chapter 2, Fundamentals of Ocular Wavefront Correction

Excerpt

For vision correction, the key is to help patients achieve good visual performance. In most cases, this means good visual acuity and good contrast sensitivity. The ocular aberrations can be considered as a combination of the spherocylindrical aberrations and irregular aberrations. In wavefront optics terminology, they are called low-order and high-order aberrations, respectively. In general, the degradation of visual performance due to the low-order aberrations is much higher than that due to the high-order aberrations. Traditional vision correction thus focuses on the correction of low-order aberrations.

However, to achieve a better standard of vision, it is not enough just to correct low-order aberrations. For example, professional shooting athletes and fighter pilots may seek supervision to enhance their performance. The correction of higher order aberrations, however, is not limited to these small groups. The average person may seek enhanced vision to provide a reserve for ageing vision or to eliminate night-vision problems, such as halos, glares, etc.

2.1 Principle of Phase Conjugation

Degradation of celestial images due to astronomical seeing has been a huge problem for centuries in astronomical observations. In 1953, Bobcock proposed a solution that has evolved into an important technology called adaptive optics.[1] The major concept in adaptive optics is phase conjugation, where optical aberrations can be compensated by a deformable mirror. Today, applications of adaptive optics can be found in astronomy, [2] the military, [3] and vision. [4]

This section discusses some of the basic concepts, such as the wavefront and the optical path difference, as well as their use in phase conjugation for the purpose of vision correction.