Posters
Characterization of posterior corneal astigmatism in a population with keratoconus: effect on total corneal astigmatism and predictive value for progression
Poster Details
First Author: R.Marques PORTUGAL
Co Author(s): P. Guerra A. Quintas W. Rodrigues
Abstract Details
Purpose:
The curvature of anterior corneal surface is traditionally used as a surrogate to estimate corneal astigmatism. In recent years, increasing importance has been attributed to posterior corneal astigmatism as an indicator. Our aim is to characterize the posterior corneal surface in a population with keratoconus, and investigate its predictive value to keratoconus progression.
Setting:
Tertiary care center (Hospital de Santa Maria, Lisbon, Portugal).
Methods:
Retrospective cohort study. Eighty-five patients (85 eyes) with keratoconus were included. Vector analysis was used to calculate anterior (ACA), posterior (PCA), and total corneal astigmatism (TCA). Multivariate logistic regression was used to assess the predictive value of posterior astigmatism to keratoconus progression, adjusting for ACA, TCA and several tomographic indices.
Results:
Mean age was 32 (SD=12.5) years. Mean TKC was 2.16 (SD=0.95), with a mean Kmax of 55.8 (SD=7.8). Mean power of PCA, ACA and TCA was respectively -0.88D (SD=0.84), 3.74D (SD=2.36), and 3.06D (SD=2.01) and its centroids were 0.44x15º, 1.65x112º, and 1.61x106º, respectively. The power of PCA was ≥ 0.50, 1.00 and 2.00D in 75.3%, 32.9%, and 3.5% of patients, respectively, inducing against-the-rule astigmatism in 60.0% of patients. On average, ACA overestimated TCA in 0.35Dx151º (p<0.01). ACA and TCA were highly correlated, but showed lack of agreement for clinical purposes. A predictive role for the magnitude of PCA was excluded.
Conclusions:
In this population with keratoconus, PCA contributed substantially to TCA. These results should be considered when monitoring for disease progression, as when considering astigmatism surgical correction.
Financial Disclosure:
None
