Subjective and objective assessments of the effect of orthokeratology - A cross-sectional study

Purpose. To determine which clinical tests are useful in orthokeratology aftercare examination, and to examine the objective and subjective characteristics of a group of orthokeratology lens wearers. Methods. Thirty orthokeratology subjects (8-19 years) who had been wearing orthokeratology lenses for over 12 months were recruited. Autorefraction, corneal topography, retinoscopy, subjective refraction and biomicroscopy were performed. Only left eyes results were analysed. Subjective ratings of symptoms and problems experienced by subjects were obtained using a questionnaire. Results. Autorefraction yielded higher residual sphere and residual cylinder by -0.54 D and -0.39 D respectively while retinoscopy yielded higher residual sphere and residual cylinder by -0.20 D and -0.03 D respectively. Corneal toricity measured by autokeratometry and corneal topography over-predicted the residual cylinder by -2.02 D and -2.08 D respectively. The mean ± SD residual spherical equivalent refractive error was -0.11 ± 0.57 D and the mean ± SD unaided post-orthokeratology visual acuity was 0.08 ± 0.14 log MAR. The unaided visual acuity was significantly related to the residual cylinder. Pigmented arc was present in 16 corneas (53%). The most common problems/symptoms experienced by the subjects were lens binding (73%), ocular discharge in the morning (69%) and blur distance vision (47%). Over 80% of the subjects found lens handling troublesome in varying degree. All, except two subjects (who disliked the lens handling), wanted to continue the treatment. Conclusions. History taking, subjective refraction, biomicroscopy and corneal topography are important in a routine orthokeratology aftercare examination. Corneal pigmented arc, ocular discharge in the morning and lens binding were the most common sign, symptom and problem respectively observed/ reported. Most orthokeratology lens wearers with low to moderate myopia and low astigmatism enjoyed reasonably good unaided post-orthokeratology vision in the daytime.