Forward ray tracing for image projection prediction and surface reconstruction in the evaluation of corneal topography systems.

A forward ray tracing (FRT) model is presented to determine the exact image projection in a general corneal topography system. Consequently, the skew ray error in Placido-based topography is demonstrated. A quantitative analysis comparing FRT-based algorithms and Placido-based algorithms in reconstructing the front surface of the cornea shows that arc step algorithms are more sensitive to noise (imprecise).

Equivalent refractive index of the human lens upon accommodative response.

Purpose: To experimentally verify the suggestion of Gullstrand (1909), i.e., that the equivalent refractive index of the human lens increases with accommodation.

Development of a ciliary muscle-driven accommodating intraocular lens.

Purpose: To develop a ciliary muscle-driven accommodating intraocular lens (IOL) that has a large and predictable range of variable power as a step toward spectacle independence.

Setting: Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands.

Methods: A concept IOL that has a rotating focus mechanism and a mechanical frame that can operate within the range of ciliary muscle contraction of a typical 60-year-old human eye was designed.

Changes in the internal structure of the human crystalline lens with diabetes mellitus type 1 and type 2.

Purpose: To investigate the effect of diabetes mellitus (DM) type 1 and type 2 on the internal structure of the lens.

Design: Observational cross-sectional study.

Participants And Controls: One hundred seven patients with DM type 1, 106 patients with DM type 2, and 75 healthy control subjects.

Constant volume of the human lens and decrease in surface area of the capsular bag during accommodation: an MRI and Scheimpflug study.

Purpose: A change in surface area of the capsular bag and a change in volume of the lens can indicate whether a change in the shape of the lens during accommodation is due to the compressibility or the elasticity of the lens material.

Methods: 3D magnetic resonance imaging (MRI) was used to image the complete shape of the lens in a group of five healthy subjects between 18 and 35 years of age. A parametric representation of the cross-sectional shape was fitted to the edges of the lens, which were determined with a Canny edge filter.