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Title	Dysthyroid optic neuropathy: the stretching component.
Abstract Nr.	3009

Purpose	Dysthyroid optic neuropathy (DON) occurs in about 5% of graves’ orbitopathy (GO). This has been primarily attributed to apical crowding and optic nerve compression. We examined a population of DON without extraocular muscle involvement in order to evaluate the association of optic nerve stretching and DON.
Methods	We retrospectively analyzed 30 patients with DON’s collected during a period of 20 years (30 patients: 21 women, 9 men, mean age :49,9 years). Patients with DON were selected using clinical exams and VEP and sorted in 3 subgroups: “compressive and stretching DON”, “compressive DON” and “stretching DON” based on the CT and/or the MRI.
Results	45,6% of eyes had compressive and stretching DON (Grp 1), 26,1 % of eyes only compressive DON ( Grp 2) and the 28,3 % only stretching DON (Grp 3). In Grp 3, 62,5% of patient had bilateral DON, with a better vision (20/25 compared to 20/32 in Grp 1 and 2) and less abnormalities of fundus (62,5% versus 73,3% and 100% in subgroup 1 and 2 respectively). In the same Grp 3, motility was normal except in one patient and proptosis was significantly less important than in Grp 1 combining stretching and compression.
Conclusion	28,3 % of our DON’s patients (8 patients and 13 eyes) presented a neuropathy without extraocular muscle involvement but with important stretching of ON. The different mechanisms will be discussed. Thus, the absence of compression and of significant increased volume of extraocular muscles do not ruled out the possibility of DON.
Conflict of interest	No

Authors 1

Last name	COUTEL
Initials	M
Department	Clinique Universitaire Saint-Luc
City	Bruxelles

Authors 2

Last name	Boschi
Initials	A
Department	Clinique Universitaire Saint-Luc
City	Bruxelles