Intraocular pressure fluctuations of growing chick eyes are suppressed in constant light conditions.

We report measurements of intraocular pressure (IOP) in growing domestic chicks at 12 h intervals, with three different lighting conditions. One group of chicks was raised in 12 h light and 12 h darkness (N), another in constant light (CL), and the third group was initially exposed to CL for three weeks then returned to N for either one week or four weeks (CLN). Pressures were measured in the middle of the light and dark periods (noon and midnight) for N and CLN birds, and at corresponding 12 h intervals for CL birds (also noon and midnight).

Plasticity in the growth of the chick eye: emmetropization achieved by alternate morphologies.

Both refractive properties of the eyes and ambient light conditions affect emmetropization during growth. Exposure to constant light flattens the cornea making chicks hyperopic. To discover whether and how growing chick eyes restore emmetropia after exposure to constant light (CL) for 3, 7, or 11weeks, we returned chicks to normal (N) conditions with 12h.

Lack of oblique astigmatism in the chicken eye.

Primate eyes display considerable oblique off-axis astigmatism which could provide information on the sign of defocus that is needed for emmetropization. The pattern of peripheral astigmatism is not known in the chicken eye, a common model of myopia. Peripheral astigmatism was mapped out over the horizontal visual field in three chickens, 43 days old, and in three near emmetropic human subjects, average age 34.

Visual accommodation and active pursuit of prey underwater in a plunge-diving bird: the Australasian gannet.

Australasian gannets (Morus serrator), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive.

The effects of light regimes and hormones on corneal growth in vivo and in organ culture.

When chicks are exposed to constant light (CL) during growth, their corneas become flatter and lighter in weight, and their anterior segments become shallower than those of chicks exposed to cyclical periods of light and dark. These effects have been correlated with CL suppression of cyclical changes in melatonin levels. The question of whether light directly influences corneal growth (e.

Photorefraction of eyes: history and future prospects.

A brief history of photorefraction, i.e., the refraction of eyes by photography or computer image capture, is given.

Morphometrics of corneal growth in chicks raised in constant light.

In this study we wish to augment our understanding of the effect of environment on corneal growth and morphology. To understand how corneal development of chicks raised in constant light differs from that of 'normal' eyes exposed to cyclic periods of light and dark, white Leghorn chicks were raised under either constant light (approximately 700 lux at cage top) or in 12 h light/12 h dark conditions for up to 12 weeks after hatching. To determine whether corneal expansion is uniform, some birds from each group received corneal tattoos for periodic photographic assessment.

Role of the pineal gland in ocular development of the chick in normal and constant light conditions.

Purpose: To evaluate the role of the pineal gland in development of the chick eye in normal and constant light (CL) conditions.

Methods: Chicks (Gallus gallus) were raised in either a 12-hour light-dark cycle (12L/12D) or in CL, with or without opaque, removable hoods that covered the top of the head for 12 hours each day. An additional group was raised with opaque eye occluders over the right eye for 12 hours daily.

Changes in the refractive state during prey capture under low light in the nocturnal cardinalfish Apogon annularis.

Many nocturnal and crepuscular fish use vision to feed and function under low light levels. However, little is known about their ability to accommodate or their visual acuity under these light levels. We used Infrared Photoretinoscopy to track the refractive state of the eye during prey capture under low light in Apogon annularis, a nocturnal reef fish.

Growth of the cornea from infancy to adolescence.

The intraocular distance and iris diameter of children and young adolescents were measured, with the aid of a measuring microscope, from photographs of their faces. True intraocular distance was measured with an intraocular caliper at the same time that the photographs were taken. These data were then compiled and horizontal visible iris diameters (HVIDs) were calculated.

Allometry and scaling of wave aberration of eyes.

The scaling of root mean square (RMS) wave aberration in an isometrically growing eye is investigated, along with changes due to measurements made at different relative pupil sizes. It is found that, relative to an initial state, if an eye expands in all directions by the factor k, and the wave aberration is then measured at a relative pupil size which has changed over the pupil size used for the original measurement by a factor b, the new wave aberration will be increased or decreased by a factor kb(n), where n is the exponent relating RMS wave aberration, to pupil radius, r, in the equation: RMS=qr(n) in the initial eye. This implies that, if wave aberration is measured in a growing eye with a constant measurement pupil size, the measured RMS will decrease by the factor 1/k(n-1).

Accommodative state of young adults using reading spectacles.

We examined the accommodative state of young adults wearing +2D and +3D reading spectacles under normal conditions and with the elimination of accommodative cues. Subjects' refractions were measured with an infrared PowerRefractor. Power of the vertical meridian was recorded for subjects viewing far and near targets in free space and through a Badal lens apparatus with and without reading spectacles.

The allometry and scaling of the size of vertebrate eyes.

We compiled data from the literature and colleagues to examine the relationship between eye axial length and body weight for vertebrates as well as birds, mammals, reptiles, and fishes independently. After fitting the data to logarithmic and semi-logarithmic models, we found that axial length of vertebrate eyes does obey a conventional logarithmic relationship with body weight rather than a semi-logarithmic relationship as suggested by the results of previous studies. The regression slopes and intercepts appear to be characteristic of various animal groups.

Compensation of corneal horizontal/vertical astigmatism, lateral coma, and spherical aberration by internal optics of the eye.

Both the anterior surface of the cornea and the internal optics (the posterior cornea, crystalline lens) contribute to the aberration of a wavefront passing through the eye. Artal, Guirao, Berrio, and Williams (2001) reported that the wavefront aberrations produced by the internal optics offset, or compensate for, the aberrations produced by the cornea to reduce ocular wavefront aberrations. We have investigated the wavefront aberrations of the cornea, internal optics, and complete eye on both the population and individual level to determine which aberrations are compensated and probable paths leading to that compensation.

Measurement of refractive state and deprivation myopia in two strains of mice.

Purpose: The mouse eye has a bright retinal image (f/number <1) but low optical quality (visual acuity about 0.5 cpd) that may render emmetropization unnecessary. However, this species is potentially a powerful model to study eye growth and myopia because its genome can be readily manipulated and has been completely sequenced.

The effects of constant and diurnal illumination of the pineal gland and the eyes on ocular growth in chicks.

Purpose: To investigate the effects of constant or 12-hour cyclic illumination of the pineal gland and the eyes on the growth of the chick eye.

Methods: Chicks (Gallus gallus, Cornell K Strain) were raised either under a 12-hour light-dark cycle of normal light or under constant light, with or without opaque removable hoods that covered the top of the head for 12 hours each day. A second group of chicks was raised under constant light with opaque eye covers that were worn on either both eyes or only the right eye for 12 hours each day.

Clinical features of the retinopathy, globe enlarged (rge) chick phenotype.

The purpose of the study reported here was to characterize the clinical aspects of the autosomal recessive retinopathy, globe enlarged (rge) phenotype in chicks (Gallus gallus). Rge/rge, rge/+ and +/+ chicks were studied from hatch to 336 days of age by general clinical examination, post-mortem examination, vision testing with an optokinetic device, ophthalmoscopy, biomicroscopy, tonometry, central corneal pachymetry, a-mode ultrasonography, infrared photoretinoscopy and photokeratometry. Additionally, preliminary electroretinographic and histopathologic investigations were performed.

Corneal power and underwater accommodation in great cormorants (Phalacrocorax carbo sinensis).

In great cormorants (Phalacrocorax carbo sinensis), corneal refractive powers, determined by photokeratometry, ranged between 52.1 diopters (52.1 D) and 63.

High order wave aberration of eyes.

This paper is concerned with the means and distribution of the wavefront variances and their root mean squares (RMS) of normal eyes, as measured by various techniques and computed for various pupil sizes. Using data from a subjective crossed cylinder aberroscope [Howland and Howland J. Opt.

Normal values and standard deviations for pupil diameter and interpupillary distance in subjects aged 1 month to 19 years.

Normal values of pupil diameters and interpupillary distances (PDs) were measured in a population of 1311 subjects (in 4294 visits) ranging from 1 month of age to slightly over 19 years of age. Subjects in this study were recruited from birth announcements in a local newspaper for a developmental vision project. Pupil sizes were measured photographically when the corneas were illuminated by 15.