ABSTRACT
AlM: To research the characteristics of positive relative accommodation ( PRA) , negative relative accommodation (NRA) and PRA/NRA ratio in myopes. To analyze the relationship among PRA, NRA, PRA/NRA ratio, spherical equivalent degree, years and habbits of wearing glasses, myopia development, and pupil diameter.METHODS: Aretrospective study of ninety eyes in the 180 th Hospital of Quanzhou from August 2014 to December 2014. PRA, NRA and PRA/NRA ratio were compared among low, moderate, high myopes and emmetropes. The correlation were analyzed among PRA, NRA, PRA/NRA ratio, spherical equivalent degree, years and habbits of wearing glasses, myopia development and pupil diameter. PRA, NRA, PRA/NRA ratio, years and habbits of wearing glasses and pupil diameter were compared between progress group and non-progress group.RESULTS: ( 1 ) Without statistical differences in age, sex and intraocular pressure, PRA and PRA/NRA ratio of myopes were lower than emmetropes, while NRA was higher. (2) Without statistical differences in age, sex and intraocular pressure, PRA, PRA/NRA ratio and NRA had no statistical differences while years and habbits of wearing glasses had statistical differences among low, moderate, high myopes. ( 3 ) With longer years of wearing glasses, PRA, PRA/NRA ratio were larger and NRA, pupils were smaller. ( 4 ) Without statistical differences in age, diopter and intraocular pressure, one group which were not easy to deepen degree had more often-wear-glasses myopia patiens and longer years of wearing glasses, the other group which were easy to deepen degree had more seldom-wear-glasses myopia patiens and shorter years of wearing glasses.CONCLUSlON: PRA and PRA/NRA ratio of myopes were lower than emmetropes, while NRA was higher. No correlated relation was detected among PRA, NRA, PRA/NRA ratio, spherical equivalent degree and myopia development. lt suggests the onset and progress of myopia are related to many factors. Wearing-glass timely and accurately can release the decline of PRA and PRA/NRA ratio and slow down degree development in myopes.
ABSTRACT
AIM:To discuss the related factors that affected the stability of posterior corneal surface after laser in situ keratomileusis ( LASIK) . METHODS:About 64 patients (64 eyes) were enrolled. The correlation among the changes in posterior corneal surface 6 month after LASIK, surgery method, corneal flap thickness ( FT ) , ablation thickness ( AT ) , postoperative residual corneal stroma thickness ( RCST ) , preoperative thinnest corneal thickness ( CT ) , flap thickness/preoperative thinnest corneal thickness ( FT/CT ) , ablation thickness/preoperative thinnest corneal thickness ( AT/CT) , postoperative residual corneal stroma thickness/preoperative thinnest corneal thickness ( RCST/CT) , anterior and posterior preoperative corneal height, the difference of the forward shift in posterior corneal surface ( diff value ) of preoperative and preoperative intraocular pressure were analyzed. RESULTS: The changes of diff value between preoperative and postoperative were related with diopter (r=0.419, P=0.014), AT (r=0.394, P=0.023), AT/CT (r=0.501, P=0.004), Diff value of preoperative (r=0.501, P=0. 004), RCST (r=-0. 385, P=0. 033) and RCST/CT (r=-0. 401, P=0. 025). The changes of height value from posterior corneal surface between preoperative and postoperative were related with diopter (r=0. 520, P=0. 002), AT (r=0.504, P=0. 003), AT/CT (r=0. 442, P=0. 013), Diff value of preoperative (r=0. 624, P=0. 000) and RCST/CT (r=-0. 394, P=0. 028). CONCLUSION: AT, RCST, AT/CT, RCST/CT and diff value of preoperative should be the key index that predicted the stability of posterior corneal surface after LASIK,the further research will give the range of safety value.