[The evaluation of visual quality in keratoconus eyes corrected by rigid gas-permeable contact lens].

OBJECTIVE

To evaluate the visual quality in keratoconus eyes corrected by rigid gas-permeable contact lens (RGPCL) and spectacles.

METHODS

Corrected visual acuity, corneal topography, wavefront aberration and contrast sensitivity were measured in 27 keratoconus patients (54 eyes) before and after the fitting of RGPCL.

RESULTS

The inclusive keratoconus eyes were divided mild 30 eyes, moderate 13 eyes and sever 11 eyes. The average myopia and average astigmatism were (6.92 +/- 3.66) D and (5.75 +/- 1.85) D respectively. Uncorrected visual acuity (VA) in 96.3% keratoconus eyes was <or= 0.3. RGPCL corrected VA was increased significantly compared with spectacles corrected VA. The VA in 59.3% of eyes corrected by spectacles were >or= 0.6, while 100% by RGPCL. The VA in 20.4% of eyes corrected by spectacles were >or= 1.0, while 66.7% by RGPCL. Corneal topography study showed corneal toricity decreased to <or= 0.75 D in RGPVA group. Ocular surface was changed to spherical and regular shapes. Root-mean-square (RMS) of wavefront aberration decreased significantly from (3.63 +/- 2.08) microm (without RGPCL) to (1.39 +/- 0.82) microm (with RGPCL) (P < 0.01). RMS of Zernike function in each order was decreased as well, second order from (2.64 +/- 1.74) microm to (0.81 +/- 0.66) microm, total high order from (2.35 +/- 1.57) microm to (1.10 +/- 0.62) microm, third order from (1.78 +/- 1.28) microm to (0.68 +/- 0.39) microm With RGPCL fitting, contrast sensitivity curve (light on and light off) were significantly higher than that with spectacles in whole range of frequency, especially in middle and high frequency.

CONCLUSIONS

Corneal distortion induced high corneal irregular astigmatism is the most frequent cause of increase of aberration and reduced ocular optical quality in keratoconus. Proper RGPCL fitting provides an effective method in reshaping of ocular surface combined with tear film. RGPCL could reduce aberrations and corneal astigmatism, improve optical quality, and finally, increase visual acuity and contrast sensitivity.