Do Eye Hospitals Have a Role in Our Future?

Eye hospitals, originally founded to care for the poor, have developed into academic centers and tertiary "hospitals of last resort." Inexorable economic pressures, especially price competition, are likely to close many of them, particularly those which are marginal in quality or management. Survival of the remainder may further depend on their ability to adapt to a rapidly changing environment and to fulfill, better than anyone else, the special mission of basic and clinical research and training. Society must be convinced that some of these complex, highly differentiated, relatively expensive eye hospitals are significant national resources, serve the public welfare, and are worth preserving.     

Behavior of horizontal semicircular canal afferents in alert monkey during vestibular and optokinetic stimulation

Summary The behavior of single vestibular nerve fibers from the lateral semicircular canal was recorded during sinusoidal oscillations of the head, during optokinetic stimulation with the head stationary, and during spontaneous oculomotor behavior in the alert monkey. The response of similar fibers to adequate vestibular stimulation was also studied in some of the animals under deeply anesthetized conditions. In the alert animals all units were spontaneously active and their discharge was modulated only by adequate vestibular stimulation. Ipsilateral horizontal rotations of the head were excitatory for all units. No modification of this basic vestibular response by visual stimulation including full-field striped drum rotation was observed. Furthermore no correlation of unit activity with oculomotor function including voluntary saccadic and pursuit eye movements was found in any of the units. The regularity of spontaneous discharge was the most consistent characteristic that differentiated the unit response into types. Most units were very regular in discharge, but a few were very irregular. The averaging of unit discharge over several cycles of oscillatory head rotation showed that the irregular type units were also consistently modulated by adequate vestibular stimulation. Both regular and irregular type units were found in the anesthetized animals. Unimodal distributions of the quantitative values for unit resting discharge rate, sensitivity, and phase relationship were found. The distributions for these three parameters were similar in the units recorded in the anesthetized animals. Thus at least these characteristics of semicircular canal response seem not to be affected by the vestibular efferent system which should be altered or eliminated in the case of the anesthetized animals.Research supported by NIH Grant EY0995-04.     

Finite-element model of the human head: scalp potentials due to dipole sources

Three-dimensional finite-element models provide a method to study the relationship between human scalp potentials and neural current sources inside the brain. A new formulation of dipole-like current sources is developed here. Finiteelement analyses based on this formulation are carried out for both a threeconcentric-spheres model and a human-head model. Differences in calculated scalp potentials between these two models are studied in the context of the forward and inverse problems in EEG. The effects of the eye orbit structure on surface potential distribution are also studied.     

家兔视觉诱发电位正常值观测

目的 观察家兔正常视觉诱发电位基本波型,测定其主波成分有关参数的正常值。     

eyeVarP: A computational framework for the identification of pathogenic variants specific to eye disease

PurposeDisease-specific pathogenic variant prediction tools that differentiate pathogenic variants from benign have been improved through disease specificity recently. However, they have not been evaluated on disease-specific pathogenic variants compared with other diseases, which would help to prioritize disease-specific variants from several genes or novel genes. Thus, we hypothesize that features of pathogenic variants alone would provide a better model.MethodsWe developed an eye disease–specific variant prioritization tool (eyeVarP), which applied the random forest algorithm to the data set of pathogenic variants of eye diseases and other diseases. We also developed the VarP tool and generalized pipeline to filter missense and insertion-deletion variants and predict their pathogenicity from exome or genome sequencing data, thus we provide a complete computational procedure.ResultseyeVarP outperformed pan disease–specific tools in identifying eye disease–specific pathogenic variants under the top 10. VarP outperformed 12 pathogenicity prediction tools with an accuracy of 95% in correctly identifying the pathogenicity of missense and insertion-deletion variants. The complete pipeline would help to develop disease-specific tools for other genetic disorders.ConclusioneyeVarP performs better in identifying eye disease–specific pathogenic variants using pathogenic variant features and gene features. Implementing such complete computational procedure would significantly improve the clinical variant interpretation for specific diseases.     

Independent contributions of the orienting of attention,fixation offset and bilateral stimulation on human saccadic latencies

In a series of experiments we examined the effects of the endogenous orienting of visual attention on human saccade latency. Three separate manipulations were performed: the orienting of visual attention, the prior offset of fixation (gap paradigm) and the bilateral presentation of saccade targets. Each of these manipulations was shown to make an independent contribution to saccade latency. In experiments 1 and 2 subjects were instructed to orient their attention covertly to a location by a verbal pre-cue; targets could appear in the attended hemifield (valid) or in the non-attended hemifield (invalid) together with a no-instruction (neutral) condition. Saccades were made under fixation gap and overlap conditions, to either single targets or two bilaterally presented targets which appeared at equal and opposite eccentricities in both hemifields. The results showed a large increase (cost) of saccade latency to invalid targets and a small non-significant decrease (benefit) of saccade latency to valid targets. The cost associated with invalid targets replicates the meridian crossing effect shown in manual reaction time experiments and is consistent with the hemifield inhibition and premotor models of attentional orienting. The use of a gap procedure produced a generalised facilitation of saccade latency, which was not modified by the prior orienting of visual attention. The magnitude of the gap effect was similar for saccades made to attended and non-attended stimulis. This suggests that the gap effect may be due to ocular motor disengagement, or a warning signal effect, rather than to the prior disengagement of visual attention. When two targets were presented simultaneously, one in each hemifield, saccade latency was slowed compared with the single target condition. The magnitude of this slowing was unaffected by the prior orienting of visual attention or by the fixation condition. The slowing was examined in more detail in experiment 3, by presenting targets with brief offset delays. The latency increase was maximal if the two targets were presented simultaneously and decreased if the distractor appeared at short intervals (20–80 ms) before or after the saccade target onset. If the non-attended stimulus was presented at greater intervals (160, 240 ms) before the saccade target, then a facilitation effect was observed. This demonstrates that the onset of a distractor in the non-attended hemifield can have both an inhibitory and a facilitatory effect on a saccade production.     

Ear and eye representation in the frontal cortex,area 8b,of the macaque monkey: an electrophysiological study

We evoked both ear and eye movements in area 8b, the rostral area of frontal cortex, in two monkeys. In some sites it was possible to evoke only ear movements or only eye movements; in other locations we evoked both ear and eye movements by varying the intensity of electrical stimulation. The electrically evoked ear movements were forward, or backward, or oblique (upward-forward; upward-backward). In two penetrations the ear movements were bilateral, in the other penetrations they were contralateral. Ipsilateral ear movements were not observed. The evoked eye movements were mainly fixed-vector saccades, contralateral and with an upward orientation of about 45°. If we considered only the sites where the threshold was equal to or lower than 50 A, the stimulation of this area evoked mainly ear movements. In addition we recorded the electrical activity of 195 neurons. Of these neurons: 74% (145/195) discharged before ear movements (ear cells); 20% (40/195) discharged before ear and eye movements (ear-eye cells); 5% (10/195) discharged only before eye movements (eye cells). Ninety-one percent (132/145) of ear cells presented a preferred direction; 90% (36/40) of ear-eye cells presented a preferred direction for ear movements, and 15% (6/40) presented a preferred direction for eye movements. Eighty-five percent (34/40) of cells did not present a preferred direction for visually guided saccades and were active when the monkey made saccades toward the unlit targets (checking saccades). Our results show that a field of area 8b is related to ear movements and to eye-ear movements. The findings that it is possible to obtain both ear and eye movements with low-intensity currents and that there are cells firing for the two types of movements suggest that area 8b may be involved in the orientation and coordination of both ear and eye. This area might be considered a rostral extension of supplementary eye field (SEF) or a different region. However, based on its distinct functional characteristics and connectivity, it is probably better regarded as a separate field. Regardless, the combination of 8b and SEF may constitute a cortical center for orienting processes.     

Randomized clinical trial of the 350-mm2 versus the 500-mm2 Baerveldt implant: longer term results: Is bigger better?

OBJECTIVE: To report the longer term results of a randomized, clinical trial comparing the 350-mm2 and the 500-mm2 Baerveldt glaucoma implants. DESIGN: Extended follow-up on a randomized, controlled trial. PARTICIPANTS: Between March 1991 and April 1993, 107 patients with uncontrolled intraocular pressure (IOP) due to non-neovascular glaucoma associated with aphakia, pseudophakia, or failed filters were randomly assigned for surgical placement of either the 350-mm or the 500-mm2 Baerveldt implant at the Doheny Eye Institute. METHODS: A random-numbers table was used to assign each patient to one of the two groups. Preoperative IOPs and visual acuities were recorded. Clinical records were reviewed to ascertain postoperative IOPs, visual acuities, number of medications used, and implant-related complications that occurred throughout the follow-up period. MAIN OUTCOME MEASURES: Success was defined as IOP of 6 mmHg or greater and of 21 mmHg or less in two or more consecutive follow-up visits without further glaucoma surgery or loss of light perception attributable to glaucoma. RESULTS: The overall success rates were 87% for the 350-mm2 group and 70% for the 500-mm2 group (P = 0.05). Average follow-up was 37 months (range, 1-76 months) for the 350-mm2 group and 34 months (range, 5-77 months) for the 500-mm2 group. The life-table success rates declined over time for both implant groups, from a high of 98% for the 350-mm2 group and 92% for the 500-mm2 group at 1 year to a cumulative success rate of 79% for the 350-mm2 group and 66% for the 500-mm2 group at 5 years. Visual acuities were better or remained the same in 50% of the patients in the 350-mm2 group and 46% of those in the 500-mm2 group. Complications during the 5-year follow-up were also statistically similar. CONCLUSIONS: The longer term results show that the 350-mm2 Baerveldt implant is more successful than the 500-mm2 implant for overall IOP control. Interval comparisons indicate a higher rate of success for the 350-mm2 implant in the first, second, third, fourth, and fifth years of implantation. Visual acuities, implant-related complications, and average IOPs were statistically indistinguishable between the two groups.     

Management of submacular hemorrhage with intravitreous tissue plasminogen activator injection and pneumatic displacement

Objective

To investigate the efficacy and safety of treating thick submacular hemorrhages with intravitreous tissue plasminogen activator (tPA) and pneumatic displacement.

High-altitude retinopathy and altitude illness

Objective

To determine the relationship between high-altitude retinopathy (HAR) and other altitude-related illnesses and establish a classification system for HAR.