Postural visual obscurations in patients with inactive thyroid eye disease; a variant of 'hydraulic' disease

Aim This investigation newly describes the characteristics and treatment for a group of patients with inactive thyroid eye disease who presented with recurrent transient visual obscuration, generally related to sudden changes in posture. Study design A retrospective case- note review of an unmatched case series. Patients and methods Clinical records were reviewed for patients with thyroid eye disease, presenting to the Orbital Clinic at Moorfields Eye Hospital with recurrent transient visual obscuration. All patients underwent orbital decompression and the response to this, and other, treatment was reviewed. Results Six patients (five female) presented to the Orbital Clinic, between the ages of 43 and 66 years (mean 54.7; median 52 years), with recurrent visual obscurations related to postural changes. Transient obscurations had been noted for between 3 weeks and 2 months, the patients having had symptoms of underlying thyroid eye disease for between 6 and 18 months. Five patients had diabetes for between 2 and 45 years, four being controlled with insulin and one with metformin. All patients had increased orbital tension on clinical assessment, intraocular pressures were raised in 5/6, and the optic disc in affected eyes was markedly swollen (with bilateral choroidal folds in two patients). Hertel exophthalmometry ranged from 22 to 27 mm, and there was a global reduction in ocular ductions in all. Bilateral orbital decompression was performed in all patients, although sequentially in one patient: 4/6 patients had three-wall decompression with an average proptosis reduction of 5.8 mm (range 2-8 mm; eight orbits) and 2/6 had decompression of the medial wall and floor alone (mean reduction 6.8 mm, range 5 - 8 mm; four orbits). In all patients, there was an almost immediate cessation of obscurations, together with a subjective and objective improvement in various visual functions. Optic disc swelling resolved over a few weeks after surgery. Conclusion The 'hydraulic' variant of thyroid eye disease - characterised by high orbital apex pressures, with secondarily raised episcleral venous and intraocular pressures - may be linked with certain orbital shapes, such as that of Asians. This variant can present with recurrent visual obscuration associated with transient postural hypotension, especially in diabetics - this possibly being due to a microvasculopathy of the orbital or optic nerve circulation.