Abstract:

Objective To evaluate the effects and safety of long-term overnight orthokeratology (ortho-k) in adolescent with low to moderate myopia. Design Retrospective study. Participants 68 myopic juvenile (135 eyes) with ortho-k lens wearing more than 5 years. Methods Subjects were divided into low-myopia
(SE -0.75~-3.00 D) and moderate-myopia (SE -3.25~-5.75 D) groups. Axial length (AL) was measured at baseline and every year after ortho-k lens wearing. The cell density (CD),  hexagonal cell ratio (HEX),  and coefficient of variation (CV) of the corneal endothelial cell layer were measured at each year. Data were analyzed using repeated one-way ANOVA and t-test analyses. Main Outcome Measures AL,  CD,  HEX,  CV. Results During the five years of observation periods,  the AL of both groups increased (F=16.863,  6.780; P=0.000,  0.000). The annual axial growth after ortho-k lens wearing for 1 to 5 years was (0.28±0.15)mm,  (0.21±0.16)mm,  (0.17±0.15)mm,  (0.12±0.08)mm and (0.11±0.06)mm in low-myopia group; and the data of moderate-myopia group was (0.25±0.14)mm,  (0.16±0.10)mm,  (0.15±0.09) mm,  (0.10±0.07)mm and (0.08±0.05)mm respectively. With time prolonged,  the annual axial elongation of both groups decreased (F=28.434,  21.296; both P<0.001),  and the moderate-myopia group represented less axial elongation after 5 years (t=6.577; P=0.01). After ortho-k lens wearing for 1 to 5 years,  the CD (F=1.239,  1.421; P =0.290,  0.216),  HEX(F=2.156,  2.227; P=0.058,  0.051) and CV(F =2.147,  2.038; P=0.059,  0.073) of the corneal endothelial cell layer remained stable,  and there was no significant difference of corneal endothelial cell layer changes between two groups (all P >0.05). Conclusions Five-year follow-up showed that ortho-k lens has a better effect on myopia control in moderate myopia than low myopia. Long term overnight wearing of ortho-k lens has no significant effect on corneal endothelial cells. （Ophthalmol CHN,  2018, 27：141-145）

Key words: orthokeratology, myopia control, axial length, corneal endothelial cell