Dynamics of ocular aberrations in keratoconus

BACKGROUND: The aim was to investigate the fluctuations in monochromatic ocular aberrations with accommodation and tear-film changes in moderate keratoconic eyes. METHODS: We measured the changes in ocular higher-order aberrations in 10 moderate keratoconic and 10 visually normal eyes to accommodative stimuli ranging from zero to 5.00 DS using a Hartmann-Shack aberrometer. In addition, the changes in ocular higher-order aberrations were measured for up to 15 seconds after a blink in eight keratoconic and eight visually normal eyes. RESULTS: These results show that ocular spherical (p = 0.68) and coma-like (p = 0.71) aberrations did not change significantly with accommodation from zero to 5.00 DS in keratoconic eyes. In contrast to normal eyes, the ocular higher-order RMS error tended to decrease in magnitude after a blink in keratoconic eyes. Vertical coma became less negative with time after a blink in the keratoconic group, therefore, reducing the manifest ocular higher order RMS error by counteracting the negative vertical coma of the cornea. CONCLUSIONS: Compared to the manifest monochromatic higher-order aberrations, any dynamic fluctuations in ocular aberrations with accommodation and tear film changes are relatively small in moderate keratoconic eyes. This implies that the correction of monochromatic higher-order aberrations in keratoconus using customised soft contact lenses will not be significantly hindered by such dynamic aberrational changes.