Periodic downbeat nystagmus

The authors observed a periodic downbeat nystagmus with a cycle of 3 minutes 30 seconds, beating downward for a period of 90 seconds every 2 minutes. It lasted 86 hours in a patient with severe hypomagnesemia associated with complications from scleroderma. There was no lesion on brain imaging, and an EEG performed during the nystagmus was normal, indicating that the most likely explanation for this periodic nystagmus is metabolic. This form of nystagmus may have resulted from severe hypomagnesemia, possibly associated with thiamine deficiency.

Automated visual field examination in children aged 5-8 years. Part II: Normative values

We determined normative values for the visual sensitivity threshold in 118 children aged 5-8 years, using automated static perimetry (Octopus 2000R, program 32). In addition, 17 normal adults were tested. The children first underwent a familiarization procedure. One week later, quantitative examination was performed according to a specially designed schedule divided into three phases. For each of the 76 points tested, mean thresholds and standard deviations were calculated as a function of age. In contrast to previous studies, sensitivity difference between adults and children over the central 30 degrees of the visual field emerged only for the youngest age groups (5- and 6-year olds). Both the response rate in false-negative trials, and values of a within-subject threshold variability index, suggested that 5- and 6-year-olds' higher thresholds were inflated by non physiological factors, such as vigilance and cognitive processes. For these ages, the data reported here should therefore be considered as an approximation of the upper level of the thresholds. In contrast, our results for 7- and 8 year-old children provided reliable normative values for light sensitivity across the visual field.

Automated visual field examination in children aged 5-8 years. Part I: Experimental validation of a testing procedure

In 106 children aged 5-8 years, we determined how much training was needed to stabilize the response strategy prior to actual visual field assessment and we evaluated the reliability and acceptable duration of automated static perimetry (Octopus 2000R). A specially designed familiarization procedure was used to train the children to: (1) gaze at the center of the visual field while paying attention to light stimuli projected onto the periphery and (2) press the buzzer only when light stimuli were perceived. The subsequent examination phase consisted of 15 successive identical blocks of 27 trials (12 stimulus trials, 12 false-positive catch-trials, and three false-negative catch-trials), and was stopped before the end if signs of fatigue appeared. Age had a marked influence both on endurance (the number of blocks performed increased significantly) and on response reliability (false-positive responses decreased between 5- and 6-year-olds). The increase in false-negative responses toward the end indicates that examination is no longer reliable, and should be stopped. We concluded that most children as young as five can undergo examination by automated static perimetry. Changes regarding learning, stimulus intensity and testing procedure are suggested in order to adapt the examination to age, level of vigilance and health condition of the children.

[Visual perception of movement. A normative study]

BACKGROUND

A battery of tests has been developed to better define the variety of defects which can occur in the process of visual perception of motion.

METHODS

The tests assessed the perception of 1) coherent motion, in each of the four cardinal directions; (2) form from motion; (3) flow in depth; and (4) motion of a target moving in depth, within or without an optic flow surround. A normative study was conducted with 34 subjects, 21 to 69 years of age.

RESULTS

Recognition of form from motion was better with upwards than with downwards motion. Perception of motion in depth was better with backward than forwards motion. The presence of an optic flow altered the perception of a motion in depth.

CONCLUSION

The recognition of form from motion demonstrated an asymmetry in threshold between the upward and downward movements. This asymmetry did not occur with global coherent motion, thus reflecting the variety of mechanisms involved in the visual process of motion. Moreover, alteration of perception of motion in depth within an optic flow reflected background effect.

The vanishing of the sun: a manifestation of cortical plasticity

In Monet's painting impression. Rising Sun, when one steadily fixates the image of a sailor in the center of the picture for several seconds, the solar disk progressively disappears, being replaced in both brightness and color by the surrounding sky. This "filling-in" phenomenon reflects a process of cortical remapping, similar to the one that occurs in the presence of visual field defects. Filling-in is largely ignored by clinicians, despite its major implications in ophthalmologic practice, especially the nonrecognition of visual field deficits.

Terminating attacks of ocular neuromyotonia

We examined a 30-year-old woman who, for 6 months, had suffered from ocular neuromyotonia, which consisted of episodic ocular depression. Apart from the ocular complaint, her medical history and the clinical findings were unremarkable. The patient discovered that she could terminate each episode of tonic ocular depression instantly by forcefully directing her gaze upward. Stretching the affected muscle might also prove to be an effective way of ending attacks of neuromyotonia in other patients suffering from this condition.

[Scotomas: assessment by the patient and by the physician. There's nothing to see]

Contrary to long-held beliefs, plasticity occurs in the adult cerebral cortex, and allows the brain to adapt to background modifications or to damage of the nervous system. Cortical changes occurring following focal visual deafferentation modify visual perception, by filling in visual field defects with information from the area surrounding the scotoma. This causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. In ophthalmological daily practice, the effects of cortical plasticity are prominent, but are usually unrecognized. They result in unawareness of field defects following retinal photocoagulation, and cause delay in recognizing visual field defects, they e.g., in early stages of simple chronic glaucoma. In addition affect the results of some procedures for testing the visual field, and increase patients' difficulty in coping with activities in everyday life. It is important to introduce into clinical practice the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process. It can be demonstrated using a "double Amsler grid test".

Improvement in visual function in an eye with a presumed optic nerve sheath meningioma after treatment with three-dimensional conformal radiation therapy

The treatment of optic nerve sheath meningiomas (ONSM) is controversial. Radiation therapy has been used with some success in patients with progressive visual loss. We report a case of visual improvement in a patient with an optic nerve sheath meningioma and progressive visual field loss, treated with conformal radiotherapy.

Plasticity in the adult visual cortex: implications for the diagnosis of visual field defects and visual rehabilitation

It has recently been shown that, contrary to long-held beliefs, sensory and motor maps are not stable in the adult cerebral cortex. Alteration of input from the periphery results in changes in topography in the cortex, including the primary visual cortex. Mechanisms involved consist mainly of reshaping the receptive field of cortical cells and increasing the sensitivity of deprived cells in the visual cortex. Cortical plasticity allows the brain to adapt to background modifications or to damage of the nervous system. It also underlies learning and attention processes. Cortical changes occurring after focal visual differentiation modify visual perception by filling in visual field defects with information from the area surrounding the scotoma. This modification causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. Although the effects of cortical plasticity are prominent in neuro-ophthalmological daily practice, they are usually unrecognized or greatly underestimated. These effects cause delay in recognizing visual field defects, and hence in receiving therapy, while affecting the results of some procedures for testing the visual field. Affected individuals who are unaware of their defects may have increased difficulty in coping with activities in everyday life. Up to now, phenomena related to plasticity in the visual system have been investigated mainly by psychophysicists and neurophysiologists. It is essential to start considering the various effects of cortical reorganization in clinical practice. It is especially important to introduce into clinics the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process, and the need to measure it. This dissociation should also be demonstrated to the affected subjects.

Multiple evanescent white dot syndrome after hepatitis B vaccine

PURPOSE

Hepatitis B vaccine has become an effective means of preventing complications of hepatitis B. However, it occasionally induces serious side effects. We report a case of multiple evanescent white dot syndrome (MEWDS) that occurred following hepatitis B vaccination.

METHODS

A 23-year-old woman with a one-week history of progressive loss of vision in the left eye and bilateral photopsia was referred for examination. Her symptoms appeared 24 hours after a booster intramuscular injection of hepatitis B vaccine.

RESULTS

Clinical examination, fluorescein angiography, and the course of events were typical of MEWDS.

CONCLUSIONS

This case demonstrates the occasional occurrence of MEWDS after hepatitis B vaccine and suggests that hepatitis B virus immunization may be a risk factor for this retinal condition.

Feasibility of automated visual field examination in children between 5 and 8 years of age

AIMS

To investigate how young children develop the ability to undergo a visual field evaluation using regular automated perimetry.

METHODS

The study included 42 normal girls aged 5, 6, 7, and 8 years. Twelve locations in the 15 degrees eccentricity were tested in one eye, using an Octopus 2000R perimeter with a two level strategy. False positive and false negative catch trials were presented. The examination was performed three times in succession. Before the examination procedure, a specially designed programme was conducted for progressive familiarisation.

RESULTS

During the familiarisation procedure, it was found that all of the 5-year-old children, seven of the 6-year-old children, and three of the 7-year-old children were unable to perform immediately, and correctly, the instructions given during the familiarisation phase; these children took from 30 seconds to 3 minutes to comply with the examiner's requests. With the exception of one 5-year-old child, all tested subjects completed the planned procedure. The mean proportion of false negative answers in catch trials was 1.6%. The mean proportion of false positive answers was 12.2%. The quadratic dependency on age suggested by the averages was not significant (F(3,116) = 0.88; p = 0.45). Detection stimulus improved with age, as shown by the fact that probability of perceiving dim stimulus increases significantly (F(3,116) = 12.68; p < 0.0001).

CONCLUSION

Children did remarkably well regarding both the duration of the examination and the reliability of the answers. A preliminary familiarisation phase with a specially designed adaptation programme was found to be mandatory with children aged 7 or under. To our knowledge, this is the first time that such an investigation has been performed.

Diplopia from skew deviation in unilateral peripheral vestibular lesions

Vertical diplopia from skew deviation is well described in brainstem lesions. The phenomenon can also result from peripheral vestibular lesions. During the past years, we have observed these ocular changes in the acute stage following unilateral vestibular neurectomy and labyrinthectomy (n = 13), as well as in series of patients suffering from idiopathic sudden unilateral peripheral vestibular or cochleo-vestibular deficit (n = 5). Diplopia from skew deviation was noted immediately following ablative vestibular procedures; in patients with idiopathic vestibular deficit, it was observed as an associated sign. In all patients, clinical evaluation revealed an acute unilateral peripheral vestibular loss, with spontaneous nystagmus toward the unaffected ear and absence of nystagmic response to caloric testing on the affected ear. Skew deviation was measured using the Hess-Weiss test, which is based on the haploscopic principle. Static visual vertical was evaluated with the original methods of vertical frame and Maddox rod techniques. Photographs were made of the ocular fundi, to measure the degree of cyclotorsion of both eyes. In our patients, we found skew deviation with hypotropia of the eye that was ipsilateral to the affected ear and conjugated cyclotorsion and tilt of the static visual vertical on the side of the affected ear. Skew deviation was the first sign to disappear within a few days; conjugated cyclotorsion and tilt of the static visual vertical persisted for weeks to months. The eye-head postural reaction, consisting of head tilt, conjugated eye cyclotorsion, skew deviation, and alteration of vertical perception directed toward the side of the lesion, is known as the Ocular Tilt Reaction (OTR). The mechanism is presumably related to a lesion of the otolithic organs and/or to changes in the afferent graviceptive pathways. In man, the OTR is often mild and unrecognized, masked by spontaneous nystagmus and marked neuro-vegetative symptoms. Our observations indicate that skew deviation, as a part of the OTR, occurs in patients with sudden peripheral vestibular lesions, whether surgical or non-surgical in origin.

Ocular tilt reaction associated with a sudden idiopathic unilateral peripheral cochleovestibular loss

We recently observed a female patient who was suffering from acute right peripheral cochleovestibular loss associated with a marked vertical diplopia. Otoneurological examination showed profound deafness, and absence of nystagmic response to caloric and pendular rotatory test in the right ear. Neuroophthalmological examination showed skew deviation with right hypotropia, excyclotorsion, and tilt of the static visual vertical directed to the right side. Immunological and serological examinations were normal. Neurological examination and extensive neuroradiological investigations failed to demonstrate any central nervous system involvement. In this patient, skew deviation and tilt of the static visual vertical were interpreted as signs of an acute unilateral otolithic dysfunction, due to a sudden idiopathic peripheral vestibular loss.

Role of the completion phenomenon in the evaluation of Amsler grid results

PURPOSE

To evaluate the limitations, particularly those related to the perceptual completion phenomenon, of Amsler grid tests in patients with central scotomas caused by macular disorders.

METHODS

We tested 15 affected eyes of 15 patients with macular lesions. In each subject, the central visual field was assessed by using four different types of Amsler grid testing and a tangent screen. Tests were conducted in a random order, and the sequence of tests was repeated once. The distance between the fixation point and the closet border of the plotted scotoma was assessed. For each patient, reproducibility in repeated examinations was evaluated by assessing changes in location of the computed center of the defects and by measuring changes in the position of the center of the scotoma.

RESULTS

The tangent screen was more sensitive than Amsler grids in delineating the borders of the scotoma, and the results were more reproducible. Furthermore, by using a tangent screen, the fixation point was found adjacent to the scotoma.

CONCLUSION

Poor sensitivity and intraindividual variations found with Amsler grid testing are at least partly a result of the perceptual completion phenomenon. This phenomenon proved to be a dynamic and fluctuating process, as the results of two successive Amsler grid tests were not comparable, even when the technique was identical and the time between tests was no more than two to 15 minutes.

[Vestibular neuritis: a frequently unrecognized cause of diplopia]

The vestibular function plays an essential role in the stabilization of the image on the retina. In addition, when the head is tilted, it contributes to maintain horizontally the plane of the gaze. Vestibular changes can result in oscillopsia and/or diplopia. The latter is related to occurrence of a skew deviation. The authors emphasize the frequent occurrence of diplopia following disorders of the vestibular nerve, specially after vestibular neuritis. In clinical practice, the causal relationship between vestibular neuritis and diplopia is often unrecognized.

[Automated static perimetry in the child: methodologic and practical problems]

PURPOSE

In a pediatric population, the use of computerized static perimetry is known as particularly difficult. The specific difficulties which may occur when testing young subjects are stability of fixation, ability to maintain concentration, resistance throughout the procedure, and reliability of the answers. It seems important to investigate and to develop appropriate strategies for the examination of children aged 8 years and younger according to their ability to undergo visual field evaluation using automated static perimetry.

PATIENTS AND METHODS

Eighty normal children aged 5 to 8 years old were evaluated using an Octopus 2000R perimeter, with a one-level strategy. Adaptation of the procedure were included.

RESULTS

The analysis of answers and false-positive catch-trials showed that children as young as five years old did remarkably well regarding both the duration of the examination and the reliability of answers.

CONCLUSIONS

Automated static perimetry examination can provide reliable results in children as young as five years old once a familiarization procedure has been conducted and if the duration of examination does not exceed the child's capacity to remain task focused.

Angioscotomata and morphological features of related vessels in automated perimetry

AIMS

To determine principles which regulate the occurrence of angioscotomata in automated static perimetry, variations in light sensitivity were correlated with the location and diameter of neighbouring retinal vessels.

METHODS

Ten normal eyes were tested with the Octopus 2000R, using a 0.431 degree light stimulus. Sensitivity was quantified in points located around the blind spot, according to a regular, 0.5 degree constant, grid pattern. From 336 to 443 locations were tested in each eye. The resulting printouts were superimposed on corresponding fundus photographs. At each tested point, the following five additional variables were evaluated: the diameters of the closest and the second closest vessel (in 0.1 degree units); the distances of the apparent location of the tested point to the closest and the second closest vessel (in 0.25 degree units); and the distance between the two closest vessels (in 0.25 degree units). Altogether, 3869 locations were tested and 23,214 values were quantified.

RESULTS

The following two conditions were found to be related to a reduction in sensitivity: (1) proximity (< 0.25 degree) to a large vessel (> or = 0.5 degree in diameter); (2) proximity (< 0.25 degree) to one of two adjacent (< 0.5 degree distant), moderately large vessels (0.3 degree to 0.4 degree in diameter). In condition 1, sensitivity was 51.3% and specificity was 92.2%; in condition 2, sensitivity was 16.2% and specificity was 98.3%; and with a combination of conditions 1 and 2, sensitivity was 67.6% and specificity was 90.5%. Increase by 0.1 degree of an adjacent vessel which was 0.4 degree in diameter markedly affected light sensitivity.

CONCLUSION

Modifications in vessel diameter are observed in a number of circumstances, including adaptive vascular response to changes in ambient conditions and obstructive disorders of retinal vessels. These findings indicate that changes in vessel diameter over time can result in fluctuation of sensitivity. It is concluded that, in contrast with what is commonly stated, when ocular media are unaltered and the subject's collaboration is adequate, temporal variations in measured thresholds do not necessarily reflect functional changes in nervous tissues in the visual pathways.

Anterior ischemic optic neuropathy in Graves' disease

Optic neuropathy occurred in two patients suffering from Graves' disease with marked limitation of eye movement. Optic nerve changes were moderate. They consisted of parapapillary flame-shaped hemorrhages, swelling of the disc, and bundle defects in the visual field on the involved side. This clinical pattern suggested that the optic neuropathy was anterior and ischemic in nature. In one patient, symptoms of optic neuropathy were noted 3 days after starting stretching exercises with the ocular muscles, performed following a friend's advice in an attempt to prevent increase in restrictive myopathy. In patients with Graves' disease, it is conceivable that mild optic neuropathy occasionally occurs as a result of elevation in intraocular pressure, and stretching exercises of the ocular muscles might consequently favor such ischemic events. In the mechanisms of optic nerve involvement associated with Graves' disease, the role of ischemia should be considered in addition to the widely accepted role of optic nerve compression by enlarged extraocular muscles, at the level of the orbital apex.

Skew deviation after vestibular neuritis

We treated five patients with vestibular neuritis who had strabismus. Three of them spontaneously noted vertical diplopia. During the following weeks and months, strabismus progressively resolved, indicating the recently acquired nature of the oculomotor condition. In three of these individuals, a change in visual vertical and cyclo-torsion of the globes suggested that strabismus was a form of skew deviation that occurred as a part of an ocular tilt reaction resulting from the peripheral vestibular lesion. Strabismus appears to occur frequently in this common vestibular condition.