Dynamic aberrometer/topographer designed for clinical measurement and treatment of highly aberrated eyes

Abstract

The human eye is a complex optical system with multiple elements. It is aspheric, nonsymmetric, and time dependent; yet, overall it has incredible performance. There have been various instruments developed over the years to measure and then to guide treatment to correct for ocular aberrations. As the development of these instruments (and treatments) has progressed, we have sought to correct more difficult cases, which may be more aberrated, time-dependent, or difficult in some other way. To this end, we have developed a new dynamic aberrometer that expands the boundaries of measurement capability with the aim of measuring and treating more difficult cases. This aberrometer has been designed that incorporates high-resolution Shack-Hartmann wavefront sensing, full gradient (spot) corneal topography, dynamic acquisition, and a subjective digital refractometer. This instrument is designed to measure extremely high aberrations and to provide information for treatment in multiple modalities. A small clinical study was conducted with subjects ranging from 23 to 64 years old to evaluate the effectiveness of the dynamic analysis at selecting a refraction. Examples are presented for measurements with keratoconus, irregular corneas, and tear-film irregularity. In the clinical study, young subjects showed an overall +0.27 D reduction in instrument induced myopia using dynamic measurement compared to a snapshot. The instrument has a large dynamic range for measuring subjects with keratoconus and other aberrated corneal conditions. The new instrument is effective at providing information needed for treatment in multiple modalities. The subjective digital refractometer corrects the fixation target for the objectively measured low-order aberrations (defocus and astigmatism). This provides immediate subjective feedback on the objective refraction and, with the ability to manually adjust the refraction parameters, the ability to compare objective and subjective refractions in the same setting.