.

Abbreviations: ART-Max, Ambrosio’s relational thickness maximum; AUROC, Area Under Receiver Operating Characteristic curves; CAIRO, Corneal Assessment Index from the Relational thickness and other Oculus values using 9 mm BFS (CAIRO 9) and 8 mm BFS (CAIRO 8); PPI-max, pachymetric progression index maximum; KC, keratoconus; AE, anterior elevation from 9 mm BFS (AE 9) and 8 mm BFS (AE 8).