Prenuclear paresis of homolateral inferior rectus and contralateral superior oblique eye muscles.

In a case of left inferior rectus paresis, it is demonstrated that the lesion must be prenuclear. On downward gaze, the left eye, although it reached the required target with a rapid saccade, drifted back towards the midline immediately afterwards. During the drift, several corrective saccades appeared. A dissociated "gaze paretic" nystagmus resulted. Synchronously, the right eye showed an incyclorotary nystagmus. We suspect a lesion of "tonic" fibers supplying the nuclear region of the left inferior rectus and the right superior oblique muscle.

Relative absence of psychopathology in benign essential blepharospasm and hemifacial spasm.

We report on the psychopathology and illness-related changes of life in patients with benign essential blepharospasm (BEB) or hemifacial spasm (HFS). Fifty-six patients with BEB and 40 patients with HFS completed the SCL 90R, a screening instrument for psychiatric symptomatology, and the Freiburg Questionnaire for Dystonia (FQD), a questionnaire about psychosocial changes in subjects with movement disorders. In both BEB and HFS patients, the mean scores on all but one subscale of the SCL 90R remained within the double standard deviation of normal. In comparing BEB to HFS patients in illness-related changes of life, BEB patients were more severely disabled in all areas of life examined. Psychological distress in BEB, but not in HFS, correlated with physical disability and in particular with impairment of vision.

Unilateral internuclear ophthalmoplegia. The lack of inhibitory involvement in medial rectus muscle activity.

Inability to adduct the left eye beyond the midline was found in a patient after brain stem infarction. Pursuit movements, refixation saccades, and the vestibulo-ocular reflex were restricted to the temporal hemifield. Only near convergence led to an adduction of 15 degrees in the left eye. Nasally directed saccades were slow, and temporally directed saccades showed glissadic back-drift. Electromyography revealed a lack of burst activity in the left medial rectus; however, inhibition of the left (homolateral) and the right (contralateral) medial rectus muscles during off-saccades and in off-positions of gaze was normal. These observations suggest that inhibition for medial rectus motor neurons is not mediated by the medial longitudinal fasciculus. The findings are compatible with the neurophysiological data, which show that reductions of activity in the medial rectus motoneurons are largely caused by disfacilitation via internuclear neurons rather than by inhibition.

Latent nystagmus. Release and suppression at will.

PURPOSE: The authors report the cases two unusual patients with infantile convergent strabismus and latent nystagmus. METHODS: Electronystagmography was used. RESULTS: The two patients were able to release and suppress their nystagmus at will. With voluntary effort, the nystagmus became as strong as it was when brought out by occlusion of the squinting eye and, in one of the patients, even stronger. The nystagmus beat toward the fixing eye, and the slow phases had slightly decreasing velocity or were linear. Both patients were able to evoke and to stop the nystagmus in front of visual contours and, one of them, also in the dark. CONCLUSIONS: This phenomenon could be the result of voluntary control of the visual input contributed by the amblyopic eye and/or a direct influence of will on the slow eye movement and fixation systems. A mechanism related to vergence eye movements is less likely. The ability to release and suppress a latent nystagmus at will is unusual and, to the authors' knowledge, has not been described before.

Internuclear ophthalmoplegia of abduction. Isolated impairment of phasic ocular motor activity in supranuclear lesions.

Abduction saccadic movement slowed to either side without any limitation in the end position occurred in a patient. This ocular motor abnormality constituted a mirror image of the well-known internuclear ophthalmoplegia of abduction. Intermuclear ophthalmoplegia of either type demonstrates that a lesion between the center for conjugate gaze and the ocular motor nuclei can impair phasic activity of the eye muscles without reducing their tonic function.

Visual localization after strabismus surgery is compatible with the "outflow" theory.

Strabismic patients pointed at visual targets, presented monocularly, without sight of the pointing arm. After surgical rotation of one eye in the orbit the pointing responses were shifted by a similar amount in the opposite direction in 13 out of 14 patients; this outcome corresponds to the predictions of the outflow theory of visual localization. Occasional differences between predicted and actual response shifts can be attributed to the well-known ambiguity of localization in strabismics.

Inherited Duane's syndrome: mirror-like localization of oculomotor disturbances in monozygotic twins.

Abnormal innervation hampered the left eye in one twin, while producing the same effect in the right eye of the other twin and in that of his mother.

[Prism correction in heterophoria]. / Prismenkorrektion bei Heterophorie.

Unlike heterotropia (= manifest strabismus), heterophoria (= latent strabismus) is not a primarily existing condition but is a reaction to an interruption of the sensory-motor feedback control system. The reaction consists of a deviation from the orthovergence position. Binocular vision causes a continuous calibration of the vergence position. This "orthophorisation" explains that in most persons, heterophoria differs only slightly from zero. Nevertheless, a small heterophoria is common (70-80% of the population). The need to compensate for heterophoria by sensory-motor fusion can cause asthenopic complaints, such as headaches with prolonged reading. Since a variety of other defects can lead to similar symptoms, a causal relationship with heterophoria can be assumed only after a thorough differential diagnosis. Prism spectacles or eye muscle surgery for heterophoria should be recommended only after prism trials in free space, which include yoked prisms as a placebo control. Heterophoria should be distinguished from "Winkelfehlsichtigkeit", which is a deviation from orthoposition that results from the "measuring and correcting methodology after H.-J. Haase" (MKH) and is based on the idea that fixation disparity, a minute deviation from orthovergence position, indicates an inability to overcome a larger "vergence angle at rest". Objective recordings have, however, revealed that the subjective tests with stereo cues applied in the MKH can mislead to the assumption of a fixation disparity although both eyes are aligned exactly to the fixation point. A trial conducted in the Netherlands concerning the therapy of asthenopic complaints showed no statistically significant advantage of prism spectacles determined with the MKH over conventional spectacles.

[Psychometric function of stereo disparity in normal persons]. / Die psychometrische Funktion des querdisparaten Tiefensehens bei Normalpersonen.

UNLABELLED: The accuracy and efficiency of threshold estimation depend on a priori knowledge of the shape of the psychometric function. Such knowledge is available for contrast detection and visual acuity, but not for disparity detection. METHODS: We studied the psychometric function for disparity detection in 26 visually normal, untrained observers by measuring detection rates over a wide range of disparities. In a two-alternative forced-choice (2AFC) task the subject had to decide whether the right or left of two vertical bars, differing in depth, was closer to them. An S-shaped Weibull function was fitted to each subjects's data using the maximum-likelihood procedure. RESULTS: In 21 of the 26 subjects the psychometric function rose with increasing disparities up to a level of about 100%. Five of the 26 subjects only reached hit rates clearly below 100% (66% to 82%), even at disparities well above the threshold. The mean slpe of the S-shaped psychometric function of disparity detection was much lower (1.2 Weibull units) than that known for visual acuity and contrast detection (about 3.0 Weibull units). The slope differed widely among subjects, but was not related to stereo acuity. CONCLUSION: For accurate and efficient estimation of stereo acuity, the shallow slope of the psychometric function requires more than 100 single trials around the threshold if a 2AFC procedure is used. In addition, several disparities well above the threshold must be presented in order to detect subjects who do not reach a hit rate of 100% at any disparity. Otherwise, stereo acuity would be underestimated in these subjects.

[The Freiburg Vision Test. A computer-assisted procedure with sequential strategy]. / Der Freiburger Visustest. Ein computergesteuertes Verfahren mit Eingabelungsstrategie.

Single Landolt Cs were presented in one of four positions on a monitor. Subjects responded by pressing one of four buttons (forced choice). A computer selected the size of the Landolt Cs on a logarithmic scale using the "Best PEST" algorithm (Best Parameter Estimation by Sequential Testing), a modern procedure to measure psychophysical thresholds. For comparison, conventional measurements according to DIN 58220 (Deutsche Industrie Norm) were performed with Landolt Cs projected in eight positions, using three out of five correct responses as the threshold criterion. Examination of 23 patients (most of them with senile cataract) did not show any significant difference between the two tests in either visual acuity or reproducibility on two consecutive days. The coefficients of variation between sessions were 22% for the Freiburg test and 26% for the DIN test and 18% between the two tests, pooled over two sessions. The Freiburg acuity test thus appears to be numerically equivalent to the DIN 58220 procedure. In addition, it has a number of advantages: (1) examiner-dependent variability is reduced; therefore, the test can be used by inexperienced examiners; (2) the forced choice technique is used rigorously; (3) mistakes in confounding oblique directions are largely avoided; (4) the procedure is about twice as fast.

[Comparison between dissociated and associated heterophoria]. / Vergleich zwischen dissoziierter und assoziierter Heterophorie.

BACKGROUND: Since Ogle (1949) dissociated heterophoria is distinguished from associated heterophoria. Dissociated heterophoria is defined as a deviation from the orthovergence position that occurs when no fusional contours are provided. Associated heterophoria is a deviation that occurs under prism correction of fixation disparity, i.e. under a viewing condition in which fusional contours are absent only in the centre of the visual field. Both dissociated and associated heterophoria have been used as indications for prismatic correction. It has been controversially discussed to what extent dissociated and associated heterophoria are comparable. METHODS: A total of 43 subjects were investigated using the white Maddox rod test for horizontal dissociated heterophoria and the cross test of Hans-Joachim Haase (a test similar to the fixation disparity test described by Ogle 1949) for horizontal associated heterophoria. In both tests subjects were asked to continually correct any deviation using Herschel prisms. Readings were taken after 1 min. RESULTS: The correlation between the results obtained with the white Maddox rod test and the cross test was r = 0.89 (p < 0.0001) and the slope of the regression line was 0.92 (95% confidence interval from 0.77 to 1.07). One subject was unable to reach a match in the cross test because she had an "obligate" fixation disparity due to a staphyloma posticum. CONCLUSIONS: Our study revealed a high correlation between dissociated and associated heterophoria. This result appears plausible since the feedback loop for fusion is disconnected in both cases, although in a different manner: When dissociated heterophoria is measured, fusionable contours are absent. When associated heterophoria is measured, any disparity of peripheral contours that could serve as an error signal is nullified by instantaneous prism correction. The high concordance of dissociated and associated heterophoria suggests that both measures are of equal value as an indication for prismatic spectacle correction. In rare cases of an "obligate" fixation disparity, however, associated heterophoria cannot be determined so that dissociated heterophoria remains as the only indication.

Aplasia of the superior oblique tendon.

The authors describe two cases with unilateral aplasia of the superior oblique tendon. The incomitance pattern could not be explained solely by the lacking torque of the superior oblique muscle. Rather, a considerable adaptation of the central nervous system had to be invoked resulting in compensatory innervation of the remaining seven vertical muscles of both eyes.

Reversed Fixation Test as a Means to Differentiate between Dissociated and Non-Dissociated Strabismus.

Dissociated vertical deviation (DVD) depends on the balance of visual inputs coming through the right and left eyes. In the classical Bielschowsky Filter Test the balance of visual inputs is altered by darkening the retinal image of the fixing eye with a filter. In the Reversed Fixation Test (RFT) the balance of visual inputs is altered by not only darkening the fixing eye (occlusion put on) but also by brightening the squinting eye (occlusion removed) and, at the same time, switching the fixation to the other eye. In a series of 30 patients the RFT revealed a DVD component of 16.3 ± 4.9± while the Bielschowsky Filter Test revealed 3.4 ± 3.2± only. In seven cases the value of the Bielschowsky Filter Test was even zero while the RFT revealed a DVD component between 8 and 20±. The RFT allows a quantitative differentiation between DVD and esotropia with elevation in adduction (= upshoot in adduction or strabismus sursoadductorius or overaction of the inferior oblique muscle), even if both types of vertical deviation occur in the same patient.

Heterophoria and fixation disparity: a review.

Heterophoria does not provide a reliable clue for ordering prisms in an asthenopic patient. The same reservation applies to associated phoria, as determined by prism correction of fixation disparity. Subjective tests for fixation disparity, even those with a fusionable fixation target, do not correctly indicate the vergence position of the eyes under natural viewing conditions. Attempts to measure fixation disparity on the basis of stereo disparity, using the "Measuring and Correction Methods of H.-J. Haase", have failed.

[Differential diagnosis of optic nerve atrophy]. / Differentialdiagnose der sehnervenatrophie.

Diseases of the visual pathway: early detection and therapy. Manual kinetic perimetry is faster in the detection of lesions of the visual pathway than automated static perimetry. When cases with a comparable reduction of visual acuity are considered, color desaturation is more pronounced in lesions of the visual pathway than in opacities of the optic media. Search for an afferent pupil defect allows the differential diagnosis between functional and unilateral organic visual impairment: in the case of bilateral visual impairment, a combination of VEP and pattern ERG is suitable for this differentiation. In chronic papilledema, secondary atrophy can best be detected in the arcuate retinal nerve fibers. Fistulation of the dural sheath of the optic nerve prevents visual loss in chronic papilledema. A similar operation could be useful in the progressive form of anterior ischemic optic neuropathy. Recently, the mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy was identified. Prolactin secreting pituitary adenomas shrink with bromocriptine treatment.

The effect of prolonged monocular occlusion on latent nystagmus in the treatment of amblyopia.

We recorded eye movements in 8 patients with latent nystagmus (LN) before and after 2 days of occlusion of the better eye. The slow-phase speed of the nystagmus (SPS) during fixation with the worse eye became lower after 2 days of occlusion of the better eye. However, the SPS during fixation with the better eye became higher after 2 days of occlusion of the better eye. The sum of SPS during fixation with the better eye and SPS during fixation with the worse eye remained the same. Oscillopsia complaints gradually disappeared over days during the occlusion. It seems likely that the alteration of the LN during prolonged monocular vision is caused by a slow-velocity bias of the neural integrator, a compensatory drift, generated by the flocculus using retinal-slip information. The difference between SPS during fixation with the better eye and SPS during fixation with the amblyopic eye in LN patients with amblyopia is probably also caused by this compensatory drift. As the compensatory drift changes its direction and magnitude slowly over days, it seems advisable to occlude the better eye in children with amblyopia and LN during days per week, and not during hours per day.

[When is the prescription of prismatic eyeglasses reasonable?]. / Wann ist eine Prismenverordnung sinnvoll?

Prismatic glasses are used to deflect rays of light. In ophthalmology, prisms are mainly used to correct double vision caused by strabismus which is acquired after early childhood. In congenital or infantile strabismus, the image of the deviated eye is usually suppressed so that double vision does not occur and prismatic glasses are not indicated. Latent strabismus is very common and only rarely leads to double vision or asthenopic symptoms so that correction with prismatic glasses is only indicated in exceptional cases. The "Measuring and Correcting Methodology after H.-J. Haase" is based on flawed assumptions, and therefore can not be recommended for the prescription of prisms.