Evaluation of the infrared reflection method for saccadic eye movement velocity analysis

Saccades are rapid eye movements that change the orientation of the eyes onto objects of interest. In an every day situation saccadic eye movements are used for e.g. reading, scanning objects and enviromnents. The neuronal control of the saccadic eye movement is complex and involves many different parts of the brain. The saccade is the fastest of eye movements and its velocity is not subject to volitional control. Velocity measurements of saccades are therefore interesting for the detection and characterization of diseases that affect the oculomotor system of the brain and the extra ocular muscles. Different techniques have over the years been developed for tracking eye movements. Among the methods, the magnetic scleral search coil (MSC) system has stood out as a "gold standard" for recording fast eye movements, as the saccade. The device is sensitive and recording noise is low. It also records at a high frequency level, which is particularly important when recording fast eye movements. However, one of the drawbacks of the method is that it involves wearing, on the surface of the eyes, rather uncomfortable silicone lenses in which a copper wire is embedded. There have been suggestions that the coil may slide on the eye surface and hence introduce an unwanted filtering effect. Moreover, the weight of the coil might affect the oculomotor signal elicited in the brainstem. For conducting saccadic eye motility research and high velocity eye-tracking in the clinics, a non invasive recording system would be of great value. The infrared reflection (M) method is able to record the eye's position and velocity at a high frequency level, but without any contact with the eyes. The system works through emitting infrared light from illuminators built into goggles against the three-dimensional surface of the eyes. The reflected light is detected and processed in a computerized system into eye movement signals. The recent developments of the IR system have not been evaluated previously for detailed saccadic eye movement velocity recordings. In the presented studies healthy subjects performed saccadic tasks with both the MSC and IR methods. The data were analysed regarding the amplitude-velocity relationship, also called the main sequence. The results showed that the IR method generated saccadic velocities that were significantly higher compared to the MSC method. Intra individual as well as inter individual variability of the main sequence was shown with both methods, but there was generally larger variability with the IR recordings. The reasons for the IR method generating higher eye velocity data compared to the MSC method may be explained by drawbacks that are related to both methods. First, there is an inherent risk of filtering in the MCS recordings if the silicon contact lens slides on the eye surface and the coil changes the oculomotor signal. Second, artefacts that are associated to the IR system may induce inaccurately high peak velocity measures. A risk that can not be left out of account is that the IR system does not merely detect eye movements, but also concurrent changes in the three-dimensional reflecting surface of the eyes and eyelids. It is also sensitive to changes in lighting conditions, which was shown in our experiments. Moreover, the inferior resolution and linearity of the IR system may introduce falsely high velocity data as well as a generally larger variability. The IR system may be used for rapid eye velocity analysis and has some advantages compared to the MSC system. However, the velocity data differ from those measured with the coil system. Intra individual and inter individual variability should be considered, especially in follow-up studies. Improving the calibration procedure, paradigms and recording conditions might increase the scope for using the method for reliable saccadic eye movement recordings, both in scientific and clinical settings

Thyroid associated ophthalmopathy : Treatment for hyperhyroidism and evaluation of methods for measuring saccadic eye movements

Thyroid associated ophthalmopathy (TAO) is the orbital manifestation of autoimmune thyroid disease that clinically affects about 30-50 % of patients with Graves disease (GD). The clinical features of TAO are in most patients mild and transient. In some cases though, a severe orbital immune reaction develops, which may lead to permanent exophthalmos and double vision. Optic neuropathy in TAO is rare and denotes very severe and sight-threatening disease. The objectives of the herein presented studies include first, the evaluation of techniques for the measurement of the velocity of saccades in normal subjects and patients with TAO and second, the assessment of the potential effect of treatment with anti-thyroid drugs or radioactive iodine for Graves hyperthyroidism on worsening or development of TAO. Objective assessment of TAO and the detection of a potential subclinical extraocular muscle involvement in TAO may be difficult. Previous studies from our eye-movement laboratory have given way to optimism about using saccade velocity measurements in the detection of early and subclinical TAO. The magnetic scleral search coil (MSC) system has long been considered as a gold standard method for measuring saccadic velocity in the laboratory milieu. A modern development of the infrared reflection (IR) method was considered as a more suitable method for eye-tracking in the clinical setting. The technique had though until now not undergone evaluations for saccadic velocity measurements. In the present studies saccadic eye movements were recorded in healthy subjects and patients with TAO with both the MSC and IR methods. The data were analysed regarding the characteristic amplitude-velocity relationship of the saccades (the main sequence). The results showed that the IR method generated saccadic velocities that were higher compared to the MSC method in healthy subjects. Intra individual as well as inter individual variability of the main sequence was shown with both methods, but was more pronounced with the IR recordings. No significant differences were shown for the main sequence relationship between patients with TAO and healthy controls with either of the recording systems. The primary treatment for most patients with Graves hyperthyroidism is either radioactive iodine or anti-thyroid drugs. The results from the here presented study showed that the patients who were randomized to treatment with anti-thyroid drugs had a significantly lower risk for development or worsening of TAO than those randomized to treatment with radioiodine. Deterioration of the eye disease was not found to be related to either therapy among the patients who had TAO already before treatment for hyperthyroidism, whereas patients with no clinically detectable eye involvement from the start showed a significantly higher proportion of de novo development of TAO in the radioiodine treatment group. Smoking was confirmed as a risk factor for TAO. In the subgroup of smokers, the mode of treatment for hyperthyroidism did not significantly influence the outcome of worsening or development of TAO

Intensified visual clutter induces increased sympathetic signalling, poorer postural control, and faster torsional eye movements during visual rotation.

Many dizzy patients express a hypersensitivity to visual motion and clutter. This study aims to investigate how exposure to rotating visual clutter affects ocular torsion, vertical skewing, body-sway, the autonomic pupillary response, and the subjective feeling of discomfort to the stimulation. Sixteen healthy subjects were exposed to 20 seconds rotational visual stimulation (72 deg/s; 50 deg visual field). Visual stimuli were comprised of black lines on a white background, presented at low and high intensity levels of visual clutter, holding 19 lines and 38 lines respectively. Ocular torsion and vertical skewing were recorded using the Chronos Eye Tracker, which also measured pupil size as a reflection of the autonomic response. Postural control was evaluated by measuring body-sway area on the Wii Balance Board. Values were compared to data retrieved 20 seconds before and after the optokinetic stimulation, as subjects viewed the stationary visual scene. The high intensity stimulus resulted in significantly higher torsional velocities. Subjects who were exposed to low intensity first exhibited higher velocities for both intensities. Both pupil size and body sway increased for the higher intensity to both the moving and stationary visual scene, and were positively correlated to torsional velocity. In conclusion, exposure to visual clutter was reflected in the eye movement response, changes in postural control, and the autonomic response. This response may hold clinical utility when assessing patients suffering from visual motion hypersensitivity, while also providing some context as to why some healthy people feel discomfort in visually cluttered surroundings

Adjuvant Treatment of Graves' Disease with Diclofenac : Safety, Effects on Ophthalmopathy and Antibody Concentrations

BACKGROUND: Orbital morphological changes are often present in patients with Graves' disease (GD) already at diagnosis, and cyclooxygenase type 2 (COX-2) is overexpressed in active Graves' ophthalmopathy (GO).OBJECTIVE: To investigate if adjuvant treatment of GD with the COX inhibitor and peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist diclofenac decreases the development of ophthalmopathy and if laboratory parameters are affected.METHODS: This is a multicenter trial where 61 subjects were randomized to methimazole (block and replace with l-thyroxine) either with or without diclofenac 50 mg 1 × 2 for 12 months. The primary end point development of GO after 24 months was evaluated. Smoking habits were registered and the thyroid parameters TSH, free T4, free T3, TSH receptor antibodies (TRAb) and anti-TPO were followed. Safety parameters (kidney, liver and blood) and adverse events were regularly registered.RESULTS: GO developed in 11% (n = 3) of the patients treated with diclofenac and in 21% (n = 6) of the controls (p = 0.273). The adverse event profile was acceptable without any severe events related to diclofenac. Both TRAb and anti-TPO concentrations decreased during treatment with methimazole, but the anti-TPO concentrations were lower in patients treated with diclofenac after 15 months (p = 0.031). The TRAb concentrations were not significantly changed between groups. Smokers had higher concentrations of TRAb than nonsmokers both at diagnosis of GD (p = 0.048) and after 15 months (p = 0.042).CONCLUSIONS: Treatment with diclofenac had no significant influence on development of GO. Diclofenac reduces anti-TPO concentrations and seems to be safe to use in GD patients

A New Homoplasmic mtDNA Mutation Described in Mother and Son with Clinical LHON

A 48 year old woman presented with acute painless sequential visual loss that progressed over two months. The patient had no previous ophthalmologic history. She was a chronic smoker with intermittent alcohol abuse and an amphetamine addiction 15 years prior

Thyroid-Associated Ophthalmopathy after Treatment for Graves' Hyperthyroidism with Antithyroid Drugs or Iodine-131.

Context: Previous randomized trials have suggested an association between radioiodine treatment for Graves' hyperthyroidism and thyroid-associated ophthalmopathy (TAO). Objectives: The aim of the study was to compare the occurrence of worsening or development of TAO in patients who were treated with radioiodine or antithyroid drugs. Design: We conducted a randomized trial (TT 96) with a follow-up of 4 yr. Patients, Setting, and Intervention: Patients with a recent diagnosis of Graves' hyperthyroidism were randomized to treatment with iodine-131 (163 patients) or 18 months of medical treatment (150 patients). Early substitution with T4 was given in both groups. Main Outcome Measure: Worsening or development of TAO was significantly more common in the iodine-131 treatment group (63 patients; 38.7%) compared with the medical treatment group (32 patients; 21.3%) (P < 0.001). Results: The risk for de novo development of TAO was greater in patients treated with iodine-131 (53 patients) than with medical treatment (23 patients). However, worsening of TAO in the 41 patients who had ophthalmopathy already before the start of treatment was not more common in the radioiodine group (10 patients) than in the medical group (nine patients). Smoking was shown to influence the risk of worsening or development of TAO, and smokers treated with radioiodine had the overall highest risk for TAO. However, in the group of smokers, worsening or development of TAO was not significantly associated with the choice of treatment for hyperthyroidism. Conclusions: Radioiodine treatment is a significant risk factor for development of TAO in Graves' hyperthyroidism. Smokers run the highest risk for worsening or development of TAO irrespective of treatment modality

Imaging in Lyme neuroborreliosis

Lyme neuroborreliosis (LNB) is a tick-borne spirochetal infection with a broad spectrum of imaging pathology. For individuals who live in or have travelled to areas where ticks reside, LNB should be considered among differential diagnoses when clinical manifestations from the nervous system occur. Radiculitis, meningitis and facial palsy are commonly encountered, while peripheral neuropathy, myelitis, meningoencephalitis and cerebral vasculitis are rarer manifestations of LNB. Cerebrospinal fluid (CSF) analysis and serology are key investigations in patient workup. The primary role of imaging is to rule out other reasons for the neurological symptoms. It is therefore important to know the diversity of possible imaging findings from the infection itself. There may be no imaging abnormality, or findings suggestive of neuritis, meningitis, myelitis, encephalitis or vasculitis. White matter lesions are not a prominent feature of LNB. Insight into LNB clinical presentation, laboratory test methods and spectrum of imaging pathology will aid in the multidisciplinary interaction that often is imperative to achieve an efficient patient workup and arrive at a correct diagnosis. This article can educate those engaged in imaging of the nervous system and serve as a comprehensive tool in clinical cases