New methods and techniques for sensing the wave aberrations of human eyes.

During the past decade, there has been a remarkable expansion of the application of wavefront-related technologies to the human eye. The ability to measure the wavefront aberrations (WA) of an individual eye has greatly improved our understanding on the optical properties of the human eye. The development of wavefront sensors has further generated an intensive effort to revise methods to correct vision. Wavefront sensors have offered the promise of a new generation of visual correction methods that can correct high order aberrations beyond defocus and astigmatism, that is, the wavefront-guided excimer laser platforms and adaptive optics, thus improving visual performance or fundus imaging at unprecedented spatial resolution. On the other hand, current wavefront technologies suffer from some inaccuracies that may limit a wider expansion in the clinical environment. Several innovative approaches have been developed to overcome the limits of standard wavefront sensing techniques. Curvature sensing, pyramid sensing and interferometry currently represent the most reliable methods to revise and improve the measurement and reconstruction of the WA of human eyes. This review describes advantages and disadvantages of current wavefront sensing technologies and provides recent knowledge on innovative methods for sensing the WA of human eyes. In the near future, we expect to benefit from these new wavefront sensor elements, including their application in the personalised correction of optical aberrations and adaptive optics imaging of the eye.

Evaluación de la película lagrimal con métodos diagnósticos invasivos vs método diagnóstico no invasivo / Invasive Diagnostic Methods vs. Non-Invasive Diagnostic Methods in the Evaluation of Tear Film

Debido a la gran importancia fisiológica y óptica que representa la película lagrimal para el correcto funcionamiento del ojo humano, una acertada evaluación y diagnostico de cualquier tipo de anomalía o alteración, ya sea en sus mecanismos de secreción, estabilidad o calidad, de una o todas sus capas, se convierte en una imperiosa necesidad para la práctica optométrica y oftalmológica. La evaluación de la película preocular lagrimal (PLPO) es de gran ayuda diagnóstica en salud visual. En muchos países se vienen empleando técnicas no invasivas, basadas en interferometría 1, 2, 3; las técnicas invasivas (BUT) tiempo de rompimiento de la película lagrimal, han demostrado no tener validez significativa por su baja reproducibilidad 4,5 y por provocar una alteración bioquímica de la película lagrimal, inducida por la fluoresceína. Este estudio se llevó a cabo con el fin de evaluar una técnica de rompimiento de la película lagrimal no invasiva (BUTNI) con Tearscope® de Keeler U.K., basada en principios físicos de interferometría, a través de colores de interferencia generados por las diferentes longitudes de onda 6, 7, 8. Este instrumento mide el espesor de la capa lipídica y el reservorio lagrimal, e igualmente permite observar la calidad de la película lagrimal. Se escogió una muestra de 60 sujetos presumiblemente sanos (n= 60), de acuerdo con los criterios de inclusión y exclusión y por medio del cuestionario validado McMonnies 9, 10, 11, para diagnóstico de ojo seco, se evaluaron ambos ojos. Con el fin de descartar alteraciones en la visión del color, los examinadores fueron sometidos a la prueba Farnsworth D1512 para evitar sesgos en la observación de los patrones de colores con el Tearscope. En una primera sesión se evaluaron el BUTNI/h 7,/h 8, BUT con fluoresceína al 2 por cien (FulGlo) y Schirmer Test I13, 14, 15 y en la segunda sesión Schirmer Test II con proximetacaína al 0,5 por cien, para evitar la interacción farmacológica entre proximetacaina y fluore...

Three-dimensional confocal microscopy of the living human eye.

Three-dimensional confocal microscopy of the living eye is a major development in instrumentation for biomicroscopy of the eye. This noninvasive optical technology has its roots in the application of optics to reflected light imaging of the eye. These instrument developments began with Leeuwenhoek's use of his single lens microscope to investigate the structure of the eye. There followed a series of connected instruments: the ophthalmoscope, the slit lamp, the specular microscope, and the clinical confocal microscope. In vivo confocal microscopy produces high contrast, reflected light images or optical sections through the depth of living ocular tissue. Stacks of registered optical sections can be transformed by computer visualization techniques into three-dimensional volume images of ocular tissues: cornea, ocular lens, retina, and optic nerve. The clinical confocal microscope has resulted in new diagnostic techniques and new cellular descriptions of ocular disorders and pathology.

The application of interferometry to optical astronomical imaging.

In the first part of this review we survey the role optical/infrared interferometry now plays in ground-based astronomy. We discuss in turn the origins of astronomical interferometry, the motivation for its development, the techniques of its implementation, examples of its astronomical significance, and the limitations of the current generation of interferometric arrays. The second part focuses on the prospects for ground-based astronomical imaging interferometry over the near to mid-term (i.e. 10 years) at optical and near-infrared wavelengths. An assessment is made of the astronomical and technical factors which determine the optimal designs for imaging arrays. An analysis based on scientific capability, technical feasibility and cost argues for an array of large numbers of moderate-sized (2 m class) telescopes rather than one comprising a small number of much larger collectors.