Variation of axial and oblique astigmatism with accommodation across the visual field

In this study we investigated the impact of accommodation on axial and oblique astigmatism along 12 meridians of the central 308 of visual field and explored the compensation of corneal first-surface astigmatism by the remainder of the eye's optical system. Our experimental evidence revealed no systematic effect of accommodation on either axial or oblique astigmatism for two adult populations (myopic and emmetropic eyes). Although a few subjects exhibited systematic changes in axial astigmatism during accommodation, the dioptric value of these changes was much smaller than the amount of accommodation. For most subjects, axial and oblique astigmatism of the whole eye are both less than for the cornea alone, which indicates a compensatory role for internal optics at all accommodative states in both central and peripheral vision. A new method for determining the eye's optical axis based on visual field maps of oblique astigmatism revealed that, on average, the optical axis is 4.88 temporal and 0.398 superior to the foveal line-of-sight in object space, which agrees with previous results obtained by different methodologies and implies that foveal astigmatism includes a small amount of oblique astigmatism (0.06 D on average). Customized optical models of each eye revealed that oblique astigmatism of the corneal first surface is negligible along the pupillary axis for emmetropic and myopic eyes. Individual variation in the eye's optical axis is due in part to misalignment of the corneal and internal components that is consistent with tilting of the crystalline lens relative to the pupillary axis

Aberrometry: the past, present and future of optometry

2 pages.-- Guest editorial for 'Optometry and Vision Science', Vol. 80, No. 1 (January 2003).Aberrometry of the human eye has progressed rapidly from research tool to clinical application. To appreciate how rapidly the field of clinical aberrometry is evolving, consider the following quotation from the editorial introduction to the 1997 Optometry and Vision Science feature issue on visual optics research:"Contemporary visual optics research is changing our mindset, our way of thinking about the optical system of the eye, and in the process is re-defining the field of visual optics. In the past, optical imperfections of the eye were conceived as simple refractive errors - defocus, astigmatism, and perhaps a bit of prism. In the future, optical imperfections of the eye will be conceived in a comprehensive theoretical framework which expresses the combined effect of all the eye’s optical imperfections as a two-dimensional aberrations map. When treated as a mathematical function, the aberration map may be used to compute image quality on the retina for simple points of light, for clinical test targets, or any complex object in the real world. Such computations will become routine optometric tools of the future for predicting the visual benefit to the patient of a full aberration correction. The aberration map will also become a prescription for the ideal correcting optics provided by a new kind of contact lens, spectacle lens, inter-ocular lens, or by refractive surgery".The future has arrived! In this issue of Optometry and Vision Science, readers will learn of new discoveries that expand our basic understanding of aberrometry and the optical quality of the eye.Peer reviewe

Aberrometry: clinical and research applications

2 pages.-- Guest editorial for 'Optometry and Vision Science', Vol. 80, No. 2 (February 2003).Optometry has a history of taking the lead in correcting the optical defects of the eye. While the primary definition of optometry has changed as the profession has expanded its scope of practice, the secondary definition of optometry has remained unchanged. The second definition of optometry is the use of an optometer. The definition of optometer is any of several objective or subjective devices for measuring the refractive state of the eye. There is no better way of measuring the refractive state of the eye than to measure its wavefront error using state-of-the-art aberrometers. State-of-the-art aberrometry opens doors for new research and clinical applications while creating a new set of issues and opportunities. We will briefly discuss a few in this editorial.Peer reviewe