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In this paper, the use of three liquid crystal displays (LCDs) as targets for an experimental corneal topographer is proposed. The main advantage is that the geometrical pattern in the target can be modified without moving any mechanical part to apply the dynamic point shifting (DyPoS) method. Some results on the capabilities of the LCDs, obtained with photo frames, for measuring a 6.37 mm radius of curvature calibration sphere, and applying the DyPoS method, are presented. It is shown that the error in measuring the radius of curvature with DyPoS is reduced to 3% of the real value and the RMS in elevation or sagitta differences is around 15 μm, 30% or 66% of the values obtained without DyPoS, respectively.

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In ophthalmology, the laser excimer corneal surface ablation used to correct the refractive eye defects, such as myopia, astigmatism and hyperopia and, more recently, presbyopia is known as refractive surgery. Typically, the characterization of the corresponding technique, as well as the laser accuracy, is performed by analyzing standard ablation profiles made on PMMA (polymethylmethacrylate) plates. A drawback of this technique is that those plates do not necessarily represent the dimensions of the cornea during the ablation. On the other hand, due to the time varying process of the eye aberrations, the direct eye refractometric measurements can produce some errors. We report in this work the interferometric analysis of the ablation profile obtained with refractive surgery, applied directly on a contact lens. In this case, the resultant ablation profile might be closer to the real profile as well as time invariant. We use, as a reference, a similar contact lens without ablation. The preliminary results of the characterization of the corresponding ablation profile are also presented.