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J M Enoch

Publications and source records attributed to J M Enoch.

At least 127 records · Page 7Linked to original sources
PubMed1976

Human psychophysical analysis of receptive field-like properties: IV. Further examination and specification of the psychophysical transient-like function.

In this paper we examine several key properties of the moving 'windmill' target used in evaluation of the psychophysical transient-like function. Magnitude of the transient-like function, herein defined as the difference in threshold-determining background field luminance between stationary and moving windmill conditions, was greatest for a rate of approximately 6-8 on-off transitions/second for the moving windmill. Increasing the light/dark ratio of the windmill also augmented the magnitude of the transient-like function. The one-, two- and four-section 'windmill' targets exhibited essentially similar results, indicating that the number and length of borders do not influence this response. In conjunction with previous stationary windmill results (Enoch and Johnson, 1976), these data define the relevant transient-like function properties and provide a basis for comparison with findings in the companion paper (Enoch, Johnson & Fitzgerald, 1976a) which describes the application of these properties to clinical populations for diagnostic purposes.

Psychophysics↗
PubMed1976

Human psychophysical analysis of receptive field-like properties: V. Adaptation of stationary and moving windmill target characteristics to clinical populations.

This paper describes the application of several key parameters of a windmill-shaped target (used in determinations of the psychophysical transient-like function) to clinical populations as a diagnostic tool for static perimetry. A technique for independently analyzing sustained- (Westheimer function) and transient-like retinally-based psychophysical responses is outlined, and stimulus characteristics, reliability and diagnostic potential of the tests are examined. Several particularly interesting clinical cases (one closure of a branch retinal arteriole) and two senile macular degeneration patients) are presented for illustrative purposes. In addition, a tentative 'working hypothesis' is presented as a basis for extensive future analysis of various clinical populations.

Aged↗
PubMed1976

Early surgery and visual correction of an infant born with unilateral eye lens opacity.

A healthy neonate born with unilateral cataract was operated upon on Life Day 4. Visual correction and testing were initiated promptly. Resolution showed continuous improvement in the normal eye, with no improvement noted in the operated eye until adequate visual correction was provided. Following correction there was prompt marked improvement of visual resolution.

Cataract↗
PubMed1976

Additivity of effects within sectors of the sensitization zone of the Westheimer function.

In this paper, the fourth in a new series, we have examined the properties associated with illuminated sectors of the annular "sensitization" zone of the psychophysical Westheimer function. The results for one-, two-, and four-sector annular background fields indicate simple additivity of effects within the sensitization region when the flashing test field was set substantially above its increment threshold. Under such conditions effects of pattern orientation and borders within the sensitization zone were found to be negligible. The present findings provide a basis for relating the newly developed "transient-like" psychophysical test (which uses a windmill-type stimulus) to the Westheimer function. These data complement earlier clinical analyses of responses by patients whose Westheimer functions were studied near visual field lesions having sharp borders. The latter study is important in localizing this response function in the retina.

Field Dependence-Independence↗
PubMed1976

Human psychophysical analysis of receptive field-like properties. I. A new transient-like visual response using a moving windmill (Werblin-type) target.

A human transient-like visual response has been revealed psychophysically with a rotating windmill target, similar to that used by Werblin in his recent studies of the retina of Necturus. The windmill pattern evoked complex perceptual phenomena (important in and of themselves) which were minimized by using a high luminance for the "criterion" flashing test field (relative to its increment threshold), and by moving the four-vaned windmill pattern at a rate of two complete revolutions per second. The transient response, herein defined as the difference in threshold between the stationary and moving windmill conditions, was greatest when the windmill vanes fell completely within the sensitization (inhibition-like) portion of the Westheimer function determined at the same retinal locus. The test has been developed so that it may be readily adapted to available clinical equipment for future diagnostic purposes .

Differential Threshold↗
PubMed1976

Some optical principles of the clinical specular microscope.

The clinical specular microscope is used to examine and photograph human endothelial cells in vivo. An optical analysis is presented here in simple form to aid the ophthalmologist or visual scientist in understanding how this instrument can be used in a quantitative manner to measure the size of the magnified endothelial cells and the thickness of the overlying cornea. An error analysis is discussed in order to demonstrate some aspects of the precision of the determination.

Cornea↗
PubMed1976

Use of inverted telescopic corrections incorporating soft contact lenses in the (partial) correction of aniseikonia in cases of unilateral aphakia.

Soft contact lenses have been successfully adapted to inverted telescope units used to restore effective binocularity to selected unilateral aphakic patients. Techniques for adapting such units to the patient have been outlined and results have been reviewed. Differences between hard and soft contact lens techniques have been contrasted. The practitioner is encouraged to utilize these methods when binocularity would be a clear advantage to the patient with unilateral aphakia. The author hopes to adapt these techniques to the treatment of infants and young children in the future.

Aniseikonia↗
PubMed1975

A erimetric technique believed to test receptive field properties: sequential evaluation glaucoma and other conditions.

We used a technique to simplify and speed up a perimetric test (Westheimer function). Through sequential testing, the technique was successfully used to evaluate pathologic findings and partially to evaluate treatment regimens in three subjects. One patient had an onset of kinetic field changes and Westheimer function alteration with primary open-angle glaucoma. Temporary remissions of alterations in the Westheimer function and kinetic visual field loss occurred in patients with glaucoma and tobacco-alcohol (complicated) amblyopia. Using these techniques it is possible to localize an anomaly in the outer retinal layer, the inner retinal layer, and central to the optic nerve head. We divided the inner and outer retinal layers on a vascular support basis.

Aged↗
PubMed1975

Best's vitelliform macular dystrophy.

A patient with Best's vitelliform macular dystrophy in his right eye had an intact vitelliform disk and drusen of the optic papilla. Although the foveola elevated by a few tenths of a millimeter, resolution was only slightly affected and the retinal receptors remained remarkably well-aligned, suggesting that mechanisms subserving receptor alignment still functioned. Hue discrimination and visual acuity were only slightly affected and the electroretinogram and visually evoked response showed essentially normal values. The vitelliform disk in the left eye ruptured by direct, blunt trauma. This same eye later developed subretinal macular neovascularization, as its visual acuity reduced, retinal sensitivity decreased, receptor orientation showed abnormalities, and hue discrimination became less efficient; the electroretinogram and visually evoked response remained normal.

Accommodation, Ocular↗
PubMed1975

Marked accommodation, retinal stretch, monocular space perception and retinal receptor orientation.

In recent years we have come to recognize that retinal receptors are probably aligned with the center of the exit pupil of the eye. It becomes crucial to define those factors influencing and determining photoreceptor alignment. Here, the effect of retinal stretch associated with marked accommodation has been considered. Assuming that a sense of direction is associated with a given retinal locus, we have used a classical monocular bisection test technique in order to see if marked accommodation altered bisection settings. Substantial changes in bisection settings were found when testing in the region of the posterior pole. These could be localized most probably in the retina and choroid. In separate studies, the effect of anterior retinal stretch upon cone receptor orientation in the region of the fovea was evaluated. Marked accommodation caused a transient nasal displacement of the peak of the Stiles-Crawford directional sensitivity function. These studies suggest that the posterior pole of the eye is routinely subject to stresses and strains. This point is of clinical significance. Our studies suggest that the presence of the blind spot influences the magnitude of change of measured parameters. We have only begun the important task of evaluating the nature of recovery processes following marked accommodation. Lastly, in order to obtain the necessary responses, we have had to train our young observers to voluntarily utilize nearly their entire accommodative capability.

Accommodation, Ocular↗
PubMed1975

Experimentally determined optical properties of goldfish cones and rods.

The optical properties of goldfish photoreceptors were evaluated using the special microscope-microspectrophotometer divice. Mode patterns transmitted were identified for both natural and reverse path illumination. Photomechanical changes with adaptive state could be identified. Complex mode interactive phenomena and cross-coupling of energy were observed. These are related to the fact that there are double cones and apposition or near apposition of neighboring receptors in this species. The directionality of individual cones and rods was quantified by making use of the principle of reversibility of light path. Radiation patterns were recorded and analyzed on a computer controlled microdensitometer. Individual cones and rods were shown to exhibit marked directionality. Light collection properites of cones were strikingly evident.

Adaptation, Ocular↗
PubMed1973

Monocular spatial distortions induced by marked accommodation.

Contraction of the ciliary muscle during marked accommodation causes the leading edge of the retina to advance as much as 0.5 centimeter. Near the posterior pole of the eye, the upward and downward extensional strains on the retina should be reasonably balanced. In the horizontal meridian an asymmetry is introduced because of the nasal location of the optic nerve head. Observers were asked to bisect the space between two parallel lines while fixating a movable line lying near the midpoint of the two lines. The test was conducted with the target far from and near the subject, in the horizontal and vertical meridians, and was repeated with accommodation paralyzed by a cycloplegic agent. Marked accommodation induced significant spatial distortions in the horizontal meridian. The effect is largely retinal.

Accommodation, Ocular↗