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At least 469 records · Page 26Linked to original sources
PubMed2000

Transcriptional regulation of atonal required for Drosophila larval eye development by concerted action of eyes absent, sine oculis and hedgehog signaling independent of fused kinase and cubitus interruptus.

Bolwig's organ is the larval light-sensing system consisting of 12 photoreceptors and its development requires atonal activity. Here, we showed that Bolwig's organ formation and atonal expression are controlled by the concerted function of hedgehog, eyes absent and sine oculis. Bolwig's organ primordium was first detected as a cluster of about 14 Atonal-positive cells at the posterior edge of the ocular segment in embryos and hence, atonal expression may define the region from which a few Atonal-positive founder cells (future primary photoreceptor cells) are generated by lateral specification. In Bolwig's organ development, neural differentiation precedes photoreceptor specification, since Elav, a neuron-specific antigen, whose expression is under the control of atonal, is expressed in virtually all early-Atonal-positive cells prior to the establishment of founder cells. Neither Atonal expression nor Bolwig's organ formation occurred in the absence of hedgehog, eyes absent or sine oculis activity. Genetic and histochemical analyses indicated that (1) responsible Hedgehog signals derive from the ocular segment, (2) Eyes absent and Sine oculis act downstream of or in parallel with Hedgehog signaling and (3) the Hedgehog signaling pathway required for Bolwig's organ development is a new type and lacks Fused kinase and Cubitus interruptus as downstream components.

Animals↗
PubMed1999

[Multiple cranial nerve deficits after eye injury and eye enucleation. A case report].

A 12-year old Simmental x Red Holstein cow was admitted to the clinic eight months after an eye laceration followed by eye extirpation. The region of the excised eye had healed, however, the cow had additional trigeminal and facial nerve palsy. Nevertheless, the cow was in good general condition, and therefore, was sent home without therapy. After delivering a sound calf, her physical condition deteriorated and she was slaughtered. Histologic examination of the brain revealed degeneration of the right optic nerve and right half of the chiasma opticum as well as left tractus opticus (opposite side); furthermore, degenerative changes with slight inflammation of the right vestibular nuclei were observed. Possible pathogenesis is discussed.

Animals↗
PubMed1992

An adjustment to eye movement measurements that compensates for the eccentric position of the eye relative to the center of the head.

We describe a procedure for modifying horizontal eye movement measurements in a way that effectively removes signal contributions due to the eccentric location of the eyes relative to the center of rotation of the head. This procedure helps standardize measured signals so that data collected under different experimental conditions and from different subjects may be compared directly. We also present techniques for accurately determining specific parameters of head geometry that are required by the procedure. This method may be used for modifying eye movement responses to visual target motion, head motion, or both, and does not assume continual fixation of the visual target. Also, this method may be employed when either curved (iso-distance) or flat display screens are used for presenting the visual stimuli.

Eye↗
PubMedDate not supplied

Causes of enucleation of the eye at Lagos University Teaching Hospital. A study of 101 eyes.

Causes of enucleation of the eye at Lagos University Teaching Hospital over a period of 10 years - January, 1976 - December, 1985 were reviewed. One hundred and one (5.7%) eyes were enucleated out of the 1758 eye operations performed over this period. Most of the patients were below the age of 30 but their mean age was 14.5 years. The three commonest causes of enucleation were tumours (41.7%) chronic inflammatory diseases (16.8%) and glaucoma (12.3%). Retinoblastoma was the commonest tumour encountered, and most of the patients presented late leaving enucleation as the main line of treatment. Staphyloma is the commonest chronic inflammatory disease, and frequently due to measles. Injury accounted for only (7.9%). Positive measures to eradicate measles and to reduce trauma are advocated.

Adolescent↗
PubMed1987

The eyes and the orbits of 2 species of fishes with "dorsal eyes".

The eyes of 2 species of fishes with dorsal eyes Uranoscopus oligolepis and Paralichthyes olivaceus were studied. In the Uranoscopus, ciliary projections were not conspicuous and in the Paralichthyes, the projections were small. 3 types of photoreceptors were observed in both species--rods, single cones and twin cones. In both species, the number of twin cones increased towards the central retinae and in the Paralichthyes, the single cones also increased in number. The rods were lowest in the central region. In the orbit, both species displayed complex solid bones. For example, the lateral border of the orbit was a complex formed by the lacrimal, suborbital, postorbital and parietal. In the Paralichthyes, the lateral orbital border was actually continuous with the orbital and parietal bones and the border was not distinct. The formation of fused plates would serve to restrict eye movement as well as to resist deep sea pressure acting from above.

Animals↗
PubMed1986

Solar radiation and the eye: a review of knowledge relevant to eye care.

Solar radiation has been implicated, with a variety of evidence, as a causative agent in photokeratoconjunctivitis, pinguecula and pterygium, nodular band keratopathies, epidermoid carcinoma, cataract, solar retinopathy, and macular degeneration. Much of the support for claims relating to chronic conditions having serious consequences and significant prevalence in the United States rests on investigations using animals and short-time exposures at high intensities. The direct applicability of these studies to humans in natural environments is uncertain, but they have been relied on because one cannot deliberately induce significant trauma in humans. The use of animal data is made difficult by the need to convert animal thresholds to human equivalents, to equate laboratory cycles and magnitudes of exposure to those in the natural environment, and to quantify the impact of avoidance and protective mechanisms. Risk can be assessed adequately only by epidemiological studies, but their potential has been only partially realized because of poorly controlled confounding variables. Epidemiologic evidence suggests that corneal trauma from ultraviolet radiation (UVR) is a risk of prolonged exposure in regions containing much ultraviolet (UV) or in highly reflective environments. The impact of UV-B on cataractogenesis has been investigated inadequately and no evidence exists for retinal trauma arising from routine exposure in even the brightest surroundings. However, there can be no question that enough solar energy reaches the earth to harm the eye if unattenuated. Damage to vision as a result of direct solar viewing demonstrates that unequivocally. The lack of clear evidence of radiation damage occurring other than in regions of high reflectivity and/or low horizons suggests that in normal surroundings there is little or no risk to the eye, although more careful epidemiological investigation is required before all concern can be ruled out completely. The major improvement required is the quantification of individual exposure histories. This step is necessary if we are to make significant progress toward better understanding the practical impact of solar radiation on the eye.

Conjunctiva↗
PubMed2003

National Eye Institute Visual Function Questionnaire in the Age-Related Eye Disease Study (AREDS): AREDS Report No. 10.

OBJECTIVES: To describe the vision-targeted, health-related quality of life, measured with the National Eye Institute Visual Function Questionnaire (NEI-VFQ), in patients with age-related macular degeneration, cataract, or reduced visual acuity; to determine the relationship between the NEI-VFQ subscale scores and clinical measures of visual function; and to assess the internal consistency and reliability of the NEI-VFQ subscales. DESIGN: The 39-item NEI-VFQ was administered at the 5-year clinic visit to 4077 Age-Related Eye Disease Study participants. RESULTS: The subscales of the NEI-VFQ had moderate to high internal consistency (Cronbach's alpha = 0.58-0.91). The NEI-VFQ scores for participants with advanced age-related macular degeneration in 1 or both eyes, severe nuclear opacity, reduced visual acuity, or cataract surgery generally were lower than scores for disease-free participants (P<.001). CONCLUSION: These findings support the use of the NEI-VFQ as a measure of vision-targeted, health-related quality of life among patients with age-related macular degeneration, cataract, or reduced visual acuity.

Aged↗
PubMed1975

Carcinoma metastatic to the eye and orbit II. A clinicopathological study of 26 patients with carcinoma metastatic to the anterior segment of the eye.

In 26 of 227 patients with carcinoma metastatic to the eye or orbit, metastasis to the anterior uveal tract was the predominating feature. There was a definite propensity for the tumor to involve the horizontal meridian of the iris or ciliary body, rather than the upper or lower portions. The site of the primary tumor in the 26 patients was as follows: lung 14; breast, 9; kidney, 2; and rectum, 1. Ocular symptoms and signs produced by the metastatic tumors at onset or during the course of the disease included decreased vision (80%), a visible mass (72%), redness of the eye (56%), pain (56%), glaucoma (56%), iridocylitis (44%), and hyphema (24%). The median survival of the 26 patients with metastasis to the anterior segment of the eye was only 5.4 months from the time of ocular surgery. This is poorer than the median survival (7.2 months) of the patients with metastasis confined to the posterior segment, and much worse than the median survival (15.6 months) of the 28 patients with orbital involvement.

Adenocarcinoma↗
PubMedDate not supplied

A critical review of the assessment of eye irritation potential using the Draize rabbit eye test.

Traditionally, the eye irritation potential of substances and products has been assessed using the Draize eye test. While this procedure has been criticized in terms of its scientific validity and its ethical acceptability, it remains the only official, government-recognized procedure for predicting the irritant effect of substances in the eye. The relative absence of serious human accidents testifies to the success of the predictions. With the development of alternative non-animal procedures to replace the Draize test, the data generated in the Draize procedure are also being used as a 'gold standard' against which the performance of alternative procedures is measured. The major sources of variability are small group size and inability of existing scoring systems to reflect the complexities of the total in vivo response. In addition, the use of algorithms to simplify the in vivo data (for comparison with in vitro data) also misrepresents the in vivo data. Addressing the above issues would inevitably increase the use of animals. This would go against the general public demand for a reduction in the use of animals. Therefore the issue is to decide upon a simple parameter (for comparison with in vitro data) that encompasses the complexity of the irritation response and accurately reflects irritation without requiring the use of additional test animals. Such a parameter could be the recovery time. In addition, controlled human testing to benchmark the Draize data would be invaluable. The future use of Draize data in the validation of in vitro alternatives is undisputed, but the utility of these data will only be enhanced by a proper understanding of the shortcomings of the Draize test.

Animals↗
PubMed1978

Development of the compound eyes of dragonflies (Odonata). II. Development of the larval compound eyes.

The development of the compound eye was analyzed by marking individual ommatidia and by studying naturally occurring pigment band patterns. New ommatidia are added to the eye along its anterior margin. This changes the directions of view of the older ommatidia with the greatest change occurring in the fovea. New ommatidia are added to the fovea medially, and old ones are removed laterally as their interommatidial angles and directions of view in the visual field change. Over one-third of the aeshnid ommatidia are foveal during at least one of the early larval instars, and are then used for peripheral vision later in development. The design of each ommatidium is a compromise so that it is adapted for all stages of development, but sometimes better adapted for one instar than for others. Factors which are balanced for best vision are lens diameter, facet admission function, interommatidial angle, and inclination of the optic axis to the eye surface. Ommatidia are described in terms of these factors throughout their life history, from initial differentiation anteriorly, through passage through the fovea, to their final relatively posterior location.

Animals↗
PubMed1992

Supplementary eye field: influence of eye position on neural signals of fixation.

Single units were recorded in the supplementary eye field of monkeys performing visual-oculomotor tasks. Two patterns of unit activity were observed while the animals fixated photic stimuli. One consisted of a step in tonic firing frequency (either an increase or a decrease, depending on the cell), lasting as long as fixation. The occurrence of this pattern did not require the continuous presence of a stimulus but the animal had to be provided with an incentive to fixate a given location. The other pattern was a monotonically varying firing rate dependent on the eye orientation along a particular axis, indicative of eye eccentricity in orbit.

Animals↗
PubMed1988

Eye-head coupling in humans. I. Simultaneous recording of isolated motor units in dorsal neck muscles and horizontal eye movements.

A tonic coupling between the horizontal component of eye position and dorsal neck muscle activity has been demonstrated in the cat and monkey. In order to demonstrate this synergy in humans and study its characteristics, we have measured the relation between the firing rate of individual motor unit of the splenius muscle and voluntary horizontal shifts of gaze using 5 degrees steps, in head-fixed subjects. Eye movement recording was achieved by conventional binocular electro-oculography and the activity of the right splenius muscle was recorded with Bronks coaxial bipolar electrodes inserted manually at the C4-C5 intervertebral level. The activity of 51 motor units in 10 subjects has been recorded. For all subjects, motor units firing rate increased when the gaze shifted to the ipsilateral side, and both increase in firing rate and recruitment were observed. These results demonstrate that the tonic eye head synergy is also present in man.

Action Potentials↗
PubMed1979

Optimal response of eye and hand motor systems in pointing at a visual target. I. Spatio-temporal characteristics of eye and hand movements and their relationships when varying the amount of visual information.

In a task requiring an optimal hand pointing (with regards to both time and accuracy) at a peripheral target, there is first a saccade of the eye within 250 ms, followed 100 ms later by the hand movement. However the latency of the hand movement is poorly correlated with that of the eye movement. When the peripheral target is cut off at the onset of the saccade, there is no correlation between the error of the gaze position and the error of the hand pointing. This suggests an early parallel processing of the two motor outputs. The duration of hand movement does not change significantly when subjects either see or not see their hand (closed or open loop). In the open loop situation, the undershoot of the hand pointing increases with target eccentricity, whatever the subjects are allowed or not to do a saccade toward the target. It suggests that the encoding of eye position by itself is a poor index for an accurately guided movement of the hand.

Adult↗
PubMed1975

The compound eye in the opaque-eye phenotype of Drosophilia melanogaster.

The compound eye of the opaque-eye mutant of Drosophila melanogaster was investigated by means of electron microscopy to determine the morphological and physical properties of ommatidial elements. These elements in the mutant were found to differ from those of the wild-type flies in the following ways: (1) The cuticular lens was thinner than that of the control and lacked the typical lamellar construction. (2) The Semper cells were irregular in shape and contained many membranous inclusions similar to those found in degenerating cells; also their nuclei contained virus-like particles. (3) The primary pigment cells contained an abundance of drosopterin-containing granules which were lacking in those of wild-type flies. (4) The superior and inferior central photoreceptor cells were misplaced and their rhabdomeres evidenced some degeneration. (5) The secondary pigment cells had only one type of pigment granules instead of the three types found in the control. These morphological changes in ommatidial elements induced physical abnormalities such as the apparent opaqueness of the eye, the lack of a pseudopupil, the probable disability of the photoreceptor cells to respond to light and the inability of the dioptric system to produce utilizable geometric images.

Animals↗
PubMed1985

Measuring eye movements with a search coil: non-linear filter allows simultaneous recording of horizontal and vertical eye position by means of the phase modulation method.

Measuring eye position from the phase angle of the signal induced by a rotating magnetic field in a search coil presents a number of advantages. So far, however, existing schemes using this principle either record eye position in one dimension only or require two search coils. We describe here a simple analog circuit which singles out a signal of given frequency from a frequency composite without changing the signal's phase. This makes it feasible to measure horizontal and vertical eye position with a single search coil by using two orthogonal rotating fields of different frequency.

Electronics↗
PubMed1989

Retinal ganglion cell number is unchanged in the remaining eye following early unilateral eye removal in the wallaby Setonix brachyurus, quokka.

The expanded visual projections which develop after unilateral eye removal have been associated in some studies, but not in others, with the survival of more ganglion cells than normal in the remaining eye. We have addressed this issue using the small wallaby Setonix brachyurus, quokka. Moreover to determine whether more ganglion cells survive when the eye is removed at a very early stage, we have compared the effect of enucleations at two ages. These were within 3 days of birth, before optic fibres innervate visual centres, and at 35-40 days postnatal, when visual projections are exuberant. At 100 days postnatal, retinal ganglion cells were retrogradely labelled from primary visual centres and tracts with horseradish peroxidase, allowing 24 h for transport. Numbers of ganglion cells were similar between animals enucleated as neonates (X = 231,000, n = 3) and at 35-40 days postnatal (X = 218,000, n = 4). These results were comparable to those of controls (X = 227,000, n = 5). Distributions of ganglion cells were also essentially similar in experimental and control series. However, mean ganglion cell soma diameter was significantly greater than normal in both the area centralis and temporal retina after neonatal enucleation. Our results indicate that in enucleated quokkas increased ganglion cell numbers do not underlie enhanced retinofugal projections.

Animals↗
PubMed1985

The in vitro assessment of eye irritancy using isolated eyes.

Rabbit eyes were removed and held in temperature-regulated chambers and irrigated with saline. A dose of 0.1 ml of test irritant was applied to each eye (six eyes per test material) and the induced change in corneal thickness measured over a 5-hour period, using a Zeiss photoslit-lamp microscope. A total of sixty materials were assessed and the results graded and compared with in vivo effects. The results show that this in vitro test can be relied upon to provide a rapid, accurate prediction of the irritancy potential in vivo, with a wide range of chemicals and, as such, offers a reliable alternative to the use of live animals.

Animals↗