PURPOSE: To quantitatively investigate the time course of changes in corneal irregular astigmatism and their relation to best spectacle-corrected visual acuity (BSCVA) in eyes with keratoconus. METHODS: Subjects were 47 patients (57 eyes) with keratoconus who had undergone videokeratography examinations at least twice, with an interval of 1 year or longer between each examination. By means of Fourier series harmonic analysis, topography data were separated into spherical component, regular astigmatism, asymmetry, and higher order irregularity. RESULTS: In eyes that showed apparent progression on color-coded maps, the yearly rate of change was significantly positive for spherical component (P = 0.03) and higher order irregularity (P = 0.006). In eyes with apparent progression, the yearly change rate of BSCVA was significantly positive (P = 0.001), but not in the eyes without apparent progression (P = 0.1655). In eyes with progression on maps, the yearly change rate of BSCVA was significantly correlated with the change rate of higher order irregularity per year (r = 0.770, P = 0.0004). CONCLUSIONS: The results indicated that progression of keratoconus is associated with deterioration of BSCVA, which is in turn significantly correlated with increases in corneal higher order irregularity.
PURPOSE: To quantitatively investigate the time course of changes in corneal irregular astigmatism and their relation to best spectacle-corrected visual acuity (BSCVA) in eyes with keratoconus. METHODS: Subjects were 47 patients (57 eyes) with keratoconus who had undergone videokeratography examinations at least twice, with an interval of 1 year or longer between each examination. By means of Fourier series harmonic analysis, topography data were separated into spherical component, regular astigmatism, asymmetry, and higher order irregularity. RESULTS: In eyes that showed apparent progression on color-coded maps, the yearly rate of change was significantly positive for spherical component (P = 0.03) and higher order irregularity (P = 0.006). In eyes with apparent progression, the yearly change rate of BSCVA was significantly positive (P = 0.001), but not in the eyes without apparent progression (P = 0.1655). In eyes with progression on maps, the yearly change rate of BSCVA was significantly correlated with the change rate of higher order irregularity per year (r = 0.770, P = 0.0004). CONCLUSIONS: The results indicated that progression of keratoconus is associated with deterioration of BSCVA, which is in turn significantly correlated with increases in corneal higher order irregularity.