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Aims: To assess the prevalence of dysthyroid optic neuropathy (DON) in patients with diabetes mellitus (DM) and Graves' orbitopathy (GO) and to investigate the complications of surgery for GO in these patients., Methods: The records of 482 consecutive patients with GO referred in a 5 year period were studied. Those patients who also had DM were selected for further study. The prevalence of insulin dependent diabetes mellitus (IDDM) and non-insulin dependent diabetes mellitus (NIDDM) was registered, as well as the prevalence and course of DON. In the patients who underwent surgery for GO the postoperative complications were recorded., Results: Out of 482 patients with GO, 15 (3.1%) also had DM. Eight (1.7%) had IDDM, 7 (1.4%) had NIDDM. Five patients (33.3%) three with IDDM and two with NIDDM developed DON with 50% improvement of visual acuity after treatment, whereas in the whole population of 482 GO patients 19 had DON (3.9%), showing 69.4% improvement of vision after treatment. 10 patients with GO and DM were operated for GO; in one of them an optic atrophy developed as a result of a postoperative haemorrhage directly after a three wall orbital decompression by coronal approach. No other postoperative complications occurred., Conclusions: The prevalence of IDDM in patients with GO is higher than in the normal population. DON occurs much more frequently in patients with GO and DM than in the total group of GO patients and seems to have a worse visual prognosis.

Aims/background: In Graves' ophthalmopathy the increase in volume of intraocular muscles and fat will cause elevated intraorbital pressure. In order to investigate the pressure levels involved, intraorbital pressure, or retrobulbar pressure (RBP) was measured continuously in orbits of patients with Graves' ophthalmopathy during surgical decompression., Methods: Retrobulbar pressure was measured before and during surgical decompression using an intraorbitally applied pressure transducer., Results: In eight patients with dysthyroid optic neuropathy (DON) RBPs between 17 and 40 mm Hg were recorded. At the end of the surgical procedure the mean RBP was reduced from 28.7 mm Hg to 18.7 mm Hg, the decrease ranging from 8 to 12 mm Hg, which showed a high correlation with the starting pressures (p < 0.001). In two cases without DON, pressures were 11 and 9 mm Hg. Forces exerted by spatula manipulation usually resulted in a RBP level of more than 70 mm Hg., Conclusions: This study shows that RBPs are markedly elevated in Graves' ophthalmopathy and that surgical decompression can result in a significant reduction in the intraorbital pressure. Optic nerve dysfunction in Graves' ophthalmopathy may not be caused exclusively by the direct pressure of swollen extraocular muscles upon the optic nerve, but also by a raised RBP. It is hypothesised that the damage inflicted upon the optic nerve can be caused in consequence by RBP induced incarceration of the nerve, compressed by surrounding periosteal lined orbital fat bulging posteriorly into the entrance of the optic canal.

Contrast sensitivity function was measured by a computer automated method on 38 eyes with dysthyroid optic neuropathy and 34 eyes with Graves' ophthalmopathy only. The results were compared with 74 healthy control eyes. Disturbances of contrast sensitivity functions were found in both groups when compared with controls. The eyes affected with dysthyroid optic neuropathy showed pronounced loss of contrast sensitivity in the low frequency range, which facilitates differentiation between the two groups.

Contrast sensitivity function (CSF) was investigated in 19 patients (34 eyes) with clinical signs and symptoms of dysthyroid optic neuropathy (DON). CSF was disturbed in 33 eyes and was shown to improve after orbital decompression. These results indicate that the CSF may be a useful supplementary test of visual function in patients with DON.