AIM: To study the effect of wearing overnight orthokeratology(OK)contact lens on corneal topography and tears in adolescents.

METHODS: The diopter, corneal curvature, corneal surface regularity index(SRI), tear break-up time(BUT), Schirmer I test, and corneal fluorescent(FL)were recordedon 40(80 eyes)adolescent myopia patients(mean age 13.68±2.32 years), who had worn OK contact lensfor more than 1 year, with mean spherical equivalent refraction -3.61±1.48D before wearing OK contact lens. These indexes were tested and recorded before the patients' wearing OK contact lens and 5 times(1wk and 1, 3, 6, 12mo after the first wearing)during the patients' overnight wearing OK contact lens for 8～10 hours per day.

RESULTS: Compared with pre-wearing, at post-wearing OK contact lens 12mo, the mean spherical equivalent refraction was apparently decreased from -3.61±1.48D to -1.39±1.31D(P<0.01). The corneal curvature was significantly flattened from 42.29±1.55D to 40.13±1.41D(P<0.01). Mean SRI was increased from 0.34±0.01 to 0.37±0.01(P<0.01). Mean BUT was decreased from 10.39±2.25s to 7.26±1.77s(P<0.01). These indexes were stable at 1wk after wearing OK contact lens overnight and had no significant differences during the following(1, 3, 6, 12mo after wearing)tests(P>0.05). There were no significant differences on Schirmer Ⅰ test during the 12mo of OK wearing(P>0.05). The cases of corneal fluorescent staining increased were mainly grade I, and the number of corneal staining grade I at 1 wk and 1, 3, 6, 12 mo after wearing were 15 eyes(18.8%), 9 eyes(11.3%),13 eyes(16.3%), 9 eyes(11.3%), and 12 eyes(15.0%). BUT of corneal staining grade I wasdecreased significantly, compared with the BUT of corneal staining grade 0 during the 12mo of OK wearing(P<0.05).

CONCLUSION: OK contact lens can significantly decrease the degree of myopia and K value of corneal curvature without changing tear volume. However, tear film stability weakens, which needs regular follow-up.