FEB 12, 2009
This article describes the significant increase in irregular astigmatism and higher-order aberrations resulting from orthokeratology. The paper finds that these changes are reversed one week after discontinuation of the therapy.
While the results of this study are encouraging with regard to the reversibility of the induced higher-order aberrations and loss of contrast sensitivity, the fact that orthokeratology induces significant aberrations and reduces contrast sensitivity in the first place calls into question the clinical relevance of this technique compared with traditional contact lens wear, spectacles and refractive surgery.
The study's authors followed 17 subjects treated with overnight keratology with four-zone reverse geometry lenses made with Bausch & Lomb's Boston XO material with a nominal Dk of 100 x 10-11 (cm2/s) (ml O2/ml·mm Hg). After 12 months, the subjects stopped using the lenses. They underwent visual examinations one week and one month later.
Study inclusion criteria required manifest spherical equivalent refraction of -4.00 to -1.00 D, refractive astigmatism up to 1.00 D, BSCVA of 20/20 or better, mean keratometry reading of 40.00 to 46.25 D, no prior use of orthokeratology and age between 20 and 37 years. Potential subjects with clinical evidence of ocular corneal pathology, a history of ocular disease or surgery or with systemic diseases, such as diabetes, were excluded. Six initial subjects dropped out of the study due to reasons including poor improvement in uncorrected visual acuity, monocular diplopia and poor adaptation to the treatment due to lens discomfort.
After 12 months of overnight orthokeratology, manifest spherical equivalent refraction among the subjects was significantly reduced from -2.17 at baseline to -0.17 and UCVA significantly improved from 0.72 to -0.06 logMAR. However, asymmetry, high-order irregularity and third- and fourth-order aberrations increased significantly and contrast sensitivity decreased significantly. All of these changes reverted to measurements similar to baseline one week after subjects stopped orthokeratology therapy. After one month, some further recovery was seen.
Dr. Hamilton receives lecture fees from Alcon Laboratories, Inc., and Allergan, Inc.