Leif Tallstedt

Eye muscle force development and saccadic velocity in thyroid-associated ophthalmopathy

BackgroundOcular motility disturbances are very common in patients with thyroid-associated ophthalmopathy (TAO). The force duction test has demonstrated that limitations of eye movements may be caused by mechanical restrictions in the muscles. A quantitative evaluation of isometric force production and ocular motility in all directions of gaze could further elucidate the mechanism of the movement disorder.MethodsIn eight patients with TAO and eight controls of the same age range, horizontal and vertical saccadic movements of both eyes were recorded by means of electro-oculography (EOG). The corresponding force development in muscles of the more affected eye in patients and the non-dominant eye in normals was measured, using a suction contact lens/strain gauge technique.ResultsSteady-state tension in the patients was increased in all directions of gaze both horizontally and vertically, most markedly for vertical fixations in the upper field of gaze. However, peak tension was increased only for the downward movements in the upper field of gaze and for the horizontal movements in the abduction field of gaze. Vertical saccadic velocity was slower than normal in downward movements, and horizontal saccadic velocity was reduced in the abduction field of gaze.ConclusionThe increased active eye muscle tension in different directions of gaze could represent an adaptational mechanism of the ocular motor system to overcome the eye movement restriction in TAO.

Test‐retest variation in macular thickness measurements with the Heidelberg Retina Tomograph

Purpose:  The aim was to evaluate the test‐retest variation of macular thickness measurements using the Heidelberg Retina Tomograph (HRT3) Retina Module and compare it with the Stratus optical coherence tomography (OCT). As no normative data has been published for the HRT Retina Module, a secondary purpose was to obtain reference values for this technique.

Changes of saccadic eye movements in thyroid‐associated ophthalmopathy

Purpose:  To establish whether or not the dynamics of saccadic eye movements are significantly changed in patients with different stages of thyroid‐associated ophthalmopathy (TAO) and, subsequently, if analysis of saccades could serve as an additional diagnostic tool for early detection of inflammatory activity in TAO.

Saccadic Eye Movement Velocity Measured with the Infrared Reflection and Search Coil Eye-Tracking Systems in Patients with Thyroid-Associated Ophthalmopathy

Background Assessment of changes in saccade velocity may be useful in the early detection of thyroid-associated ophthalmopathy (TAO). Two eye-tracking systems were used to measure the velocity of saccadic eye movements in patients with TAO. Method Fourteen patients with active TAO and 14 healthy controls were enrolled for recordings with two eye-tracking systems: the magnetic scleral search coil (MSC; Skalar Medical) and the infrared reflection systems (IR; Orbit XY-1000). The MSC is generally considered the “gold standard” method for tracking of rapid eye movements. The IR system uses novel computer technology and is based on sampling of reflected infrared light from the surface of the eyes. Main sequence plots constructed from the recorded saccadic peak velocity and amplitude were analyzed for differences between patients and healthy controls. Results There were no significant differences between patients with TAO and healthy controls in the constructed main sequence plots of maximum velocity (VMAX) and the slope constant (C). Conclusions Main sequence analysis of saccadic eye movements was not useful for detecting TAO in this experimental setting with either of the two eye-tracking methods. This is hypothesized to be due to compensation for the early orbital changes in TAO by neural adaptation of the saccades in the brain stem. The contradictory results between this and previous studies cannot be easily explained. We assume that there is a large heterogeneity in the saccadic eye movement performance in both the normal population and the TAO-population. Also, differences in the study design may cause dissimilar outcomes and hence incoherent conclusions. A non-invasive recording system that is able to generate a minimum amount of intra- and inter-individual variability and a study design where normal variability can be reduced to a minimum may be useful for future identification of early eye muscle changes in TAO.