A new computerised video-aberroscope for the determination of the aberration of the human eye.

We have developed a video-based system for the acquisition and analysis of images produced by an aberroscope. The aberroscope uses a helium-neon laser to project a shadow image of a grid onto the retina. The retinal image is, in its turn, imaged onto a CCD video camera. As the grid forms a shadow image, the position of each grid intersection at the retina is affected by the aberrations of the eye. The emergent beam is imaged by the whole pupil, hence the grid shape is little affected by the eye's optics. We compute the aberrations of the eye by measuring the distortions of the grid. A video-digitiser converts the video camera image into data that can be processed by an Apple Power Macintosh computer using an image processing program (NIH Image V1.57). The program locates the grid intersection positions and computes the coefficients of a Taylor polynomial that describes the wavefront aberration. This technique has significant advantages over photographic methods that use manual image assessment. It gives immediate image storage and analysis, the ability to screen out poor quality images, requires significantly less or no operator interaction and is less labour intensive.