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The present paper reports a case of spontaneous regression of a retinoblastoma leaving the eye with normal vision. The mode of regression is briefly discussed and the literature is reviewed.

The ability to see is one of the truly remarkable characteristics of living beings. It enables them to perceive and assimilate in a very short time an incredible amount of knowledge about the world around them. The scope and variety of that which can pass through the eye and be interpreted by the brain is nothing short of astounding. Mankind has increased this basic capability by inventing devices that can detect electromagnetic radiation at wavelengths far outside the range of normal vision and at energy levels orders of magnitude below what the eye is able to perceive by itself. By the use of X-rays or sound waves it is possible to “see” inside objects and into places that have been invisible to living beings since the dawn of creation. Ultra-fast photography can stop a speeding bullet or freeze a flying humming bird’s wing.

1. We used the behavioral technique of conditioned suppression to measure spatial and temporal contrast sensitivity to counterphased, sine-wave gratings in eight cats. These included two normally reared cats before and after bilateral ablations of cortical area 17 and part of area 18, two cats raised in total darkness, two cats raised with binocular lid suture, and two cats raised with monocular lid suture, Visual deficits induced by cortical lesions or visual deprivation were evaluated with respect to the preoperative data of the normally reared cats. 2. The cortical lesions had virtually no qualitative effect on the cat’s visual capacities. Contrast sensitivity was reduced at higher but not lower spatial frequencies, and this can be described succinctly as a loss of spatial acuity. 3. Dark-reared and binocularly sutured cats qualitatively exhibited poorer visual capacity than that of the cortically ablated animals. The contrast sensitivity resultant from these two forms of binocular deprivation was basically similar and consisted of significant sensitivity losses at all spatial and temporal frequencies. Much more than high spatial frequencies was affected, and this amblyopia cannot be characterized simply as a spatial acuity loss. 4. Monocularly sutured cats had normal vision and contrast sensitivity with the nondeprived eye, but with the deprived eye they displayed the most severe amblyopia and poorest contrast sensitivity of any of the cats. Again, sensitivity losses were evident for all spatial and temporal frequencies, and this amblyopia is more severe than a loss of spatial acuity. 5. These psychophysical data are related to the status of W-, X-, and Y-cell pathways in these cats. Sensitivity to low spatial frequencies and integrity of the Y-cell pathway is correlated with good visual capacity. Since Y-cells are uniquely sensitive to low spatial frequencies, then the Y-cell pathway seems sufficient and perhaps necessary for reasonable visual performance. 6. Finally, because the amblyopia of normally reared cats with lesions of striate cortex is far less severe than that of the lidsutured and dark-reared cats, it follows that the constellation of deficits reported for striate cortex in these visually deprived cats cannot provide an adequate neural explanation for their amblyopia. Attempts to relate deprivation amblyopia to striate cortex abnormalities should thus be reconsidered.

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between disease states which involve visual image degradation and refractive error. Refractive data from 1023 normal vision children were used as a control. The low vision children were grouped according to their disease classification and the acknowledged age-of-onset of their visual disability. It was found that there was an overall inability to emmetropize and a trend towards myopia. It was also observed that the diseases which led to myopia were associated with a peripheral or peripheral plus central impairment of vision and that those conditions in which foveal vision was primarily impaired showed a mild hypermetropic trend. Eyes in which the visual impairment was not congenital but occurred before the age of 3 years tended to develop hypermetropia. The deviation from emmetropia decreased with increasing age-of-onset of the visual impairment, as did the variation about the mean refraction. The plastic period for emmetropization is estimated to end at 8 to 9 years of age.

Human subjects with maintained reversal of their horizontal field of vision exhibit very substantial adaptive changes in their ‘horizontal’ vestibulo-ocular reflex (v.o.r.). Short durations (8 min) of vision reversal during natural head movement led to 20 % v.o.r. attenuation while long periods (4 weeks) eventually led to approximate reversal of the reflex. The reversed condition is approached by a complex, but highly systematic, series of changes in gain and phase of the reflex response relative to normal. Recovery after return to normal vision exhibits a similar duration, but different pattern, to that of the original adaptation. A chronic cat preparation with long-term optical reversal of vision has now been developed and shows similar adaptive and recovery changes at low test stimulus amplitudes, but different patterns of adaptive response at high amplitudes. An adaptive neural model employing mown vestibulo-ocular pathways is proposed to account for these experimentally observed plastic changes. The model is used to predict the adapted response to patterns of stimulation extending beyond the range of experimental investigation.

WHEN the eye has been adapted to a bright yellow light, a marked loss of sensitivity to short-wavelength stimuli may be recorded immediately after the extinction of the adapting field. This phenomenon, first described by Stiles1, was termed transient tritanopia by Mollon and Polden2. They supposed that a recovering long-wavelength mechanism may inhibit or otherwise suppress the blue cone signal during early dark adaptation. Transient tritanopia was found in one protanope and, in a modified form, in one deuteranope. This indicates that each of the red or green mechanisms or both in combination may give rise to the inhibition effect. It is of particular interest in this connection to know if this kind of inhibition is present in persons without red or green cones. In blue cone monochromacy, a unique kind of colour vision anomaly, there are only blue cones and no functioning red or green cones. We report here the experimental results obtained with such a person where no suppression effect upon the blue mechanism could be demonstrated. The results are compared with those of a typical rod monochromat and a person with normal vision.

In order to clinically evaluate the optical performance of the crystalline lens as well as that of intraocular implant lenses, measurements were made of the brightness of two markedly different and easily sited landmarks on the retina (the papilla and the macula) using the photopapillometer. The contrast transfer ratio (CTR) thus generated permitted investigation of three groups of subjects: Normal persons (n = 53) with visual acuity of 1.0 (20/20) from each mature decade of life provided values indicating the age-related changes in eyes not necessarily tending toward lens opacification. Relatively constant CTR values (approximately 2:1) were observed up to 60 years, after which the ratio fell significantly to about 1.5:1 (ranging from 1.41:1 to 1.68:1, depending on the site measured on the papilla). Such a finding in subjects with normal vision was considered to demonstrate the tendency for older lenses to become yellow, which would reduce the CTR. Patients (n = 33) who were being followed clinically for developing lens opacification had their CTRs measured for correlation with their visual acuities. Here, strong correlation (P less than 0.001) was observed. Evaluation of the improvement wrought by the implantation of an intraocular lens in yet another group of patients (n = 38) revealed an increase in the CTR to a virtually normal level (1.97:1). This method provides information about the actual optical efficiency of the lens when the other ocular media are clear, supplementing other methods for evaluating lens density and clarity, and thus further facilitating critical assessment of the progress of lens opacification.

The discrimination of contrast in a bipartite field with a stabilized retinal image was studied in relation to several parameters. The percentage of time (V) for which the luminance difference is perceived is always very much lower than in normal vision. V is (a) independent of field luminance; (b) increases with luminance difference; (c) increases with sharpness of boundary; (d) at first increases and then decreases as field size is increased; (e) decreases when the target is moved away from the centre of the visual field. White, red, green and yellow (minus blue) illumination give very similar results. Important differences are found with blue light when the target is mainly within the fovea. Many of the results can be explained in relation to spatial interaction over about 2′ in the fovea (for colours other than blue) and over larger distances outside the fovea. The range of interaction for blue within the fovea is 7′. Some results require the existence of at least two partly independent “signals” which lead to perception of contrast.

Stabilization experiments are described in which an object, mounted in the rotor of a small electric synchronous motor, can be rotated eccentrically. This motor is fixed in a cap which is sucked onto the eyeball. In this way it was possible to imitate the drift, the saccadic and the tremor movements of the eye, and to study their influence on perception. It was found that drift imitating movements regenerate (fill in) a disappeared object. The movements imitating the saccades and tremor were never effective in restoring normal vision. The influence of the location on retina was studied. An analysis of the observed effects is given according to the model of activity spread and spread preventing barriers. The explanation makes clear that, in normal vision, the drift is responsible for continued perception and that the tremor and saccades do not function for this purpose.

Twenty US Infantry soldiers with normal vision were presented 108 targets at distances ranging from 30 feet to 120 feet on two sites in a Canal Zone evergreen rainforest. Observers were presented 18 each of the following targets: olive drab silhousettes, olive drab cylinders, double white discs, single white discs, silhouettes camouflaged by the USAERDL four-color 1948 pattern, and human targets in fatigue uniforms. Comparisons between human targets and standard visibility objects were made using four criteria: 50% detection thresholds, total number of detections, visibility gradients, and observer response variability. Quantitative comparisons showed that both the olive drab silhouette and the olive drab cylinder closely approximated the detectability of the human targets; of the two objects, the silhouette was considered superior. The USAERDL four-color camouflage cloth effectively and significantly reduced detections by ground observers in jungle vegetation.

This study was conducted to determine the effect of amount of light transmission through fixed filter visors on the visibility of targets. The maintenance of proper visual acuity is of utmost importance to a naval aviator. For safety of flight reasons, he must be able to detect the presence of other aircraft at the greatest possible distance. Any goggles or visors provided for the protection of his vision must not seriously degrade visual acuity. Part I of this study measured visual acu ity under field conditions. It was conducted using the taxiway of the local airport at West Point, Virginia. In Part II of this study, standard measures of visual acuity were obtained, using a Snellen chart, under four levels of illumination. As in the first part, the three visors were used and were again compared with normal vision. For this part of the evaluation, four subjects were used, each of whom had 20/20 vision with one being corrected to this level by glasses. Results of Part II also are presented in the appendix.

Red/green sensitivity was measured in 197 normal subjects by two different methods. In the first a fixed yellow light ( λ=590 mμ ) was matched by a mixture of red and green in an anomaloscope and the red/green ratio found. This depends upon the nature of the red and green cone pigments but not upon the amount of each present. In the second test the brightness of a green light was equated to that of a fixed red light by flicker photometry. This might be expected to depend upon the relative amounts of red and green cone pigments as well as upon their nature. To learn whether relative red/green brightness did depend upon the relative amounts of red/green-sensitive pigments on the fovea, these were measured by retinal densitometry in some twenty subjects who were specially red-sensitive or green-sensitive by flicker measurements. With one exception all those who were red-sensitive had a high red/green pigment ratio; all who were green-sensitive a low red/green pigment ratio. The variations in flicker settings in our population show a standard deviation about four times that of the anomaloscope settings, and there was little association between the two.

THE optical aids conventionally used for the improvement of sub-normal vision at near viewing distances (for example, reading) comprise compound, short microscopic systems of varying magnifications, often obtained by placing an additional convex lens over the objective of a Galilean telescopic unit. These microscopic spectacles present a number of disadvantages; thus they have a very restricted field of view (usually less than 30°), they cause changes in spatial perception and, moreover, are heavy, conspicuous, and, in Australia, very costly. Compound systems are employed because of the contention, expressed throughout the literature, that single high-power convex lenses could not provide the necessary field properties.

The EEG potential evoked by repetitive 3.2/sec flashes of light to the right eye was measured in six subjects; at the same time the left eye viewed various continouslyy presented targets, both in normal and in stabilized vision. The folloing observations were made: 1. 1. In stabilized vision, no significant change could be detected in the amplitude of the evoked potential during periods of clear visibility or of spontaneous fade-out. Thus, the changes in the state of CNS activity, indicated by low voltage fast EEG during periods of image visibility versus alpha activity during periods of fade-out, are not reflected by the evoked responses. 2. 2. The presentationoof a structured target to the left eye in normal vision reduced the amplitude of the potential evoked by flashes to the right eye. If the same target was stabilized on the retina, there was less reduction in the amplitude of the evoked potential. . The greater reduction of amplitude of the evoked potentials during observation of the target in normal vision compared with the reduction measured during stabilized vision is interpreted as resulting from increased loading of the higher levels of the visual system in the former case; in this condition, fewer elements are available to participate in the evoked response to unpatterned light.

WHEN a simple target is viewed as a currently occurring retinal image which is confined to a specific locus, the target has been reported to lose contrast and to disappear1–3. The restriction of an image to a specific retinal locus is commonly termed a “stabilized retinal image”. This is the reverse situation to that encountered in normal vision where eye movements change the position of the retinal image several times a second. For more complex targets such as geometrical figures viewed as stabilized retinal images, intermittent disappearance and reappearance of the figure in whole or in part have been reported4–7. This striking phenomenon, usually outside the subject's previous visual experience, has been termed “fragmentation”. The common methods of investigating fragmentation are voluntary steady fixation, viewing as a partially stabilized retinal image using a contact lens and as a prolonged after-image (a completely stabilized retinal event)4–7. These methods in order progressively impose restraint on the image with respect to its retinal locus. Another method of investigating fragmentation was described by Evans8 and McFarland9. who note reports of fragmentation by subjects viewing geometrical figures for brief time intervals. Typically, the stimulus is viewed tachistoscopically near the recognition threshold after which the subject records his observations. This sequence is then repeated for many trials. We wish to describe another method of producing and studying fragmentation, by viewing a geometrical figure under intermittent illumination.

An analytical anomaloscope is described with a wedgeW controlling the intensityE of light (e.g., yellow) to be matched. A knobq controls, linearly, the red/green proportion that matches. The instrument has a useful property. Set by the protanope so that the red and green primaries look equal (“prot. mode”), matches are unaffected by theq settings, andEλ for each λ gives directly the protanope sensitivity curve. If the chlorolabe of the protanope was a normal pigment, normals (who need bothq andW adjustments for a perfect match on λ) would make the sameWλ settings as the protanope did. They do so exactly. So do protanomalous though theirq values are abnormal. Exactly similar results were found for deuteranopes, normals and deuteranomalous in the “deut mode”.

WHEN an object is viewed through some optical system which stabilizes its image on the retina a breakdown of normal vision occurs and the target may disappear1,2. When complex targets are viewed under these conditions disappearances may be partial3, and the fragmentations which occur may consist of distinctly ordered, non-random segments of the original figure4.

To furnish control data for future tests of visual performance aids in the Canal Zone, detection thresholds for uniformed human targets were established in the evergreen tropical forest during the rainiest part of the wet season. Thirty artillery observers, with normal vision, were presented 40 randomly appearing targets in a 180-degree field of search at three different sites. Overall detection thresholds (point of 50% detectability) averaged approximately 70 feet, with no significant differences among the sites. One hundred feet was the near-limit of target detectability. The palms and other plants with large leaves in the undergrowth and the extremely low levels of illumination caused by the forest canopy were the greatest deterrents to target detection. Horizontal target placement, individual differences among observers, past experience, and immediate practice had little or no effect on target detectability within the ranges investigated. A comparison of the results of this study and a previous one conducted in a semideciduous tropical forest is included.

There is a striking discrepancy between the stable and continuous impression of the visual world we experience when contrasted with the spatially and temporally discontinuous series of retinal images which occur in the ordinary course of vision. The information about the environment gained through the eye is defined at each instant by the character of the image sensed by the photoreceptors, which in turn is defined by the position of the eye with respect to the external scene. During normal vision the position of the eyes ordinarily shifts abruptly at an average rate of from two to four times per second, so that there is a corresponding change in the neural input to the brain associated with each shift of the visual image. Although there has been considerable theoretical speculation on the nature of the central mechanisms which might stabilize the visual percept in the face of the discontinuity induced by the saccadic eye movements (Sperry, 1950; von Holst and Mittelstaedt, 1950; Teuber, 1960; MacKay, 1966) neurophsyiological studies of the visual system have largely ignored the implications of these frequency shifts of the retinal image for the processing of afferent information.

During the past two decades reports in the United States and Europe have been unanimous that the best treatment of angiomatosis retinae is diathermy coagulation of the classic "bee's nest" lesion and the vessels extending to it. If the angiomatous lesion is early in development, localized, and located peripherally, the prognosis for useful vision is good, though there is always the possibility of cerebellar involvement. In 1943 Cordes and Dickson reported favorable results with x-ray irradiation, but during the intervening years these authors have come to prefer diathermy coagulation. In 1943 Guyton used coagulation diathermy upon both eyes of a 13-year-old girl. The early lesion eye retained normal vision, and the late lesion eye was retained, though it did not regain vision. Eight years later the process extended into the cerebellum and the patient died. In 1948 Lewis reported two patients whom he had treated with diathermy and had followed

Four pilots with normal vision were tested for the effects of the standard indirect red and red-flood aircraft lighting systems on dark adaptation. Data were gathered in a completely blacked-out cockpit while the aircraft was in a hangar and also during conditions of normal night flight. Significant differences in dark adaptation thresholds were found between the hangar and flight phases and between the low and high levels of light intensity used. No significant differences were found between the types of lighting systems used. It is concluded that the flight conditions of starlit night sky affect dark adaptation levels to a significant degree.

Current views of colour blindness are varied. There is agreement, however, that forms of vision should be classified on the basis of what stimuli the observer will find to be equivalent. Primary theoretical interest has so far centred around the so-called reduction forms of normal vision, forms in which the observer not only makes colour confusions but also fails to detect any difference between stimuli found to be equivalent by the normal observer except the difference ascribable to a variation in ocular pigmentation. Such observers are classed as dichromats or monochromats depending on whether they experience a two-fold of colours or simply experience colours varying in one dimension only. The equivalent colour stimuli, or metamers, of the normal and reduction forms of vision are well-known and can be expressed in terms of any one of a triple infinity of sets of primary colours. For any of these sets the tristimulus values of the spectrum can be calculated from those of the standard observer by a linear homogeneous transformation from the standard co-ordinate system (X, Y, Z). Theories of vision have been concerned with the identification of physiological processes functionally distinct within the visual mechanism, and the diverse postulates that have received serious attention so far have the common property that they yield correctly not only the normal metamers, but also those characterizing the reduction forms.

Retrobulbar hemorrhage in a hemophiliac has not been reported in the Anglo-American literature. The dangerous nature of this complication of hemophilia is well-illustrated in the following case report. Report of Case A 14-year-old white boy was admitted to Boston City Hospital 2 days after having struck his right eye lightly against a door. Over the 2 days prior to admission he noted progressive swelling and bluish discoloration which originated from the right lateral canthus and then spread throughout the right orbital region. On previous examinations he was found to have normal vision in both eyes, but a few hours prior to admission he reported some diminution of vision in his right eye. Ten years before admission, he was hospitalized with persistent hemorrhage from a minor lip laceration and was shown to have a deficiency of antihemophilic globulin. Three brothers and his maternal uncle and cousin also have classical hemophilia. He

At vertical resolutions of 12-, 10-, 8-, and 6-scan lines per symbol height, the legibility of Courtney alphanumeric symbols, designed especially for television, was compared with that of standard Leroy symbols. These symbols were presented singly on a 525-line TV monitor, and the speed and accuracy with which they were identified by groups of subjects having normal vision were recorded. A group of subjects viewed only the Courtney symbols, while another viewed only the Leroy. The results showed that, at any resolution value, identification of Courtney symbols was no better than for Leroy. Some practice was required with the Courtney symbols before it was possible to obtain a performance equal to that of the Leroy. This study supports the findings of other experiments: that a resolution of 10 lines per symbol height remains the lowest value recommended for TV displays.

This chapter discusses the measurement of visual acuity and method for its correction. Visual acuity is referred as a measurement of what one can see. Visual acuity is expressed as a fraction. Normal vision is referred to as 6/6 vision—at a distance of 6 m, the patient can read a certain line of letters on the sight testing chart. This is called the 6/6 line. However, the patient may be unable to read this line and, for example, may only be able to see the very top letter on the chart. For practical purposes, refractive errors in school children are corrected by spectacles. The responsibility for seeing that the spectacles contain the correct lenses belongs to the person who tested the patient's eyes. This would be either a doctor or a sight testing (ophthalmic) optician. If there is any doubt that the child cannot see properly with his glasses, he should be referred back to whoever tested him immediately. The responsibility for actually fitting the frames of the glasses and for seeing that the lenses prescribed by the sight tester are correctly inserted into the frames belongs to the dispensing optician.

USE of the operating microscope has now become a sine qua non for good otologic surgery. Effective use of the microscope demands comfort and in a prolonged operation this requires not only practice, but optimal adjustment of the instrument. If your eyes seem to strain to focus after using the microscope for a few minutes or you are having to refocus with each change in magnification, it is quite likely that the optics of your microscope are not optimally adjusted to you . (It is also possible that you have a refractive or accommodation error which cannot be compensated for by the usual adjustments of the microscope.) This article will describe a series of steps by which the optimal setting of the eyepieces can be easily derived, and a modification of the eyepiece assembly which will compensate for astigmatic refractive errors. Normal Vision For those with normal vision in both eyes

The purpose of the study was to explore the use of nonmagnifying yellow lenses to enhance personnel detection in the evergreen rainforest. Twelve US Infantry soldiers with normal vision, using spectacles fitted with yellow lenses, were each presented 45 randomly appearing human targets within a 180 deg. field of search. The targets, who were dressed in standard Army field clothes, stood motionless at predetermined distance markers facing the observer. Tests were conducted on three sites in the evergreen rainforest of the Canal Zone during the dry season (April 1965). Results were compared with those obtained from 18 additional observers with unaided vision, who were tested on the same sites and under the same conditions. The major effect of using the yellow lenses was to restrict rather than increase detectability of human targets. Perceptually, the lenses made the targets appear farther from the observers, resulting in significant distance overestimation. Detection times and practice effects were not affected by use of the lenses.

Seeing is a complex human activity involving more than the visual sense and its ability to convert the stimulus, radiant energy, into sensations of brightness and color. Seeing is accomplished by the human being operating as a human seeing-machine. Therefore, efficient, certain, comfortable, and easy seeing involves psychophysiological factors and effects of seeing as well as the psychophysical characteristics of the visual task and its environment. There is some confusion and some difference of opinion in regard to levels of illumination that are now being recommended. This is not surprising inasmuch as recommended footcandle levels are very generally compromises involving many aspects of economics, practicability, and conservation. Adequate specifications of light, lighting, brightness, and color do not arise from a single study or even a limited group of studies. Pertinent data are yielded by researches along various major avenues involving achievement, conservation of human resources, subnormal as well as normal vision, supra-threshold as well as threshold visibility, and proper considerations of footcandle level as a means to the ends which are brightness level and visibility level. The author presents data and analyses which reply specifically to certain criticisms and which, he believes, support the conclusion that footcandle levels recommended by the Illuminating Engineering Society, as well as by himself and colleagues, are conservative in relation to the indicated ideal levels for various tasks of prolonged critical seeing.

THIS CASE was first reported by me 1 in 1921, three years after treatment. The patient, at the age of 17 months, was referred to me on Nov. 22, 1917, by Dr. John Kerrigan. On Nov. 24 the right eye was removed by him and sent to me for pathological examination. I found it three-fourths filled with a retinoblastoma, containing many rosettes. The tumor had not involved the optic nerve or choroid. On May 2, 1918, the patient was again referred to me by Dr. Kerrigan. I now found in the retina of the left eye in the lower outer quadrant a white opaque elevated mass, irregularly oval in shape and about 4 P.D. in greatest diameter. It did not reach to the limit of the ophthalmoscopic field. Near this mass, but entirely separate from it, were two small white spots each about ¼ P.D. in size. The patient was

I have not infrequently encountered cases of astigmatism in which, after having corrected the error in each eye separately, and on testing both eyes simultaneously, in binocular vision, have found that vision proximum was not perfect, and in order to attain normal vision near at hand, in binocular sight, the angle denoting the axis of the cylindrical glass must be changed in one or both eyes. In correcting this binocular defect, types and the astigmatic bars were employed. If the patient looks upon the floor it will seem to incline to the right or left, and on changing the axis of one or both cylinders, the surface will appear level. But the same defect will be apparent if a board 12 × 3 inches, with parallel sides, be held in front of the patient at one metre, and on a level with the eyes. In these cases then, the answer

In normal vision, the various “gestalt-free” combinations which form early in a percept, are repressed by the emergence of the veridical composite perception; but in schizophrenic vision, with its inadequate repressive powers, the early combinations emerge as the completed composite. This completed composite, if at all veridical, is so only partially. Rorschach studies support the idea of a range of perceptual abortions among schizophrenics, varying directly with the process-reactive range.

The specificity of learning hypothesis predicts that the removal and addition of vision causes a deterioration in aiming performance, and further that this detrimental effect increases as a function of practice (Proteau, 1992). The purpose of this study was to determine the effects of the addition and removal of visual information from a task emphasising the directional component of the movement. Subjects practised the task for a moderate and extensive number of trials in a target-only or normal vision condition. Following each practice phase, subjects were transferred to the other condition. The data indicated that while subjects' directional aiming error increased following the removal of vision, there were no detrimental effects following its addition. In fact, directional error was reduced when transferring to the normal vision condition. These positive effects of the addition of visual information relating to the directional component are not consistent with the present version of the specificity of learning hypothesis.

The purpose of the study was to investigate the occurrence of stride regulation at the approach phase of the long jump in athletes with normal vision and visually deprived Class F12 and F13 athletes. All the athletes exhibited the presence of a regulatory mechanism. In the normal vision group this occurred on the fifth-to-last stride. In Class F12 athletes regulation commenced on the fourth-to-last stride for males and third-to-last stride for females. Class F13 males commenced regulation, like the control group, on the fifth-to-last stride; but females commenced on the fourth-to-last stride. The study demonstrated that reduced vision does not prevent Class F12 and F13 athletes from applying a regulatory mechanism similar to that observed in sighted athletes. However, the control mechanism of regulation emerged earlier in non-visually deprived long jumpers and the least visually impaired Class F13 athletes, signifying the importance of visual function in the regulatory stimuli.

A visual-evoked-potential (VEP) masking technique was used to assess the effects of short- and long-term monocular deprivation on the development of visual inhibitory interactions in kittens. VEP contrast-response curves were recorded in response to contrast-reversed sinusoidal gratings, both with and without superimposed high-contrast masks. The contrast-response curves measured from the nondeprived eye were similar to those of normal cats: with no mask VEP amplitudes increase with contrast up to saturation at about 10% contrast; parallel masks shift the curves to the right, decreasing thresholds; and orthogonal masks decrease the slope of the contrast-response curves without affecting thresholds. After monocular deprivation (either brief or extensive), the contrast-response curves without mask did not show the typical response saturation, and neither parallel nor orthogonal mask had any effect on the contrast-response curves. The masking effects did not return after 100 days of normal vision, although contrast sensitivity and acuity recovered to about half of the normal levels during that period. The results indicate that the inhibitory intracortical circuitry that mediates the orientation-dependent masking effects are highly vulnerable to visual experience.

Deprivation of form vision by the fitting of translucent occluders suppressed the diurnal cycling of enkephalinergic amacrine cells (the ENSLI amacrine cells), in the chicken. Daily periods of normal vision or enforcing temporal contrast using strobe lighting appeared to restore normal functioning of the ENSLI cells. These results suggest that the ENSLI cells are involved in retinal circuits that assess the quality of the visual image and control eye growth.

Human adults with normal vision can combine visual landmark and non-visual self-motion cues to improve their navigational precision. Here we asked whether blind individuals treated with a retinal prosthesis could also benefit from using the resultant new visual signal together with non-visual information when navigating. Four patients (blind for 15-52 years) implanted with the Argus II retinal prosthesis (Second Sight Medical Products Inc. Sylmar, CA), and five age-matched and six younger controls, participated. Participants completed a path reproduction and a triangle completion navigation task, using either an indirect visual landmark and non-visual self-motion cues or non-visual self-motion cues only. Control participants wore goggles that approximated the field of view and the resolution of the Argus II prosthesis. In both tasks, control participants showed better precision when navigating with reduced vision, compared to without vision. Patients, however, did not show similar improvements when navigating with the prosthesis in the path reproduction task, but two patients did show improvements in the triangle completion task. Additionally, all patients showed greater precision than controls in both tasks when navigating without vision. These results indicate that the Argus II retinal prosthesis may not provide sufficiently reliable visual information to improve the precision of patients on tasks, for which they have learnt to rely on non-visual senses.

Motivated by recent findings of improved perceptual processing and perceptual-motor skill following stroboscopic vision training, the current study examined the performance and acquisition effects of stroboscopic vision methods that afford a different visual experience. In Experiment 1, we conducted a within-subject design study to examine performance of a multiple object tracking (MOT) task in different stroboscopic vision conditions (Nike Vapor Strobe®, PLATO visual occlusion, and intermittent display presentation) operating at 5.6, 3.2, or 1.8 Hz. We found that participants maintained MOT performance in the Vapor Strobe condition irrespective of strobe rate. However, MOT performance deteriorated as strobe rate was reduced in the other two stroboscopic vision conditions. Moreover, at the lowest strobe rate (1.8 Hz) there was an increase in probe reaction time, thus indicating an increased attentional demand due to the stroboscopic vision. In Experiment 2, we conducted a mixed design study to examine if practice in different stroboscopic vision conditions (Nike Vapor Strobe® and PLATO visual occlusion) influenced acquisition of a novel precision-aiming task [i.e., multiple object avoidance (MOA) task] compared to a normal vision group. Participants in the PLATO visual occlusion group exhibited worse performance during practice than the Vapor Strobe and normal vision groups. At post-test, the Vapor Strobe group demonstrated greater success and reduced end-point error than the normal vision and PLATO groups. We interpret these findings as showing that both an intermittent perturbation (Nike Vapor Strobe®) and elimination (PLATO visual occlusion and intermittent display presentation) of visual motion and form are more attention demanding (Experiment 1), however, the intermittent perturbation, but not elimination, of visual motion and form can facilitate acquisition of perceptual-motor skill (Experiment 2) in situations where it is necessary to maintain and update a spatio-temporal representation of multiple moving objects.

A case of bacterial endophthalmitis secondary to a penetrating injury was successfully treated with intracameral topical and subconjunctival injections of gentamicin. After treatment the patient had normal vision and there was no evidence of toxic side-effects on the anterior segment of the eye including the endothelium, angle structures, and lens. The potential pathogenicity of Staphylococcus epidermidis is again emphasized.

In Reply. —A driver with normal vision can be used fairly to judge the bioptic telescopic spectacle (BTS) because both the small magnified area and the area blinded to traffic while changing fixation to read the road sign are the same as seen through the telescope, whether the vision is 20/20 or 20/200. The hazardous blind area in the field is not related to the central vision. There is no evidence that the BTS is a safe device for operating a motor vehicle. The evidence is that the BTS is more of a hazard than an aid. Approach magnification has the obvious advantage of always being available. Furthermore, it can be varied, it does not impair the peripheral vision, and it is safer. The states have an obligation to the visually handicapped to grant a waiver for impaired vision, otherwise the states are endorsing the exploitation of the handicapped by

Summary.-The Farnsworth-Munsell 100-Hue Test was administered to 120 familial right-handed color-normal males. The range of errors indicative of low, average, and superior color discrimination varied from published norms. Subjects made significantly fewer errors on the first quarter-series so that the assumption of random errors by color-normal males was not met. The Farnsworth-Munsell 100-Hue Test' (1957) was designed to measure hue discrimination using a total of 85 color discs arranged between pilot colors at both ends of four quarter-series, the first quarter-series containing 22 color discs. Use of the test norms is limited by the lack of specification of the characteristics of subjects composing samples for whom error scores are given. Average color discrimination is defined as a total error score on the first test between 20 and 100, a range encompassing the middle 68% of the scores or -C 1 standard deviation. Superior discrimination ( 16% ) ranges from total error scores of 0 to 19. Low discrimination (16%) is indicated by a total error score greater than 100. These categories are used to make statements about the color discrimination of normals, individuals who do not give colorblind responses on such tests as the Ishihara Plates and who make seemingly random errors on the Farnsworth-Munsell 100-Hue Test, such that errors do not occur more often in one quarter-series than another. As the final part of the experimental procedure in a series of color discrimination experiments, the Farnsworth-Munsell 100-Hue Test was individually administered to each subject. The performance of the subjects on this test was not in agreement with the aforementioned normative data in several regards and it therefore seemed important to report out findings. A group of 120 familial right-handed undergraduate males, aged 17 to 36 yr. (M = 20, SD = 2.38), participated. They had normal vision without color defects as determined by a Bausch and Lomb Modified Orrhorater and the Dvorine Pseudo-Isochromatic Plates. Administration and scoring procedures followed those suggested by the manual, each quarter-series being given in the same order under daylight fluorescent illumination. . Mean error scores and standard deviations are given in Table 1. In terms of the color-discrimination norms mentioned previously, 84% were average scores, only 2% were superior and 14% were low. Clearly the range of error scores for superior color discrimination is too restricted or our sample is in

Orientation discrimination of a single line was measured for different orientations using a sequential discrimination task in six normal subjects. Both the method of single stimuli (Orban et al., 1984) and a transformed Up Down staircase method (Wetherill & Levitt, 1965) were used.

To the Editor. —I have recently observed an ocular hypertensive response to topically administered dexamethasone that was greater in magnitude and more abrupt in onset than any previously reported in the literature. I thought I might share this with the readership of theArchives. A highly myopic 45-year-old man was first seen in December 1974 with a retinal detachment in his right eye. This detachment was successfully repaired, with restoration of normal vision. Several months after the surgery, the patient was seen again, this time for a change of glasses. Results of his entire examination at that time were normal with the exception of his considerable myopia and evidence of the successful scleral buckling procedure. Although his intraocular pressure was 20 mm Hg in both eyes, the heads of both optic nerves appeared somewhat saucerlike and raised the suspicion of possible glaucomatous excavation. In an attempt to at least define

To the Editor. —The empty sella is an acquired anatomic condition in which the subarachnoid space protrudes into the cavity of the sella turcica and the pituitary gland is flattened against the sellar floor or walls. Cases not associated with prior pituitary irradiation or surgery are termed primary. Although most patients with primary empty sella have normal vision, a sizable minority show some degree of visual compromise. We describe herein a case of primary empty sella associated with visual loss in which the clinical and radiographic findings suggest the mechanism responsible for damage to the visual pathways. Report of a Case. —A 38-year-old obese black woman stated that she experienced visual loss in both eyes two years previously. No further change in vision had been noted since then. On examination, her visual acuity was 20/30 OD and 20/40 OS. Both optic discs were pale. Visual fields showed a superotemporal defect

ALTHOUGH normal visible light is generally considered to extend from 7500 A. to 4000 A., most spectroscopists are familiar with the fact that the 3650 line of the mercury spectrum is oluite visible. Saidman and Dufestel reported1 that this latter line is visible after a period of accommodation, and that its colour sensation is identical with that of the 4047 A. line. They report that no lines farther in the ultra-violet are visible. I have recently found with the new Muller-Hilger universal double monochromator normal vision down to 3125 A. This instrument gives monochromatic light of a high intensity and of a very high degree of purity. The purity was confirmed by means of calibrated filters. The object for these tests was the slit of the monochromator, across which were placed two wires in apart. Most of the observations listed below have been confirmed by eight observers. There were no failures to confirm.

Subjects responded in accordance with the apparent distance of a target, alternating between normal vision and minification. The training procedure of Foley & Abel (1967) was modified in an attempt to facilitate appearance of a phenomenon predicted by Taylor (1962). His expectation that effects and aftereffects would decline with repetition of the changes in visual condition was again not confirmed.

While conservative treatment resulted in slight improvement in the visual acuity, rapid betterment and ultimate normal vision followed the removal of infected tissue from the maxillary sinus. It is fair to conclude that the infection within the antrum was the cause of the optic neuritis. Conservative measures should be instituted while the search for foci of infection is progressing but once a focus is definitely established it must be eliminated without delay. Careful investigation and planning should precede nasal surgery.