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Under natural conditions, shifts of spatial attention are often followed by matching eye movement. Recent evidence suggests that this close coupling is reflected in the ability of the same cortical area to shift eye position and the locus of attention.
Eye fixations during reading were monitored to examine the relationship between individual differences in working memory capacity-as assessed by the reading span task-and inferences about predictable events. Context sentences predicting likely events, or non-predicting control sentences, were presented. They were followed by continuation sentences in which a target word represented an event to be inferred (inferential word) or an unlikely event (non-predictable word). A main effect of reading span showed that high working memory capacity was related to shorter gaze durations across sentence regions. More specific findings involved an interaction between context, target, and reading span on late processing measures and regions. Thus, for high- but not for low-span readers, the predicting condition, relative to the control condition, facilitated reanalysis of the continuation sentence that represented the inference concept. This effect was revealed by a reduction in regression-path reading time in the last region of the sentence, involving less time reading that region and fewer regressions from it. These results indicate that working memory facilitates elaborative inferences during reading, but that this occurs at late text-integration processes, rather than at early lexical-access processes.
Smooth pursuit eye movements are known to be driven by a mixture of visual feedback and predictive strategies. Prediction in pursuit allows humans to track predictable stimuli with minimal phase lag. But in certain disease states and focal neurological lesions, normal phase relationships are lost and humans track with increased phase errors. Using a sinusoidal pursuit paradigm, we sorted patients into those with large phase errors and those without. Then, working on the premise that large phase errors may have resulted from lack of prediction, we compared predictive and non-predictive ocular pursuit in patients with large phase errors, patients with normal phase errors and control subjects. Subjects sat in darkness and pursued an intermittently illuminated target moving with constant velocity to the right or left. When the movements were in alternate directions and predictable, all the groups possessed the ability to preprogramme appropriate anticipatory eye movements before target onset, and to use this for predictive pursuit. The difference between patients with large phase errors and normal subjects was not an absolute lack or possession of predictive ability but a difference in the timing at which a preprogrammed motor behaviour was initiated or terminated. The timing variability was wide and formed a graded continuum, the control subjects initiating anticipatory pursuit earlier, and the patients with large phase errors initiating much later. In a second experiment, subjects pursued a predictable ramp stimulus presented at various fixed frequencies. We found that in patients where anticipatory pursuit seemed abolished at one frequency of target presentation, changing the frequency of presentation elicited an anticipatory response. Patients adjusted their pursuit latencies to match the temporal demands of target presentation. At target frequencies above 0.8 Hz, there was a significant positive correlation between latencies in ramp pursuit and phase lags in sinusoidal pursuit. None of our patients showed complete loss of prediction irrespective of how large the phase errors were. Even when severe time delays in the system made it impossible for a subject to initiate anticipatory pursuit before target onset, prediction could still be demonstrated by the significant velocity and timing advantage the subject had in the pursuit of a predictable target stimulus or by the technique of unexpectedly blanking the target.
The Age-Related Eye Disease Study includes a clinical trial of high dose antioxidant and zinc supplements for age-related macular degeneration and a clinical trial of high dose antioxidants for cataract. The clinical trials were initiated largely because of the widespread public use in the United States of commercially available pharmacological doses of vitamins and minerals to treat these two eye conditions and the absence of definitive studies on the safety and efficacy of their use. This report focuses on the clinical trial of zinc and the possibility that this elderly study cohort, who were randomly assigned in a factorial design to receive zinc, antioxidants and placebo, could be assessed for zinc effects other than those currently addressed by the trial.
This research investigated whether eye movements are informative about retrieval processes. Participants learned facts about persons and locations, and the number of facts (fan) learned about each person and location was manipulated. During a subsequent recognition test, participants made more gazes to high-fan facts than to low-fan facts, and gazes to high-fan facts had a longer duration than gazes to low-fan facts. However, there was no relation between the order in which items were fixated and the relative effect of person or location fan. The effect of person and location fan on gaze duration also did not differ with whether it was the person or location being fixated. A model assuming that the process of retrieval is independent of eye movements was successfully fit to the data on the distribution of gaze durations. According to this model, the effect of fan on number of gazes and gaze duration is an artifact of the longer retrieval times for high-fan facts.
The latency and variability of latency of single-unit responses to identical visual stimulation were measured in the frontal eye field (FEF), supplementary eye field (SEF), and anterior cingulate cortex (ACC) of macaque monkeys performing visually guided saccades. The mean visual response latency was significantly shorter in FEF (64 ms) than in SEF (81 ms) or ACC (100 ms), and latency values determined by four methods agreed. The latency variability of the visual response was respectively less in FEF (21 ms) than in SEF (37 ms) or ACC (41 ms). Latency, variability of latency, and magnitude of the visual responses were correlated within FEF and SEF but not ACC. These characteristics of the visual response are consistent with the degree of convergence of visual afferents to these areas and constrain hypotheses about visual processing in the frontal lobe.
1. The companion paper reported that a substantial proportion of cells in the supplementary eye field (SEF) of macaque monkeys show significant evolution of neuronal activity as subjects learn new and arbitrary stimulus-saccade associations. The purpose of the present study was to compare and contrast the activity of the SEF and the frontal eye field (FEF) during such conditional oculomotor learning. 2. In both SEF and FEF, we observed learning-dependent and learning-selective activity, defined as significant evolution of task-related activity as monkeys learned which of four saccades was instructed by a novel stimulus. By definition, in addition to changes as the monkeys learned the instructional significance of a novel instruction stimulus, learning-dependent activity also showed task-related modulation for trials instructed by familiar stimuli, whereas learning-selective activity did not. Of the 186 SEF neurons adequately tested, 81 (44%) showed one of these two categories of learning-related change. By contrast, of the 90 FEF neurons adequately tested, only 14 (16%) showed similar properties. This difference was highly statistically significant (chi 2 = 21.1; P < 0.001). 3. We also observed persistent differences in activity for trials with familiar versus novel instruction stimuli, which we termed learning-static effects. In some cases, the learning-static effect coexisted with learning-dependent or learning-selective changes in activity, although in others it did not. In the former cases, activity changed systematically during learning, but reached a level that differed from that for familiar stimuli instructing the same saccade. In the latter cases, the activity did not change significantly as the monkey learned new conditional oculomotor associations, but did show a significant difference depending upon whether a novel or familiar stimulus instructed a given saccade. Overall, 66 of 186 (35%) cells in the SEF and 17 of 90 (19%) cells in the FEF showed learning-static effects in one or more task periods. This difference was statistically significant (chi 2 = 7.9; P < 0.005). 4. The significant difference in the properties of SEF and FEF cells suggests a functional dissociation of the two areas during conditional oculomotor learning. In this respect, the FEF resembles the primary motor cortex, whereas the SEF resembles the premotor cortex.
To ascertain the cell types expressing S-100 protein in eyes with retinoblastoma, a follow-up study was made on 88 formalin-fixed and paraffin-embedded retinoblastoma specimens histopathologically and immunohistochemically, using antibodies against S-100 protein. In normal retinas and morphologically normal retinas with retinoblastoma, both astrocytes and ganglion cells were stained positively for S-100 protein. In the retinoblastomas, not only the reactive astrocytes in most cases, but also large tumor cells with large cell bodies, prominent nucleoli and well-differentiated figures were positive for S-100 proteins in 2 cases. These large tumor cells were thought to be neuronal and were called ganglion-like cells because they were morphologically and immunohistochemically compatible with the large ganglion cells in normal retina. The results indicate that in eyes with retinoblastoma, S-100 protein has both neuronal and glial immunologic properties and could have a limited value as a glial marker for the histogenesis study of retinoblastoma.
The effect of eyelid closure on the response to rotational vestibular stimulation was assessed by evaluating 16 normal human subjects with both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotations with either eyes closed (EC) or eyes open in the dark (EOD). Results indicated that for EVA rotation, the subjects' responses were of larger magnitude and less variable with EOD than with EC. However, for EHA rotation, responses were of larger magnitude and equally variable with EC as compared to EOD. Our data also indicated that the quality of the EHA response with EC was altered because eyelid closure influenced the amount of periodic gaze. We conclude that eyelid closure has an effect upon both canalocular and otolithocular reflexes and suggest that both EVA and EHA rotational testing be performed with EOD rather than with EC.
Many patients with symptomatic eye conditions present initially to their primary care physician. Comprehensive treatment of such conditions as dry eye syndrome, blepharitis, styes, chalazia, conjunctivitis, congenital nasolacrimal duct obstruction, superficial foreign bodies, corneal abrasion, and subconjunctival hemorrhage can often be provided in the primary care setting. Patients with persistent or severe conditions, particularly those involving foreign bodies and corneal abrasions due to high-velocity injuries, should be referred for immediate care by an ophthalmologist.
The outer layers of the normal retina depend on indirect nutrition originating in the choriocapillaris and supplied to the retina by way of the pigment epithelium. An eye with exophytic retinoblastoma is used to demonstrate increased vascularity and tissue substance in the adjacent choroid believed to be indirectly induced by a regional increase in nutritional requirements in the retinal zone of a developing eye.
PURPOSE: An experimental animal study was conducted to analyze the delay for ocular bathing in the treatment of severe ocular ammonia burns. Two solutions of ocular wash, saline solution and Diphotérine were compared. MATERIAL: and methods: The study included 23 eyes of New Zealand albino rabbits that received for 1 minute 100 microl of 15.3% ammonium solution. Each eye was then washed with 250 of saline solution or 250ml Diphotérine after a delay of 1, 3, 5, 10 or 30 minutes. Effects were assessed on the basis of changes in anterior chamber pH, ammonia concentration in the anterior chamber, and cytopathology examination of the burned corneas. RESULTS: Ocular wash with Diphotérine in the first minutes following ocular burn induced an inflexion of the pH curve unlike ocular wash with saline solution. At 30 minutes, there was no inflexion of the pH curve and the ammonia concentration in the anterior chamber was low. Contrary to ocular wash using Diphotérine, stromal edema was seen at cytopathological analysis after washing with saline solution. CONCLUSIONS: This study provides evidence of the interest of ocular bathing in the first minutes following ocular burn by ammonia. The efficacy of external ocular washing with Diphotérine was proven by biochemical and cytopathological demonstrations. The importance of sequelae were related to the degree of initial stromal edema.
An interrupted 5 mm diameter hexagonal keratotomy was modified to include six paracentral transverse incisions to augment the central corneal steepening. This combined modified-hexagonal and transverse (or hexagonal-transverse) keratotomy was performed on human eye bank eyes to an estimated 85% corneal depth yielding a mean of 7.50 +/- 1.69 diopter increase in central keratometric power (P less than .001); this finding was confirmed by keratography. These results encourage further studies of this procedure and its potential to surgically correct mild amounts of hyperopia.
For the treatment of an orbital defect after exenteratio orbitae, an eye prosthesis with flexible upper eyelid was developed. The artificial eyelid moves synchronously with the natural contralateral upper eyelid by electronic control. The electric signal of a light barrier mounted on to a spectable frame in front of the intact eye is intensified and transmitted to an electromagnet. The electromagnet is located in the obturator prosthesis and lifts the artificial eyelid.
A total of 477 perforating eye injuries (PEIs) were treated at Helsinki University Eye Hospital during the years 1970 to 1977. This study concerns perforations in children and those in adults during leisure time, the two categories representing 60% of all perforations. The results were compared with two previous series from this clinic from 1950 to 1959 and 1930 to 1939. The proportion of children was 27% of all perforations, a clear decrease from the 1950s (32%). The proportion of males was 78% both in children and in adults. Sharp objects were the most common cause of injury in children; explosions had diminished remarkably as compared with the 1950s and 1930s, there is a great increase in the number of assaults and road accidents. Prognosis was better for children than for adults. This reflects the better outcome of anterior segment injuries, which formed the majority of children's perforations, 71%, but only 48% of adult perforations.
The organizational stages of diagnosing the eye diseases associated with ocular hydro- and hemodynamic disorders are classified. Soft- and hardware specifications are defined and new effective ophthalmological devices used at all stages of examining patients with eye diseases have been developed.
Many developing countries face the overwhelming problem of addressing preventable and curable blindness. United States-based ophthalmologists can make important contributions in this regard by volunteering to teach and deliver eye care overseas. However, there are a number of potential risks and difficulties. Surgical Eye Expeditions (SEE) International has developed a logistical outline and planning checklist designed to minimize or avoid such problems. Critical components include a firm timetable, advanced planning, advance contact with a local ophthalmologist or organization, and a thorough understanding of the importance of adapting to the needs of other cultures. With a little planning, the average philanthropic ophthalmologist can make major contributions to individuals and communities in developing nations.
In continuation of part I and II (Klin. Mbl. Augenheik. 169 [1976] 647, 774) of this essay deals with eye damage afflicting both eyes (caused by an accident or pre-existing lesion) regarding the approbiate disablement benefit. In these cases the degree of disablement should be set between 30 and 70%.