Radiologic measurement of extraocular muscle volumes in patients with Graves' orbitopathy: a review and guideline

OBJECTIVE: To evaluate and compare techniques for extraocular muscle (EOM) volume measurement and to provide guidelines for future measurements. DESIGN: Systematic review. RESULTS: Existing techniques used to measure extraocular muscle volumes on radiologic scans can be divided into manual outlining, computer assisted and automated segmentation. Both computed tomography (CT) and magnetic resonance (MR) image datasets can be used. On CT scans, one best measures muscle volume using region grow segmentation, accepting an overestimation of true volume by inevitable inclusion of non-muscular tissue. On high resolution MRI scans, single muscles can be outlined manually, but measurements include only part of the muscle due to poor tissue contrast at the orbital apex. Measurement errors can be reduced 3.5% by exact horizontal repositioning. A measured volume change of at least 6-17% is required to demonstrate a significant difference. CONCLUSION: Currently the best choice for EOM volume measurements on CT images is computer assisted grey value segmentation and on MRI images is manual outlining of individual muscles. Because of the time required and the complexity of the measurements, present EOM volume measurement is as yet only suitable for research purpose

Parallax-free exophthalmometry: a comprehensive review of the literature on clinical exophthalmometry and the introduction of the first parallax-free exophthalmometer

PURPOSE: To present the first parallax-free exophthalmometer design. BACKGROUND: Exophthalmometry is an important clinical tool. We provide a historic overview of clinical exophthalmometer designs, and we review current problems encountered in exophthalmometry. METHODS: We present a new and parallax-free exophthalmometer design that we have evaluated in 49 patients visiting our orbital clinic. RESULTS: The mean age of the patients was 49.8 years and 72% were female. The Pearson interobserver variation was 0.97, and 94% of the Hertel values measured by the two observers were within the limits (1.6 mm) of agreement. CONCLUSION: This meter appears to be a reliable instrument for exophthalmometry. It is the first instrument that allows for a complete parallax-free measurement

Comparison of cyclodeviation and duction measurement in Graves' orbitopathy patients using different devices

To compare measurement outcomes of different devices measuring cyclodeviation and ductions in Graves' orbitopathy (GO) patients. Cyclodeviation in GO patients was measured using the Harms tangent screen (HTS), the cycloforometer of Franceschetti, and the synoptometer. Ductions were measured using the modified perimeter, the Goldmann perimeter and the Maddox tangent scale (MTS). In 13 patients, cyclodeviation in primary position, up-, and downgaze was measured with the above-mentioned devices. The mean differences ranged from 0.3º to 3.1º and were smallest between the HTS and the cycloforometer (89% of all measurements within 2º difference). Measurement of abduction, adduction, elevation, and depression using the modified perimeter, Goldmann perimeter, and MTS were obtained in another 13 patients. The mean differences ranged from 1.2º to 12.9º and were smallest between the modified perimeter and the Goldmann perimeter (92% of all measurements ≤ 8º). The HTS and cycloforometer produce interchangeable measurement outcomes. The modified perimeter and the Goldmann perimeter are interchangeable as well. However, the synoptometer and the MTS are not suitable for comparative analysi

Anomalous relation between axial length and retinal thickness in amblyopic children

To investigate the relationship between retinal thickness and axial length in amblyopic eyes compared to healthy eyes. In this observational, transversal study, 36 amblyopic children and 30 healthy controls underwent full ophthalmological and orthoptic examinations, volume scanning of the macula with spectral domain optical coherence tomography (3D OCT-1000; Topcon Corporation, Tokyo, Japan), and measuring of axial length using the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany). The average pericentral retinal thickness was calculated. A strong correlation was observed between the axial lengths of both eyes in the control group (R = 0.98, P < 0.01) and between the axial lengths of the amblyopic and fellow eye in the amblyopic group (R = 0.77, P < 0.01); the amblyopic and their fellow eyes were significantly shorter than the nonamblyopic control eyes. The pericentral retinal thickness of both eyes of an individual is highly correlated in nonamblyopic controls (R = 0.92, P < 0.01) and in amblyopic children (R = 0.82, P < 0.01). There is no significant difference in mean pericentral retinal thickness between healthy, amblyopic, and fellow eyes. In healthy eyes a moderate inverse correlation exists between axial length and pericentral retinal thickness (R = -0.41, P = 0.02); this relationship was not found in the amblyopic eyes or the normal fellow eye. In this patient cohort, there was an anomalous relation between the axial length and the pericentral retinal thickness in both amblyopic and their fellow eye