Trends in Corneal Topography and Tomography Imaging for Keratoconus Management

Figures & data

Table 1 Clinical and Demographic Characteristics of Keratoconus Patients

Parameters	Total KCN Patients (N=873)	Adult KCN Patients (N=791)	Pediatric KCN Patients (N=82)
Diagnosis age (years ± SD)	40.3 ± 17.1	43.0 ± 15.7	14.9 ± 2.5
Female (n, %)	295 (33.8)	266 (33.6)	29 (35.4)
Race (n, %)
Caucasian	360 (41.2)	343 (43.4)	17 (20.7)
Black	77 (8.8)	74 (9.4)	3 (3.7)
Asian	67 (7.7)	57 (7.2)	10 (12.2)
Other	244 (27.9)	206 (26.0)	38 (46.3)
Unknown/declined	125 (14.3)	111 (14.0)	14 (17.1)
Developmental disability (n, %)	57 (6.5)	55 (7.0)	2 (2.4)
Tomography first visit (n, %)	210 (24.1)	178 (22.5)	32 (39.0)
Topography first visit (n, %)	450 (51.5)	408 (51.6)	42 (51.2)

Abbreviation: KCN, keratoconus.

Figure 1 Change in the rates of corneal topography and corneal tomography usage near the first visit over time. Corneal topography usage at the first visit stayed relatively constant from 2012 to 2019, whereas corneal tomography usage increased significantly since it was introduced in February 2015. Imaging near the first visit was defined as having either corneal topography or tomography done ±7 days from the first visit.

Table 2 Association of Imaging Modality and Intervention

Variable	CXL (β Coefficient, %)	SE (%)	P value
Topography first visit	−2.7	1.4	0.047*
Tomography first visit	9.9	1.8	<0.001**
Pediatric patient	23.5	2.3	<0.001**
Developmental disability	6.2	2.7	0.022*
Year of first visit	0.004	0.001	<0.001**
Variable	Surgical Intervention† (β Coefficient, %)	SE (%)	P value
Topography first visit	−3.2	1.9	0.088
Tomography first visit	−5.4	2.5	0.032*
Pediatric patient	−11.9	3.2	<0.001**
Developmental disability	0.6	3.7	0.862
Year of first visit	−0.006	0.001	<0.001**

Notes: *P<0.05; **P<0.001. †Surgical interventions are defined as intrastromal corneal ring segments, lamellar keratoplasty, or penetrating keratoplasty.

Abbreviation: CXL, corneal collagen cross-linking.

Figure 2 Differences in interventions by the most recent visit for patients who did receive corneal tomography near the first visit compared to those who did not. (A) The percentage of patients with corneal collagen cross-linking (CXL) was significantly greater in those who did receive corneal tomography imaging near the first visit (P<0.001). (B) In contrast, the percentage of patients requiring another surgical intervention for keratoconus (defined as having ICRS, lamellar keratoplasty, or penetrating keratoplasty) was significantly lower in patients who did have corneal tomography near the first visit compared to patients without tomography (P=0.048). Statistics: Multivariate linear regression controlling for year of the first visit. *P<0.05, **P<0.001.

Figure 3 Correlation between keratometry measurements from corneal topography and corneal tomography for patients at their first visit. Patients with corneal topography and tomography within 30 days from each other were included (N=690 eyes). (A) The correlation between the average keratometry from corneal topography (AveK) and tomography (Km) had an adjusted R² of 0.16 (P<0.001). (B) The adjusted R² value for the correlation between the steep K from corneal topography (Ks) and tomography (K2) was 0.21 (P<0.001). (C) The adjusted R² value for correlation between the flat K from corneal topography (Kf) and tomography (K1) was 0.04 (P<0.001). All K values are in diopters (D).