AIM: To explore the correlation between eccentricity in the optical treatment area and tear film function and corneal morphology after orthokeratology.

METHODS:Eighty patients(80 eyes)with myopia who were treated with orthokeratology were selected as subjects. The eccentric distance, tear film function and corneal morphology of the patient's optical treatment area were detected at different time points before and after wearing the lens. According to the median eccentric distance, the patients were divided into low eccentricity group and high eccentricity group. The differences of tear film function and corneal morphology at different time points before and after wearing were compared between the two groups. Pearson correlation coefficient was used to analyze the correlation between total eccentricity and tear film function and corneal morphological parameters at 12mo after wearing glasses.

RESULTS:Compared with before wearing lenses, the corneal surface asymmetry index and corneal surface regularity index of the two groups were significantly increased at 1wk, 3, 6 and 12mo after wearing lenses(P<0.05). Patients in the high eccentric group were more significantly elevated than in the lower eccentric group, and the differences were statistically significant(P<0.05). The time of tear film rupture, corneal curvature, basic tear secretion, and central corneal thickness were significantly lower, and the differences were statistically significant(P<0.05). Compared with the patients with lower eccentricity, the patients with high eccentricity group had more significant reduction in tear film rupture time and basic tear secretion, and the difference was statistically significant(P<0.05), however, the degree of corneal curvature and central corneal thickness decreased less(P<0.05). There was no significant difference in corneal endothelial cell density between 1wk after wearing lenses and 3mo after wearing lenses(P>0.05). The difference was statistically significant at 6mo and 12mo after wearing lenses(P<0.05). At 12mo after wearing the lens, the total eccentric distance was positively correlated with the asymmetry index of the corneal surface and the regularity index of the corneal surface(r=0.869, 0.815; P<0.05). At 12mo after wearing the lens, the total eccentric distance was negatively correlated with tear film rupture time, corneal curvature, basic tear secretion, and central corneal thickness(r=-0.865, -0.745, -0.912, -0.713; all P<0.05), and there was no significant correlation with corneal endothelial cell density(r=0.185, P=0.199).

CONCLUSION:The eccentricity of the optical treatment area occurs at the beginning of wearing lenses. And the total eccentric distance has a significant correlation with the changes of tear film function and corneal morphology after keratoplasty.