PubMed HealthSearch

PubMed · 874592

Aberration tolerances for visual optical systems.

Abstract

The effects of aberrations on images formed by a total system, including the eye, are assessed in terms of modulation threshold, grating detectability, and modulation transfer functions. The effects of approximately one and two waves of third-order spherical aberration, coma, and astigmatism on the total system modulation transfer function are investigated using three-bar resolution targets and Ronchi rulings in two separate psychophysical experiments. The results of both experiments indicate that the experimentally determined system modulation transfer function is closely approximated by the theoretically calculated modulation transfer function of the total system optics (dioptrics included) in the presence of instrument aberrations. The data indicate that the eye accomodates of a "best focus" when spherical aberration and astigmatism (but not coma) are present in the instrument. The quantitative data are used to determine aberration tolerances for instruments that are designed for specific visual tasks and that employ simple targets similar to those investigated.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M K Giles. 1977. Aberration tolerances for visual optical systems.. https://doi.org/10.1364/josa.67.000634

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Development of accommodation and convergence in infancy.

Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.

Accommodation, Ocular

Steady-state accommodation and ocular biometry in late-onset myopia.

The steady-state accommodative responses of emmetropes and late-onset myopes was measured for an array of numbers located at -1, -3 and -5 dioptres using an objective infra-red optometer. Responses were compared for passive (reading numbers) and active (adding numbers) conditions. For the passive condition, the late-onset myopes showed a significantly lower accommodative response than the emmetropic group. No significant differences were found between the two groups for the active condition. Ocular biometric characteristics were also measured in emmetropes, late-onset myopes and early-onset myopes using keratometry and ultrasonography. No significant differences in corneal curvature, anterior chamber depth and crystalline lens thickness were found between the groups. Late-onset myopes exhibited significantly deeper vitreous chambers than emmetropes, which more than accounted for the difference in refractive error between the two refractive groups. We conclude that, while significant differences exist in the accommodative responses of late-onset myopes and emmetropes, late-onset myopia is due predominantly to elongation of the vitreous chamber.

Accommodation, Ocular

Focusing and accommodation in the brown kiwi (Apteryx australis).

Brown kiwis are an endangered species of nocturnal, flightless birds which are native to New Zealand. The resting focus of two specimens has previously been studied by retinoscopy in a zoo while the birds were restrained by their keeper (Sivak and Howland 1987). Those birds appeared to be hyperopic (farsighted) by 2-7 D. In this study, examination with infrared photorefraction of the focusing of two unrestrained, feeding birds showed that they could focus objects at infinity and objects in their immediate environment and that they had modest powers of accommodation. Measurements on two 6 month old kiwi chicks showed their corneal radius of curvature to be between 2.90 and 3.00 mm (117 D and 101 D in power).

Accommodation, Ocular