Comparison of a ray-tracing refractometer, autorefractor, and computerized videokeratography in measuring pseudophakic eyes

Abstract

Spherical and cylindrical refractive data obtained with the Tracey system correlated well with those derived from MR; however, there was a mean spherical error of approximately 1.10 D. Further work is required to refine the accuracy and range of this device.

Repeatability of topographic and aberrometric measurements at different accommodative states using a combined topographer and open-view aberrometer

“…In addition, it can achieve a high sampling rate even with small pupils because the number of spots does not depend on the pupil size. 3,9,16 On the other hand, this nonconstant spot separation also results in lower resolution for larger pupils.…”

“…A good correlation between refractive data obtained with the device and subjective manifest refraction has been shown. 9 The subjects fixated on targets through the viewing path of the aberrometer. Because variations in the subjects' line of sight could cause off-axis readings and lead to differences in measurement results, 4,10 an elongated target holder was installed on top of the instrument to ensure carefully aligned near targets at 0.4 to 1.0 m (2.5 to 1.0 D) ( Figure 1).…”

Comparison of laser ray-tracing and skiascopic ocular wavefront-sensing devices

“…The device projects 64 light rays in programmable scan pattern (in default on four concentric circles) across the pupil in succession and detects the retinal location of reflection with the help of two linear charged coupled device (CCD) arrays. 13,14 On the basis of these measurements, the device calculates the retinal point spread function and subsequently the wavefront aberrations. In default setting of automatic mode, it scans at the largest possible pupil area and displays wavefront data.…”

“…There have been several other studies of wavefront measurement device reproducibility. 13,14,22 These have included the Tracey device and the WaveScan system (VISX, Santa Clara, CA, USA) as well as a method using Hartmann-Shack techniques. These studies found that the standard deviation of the conventional refractive index measured by wavefront devices was between 0.1 and 0.5D.…”

Desempenho visual na correção de miopia com óculos e lentes de contato gelatinosas

“…As aberrações ópticas, neste estudo, foram medidas com o aberrômetro Zywave ® que utiliza o sensor de Hartmann-Shack, o qual mede as aberrações oculares totais. Outros videoceratoscópios computadorizados podem medir a forma corneana, desenhar mapas de elevação e realizar a decomposição polinomial que é utilizada para determinar as aberrações cornea- nas (15)(16) . O conhecimento das aberrações de frentes de onda corneana e lenticular é essencial para o entendimento da natureza de cada aberração e para sua correção.…”