Corneal thickness and endothelial observation for youth myopia patients fitted with ortho-k lens for seven years

Abstract

To observe the changes of the corneal thickness and endothelial cell for youth myopia patients fitted with long-term orthokeratology (Ortho-K, OK). Retrospective case series study. During 2000 to 2005, 30 patients with OK lens wearing more than seven years in the Bei Yi Optometry & Ophthalmology Center had been chose in this study, and all the right eye of each person was selected for retrospective case statistics (30 eyes). the measure instruments, including A scan pachymeter and endothelium microscope, were used to the long-term continuous supervise, which involved the central and para-peripheral corneal thickness, corneal endothelium and corneal conjunctival complications rate. Then the 30 patients were divided into two groups: the moderate-low myopia group is less than -4.00 D with 12 patients (24 eyes), and the high myopia group is more than -5.00 D with 10 patients (20 eyes). And the difference between two groups was involved in this research. The one-way analysis of variance was used to compare before, after six months, after one year, after three years, after five years and after seven years OK lens wearing for the patients. And the variance analysis was used to compare between moderate-low and high myopia groups. Corneal thickness analysis during these seven years: the average central corneal thickness before and after seven-years wearing are (549.45 ± 33.72) and (538.97 ± 34.28) µm, respectively, and the central corneal thickness had no significant changes (F = 1.749, P = 0.076); The corneal thickness of nasal, superior, temporal and inferior also had no significant changes (P > 0.05). The average corneal endothelial cell densities before and after seven-years wearing are (3188.53 ± 272.25) and (3186.64 ± 278.69) num/mm(2), respectively, and the corneal endothelial cell density had no significant changes during seven years wearing (F = 2.204, P = 0.088). The average hexagonal cell ratio before and after seven-years wearing are 66.18% ± 6.42% and 64.65% ± 8.03%, respectively, and the hexagonal cell ratio had no significant changes during seven-years wearing (F = 2.097, P = 0.085). The average cell area and coefficient of variation also had no significant change during seven-years wearing (F = 2.143, 2.114; P > 0.05). There was also no statistics significance between moderate-low and high myopia of the endothelial cell and the corneal thickness change with long-term OK lens wearing. The slight corneal conjunctival complication was occurred during seven-year wearing, such as corneal fluorescence stain (less than 7%), and no serious complication was happened during seven-year wearing. In generally, it is safety for youth with long-term scientific and standardized wearing high Dk material orthokeratology contact lens.