THz optical beat-note detection with a fast superconducting hot electron bolometer operating up to 31 GHz

We study the performance of a hot-electron bolometer (HEB) operating at THz frequencies based on superconducting niobium nitride films. We report on the voltage response of the detector over a large electrical detection bandwidth carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.5 K has a 3 dB cutoff around 2 GHz. Remarkably, detection capability is still observed above 30 GHz in an heterodyne beating experiment using a THz quantum cascade laser frequency comb. Additionally, the HEB sensitivity has been evaluated and an optical noise equivalent power NEP of 0.8 pW/√H z has been measured at 1 MHz.

Minimal-invasive Therapie der Epiphora durch Ballonkatheterdilatation und Stentimplantation

PURPOSE

To examine the clinical outcome of the ballon dilatation in stenosis and obstruction of the nasolacrimal duct.

MATERIAL AND METHODS

63 patients (69 nasolacrimal duct systems) with epiphora and proven obstruction of the nasolacrimal duct were treated with ballon dilatation, respectively Stentimplantation. In 55 cases there was a pre- or postsaccal stenosis, in 14 cases an occlusion of the nasolacrimal duct system. The diagnosis was established by dacryocystography.

RESULTS

Technical success was obtained in 61 cases (n=50/55 stenosis; n=11/14 occlusions). Over a mean follow-up of 6 months patency of the nasolacrimal duct system was achieved in 83,6% (46/55) in stenosis. In occlusion the clinical outcome was 42,9% (6/14).

CONCLUSION

Balloon dacryocystoplasty and Stentimplantation are minimal-invasive alternatives, performed in local anesthesia that recover the normal anatomy of the nasolacrimal duct system. They are a good alternative in the treatment of epiphora caused by nasolacrimal duct obstructions.

[Balloon dilatation of the canaliculus communis for chronic epiphora]

PURPOSE

To examine the clinical outcome of the balloon dilatation in stenosis of the canaliculus communis.

METHOD

18 nasolacrimal ducts with epiphora and proven obstruction of the canaliculus communis by dacryocystography (DCG) were treated with balloon dilatation in local anaesthesia. All patients were treated electively.

RESULTS

In 16/18 cases the balloon dilatation was technically successful, in 2 patients the guide wire failed to pass the obstruction and the wire could not be placed in the nasal cavity. There were no complications. Over a mean follow-up of 6 months there were 2 reobstructions, one of these led to an occlusion of the canaliculus communis. 14/18 (77,8%) cases after DCP were treated successful, 11/18 cases were free of symptoms after DCP, in 4/18 cases the epiphora improved.

CONCLUSIONS

Until recently in stenosis of the canaliculus communis the only therapeutic option was surgical procedure followed by silicone tube intubation. The results were often disappointing. In contrast to this balloon dacryocystoplasty is a minimally-invasive alternative in the therapy of stenosis of the canaliculus communis resulting in good clinical outcome during follow up.

Bilateral non-arteritic anterior ischemic optic neuropathy in a patient with autoimmune thrombocytopenia

PURPOSE

To describe a patient with bilateral non-arteritic anterior ischemic optic neuropathy (NAION) and idiopathic autoimmune thrombocytopenia (ITP) with an extremely low platelet count.

METHOD

Case report.

RESULTS

Remarkably good recovery of visual acuity.

CONCLUSIONS

Bilateral non-arteritic anterior ischemic optic neuropathy can develop in the presence of a very low platelet count.

[Retrobulbar neuritis--diagnosis and differential diagnosis]

The American multicenter study 'A randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis' (5) showed how a retrobulbar neuritis should not be treated, Oral steroids (1 mg per kilogram of body weight per day) are not only ineffective but also associated with a higher rate of recurrences compared to high dose i.v. methylprednisolone. In the light of this study, 'low-dose' steroid therapy for retrobulbar neuritis is contraindicated. High-dose methylprednisolone speeds up recovery of the visual function and lowers the recurrence rate two years after treatment; however, this protective effect could not be demonstrated after three years. These recommendations are valid only for primary demyelinating retrobulbar neuritis. Other less common optic neuropathies, such as these of microvascular origin, respond to 'low-dose' steroids; therefore, the diagnosis of primary demyelinating retrobulbar neuritis must be made with caution as a diagnosis of exclusion. This paper discusses a number of important optic neuropathies and gives recommendations for investigations. Compressive optic neuropathies and chiasmal disease will not be covered here.

[Endonasal dacryocystorhinostomy with transillumination of the lacrimal sac: implementation and results]

PATIENTS

Since Mai 1991 we performed a total of 17 endonasal dacryocystorhinostomies under transillumination of the lacrimal sac on 15 patients with lacrimal obstruction aged 11 to 88 years. 11 patients with 12 operations were followed up between 40 and 393 days (mean of 5.6 months).

RESULTS

In all cases the connection between the lacrimal sac and the nasal cavity remained functionally open. One patient developed a secondary canalicular stenosis which made silicon tubing necessary.

CONCLUSIONS

We consider the operation an elegant and as far as our experience goes reliable method to recanalize the lacrimal drainage system avoiding a cutaneous incision. It is simplified by the transillumination of the lacrimal sac under videoendoscopic conditions.

[Indications for biopsy of the temporal artery]

Indications for Temporal Artery Biopsy are often discussed in the diagnosis of temporal arteritis. In this retrospective study we have reviewed the clinical records of 150 patients who underwent temporal artery biopsy between 1983 and 1990 in Kantonsspital Aarau/Switzerland. In 18.6% biopsies were histologically classified as temporal arteritis. To judge the indication for temporal artery biopsy the combination of symptoms leading to biopsy and the histologic results were compared. Symptoms were divided in unspecific, such as fever, loss of weight or malaise, and more specific symptoms as headache, jaw claudication, loss of visual acuity and diplopia, tenderness of temporal artery, or polymyalgia rheumatica. In conclusion the result of this study is that temporal artery biopsy may be an important help in the diagnosis of temporal arteritis in cases with one or two specific symptoms, at which polymyalgia rheumatica is a questionable indication. In our opinion temporal artery biopsy is not indicated in cases with isolated elevation of ESR, one or more unspecific symptoms and three or more specific symptoms, because there no diagnostic profit can be suspected.

[Long-term study following photocoagulation in diabetic retinopathy]

Diabetic Retinopathy can be stabilized for years by ophthalmological measures. Proliferation in slowed down by photocoagulation and laser coagulation, but they do not prevent other vascular complications. Angiopathy of the arteries and arterioles of the retina and optic nerve can lead to additional, unexpected complications.

Septo-optic pituitary dysplasia. Observations on three patients

Septo-optic pituitary dysplasia is a relatively rare but pathophysiologically interesting malformation of the brain midline structures including optic chiasm and nerves, hypothalamus, neurohypophysis and septum pellucidum. The lesion develops between the 5th and 8th week of pregnancy. The cause is unknown but heredity seems unlikely. Symptoms result from hypothalamic and neurohypophyseal insufficiency of variable severity combined with reduced vision due to hypoplasia of optic nerves and chiasm. Prognosis is variable, depending on the severity of the defect as well as on the earliest time of diagnosis followed by suitable hormone substitution and specialized care of blindness. We present the clinical course in three patients and the pathological findings in one patient who died in the 14th month of life.