Evaluating keratoconus progression prior to crosslinking: maximum keratometry vs the ABCD grading system

Abstract

Purpose: To evaluate the correlation between changes in maximum keratometry (Kmax) and ABC values from the ABCD Progression Display (Pentacam) in progressive keratoconus (KC) and to evaluate whether the ABC changes were able to detect progression earlier than Kmax. Setting: Humanitas Clinical and Research Center, Rozzano, Milan, Italy. Design: Retrospective study. Methods: Kmax, ABC values, and thinnest point (ThCT) were recorded at the day of corneal crosslinking (CXL) (T0) and previous follow-up (T-1). In patients without earlier progression in Kmax, follow-up examination (T-2) was used to determine whether any of the ABC parameters reached statistical significance for progression. Results: Seventy-six eyes of 63 patients scheduled for CXL with documented progression (Kmax increase of >1.00 diopter) were included. There was a significant, albeit moderate, correlation between the change in Kmax between T0 and T-1 and the change in both A (ρ = 0.391) and B values (ρ = 0.339). There was no significant correlation between the change in Kmax between T0 and T-1 and the change in either C or ThCT. In patients with T-2 examinations, 16 (51.6%) of 31 patients showed a statistically significant change on the ABCD progression display that was not detected with Kmax. Conclusions: This study showed a significant, but moderate, correlation between the change in Kmax and the change in A and B values in progressive KC. Moreover, more than half of the cases showed documented progression earlier with the ABCD progression display than that detected by standard Kmax changes. This study suggests possible changes in progression criteria to allow for earlier intervention.

An inter-day assessment of the ABC parameters in the evaluation of progressive keratoconus

“…The latter population is suggested to be more representative of milder cases of keratoconus. It has been proposed that the ABCD progression display could be used to detect progression earlier than the commonly used maximum keratometry reading, K max 9 .…”

Three-year results of accelerated transepithelial cross-linking (30 mW/cm2× 3 min) for keratoconus: a prospective study

“…Further follow-up of more patients is needed. Another limitation is that we did not assess the posterior keratometric change, whose importance 34 is emphasised in the global consensus 35 which was published after our study had started. CONCLUSION This is the first report of 3-year results of ATE-CXL with 30 mW/cm 2 × 3 min.…”

Forecasting Progressive Trends in Keratoconus by Means of a Time Delay Neural Network

“…Additionally, this selection complies with the specifications of the global consensus to define KC progression [ 41 ]. Well-known indices, such as A and B (from the ABCD progression display) or BADD, while sensitive and specific for KC progression [ 12 , 42 ], were not included as they are specific to Pentacam, and their underlying calculations are not public. More than half of the KC showed progression by an ABCD progression display earlier than by the standard criterion based on maximum keratometry in a recent publication [ 12 ].…”

“…Well-known indices, such as A and B (from the ABCD progression display) or BADD, while sensitive and specific for KC progression [ 12 , 42 ], were not included as they are specific to Pentacam, and their underlying calculations are not public. More than half of the KC showed progression by an ABCD progression display earlier than by the standard criterion based on maximum keratometry in a recent publication [ 12 ]. In this work, we wanted to go one step further and verify not only whether progression occurred but also whether progression could happen shortly.…”

“…These clinical variations, as well as the effectiveness of corneal cross-linking (CXL) [ 10 ], have led to a renewed interest in assessing the risk factors for a faster KC evolution [ 11 ]. Although stabilization via CXL may be performed based on other factors (e.g., an unstable refraction that requires regular, costly updates of the refractive correction), many national CXL protocols require proof of KC progression to qualify for reimbursement [ 12 ]. Progression is typically established by inviting the patient for a follow-up visit about 6 months later.…”