[Changes of ocular higher order aberration in keratoconus eyes wearing rigid gas-permeable contact lens]

To compare the wavefront characteristics of normal and keratoconus eyes with and without rigid gas-permeable contact lens (RGPCL), and to evaluate the visual quality in keratoconus eyes corrected by RGPCL.

Retrospective study. Higher order aberrations (HOAs) of 90 eyes in 56 keratoconus patients and 30 eyes of 17 subjects with refractive errors were quantified with a Bausch&Lomb Zywave Wavefront Analyzer. The keratoconus eyes were divided into mild (28 eyes), moderate (33 eyes) and severe (29 eyes) groups. Zernike's polynomial was used to describe the wavefront measurements. Root mean square (RMS) values of the total HOAs, S3, S4, S5, total coma (T. Coma) and total spherical aberrations (T. Sph) were obtained in the same eye with and without contact lenses. We used paired sample t-test and independent-samples t-test to analyze the data.

Mean RMS values for High (F = 72.12, P(1) = 0.00), S3 (F = 68.15, P = 0.00), S4 (F = 24.95, P(1) = 0.00), T. Coma (F = 44.67, P = 0.00), T. Sph (F = 28.90, P = 0.01) increased significantly from mild to sever keratoconus eyes RMS values of the total HOAs (t = 4.83), S3 (t = 4.39), total coma (t = 3.71) of refractive error eyes decreased significantly after fitting with RGPCL (P < 0.05). RMS values of the total HOAs (t = 8.27), S3 (t = 8.14), S4 (t = 2.29), total coma (t = 4.38) of mild keratoconus eyes decreased significantly after fitting with RGPCL (P < 0.05) RMS values of the total HOAs (t = 8.03), S3 (t = 7.22), s4 (t = 4.38), S5 (t = 4.53), total coma (t = 5.26) and total spherical (t = 2.77) of moderate keratoconus eyes decreased significantly after fitting with RGPCL (P < 0.05). Every high front-wave aberration of mild keratoconus eyes decreased to refractive error eyes'level after RGPCL fitting. Moderate (t(HOAs) = 0.63, t(s3) = 0.31, t(s4) = 1.70, t(s5) = 0.95, t(coma) = 0.06, t(spherical) = 1.99) and sever keratoconus eyes' higher order aberrations decreased significantly after RGPCL fitting (t(HOAs) = 7.50, t(s3) = 5.25, t(s4) = 5.50, t(s5) = 3.02, t(coma) = 5.90, t(spherical) = 4.60), but they still degrade compared with refractive error eyes (P < 0.05).

RGPCL could reduce high aberrations and improve optical quality in keratoconus eyes. But the visual performance in moderate and severe keratoconus eyes with a RGPCLs is still poorer than that of normal eyes even if the corrected visual acuity is good.