Eye muscle force development in thyroid‐associated ophthalmopathy in different stages of disease

Abstract

. Purpose: Ocular motility disturbances are common in patients with thyroid‐associated ophthalmopathy (TAO). A quantitative evaluation of the isometric force of the eye muscles in TAO might be useful in the detection of early stages of this disease. Methods: A total of 32 patients with TAO were divided into three groups according to whether they had mild active, pronounced, active, or longstanding, inactive disease. A group of six patients with Graves' disease without clinical signs of TAO and a group of 10 control subjects were also studied. The development of isometric force during saccadic eye movements of 5‐, 10‐ and 20‐degree amplitude in horizontal and vertical directions of gaze were recorded in the more affected eye in patients and the non‐dominant eye in normal subjects, using a suction contact lens/strain gauge technique. Results: Peak tension (Fp) in vertical and horizontal saccadic movements was not significantly different between groups. Steady‐state tension (Fs) was significantly higher in the groups with pronounced, active and longstanding, inactive disease than in the other groups for vertical (p < 0.01) and horizontal movements (p < 0.05). Abnormal force development in any of the gaze directions was seen in all patients with pronounced, active and longstanding, inactive TAO, and in some of the patients with mild, active TAO and Graves' disease without TAO. Conclusions: Increased eye muscle tension was recorded in different gaze directions, confirming multiple extraocular muscle involvement in TAO. It is suggested that the increased force development reflected contractile compensations for restrictions of ocular motility due to higher muscle stiffness in thyroid‐associated eye muscle disease. Tension measurements can be used to identify muscle involvement in TAO.

Effects of Elevated Thyroid Hormone on Adult Rabbit Extraocular Muscles

“…6,33 When the effect of elevated thyroid hormone on EOM force was assessed in patients with both active and chronic, mild and severe TED, the muscles from all patients showed abnormal tension, even those with no clinical signs of eye movement disorders. 34 The authors hypothesize that this abnormality had to be due to direct EOM changes in these patients, and this hypothesis is supported by our current analysis. Although magnetic resonance imaging studies demonstrate significant enlargement of one or more of the EOM in patients with TED, these patients have already developed eye signs.…”

Changes of saccadic eye movements in thyroid‐associated ophthalmopathy

“…Further support for this notion is supplied in the study of Tian et al (2007), reporting abnormal force development in any of the gaze directions in all patients with pronounced active and long-standing inactive TAO and in about half of the patients with mild TAO and hyperthyroidism without TAO. This would be evidence for the notion that functional changes had occurred in the eye muscles even before clinical signs of any eye movement disorder could be seen, in terms of restrictions of eye movements or strabismus.…”

Surgical Responses of Medial Rectus Muscle Recession in Thyroid Eye Disease-Related Esotropia

“…The reduced surgical dose-responses of MR recession in TED-related ET could be related to pathologic changes in the EOMs and other periorbital tissues that are not present in patients without underlying TED. The fibrotic changes and MR muscle thickening that occur in TED are resistant to the recession procedure [ 32 ]. Other structural changes in the orbit also might affect surgical response.…”