Aspheric topographical features of the anterior surface of the human crystalline lens / 国际眼科杂志(Guoji Yanke Zazhi)

ABSTRACT

AIM: To investigate the topography of the anterior surface of the human crystalline lens. ·METHODS: A Non-contact three-coodinate measuring system was utilized to scan the anterior surfaces of 8 human eye lenses in vitro. Acquired data were processed and computer models of the anterior lens surfaces were made using the program (Surfacer v 10.0). The to-pography of the anterior lens surfaces were established. Radii of curvature were measured at preset spots over the lens surfaces and two way analysis of variance was performed. The data were analysed to determine whether the radius of curvature varied systematically with the position on the lens surface from which the measurement was made. Lens surface asymmetric index (LSAI) was defined and calculated. The vertical and horizontal meridians of the modeled lens were calculated, and the best curve fit to any conic section was determined. ·RESULTS: The topography of the anterior lens surface indicated that the central zone (the central radius of curvature is (9.09±0.80)mm was steeper than that of the peripheral zone(17.05±2.20)mm. Two way analysis of variance of the radii of curvature at preset spots over the lens surfaces showed that the differences were statistically significant (P ＜ 0.05). Curve regression of radii of curvature at preset spots and their distances to the surface center revealed that the correlation of them was the third power function. LSAI increased steadily from the lens surface center(0.013±0.005) to the periphery(0.184± 0.065). The dots on the horizontal and vertical meridians were fit to four kinds of curves, and the determinate coefficient of hyperbola fit were the largest (0.9989-0.9999). ·CONCLUSION: The anterior lens surface is imperfectly rotational symmetric. Moreover, the nearer to the center, the more rotational symmetric it is. Radii of curvature increase nonlinearly from the surface center to the periphery. Anterior lens surface is typically hyperbolic.