Principles and Clinical Applications of Ray-Tracing aberrometry (Part I)

Resumen

ABSTRACT: The visual quality of the eye depends on several optical and neural factors. In the nineteenth century, Helmholtz found optical errors that could not be corrected using existing optical theory. In the process of image formation in the human eye there are three major sources of degradation: A) Diffraction B) Scattering and c) Optical Aberration. Optical aberrations are the most important source of impairment of the quality of the optical system. The definition of an optical aberration is a departure of the performance of an optical system from the predictions of paraxial optics. In an imaging system, it occurs when light from one point of an object does not converge into (or does not diverge from) a single point after transmission through the system. Aberrometers are currently the most important tools for estimating optical conditions so that a more complete understanding of optical error can be quantified and corrected . A variety of principles are used, such as Hartmann-Shack, Tscherning, Ray Tracing and automatic retinoscopy. Aberrometry presents diagnostic and therapeutic applications. We can determine the visual quality and objectively interpret the eye´s ability to resolve spatial frequency and contrast sensitivity. At other times analyze refractions on a multi-zone basis, assess aberropia in the most complex cases (corneal transplants, irregular corneas, cataracts ..) that cannot be measured with other devices. Aberrometry can also be applied in therapeutics goals such as wavefront-guided treatments, designing lenses to compensate optical aberrations or Adaptive Optics. In this review we analyze the Ray-tracing aberrometry and its application to daily clinical practice.The ray tracing principle is a serial, double-pass method using forward projection that can be implemented in both an objective and subjective manner. By integrating corneal topography with wavefront aberrometry, the iTrace provides a unique analysis that substracts corneal from total aberrations in order to isolate the internal anerrations of the eye. It also can measure accommodation with a near-point refraction feature