Visual optics in toads (Bufo americanus)

Mathis, Ute; Schaeffel, Frank; Howland, Howard C.

doi:10.1007/bf00612429

Cited by 44 publications

(32 citation statements)

References 29 publications

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“…5C) is slightly higher than the average of the ratio taken from many other vertebrate species (about 0.6; Hughes 1977, p 654). The f/number declines slightly with age, resulting in a 30% brighter image at day 60 than at day 10; this change is less than in the chicken (50 versus 1 day of age: + 49%; Schaeffel et al 1986) or in the toad (adult toad versus tadpole: + 350%; Mathis et al 1988). …”

Section: Schematic Eye Modelling and Calculation Of Image Magnificatimentioning

confidence: 99%

Emmetropization and optical development of the eye of the barn owl (Tyto alba)

Schaeffel

Wagner

1996

J Comp Physiol A

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1. We have studied the development of the refractive state in young barn owls (Tyto alba pratincola). Strikingly, the eyes had severe refractive errors shortly after lid opening (which occurred around day 14 after hatching; average from 6 owls: 13.83 _ 1.47 days). Refractive errors vanished in the subsequent one or two weeks (Fig. 1, Fig. 2). 2. Refractive errors did not differ by more than 1 diopter (D) in both eyes of an individual (Fig. 2). Thus, non-visual control of eye growth was sufficient to produce non-random refractions. However, visual input was finally required to adjust the optical system to emmetropia. 3. Using in-vivo A-scan ultrasonography of ocular dimensions (Fig. 4A), photokeratometric measurements of corneal radius of curvature (Fig. 4B), and frozen sections of excised eyes (Fig. 3), we developed paraxial schematic eye models which described age-dependent changes in ocular parameters and were applicable through the ages from lid opening to fledging (Table 1). A schematic eye for the adult barn owl (European subspecies: Tyto alba alba) is also provided. Eye sizes in an adult owl of the American (Tyro alba pratincola) and the European subspecies (T. alba alba) were similar despite of different body weights (500 g and 350 g, respectively). 4. The schematic eyes were used to test which ocular parameters might have caused the recovery from refractive errors. However, none of the ocular dimensions measured underwent obvious changes in their growth curves as visual input became available. Apparently, F. Schaeffel ([5~)

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Section: Schematic Eye Modelling and Calculation Of Image Magnificatimentioning

confidence: 99%

Emmetropization and optical development of the eye of the barn owl (Tyto alba)

Schaeffel

Wagner

1996

J Comp Physiol A

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“…Under natural conditions, adult Xenopus are active at night and inhabit murky water, making it unlikely that vision is used to detect objects at great distances (Elepfandt 1996). Mathis et al (1988) found that Xenopus are hyperopic in water, also indicating that vision is not highly developed for image formation. Little is known about the behavioral development of visual sensitivity in tadpoles over metamorphosis.…”

Section: Role Of Other Sensory Cuesmentioning

confidence: 99%

Lateral line-mediated rheotactic behavior in tadpoles of the African clawed frog (Xenopus laevis)

2004

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Tadpoles (Xenopus laevis) have a lateral line system whose anatomical structure has been described, but whose functional significance has not been closely examined. These experiments tested the hypothesis that the lateral line system is involved in rheotaxis. Tadpoles in developmental stages 47-56 oriented toward the source of a water current. Orientation was less precise after treatment with cobalt chloride or streptomycin, but was similar to that of untreated animals after exposure to gentamicin. In no current conditions, tadpoles exhibited a characteristic head-down posture by which they held themselves in the water column at an angle around 45°. This body posture became significantly less tilted in the presence of water current. Treatment with cobalt chloride or streptomycin increased the angle of tilt close to that seen in no current conditions, while gentamicin treatment tended to decrease tilt angle. The data are consistent with anatomical and physiological findings that tadpole neuromasts are similar to superficial, but not canal, neuromasts in fishes, and they suggest that the lateral line system is involved in both directional current detection and currentrelated postural adjustments in Xenopus.

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“…If the LEDs are flashed in sequence, the fundus reflex appears to move in the pupil. Although this procedure proved to be very useful for refracting freely behaving animals (Mathis, Schaeffel & Howland, 1988;Schaeffel & Mathis, 1991;Wagner & Schaeffel, 1991), it is not very useful for a dynamic photorefraction because (1) the resolution of the technique is optimal only for a certain eccentricity and LEDs at that particular eccentricity are only flashed one-fifth of the time, and (2) the edge of the light crescent cannot easily be detected by imageprocessing computer programs because of scattered light in the eye (Hodgkinson, Chong & Molteno, 1991;Schaeffel & Howland, 1991). A program of this kind detects an edge of a light crescent in the pupil even if it is not present because there is always a brightness gradient in the pupil due to the scattered light.…”

Section: Methodsmentioning

confidence: 99%

Inter‐individual variability in the dynamics of natural accommodation in humans: relation to age and refractive errors.

Schaeffel

Wilhelm

Zrenner

1993

The Journal of Physiology

241

225

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SUMMARY1. To study the relationship between accommodation under natural viewing conditions, age and refractive errors, we have measured time courses of accommodation in thirty-nine human subjects aged 5-49 years using a newly developed technique. The technique is based on infrared photoretinoscopy and involves fully automated on-line image processing of digitized video images of the eyes with a sampling rate of 5 3 Hz.2. The distance between the subject and the video camera was about 13 m. Head movements of the subject required little restriction because the eyes were automatically tracked in the video image by the computer program. All subjects were tested under binocular viewing conditions. 3. Both refraction of the right eye and pupil diameter were measured with a precision of 0-2-0{4 dioptres (D) and 041 mm, respectively, and were plotted on-line. The data were subsequently automatically analysed. 4. Automated infrared photoretinoscopy proved to be very convenient and easy to handle in both children and adults.5. The maximal speed of accommodation for a target at a distance of 5 D declined in the subjects with age (from up to 2P7 ID s-' for accommodation and 32 7 D s-' for subsequent accommodation to a distant target ('near to far accommodation') in children down to 2-18 D s-' in adults). There was a striking inter-individual variability in the maximum possible speed of accommodation and near to far accommodation.6. Speed of accommodation and of near to far accommodation was correlated for each subject. However, in most of the subjects, the process of near to far accommodation was faster than accommodation (P < 0005, if averaged over all subjects). This correlation was independent of age.7. The accommodation-induced pupillary constriction (pupillary near response) was absent in children for a 4 D target; even at 10 D, there was no reliable pupillary response. The pupillary near response increased to about tP6 mm D-of accommodation at the age of 47. Since a pupillary near response could still be elicited MUS 1:313

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Visual optics in toads (Bufo americanus)

Cited by 44 publications

References 29 publications

Emmetropization and optical development of the eye of the barn owl (Tyto alba)

Emmetropization and optical development of the eye of the barn owl (Tyto alba)

Lateral line-mediated rheotactic behavior in tadpoles of the African clawed frog (Xenopus laevis)

Inter‐individual variability in the dynamics of natural accommodation in humans: relation to age and refractive errors.

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