Influence of the Diameter and Decentration of the Treatment Zone on Optical Quality and Visual Performance after Orthokeratology

Abstract

Objective: To analyze the changes in corneal higher order aberrations (HOAs) and contrast sensitivity (CS) after orthokeratology (ortho-K) treatment, and their correlation with the magnitude of lens decentration. Methods: This was a prospective study. Thirty-one patients (31 eyes) who had undergone orthokeratology treatment from March to August 2017 in 3rd Affiliated Hospital of Wenzhou Medical University were chosen for the study. Corneal topography, CS and corneal HOAs were measured before and one month after ortho-K lens treatment, in addition, the diameter and decentration of the treatment zone and their inf luence on corneal HOAs and CS were analyzed. CS was expressed as area under log contrast sensitivity function (AULCSF) was a paired-t test, pearson correlation and stepwise multiple linear regression were used to analyze the data. Results: The mean TxZ diameter was 3.48±0.49 mm, while the mean decentration of TxZ was 0.64±0.27 mm, mostly toward the inferior temporal quadrant (45%). The root mean squares (RMS) of the total corneal HOAs, corneal spherical aberrations corneal vertical coma aberrations and corneal horizontal coma aberrations increased after one month of treatment (t=10.99, 10.19, -2.21, -3.50, P<0.05). The vertical decentration of TxZ was significantly correlated with the corneal vertical coma aberrations (standard B=0.620, P=0.001), while the horizontal decentration was significantly correlated with the corneal horizontal coma aberrations (standard B=0.422, P=0.049). The photopic and mesopic AULCSF tended to decrease, but there were no significant differences. The change in photopic AULCSF only correlated with the change in diopters (standard B=0.452, P=0.021), while the change in mesopic AULCSF correlated with both the change in diopters (standard B=0.528, P=0.004) and the decentration of TxZ (standard B=0.458, P=0.027). Conclusions: Decentered othokeratology lenses increase corneal HOAs but do not affect CS. Key words: orthokeratology; decentration; corneal higher-order aberrations; contrast sensitivity; treatment zone